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threeC H A P T E R
D E S I G N C O N S I D E R A T I O N S
Precast concrete’s high level of quality fabrication and its
array of benefits help architects meet a variety of design chal-
lenges.These goals can range from projecting the appropriate
image today to maintaining that appearance and retaining all
functional activities for decades into the future. Maximizing
the performance of the material requires an understanding of
its capabilities and limitations related to each goal.
Aesthetics_______________ 3A
Integration &
Coordination with
Other Building Systems ____ 3B
Team Responsibilities _____ 3C
Initial & Life-Cycle Costs_____ 3D
Sustainability & LEED______ 3E
Health & Indoor
Air Quality_______________ 3F
Acoustics________________ 3G
Safety & Security_ ________ 3H
DESI GNING WIT H PRECAST & PREST RESSED CONCRET E

The aesthetic options available with architectural precast con-
crete components, especially wall panels, are considerable.They
can mimic a wide variety of other masonry alternatives, includ-
ing brick and stone, providing many options for duplicating ex-
isting architectural styles used with surrounding buildings.This
holds true whether the styles are historic or contemporary.
In many cases, architectural finishes also can be provided for
structural precast components, combining functions and saving
material cost and construction time. Precast components also
mesh well with other materials, including curtain walls, and
they can accommodate any required penetrations. Special con-
siderations will aid the installation of mechanical systems and
vapor barriers, all of which can be accommodated easily.
Precast concrete’s economy aids owners and designers in
meeting their budgetary needs and helps make funds available
that are typically needed for design consideration for other
key elements. Its economy not only reduces the immediate
in-ground cost but also continues to save operating expenses
over the life of the building through extended durability and
lower maintenance costs. Precast concrete can also aid in meet-
ing sustainability goals set by the owner, including certification
standards set by the Leadership in Energy & Environmental
Design (LEED) program instituted by the U.S. Green Building
Council (USGBC).
A variety of additional design challenges, such as maximiz-
ing fire resistance, heightening acoustic control, and providing
safety provisions, can all be met by designing precast concrete
components to the appropriate specifications. Architects who
work closely with their local precaster during the design phase
and throughout the development of the contract documents
can ensure their projects make efficient use of the material’s
wide range of capabilities to provide optimum value and quality
while minimizing construction cost.

These swatches illustrate the different shades that can be
created in architectural precast using a single pigment at
many different concentrations. They represent addition
rates of red pigment from 1/4% to 7% in a white cement
base.
a•
C H A P T E R T H R E E
Precast concrete is a visually rich material that allows the architect to be innova-
tive and attain design objectives that cannot be achieved with any other material.
The architect’s selection of color, form, and texture is critical to the aesthetic ap-
pearance of architectural precast concrete components. The choice of appro-
priate aggregates and textures, combined with well-conceived production and
erection details, can achieve a wide variety of design objectives.
Design flexibility is possible in both color and texture of precast concrete by
varying aggregate and matrix color, size of aggregate, finish processes, and depth of
aggregarate exposure. Combining color with texture accentuates the natural beauty
of aggregates.
With the vast array of colors, textures, and finishes available, designers can use
precast concrete to achieve almost any desired effect.
Color
Color is a relative value, not an absolute and unvarying tone. It is affected by
light, shadow, density, time, and other surrounding or nearby colors. Color selec-
tion should be made under lighting conditions similar to those under which the
precast concrete will be used, such as the strong light and shadows of natural
daylight. Surface texture influences color. The building’s appearance is a function
of the architect’s use of light, shadow, texture, and color.
Cement combined with a coloring agent exerts the primary color influence on
a smooth finish, because it coats the exposed concrete surface. As the concrete
surface is progressively removed and aggregates are exposed, the panel color
increasingly exhibits the fine and then the coarse aggregate colors. The color of
the cement always has an effect on the general tone of the panel. Cement may be
gray, white, or a mixture. All cements have inherent color and shading differences,
depending on their source.
Aesthetics
DESI GNING WIT H PRECAST & PREST RESSED CONCRET E 3A-1

Pigments and pigmented admixtures are often added to the cement matrix to
obtain colors that cannot be created through combinations of cement and fine
aggregate alone. White portland cement will produce cleaner, brighter colors and
where color is important should be used in preference to gray cement with pig-
ments, especially for the light pastels such as buff, cream, pink, rose, and ivory.
Fine aggregates have a major effect on the color of white and light buff-colored con-
crete and can add color tones when the surface is given a shallow profile to increase
the aggregate’s exposure. Coarse aggregate colors become dominant as the surface
of the concrete is removed to obtain a medium or deep aggregate exposure profile.
Some finishing processes change the appearance of aggregates. Sandblasting
will give the aggregates a matte finish, while acid-etching may increase their
brightness. Exposure by retardation of the surface cement normally leaves the
aggregates unchanged.
Maintaining consistency of color throughout the production run requires attention
to detail and proper specification. Eight key factors should be closely controlled
when color consistency is critical:
1. Type and color of cement.
2. The quality and quantity of the coloring agent.
3. Proper batching and mixing techniques and the coloring agent’s effect on the
concrete’s workability.
4. Quality (that is, freedom from impurities) of the fine and coarse aggregates.
5. Uniform quantities and gradation of the fine materials (capable of passing
through a No. 50 sieve, including the cement) in the concrete mix.
6. Careful attention to curing and uniform duplication of curing cycles.
7. Constant water-cement ratio in the mix.
8. Consideration of the factors that can contribute to efflorescence. Its appearance on
the concrete’s surface can mask the true color and give the appearance of color
fading. Should efflorescence occur, it can be washed off when its appearance on
the panel is noticed.
The ease of obtaining uniformity in color is directly related to the ingredients
supplying the color. Optimum uniformity is obtained by using white cement.
Extreme color differences between aggregates and matrix should be avoided.
Color should be judged from a full-sized sample that has the proper cement
matrix and has been finished in accordance with planned production techniques
(see Reference 1).
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3A-2

The Anadarko Tower located in The Woodlands, Tex.,
was clad with light and medium sandblast, textured
precast panels composed of a single-face mix design.
Some of the panels were supplemented with thermal
finished Luna Pearl granite insets. The mix was
composed of 100 percent white portland cement,
coarse aggregates, fine aggregates, and pigment.
Photo: Gensler.
The single concrete mix shown here has three different
finishes. From left to right, they are acid etch, sandblast,
and retarded. This multiple-finish technique offers an
economical, yet effective, way to heighten aesthetic interest.
Textures
Texture allows the naturalness of the concrete ingredients to be expressed, provides
some scale to the mass of the building, expresses the creative aspect of the concrete,
and improves the weathering characteristics of the element surface. A variety of
textures can be achieved, ranging from a honed or polished surface to a deeply
exposed, 3-in.-diameter, uncrushed aggregate surface.
The final appearance of any precast concrete finish will depend on the selection of
aggregate color and size, matrix color, shape details or form, surface finish, and depth
of aggregate exposure. Four major factors should be considered in choosing a texture:
1. The area of the surface. Coarse textures are difficult to use on small areas.
Dividing large, flat areas by means of rustications tends to deemphasize any
variations.
2. The viewing distance. From a greater distance, different textures will provide
different tonal values. Determining the normal viewing distance in the final use
will impact which textures and sizes of aggregates should be used.
3. The orientation of the building’s wall elevation. The siting determines the amount
and the direction of light on the surface and how the panel will weather.
4. Aggregate particle shape and surface characteristics. Both the shape and
surface characteristics determine how the surface will weather and reflect
light (see Reference 2.).
There are three key levels of exposure that are used in creating a finished
appearance:
1. Light exposure involves removing only the surface skin of cement and sand.
This sufficiently exposes the tips of the closest coarse aggregate.
2. Medium exposure requires further removal of cement and sand to cause the
coarse aggregates to appear approximately equal in area to the matrix.
3. Deep exposure requires cement and sand to be removed from the surface so
the coarse aggregates become the major surface feature (see Reference 3.).
Finishes
A wide range of surface finishes are available, achieved through a variety of
processes. Before a specific finish is specified, sample panels should be created
to ensure the finish achieves the desired aesthetic and functional goals.
Samples may be provided by competing producers initially in small, 12-in.
squares. The selected producer should then provide three 4 ft2
or 5 ft,2
samples to
determine color range. The range of acceptable variations in color, texture, and
uniformity should be determined when these mockup units are approved. Full-
scale mockups should be specified by the architect to arrive at a final approval of
the desired design (see Reference 4).
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3A-3

Examples of light, medium, and heavy sandblast textures.
Examples of light, medium, and heavy acid-washed textures.
388 Market Street building in San Francisco,
Calif., is clad with 1 1/4 in. (3 cm) granite
anchored to precast concrete. Architect:
Skidmore, Owings Merrill; Photo:
Skidmore, Owings Merrill San Francisco.
The most common types of finishes available include:
• Smooth as-cast finishes show the natural look of the concrete without trying
to simulate any other building product. Fine surface details and sharp arrises
can be achieved. When a high level of color uniformity is required, this finish is
strongly discouraged (see Reference 5).
• Exposed-aggregate finishes, via chemical retarders or water washing, are
achieved with a non-abrasive process that effectively brings out the full color,
texture, and beauty of the coarse aggregate. The aggregate is not damaged
or changed by this exposure method (see Reference 6).
• Formliners provide an almost unlimited variety of patterns, shapes, and
surface textures. The concrete is cast against liners made of a range of
materials, including wood, steel, plaster, elastomeric, plastic, or foam plastic
(see Reference 7).
• Sand or abrasive blasting provides all three degrees of exposure noted
above. This process is suitable for exposure of either large or small aggregates.
Uniformity is directly proportional to the depth of material removal
(see Reference 8).
• Acid etching dissolves the surface cement paste to reveal the sand, with only
a small percentage of coarse aggregate being visible. It is most commonly
used for light or light-to-medium exposure (see Reference 9).
• Tooling, usually called bushhammering, mechanically spalls or chips the
concrete surface using any of a number of hand or power tools, producing
an abraded aggregate texture. Each tool produces a distinctive surface effect
and a unique shade of concrete color (see Reference 10).
• Hammered-rib or fractured-fin designs are created by casting ribs onto the
surface of the panels and then using a hammer or bushhammer tool to ran-
domly break the ribs and expose the aggregate. The effect is a bold, deeply
textured surface (see Reference 11).

Panels on the Shriners Hospital for
Crippled Children, Sacramento, Calif.,
are 6 in. thick and have a horizontal
band of 1 1/4 in. granite attached with
one anchor per 2 ft2
. Architects: Odell
Associates; and Associate Architect: HDR.
Arizona red sandstone, 1 1/4 in. to 1 3/4 in. thick,
was anchored to 4-in.-thick concrete panels for the
Sacramento Municipal Utility District’s Customer Service
Center, Sacramento, Calif.; Architect: Williams + Paddon
Architects Planners/Inc.
• Sand embedment creates a bold and massive appearance for the panel,
using 1- to 8-in.-diameter stones or flagstones. The stones typically are placed
in a sand bed at the bottom of the mold, and finishing reveals the stone face,
resulting in the appearance of a mortar joint (see Reference 12).
• Honing or polished finishes are achieved by grinding the surface to produce
smooth, exposed-aggregate appearances. Polished, exposed-aggregate
concrete finishes compare favorably with polished natural stone façades,
such as granite (see Reference 13).
• Painting or staining is used purely for decorative purposes, due to the high-
strength, durable nature of precast concrete panels. There is a vast difference
in paint types, brands, prices, and performance, and knowledge of composi-
tion and performance standards is necessary to obtain a satisfactory result.
In some cases, the precast concrete surface can be so smooth that it makes
adhesion difficult to obtain, so a decision on painting should be made prior to
casting if possible (see Reference 14).
Multiple mixtures and textures in the same unit provide design flexibility. Color
and texture variations can be obtained by manipulating aggregates and matrix
colors, size of aggregates, formliners, finishing processes, and depth of expo-
sure. A rustrication feature needs to be detailed to separate the different colors
and/or finishes.
Combinations of various finishes on the same unit depend on the shape of the
unit. Some finishes, such as acid etching, can’t be easily applied to only one portion
of a unit. The combination of a polished or honed surface and acid etching provides
a surface that exposes a very high percentage of aggregate (see Reference 15).
Facing Products And Architectural Trim Units
Clay product-faced precast concrete panels combine the pleasing visual
appearance of traditional masonry products with the strength, versatility, and
economy of precast concrete. Clay products that can be cast integrally with
precast concrete panels include brick, ceramic tile, and terra cotta. The clay
product can cover the entire exposed-panel surface or only a portion, serving as
an accent band or contrasting section. Marble, glass, and ceramic mosaics can
also be cast integrally (which is preferred) or applied to the hardened concrete
(see Reference 16).
The combination of precast concrete and clay products has several advantages
over site-laid-up masonry. By using precast concrete panelized construction, the
need for on-site scaffolding and significant on-site labor is eliminated, which can
be a significant cost savings over masonry construction.

One-in.-thick brick cladding on 5-in.-thick concrete panels was used on the first three floors of the Sacramento County
System and Data Processing Building in Sacramento, Calif. Terracotta medallions were placed on spandrels
and column covers. Architect: HDR Architecture Inc. formerly Ehrlich-Rominger; Photos: HDR Architecture Inc.
Structural design, fabrication, handling, and erection aspects of clay product-
faced precast concrete units are addressed similarly to those for other precast
concrete wall panels except that special consideration must be given to the
dimensional layout of the clay product and its embedment in the concrete. The
physical properties of the clay products must be compatible with the properties
of the concrete backup. The most significant property is the coefficient of thermal
expansion, which causes volume change. It is best to select material with similar
coefficients of expansion along with tight dimensional tolerances.
Reinforcement of the precast concrete backup should follow recommendations
for precast concrete wall panels relative to design, cover, and placement. Uniform
and even coursing without cutting any units vertically or horizontally except as
necessary for running bond allow for economical production. To achieve this thin
brick conforming to the PCI standard for embedded brick should be specified
(see Reference 17).
Natural stone has been widely used in building construction due to its strength,
durability, aesthetic effect, availability, and inherent low-maintenance costs. Stone
veneers for precast concrete facings are usually thinner than those used for conven-
tionally set stone, with the maximum size generally determined by the stone strength.
When purchasing stone, a qualified individual should be appointed to be re-
sponsible for coordination, which includes delivery and scheduling responsibility
and ensuring color uniformity (see Reference 18).
Architectural trim units (cast stone) are manufactured to simulate natural cut stone.
They are used in masonry work mostly as ornamentation and architectural trim for
stone bands, sills, lintels, copings, balustrades, and door and window trimming. They
replace natural cut stone or terracotta in these applications (see Reference 19).

Architectural precast panels for the new wing of the
Joslyn Art Museum, Omaha, Neb., are clad in Georgia
marble to match the original stone building constructed
in 1931. Labor and material cost were reduced using this
system compared to traditional stone cladding systems.
Architect: Henningson, Durham Richardson Inc.
Architectural precast concrete panels both inside and
out bring drama and quality to the recent 3 million-ft2
expansion of McCormick Place in Chicago, Ill. Photo:
Brian Gassel/TVSAssoc.
Matching Precast With Cast-In-Place Concrete
Precast concrete panels are often used in conjunction with architectural cast-
in-place concrete. Matching these finishes to create a monolithic look must be
planned before construction starts to allow adjustment of mix design, placement
technique, methods of consolidation, and finishing procedures. Samples and full-
scale mockups should be prepared for both the precast and cast-in-place panels,
and differences should be resolved prior to finalizing either finish.
When both products will be used in the same plane, the cast-in-place toler-
ances must be strictly enforced. Differences in curing methods between the two
techniques, even with identical mixes, may cause color variation in the finish,
particularly if the precast concrete uses accelerated, high-temperature curing.
Different weathering patterns may result in dissimilar appearances due to different
concrete densities (see Reference 20).
Interior Finishes
The interior side of architectural precast concrete panels can also be given an
aesthetic finish, eliminating the need to provide an additional finished wall, saving
materials, time, and cost. Exposed interior surfaces should have finishes that are
realistic in terms of exposure, production techniques, configuration of the precast
concrete units, and quality requirements.
A variety of finishes for the back of a precast concrete panel can be provided.
They include screed, light broom, float, trowel, stippled, or waterwashed or retarded
exposed-aggregate finishes or sandblast finish. If the finish is to be painted, a
stippled concrete finish normally will be the most economical. A trowelled finish
is the most common interior finish, but it frequently darkens the surface in uneven
patterns.
The treatment of joints and connections with regard to interior-finish requirements
should be considered if panels are to remain exposed. Load-supporting connec-
tions at the top and bottom of the panel should be hidden above the ceiling panels
and below the floor level, respectively. If they are exposed, they should be recessed
(see Reference 21).
Acceptability Of Appearance
Contract documents should spell out who the accepting authority for the panel
color, finish, and texture will be. This is typically the owner, architect, general
contractor, or site inspector. One person must have final authority on all issues of
appearance. Determing acceptable uniformity of color, finish, and texture is by
visual examination, and is generally a matter of subjective, individual judgment
and interpretation. The acceptable variations should be determined at the time
the visual mockups or initial production units are approved. Suitable criteria for
acceptability require that the finished concrete face surface should have no read-
ily visible imperfections other than minimal color and texture variations from the
approved samples or evidence of repairs when viewed in good, typical daylight
illumination with the unaided, naked eye at a 20 ft or greater viewing distance.

Built in 1906, the architectural landmark 88
Kearney St. in San Francisco had its terra
cotta removed and reassembled on precast
panels for an all-new structure of taller
height. Architect: Skidmore, Owings
Merrill; Photo: Skidmore, Owings Merrill.
Appearance of the surface should not be evaluated when light is illuminating the
surface from an extreme angle, as this tends to accentuate minor surface irregu-
larities due to shadowing.
Building façades may be oriented such that sunlight just grazes the surface at
a particular time of day. This causes otherwise imperceptible ripples, projections,
and misalignments on the surace to cast long shadows and be grossly exagger-
ated in appearance. The shadows may last briefly. The actual time at which they
appear varies with the season for a particular wall. Precast concrete, like any
building surface, is subject to manufacturing and alignment tolerance so that the
effect cannot be avoided.
Units should be assessed for appearance during dry weather. In climates with
intermittent dry and wet conditions, drying-out periods may produce temporary
mottled appearances.
Minor surface abnormalities and blemishes will occur on occasion, and precast-
ers can adequately repair minor problems quickly. There are key finish defects and/
or problems that are considered unacceptable in the fabrication of high-quality,
PCI-certified architectural precast concrete (see Reference 22). These should be
addressed as soon as they appear to ensure that the condition that caused the
defects is corrected early in the production sequence. The unacceptable conditions
for architectural concrete are:
• Ragged or irregular edges.
• Excessive air voids (“bug holes” or “blow holes”) in the exposed surface.
• Adjacent flat and return surfaces with noticeable differences in texture and/or
color from the approved samples or mockups.
• Casting and/or aggregate segregation lines evident from different concrete
placement lifts and consolidation.
• Visible form joints or irregular surfaces of or larger than those acceptable in
the approved samples or mockups.
• Rust stains on exposed surfaces.
• Excessive variation of texture and/or color from the approved samples, within
the unit, or compared with adjacent units.
• Blocking stains or acid stains evident on panel surface.
• Areas of backup concrete bleeding through the face concrete.
• Foreign material embedded in the face.
• Repairs visible at 20 ft or greater viewing distance.

The flagship retail store for Tommy Hilfiger used
180 GFRC panels and decorative architectural
details to create a striking façade on the corner
of Santa Monica Boulevard and Rodeo Drive in
Beverly Hills, Calif. Architect: Allan Greenberg,
Architect Washington, D.C. Photo: Derek Rath.
GFRC with horizontal striations relate the
Pleasanton Corporate Campus buildings to the
hills, creating the texture and shadow pattern
HOK/SF Inc. Architects were looking for.
Photo: HOK/SF Inc.
• Reinforcement shadow lines.
• Visible cracks at a 20 ft or greater viewing distance.
Precast concrete generally undergoes far less cracking than cast-in-place
concrete. This resistance results in part from the high compressive and tensile
strength of the precast concrete. A certain amount of cracking may occur without
having any detrimental effect on the structural capacity of the member, and it is
impractical to impose specifications that prohibit cracking. Cracks can be un-
sightly and create potential locations for concrete deterioration, so any cracking
should be avoided and those cracks that do appear should be inspected to de-
termine acceptability. Cracks may be repaired and effectively sealed by pressure-
injecting a low-viscosity epoxy.
The best methods to minimize cracks are to provide proper reinforcement loca-
tions, prestressing when appropriate, and proper handling. Whether cracks are
acceptable will depend on an evaluation of the cause of the cracking and the
service condition requirements, structural significance, and aesthetics.
Erected panels not complying with the contract documents may require addi-
tional work. Trial repairs should be applied to the project mockup or small sample
panels and allowed to cure, followed by a normal drying period. Acceptability
criteria for repairs should be agreed on at an early stage of the project. A certain
amount of repair is to be expected as a routine procedure. Repair and patching of
precast concrete is an art that requires expert craftsmanship and careful selection
and mixing of materials (see Reference 23).
Repairs should be done only when conditions exist that ensure the repaired area
will conform to the balance of the work’s appearance, structural adequacy, and
durability. Slight initial color variations can be expected between the repaired area
and the original surface due to the different age and curing conditions of the repair.
Time will tend to blend the repair into the rest of the component to make it less
noticeable.
Glass Fiber–Reinforced Concrete (GFRC)
Glass fiber–reinforced concrete, commonly known as GFRC, is a composite
concrete product fabricated by many precast concrete manufacturers. It con-
sists of a portland-cement-based composite that is reinforced with an absolute,
minimum of 4% by weight of alkali-resistant glass fibers to total mix, which are
randomly dispersed through the material. The fibers serve as reinforcement to
enhance the concrete’s flexural, tensile, and impact strength.
The manufacture of GFRC products requires a greater degree of craftsmanship
than other precast concrete products. Many combinations of shapes, sizes, colors,
and textures are possible with this product. Typically, the fibers in a GFRC compo-
nent make up at least 4% by weight of the total mix, with a minimum design thick-
ness of 1/2 in. for the piece. The alkali-resistant glass fibers are specially designed
for use in these components, and no others should be used (see Reference 24).

Recalling Art Deco architecture, the Esquire Plaza
office tower and mixed-use building in Sacramento,
Calif., takes its design cue from the two existing theater
façades incorporated in the building. Precast concrete
panels on the lower levels and GFRC on the upper
portion made the highly articulated façade possible at
an affordable cost. Architect: HOK/SF.; Photo: Ed Asmus
Photography.
Located in downtown Chicago, Ill., the new residence
hall for the School of the Art Institute is clad in GFRC
panels, which emulate the look of the Windy City’s
historic buildings finished in terra cotta. The dormitory
is composed of two connected buildings and a rear link.
Architect: Booth Hansen Associates Inc., Chicago;
Photo: ©Brian Fritz Photography.
GFRC is manufactured by hand-spraying a cement/sand slurry and glass fibers into
molds of the desired shap and size. GFRC also can create highly detailed, ornamental
pieces. Panels can be produced with or without a face mix of conventional concrete
with decorative 1/4 in. maximum size aggregates. With a face mix, GFRC cladding
panels, when given an architectural finish, are indistinguishable in exterior appearance
from conventional concrete panels.
The variety of sculptural shapes made possible through the GFRC manufcturing pro-
cess enables a wide range of creative architectural designs. The designer can choose
from deep reveals to complex rectilinear and curvilinear shapes such as short radius
curves, wide sweeping arcs, or 90-degree angles. The degree of such complex shap-
ing has minimal effect on the cost of the panel due to GFRC’s inherent design flexibility.
The low weight of GFRC panels decreases superimposed loads on the building’s
structural framing and foundation, providing potential savings in multistory construction
and in areas with poor supporting soil. Its light weight also makes it ideal for use on
low-rise frame buildings where heavier cladding systems would increase the size of
framing members required.
Unless the panels have a functionally strengthening shape, GFRC properties dictate
the use of stiffeners on panels of any appreciable size.
Stiffeners may be prefabricated, plant-attached steel studs or structural tubes, or in-
tegral ribs formed on the back of the panel by over-spraying hidden rib formers, such
as expanded polystyrene strips or adding an upstanding single skin rib on the back
of the panel. Either method stiffens the panel and provides a means for connection to
the supporting structure. The steel panel frame is usually the more economical and
preferred method for stiffening.
It is important when evaluating costs to realize that GFRC panels provide more than
an exterior finish. The steel stud frame provides a surface for applying the interior fin-
ish, such as drywall, as well as the window frame. It also provides a cavity for installa-
tion of insulation, plus electrical, mechanical, and telephone conduits. This decreases
the floor space needed for these items and eliminates trade overlap problems.
Panel design usually prevents stud or tube spacing from being coordinated with
interior drywall modules. Therefore, it is recommended that if the studs are to receive
interior drywall or similar treatment, drywall be mounted on shimmed, transverse fur-
ring channels rather than directly to the studs.
Windows should be attached directly to the head and sill tracks of the panel frame
(or to a separate framing system) with only sealant contact to the GFRC.
Clay products, such as veneer-thickness brick, facing tile, and architectural terra-
cotta, are not recommended due to volume change considerations. For more about
this topic, see Reference 25.

Other Resources:
Architectural Precast Concrete Color and Texture
Selection Guide, Second Edition, PCI, 2003.
DN-1-98: Designer’s Notebook: Bullnoses.
DN-2-98: Designer’s Notebook: Cornices.
DN-3-98: Designer’s Notebook: Reveals.
DN-4-99: Designer’s Notebook: Multiple Mixes/
Textures.
DN-5-99: Designer’s Notebook: Window Panels.
DN-6-00: Designer’s Notebook: Corners Returns.
DN-7-00: Designer’s Notebook: Stone Veneer.
DN-8-01: Designer’s Notebook: Clay Products.
DN-9-01: Designer’s Notebook: Radiused Precast.
DN-10-01: Designer’s Notebook: Sculptural Forms .
DN-11-02: Designer’s Notebook: Design Economy.
DN-12-02: Designer’s Notebook: Benefits
Advantages.
DN-13-03: Designer’s Notebook: Specification
Guidance.
PCI MNL-117-96: Manual for Quality Control for
Plants and Production of Architectural Precast
Concrete Products, Third Edition.
PCI MNL-120-04: PCI Design Handbook, Sixth
Edition
PCI MNL-122-07: Architectural Precast Concrete,
Third Edition.
MNL-130-91: Manual for Quality Control for Plants
and Production of Glass Fiber–Reinforced Concrete
Products.
Ascent:
“Precast Cladding Gives Dorm Terra Cotta Look,
Building Awards,” Ascent, Fall 2002, pp. 16-17.
PCI Journal:
“Concrete: From Mix Selection to the Finished
Structure—Problems En Route,” PCI Journal,
November-December 2004, pp. 70-79.
“GFRC Panels Give Terra Cotta Look to Chicago Art
Institute Residence Hall,” PCI Journal, January-
February 2002, pp. 14-25.
“History of Exposed Aggregate (Mo-Sai) Archi-
tectural Precast Concrete,” PCI Journal, May-June
2004, pp. 22-33.
1. Chapter 3, Section 3.4.1, “Colors,” PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
2. Chapter 3, Section 3.4.2, “Textures,” PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
3. “Introduction: Textures,” Architectural Precast Concrete Color and Texture Selection Guide, Second Edition,
PCI, 2003.
4. Chapter 3, Section 3.2, “Uniformity and Development of Samples,” PCI MNL-122-07: Architectural Precast
Concrete, Third Edition.
5. Chapter 3, Section 3.5.2, “Smooth Off-The-Mold Finishes,” PCI MNL-122-07: Architectural Precast Concrete,
Third Edition.
6. Chapter 3.5.3, “Exposed Aggregate By Chemical Retarders and Water Washing,” PCI MNL-122-07: Architec-
tural Precast Concrete, Third Edition.
7. Chapter 3, Section 3.5.4, “Form Liners,” PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
8. Chapter 3, Section 3.5.5, “Sand or Abrasive Blasting,” PCI MNL-122-07: Architectural Precast Concrete, Third
Edition.
9. Chapter 3, Section 3.5.6, “Acid Etching,” PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
10. Chapter 3, Section 3.5.8, “Tooling or Bushhammering,” PCI MNL-122-07: Architectural Precast Concrete,
Third Edition.
11. Chapter 3, Section 3.5.8, “Hammered Rib or Fractured Fin,” PCI MNL-122-07: Architectural Precast Concrete,
Third Edition.
12. Chapter 3, Section 3.5.9, “Sand Embedment,” PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
13. Chapter 3, Section 3.5.11, “Honed or Polished Finishes,” PCI MNL-122-07: Architectural Precast Concrete,
Third Edition.
14. Chapter 3, Section 3.5.14, “Applied Coatings,” PCI MNL-122-07: Architectural Precast Concrete, Third
Edition.
15. Chapter 3, Section 3.5.13, “Multiple Mixtures and Textures within a Single Unit,” PCI MNL-122-07: Architec-
tural Precast Concrete, Third Edition.
16. Chapter 7.5.2, “Clay Products,” PCI MNL-120-04: PCI Design Handbook, Sixth Edition.
17. Chapter 3, Section 3.5.10, “Clay Product-Faced Concrete Panels,” PCI MNL-122-07: Architectural Precast
18. Chapter 3, Section 3.5.12, “Stone Veneer-Faced Precast Concrete Panels,” PCI MNL-122-07: Architectural
Precast Concrete, Third Edition.
19. Chapter 3, Section 3.5.14, “Architectural Trim Units,” PCI MNL-122-07: Architectural Precast Concrete, Third
Edition.
20. Chapter 3, Section 3.5.15, “Matching of Precast and Cast-in-Place Concrete,” PCI MNL-122-06: Architectural
21. Chapter 3, Section 3.5.16, “Finishing of Interior Panel Faces,” PCI MNL-122-07: Architectural Precast
22. Chapter 3, Section 3.5.17, “Acceptability of Appearance,” PCI MNL-122-07: Architectural Precast Concrete,
Third Edition.
23. Chapter 3, Section 3.5.18, “Repair/Patching,” PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
24. “Glossary,” MNL-130-07: Manual for Quality Control for Plants and Production of Glass Fiber–Reinforced
Concrete Products.
25. MNL-130-91: Manual for Quality Control for Plants and Production of Glass Fiber–Reinforced Concrete
Products.
References:

©PhotoDisc.
b•
Precast concrete is used in a wide range of building types, and its integration
with mechanical, plumbing, lighting, and other systems can be achieved eas-
ily if designers understand the specifics of each project and precast concrete’s
requirements. Because of increased environmental demands, the proportion
of costs related to mechanical and electrical installations in the overall budget
has increased substantially in recent years. Working closely with the precaster
to satisfy all of the service requirements will ensure an economical solution that
produces cost-efficient, functional, and aesthetically pleasing results.
Integration Coordination
with Other Building Systems
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3B-1

Metal panels attached at the bottoms of the stems create ducts, and diffuser panels provide a flush ceiling.
Large openings in floors and roofs are made during
the manufacture of the units; small openings are field
drilled. Some common types are shown here.
Mechanical
Spaces within stemmed precast concrete members, or the voids in hollow-core
slabs, can be used for distribution ducts for heating, air-conditioning, and exhaust
systems. In stemmed members, three sides of the duct are provided by the bot-
tom of the flange and the sides of the stems. The bottom of the duct is completed
by attaching a metal panel to the tee stems.
The ducts can be connected in several ways, including powder-activated fas-
teners, cast-in inserts, or reglets. Field-installed devices generally offer the best
economy and ensure placement in the exact location required. Inserts should be
cast-in only when they can be located during the design stage of the job, well in
advance of casting the precast members.
If high-velocity air movement is desired, the enclosed space becomes a long
plenum chamber with uniform pressure throughout its length. Diffusers are
installed in the ceiling to distribute the air. Branches can consist of standard
ducts installed along the column lines. Branch ducts of moderate size can also
be accommodated by providing block-outs in the stems of tees or beams. These
blockouts should be repeated in size and location to handle all conditions
demanded by mechanical, electrical, or plumbing runs to remain economical,
even if this results in some openings being slightly larger than required.
When ceilings are required, proper selection of precast concrete components
can result in shallow ceiling spaces to accommodate required ducts, piping, and
lighting fixtures.
Prestressed concrete box girders can serve a triple function as air conditioning
distribution ducts, conduit for utility lines, and structural supporting members for
the roof-deck units. Conditioned air can be distributed within the void area of the
girders and then introduced into the building work areas through holes cast into
the sides and bottom of the box girders. The system is balanced by plugging
selected holes.
Vertical supply and return-air trunks can be carried in the exterior walls, with
only small ducts needed to branch out into the ceiling space. In some cases,
the exterior wall cavities are replaced with three- or four-sided precast concrete
boxes stacked to provide vertical runs for the mechanical and electrical systems.
These stacked boxes also can be used as columns or lateral-bracing elements
(see Reference 1).
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3B-2

The three parking structures for the Shops at Willow Bend Mall in Plano, Tex., provide a light, bright interior. JPRA
Architects Inc., Farmington Hills, Mich. Photo: J. Bendist Photographic/Dallas.
Electrical Systems
For many applications, designers can take advantage of prestressed concrete’s
reflective qualities and appearance by leaving the columns, beams, and ceiling
structure exposed. The lighting system should parallel the stems of tee members
to achieve uniform lighting free from distracting shadows.
A high level of illumination can be achieved at a minimum cost by using a reflec-
tive paint and proper spacing for high-output fluorescent lamps, which should be
installed in a continuous strip. In special areas, lighting troffers can be enclosed
with diffuser panels fastened to the bottom of the tee stems, providing a flush
ceiling. By using reflective paints, the precast concrete lighting channels can be
made as efficient as conventional fluorescent fixtures (see Reference 2).
The increasing use of networks for office machines, computers, and telephones
and the continual adaptation of office space to new functions and staff needs
have made adequate and flexible systems more critical in buildings to ensure
this equipment can be handled efficiently. Since a cast-in-place topping is often
placed on prestressed floor members, conduit runs and floor outlets can be easily
buried within this topping. Burying conduits in toppings of parking structures,
however, is not recommended because of the possibility for conduit corrosion.
Most systems can be included easily in a 2- to 4-in.-thick topping. When the
system is placed in a structural-composite slab, the effect of ducts and conduits
must be carefully examined and their locations coordinated with the placement of
reinforcing steel. Voids in hollow-core slabs also can be used as electrical race-
ways. Spaces requiring large quantities of flexible wiring systems are typically
addressed by specifying raised-access flooring.
Because of the high load-carrying capability of prestressed concrete members,
high-voltage substations, with heavy transformers, can be located near the areas
of consumption with little or no additional expense. For extra safety, distribution
feeds can be run within the channels created by stemmed members. Such mea-
sures also aid the structure’s economy by reducing the overall story height and
minimizing maintenance expenses (see Reference 3).

Velocity Multifamily Residential Condominiums,
Hoboken, N.J.; Architect: Equus Design Group;
Photos: Oldcastle Precast Building Systems.
Building Penetrations
Architectural precast concrete wall panels can be adapted to combine with
preassembled window or door units. Door or window frames, properly braced
to prevent bowing during concrete placement, can be cast into the panels, after
which the glazing or doors can be installed, prior to or after delivery to the jobsite.
If the glazing or doors are properly protected, they can also be cast into the panel
at the plant.
Repetition of the design produces the most economy in a precast concrete
panel, so windows and doors should be located in identical places for all panels
whenever possible. However, virtually any design and window or door place-
ment or combination of these units can be accommodated with precast concrete
panels (see Reference 4).
Penetrations into precast concrete components are the most significant because
they will allow energy transference that will reduce efficiency of HVAC equipment.
A thorough analysis of air leakage is complex and involves parameters such as
wall construction, building height, and orientation. An air barrier can stop outside
air from entering the structure through the walls, windows, or roof, and it can pre-
vent inside air from exfiltrating through the building envelope and any penetrations.
An air-barrier system must be virtually air-impermeable. Materials such as
polyethylene, gypsum board, precast concrete panels, metal sheeting, or glass
qualify as low air-permeable materials when joints are properly sealed. Materials
that do not qualify include concrete block, acoustic insulation, open-cell polysty-
rene insulation, and fiberboard.
One relatively new approach to sealing joints involves using an interior foam
backer rod and sealant along with a thermal-fusible membrane seal around the
panel, which covers the gap between the structure and the panel. In the case of
construction assemblies that do not lend themselves to sealing interior surfaces,
the use of a separate vapor retarder must be considered (see Reference 5).
Fittings installed in outer walls, such as electrical boxes, should be completely
sealed against moisture and air passage. They should be installed on the warm
side of unbroken vapor retarders or air barriers that are completely sealed.

HeatTransmittance,U
Outside Temperature, °F
Relative humidity at which visible condensation occurs
on inside surface. Inside temperature, 70 °F.
Vapor Barriers
Water-vapor diffusion occurs when water-vapor molecules diffuse through solid
interior materials at a rate dependent on the permeability of the materials, the vapor
pressure, and the temperature differentials. Generally, the cooler the outside tem-
perature is, the greater the pressure is for the water vapor in the warm interior air
to reach the cooler, drier, outside air.
Concrete in general provides a relatively good vapor retarder, provided it remains
crack free. Permeance is a function of the ratio of the concrete’s water and
cementitious materials. A low ratio, such as those used in most precast concrete
members, results in concrete with low permeance. Where climatic conditions re-
quire insulation, a vapor retarder is generally necessary to prevent condensation.
A closed-cell insulation will serve as its own vapor retarder.
The function of a vapor retarder made of low-permeability material is to stop
(actually, to retard) the passage of moisture as it diffuses through the assembly
of wall materials. In temperate climates, vapor retarders should be applied on or
near the warm side (inner surface) of assemblies. Vapor retarders can be structur-
al or take the form of thin sheets or coatings. They can be positioned part way into
the insulation, but they should be placed no farther inside than the point at which
the dew-point temperature is reached to avoid condensation.
In climates with high humidities and high temperatures, especially where air-
conditioning is virtually continuous, the ingress of moisture may be minimized by
a vapor-retarder system in the building envelope near the outer surface. For air-
conditioned buildings in hot and humid climates without extended cold periods,
it may be more economical to use only adequate air-infiltration retarding systems
rather than vapor retarders, since the interior temperature is rarely below the
outside dew point.
High thermal-conductance paths reaching inward from or near the colder sur-
faces may cause condensation within the construction. High conductance paths
may occur at junctions of floors and walls, walls and ceilings, and walls and roofs.
They may also occur around wall or roof openings, at perimeters of slabs on the
ground, and at connections.
When a material such as plaster or gypsum board has a permeance that is too
high for the intended use, one or two coats of paint frequently will suffice to lower
the permeance to an acceptable level, or a vapor barrier can be used directly be-
hind such products. Polyethylene sheet, aluminum foil, and roofing materials are
common applications. Proprietary vapor barriers, usually combinations of foil and
polyethylene or asphalt, are typically used in freezer and cold-storage construc-
tion (see Reference 6).

Sources:
Ideas By Design, Vol. 1, No. 1, March 2000: Justice
Facilities.
MK-24-00: Concrete Cell Modules.
PCI MNL-120-04: PCI Design Handbook, Sixth
Edition.
1. Chapter 9.10.4, “Ductwork,” PCI MNL-120-04:
PCI Design Handbook, Sixth Edition.
2. Chapter 9.10.2, “Lighting and Power
Distribution,” PCI MNL-120-04: PCI Design
Handbook, Sixth Edition.
3. Chapter 9.10.3, “Electrified Floors,” PCI MNL-
120-04: PCI Design Handbook, Sixth Edition.
4. Chapter 9.10.5, “Other Sub-Systems,” PCI
MNL-120-04: PCI Design Handbook, Sixth
Edition.
5. Chapter 9.1.7.1, “Air Barriers,” PCI MNL-
6. Chapter 9.1.7.2, “Vapor Retarders,” PCI MNL-
7. Chapter 9.10.6, “Systems Building,” PCI MNL-
8. Chapter 9.10.7, “Prison Cell Box Module,”
PCI MNL-120-04: PCI Design Handbook,
Sixth Edition.
References:
Photos: Tindall Corporation/Correctional Division.
Modular Units
Precast concrete provides an ideal material with which to create entire structures,
particularly housing units, that require identical spaces that can be completed quick-
ly. These designs work well because so many of the mechanical systems and other
services can be installed in the units prior to delivery to the site, requiring only a final
hookup after the unit is erected in its final location. This approach limits the amount
of on-site labor that is required, saving time and adding safety. School classrooms,
housing units, and prison cells all benefit from this type of fast, replicated unit and the
advance installation of plumbing, electrical, mechanical, and even finishing systems.
For housing or school applications, electrical conduit and boxes can be cast into
the precast wall panels, which requires coordination with the electrical contractor. The
metal or plastic conduit is usually pre-bent to the desired shape and delivered to the
casting bed already connected to the electrical boxes. Telephone and communica-
tion accessories have also been cast-in using the same procedure.
Plumbing units are often connected and assembled prior to delivery for kitchen
or bathroom modules. To eliminate a double floor, the module can be plant-built on
the structural member or the walls of the unit can be designed for all fixtures to be
wall-hung. Some core modules also feature HVAC components, which are packaged
in one unit. These modules can be accommodated in prestressed structural systems
by placing them directly on the prestressed members with shimming and grouting
(see Reference 7).
Prisons maximize the use of these modules by creating multiple-cell units. They
generally consist of cell walls, chase walls, and a floor and/or ceiling. All compo-
nents of each cell are installed at the plant. These components include windows,
beds, mirrors, desks, air vents, light fixtures, sinks, water closets, and associated
chase plumbing and wiring. Erection at the site is rapidly completed and field work
is greatly reduced. The result is a safe, functional, and economical prison facility in
the shortest construction time (see Reference 8).

©PhotoDisc.
c•
Team Responsibilities
Design and construction of a high-quality structure is a complex process requir-
ing teamwork among all of the professionals involved. The project’s success relies
on defining the scope of work and the responsibilities of the involved parties by
means of contract documents. To that end, the scope of the precast concrete
work and the responsibilities of each party should be established early in the
project’s development to maintain the schedule.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3C-1

One of the basic principles of the construction industry is that responsibility and
authority must go hand in hand. Another principle is that every party should be
responsible for its own work. These principles are sometimes violated in practice,
leading to adversarial situations that can damage a project’s success.
The complexity of structures today makes it essential to have design input from
subcontractors, whether the project will follow a conventional design-bid build,
design-build, or alternative construction formats. This input can take three forms:
• Value-engineering proposals
• Response to performance requirements
• Suggestions for design alternatives
Gaining the precaster’s aid and insight during the conceptual stage can ensure
that the design provides the most cost-efficient, aesthetically pleasing, and
functional plan possible. The precast concrete manufacturer can consider many
aspects, including transportation and erection, that may otherwise be overlooked
and become costly after the fact (see Reference 1).
(For more on the benefits provided by early input by the precaster, see Chapter
1D, “Construction Issues.”)
The Design Process
The design considerations for the precast concrete components of a project
consist of three stages:
1. Conceptual design. The general ideas of what the owner wants to accom-
plish in function, image, budget, and other factors can be discussed with the
precaster. This will often aid the project’s completion even if the original intent
was not to use precast concrete, especially if stone or masonry was desired.
2. Preliminary design. This planning stage gains from precaster input on the
general layout, overall dimensions, typical details, and other specifics. This
input can be relatively simple, such as with the layout of a hollow-core flooring
plan, or complex if the design will feature a total-precast concrete structural
system and intricate finishes on architectural precast concrete components.
3. Final design. The specific details of the components, such as strand patterns,
connections, embedded items, and other elements, are decided at this point,
and shop drawings are produced.
Because of the range of input that can be provided at each stage, the precaster
typically participates in the design process with the project-management team,
especially to provide input on costing. The capacity to participate varies with
each precaster and with each job.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3C-2

In general, the precaster can provide the following information:
• Design properties unique to his or her product, such as section properties,
normal concrete strengths, and strand patterns (if needed by the structural
engineer).
• Detailed specifications for the manufacture of the components using propri-
etary equipment.
• The detailed design of the specific components as agreed in the preliminary
design phase.
• Detailed layout drawings locating each component type in the structure.
• Support and joint details.
• Product drawings showing details, including dimensions and the location of
lifting and connection hardware.
• The erection procedure.
In some cases with fast-track projects, some precast concrete components go
to the shop-drawing stage before the final specifics of the design are completed.
Because precast concrete components combine customization with a highly con-
trolled manufacturing process, fabrication in some cases can go forward on this
accelerated basis to meet a tight deadline that cannot wait for all of the contract
drawings to be completed first. This ability can keep a project on schedule when
the use of other materials would not have been able to improve the timeframe
(see Reference 2).
Responsibilities of the Architect
The architect has responsibility and authority for all aspects of the precast
concrete design. This generally requires that a registered professional engineer or
architect accepts responsibility as the engineer of record for ensuring that these
requirements are met. The engineer of record seals the contract documents,
which constitute the structural design. They are customarily submitted to regula-
tory authorities for a building permit.
The engineer of record will also approve shop drawings and may have other
ongoing responsibilities during construction.
The architect may specify in the contract documents that design services for
portions of the work are to be provided by the precaster and must be performed
by a licensed engineer employed or hired by the precaster. The division of
responsibility between the engineer of record and the precaster’s structural
specialty engineer must be worked out in advance.
The contract and the design documents should state clearly the scope of both
the precast concrete design and review responsibilities, as well as the responsi-
bilities of others providing design services.

The contract drawings prepared by the architect should provide the overall
geometry of the structure, member, or panel sizes (including permissible alternative
sizes) and typical connection locations and concepts. This detail allows everyone
to estimate based on the same information. These drawings and the specifications
become a part of the contract documents used by contractors to construct the
structure (see Reference 3).
The contract documents provided by the architect should include:
• Reveals or design articulation, letting the precaster determine panel sizes
suitable to their handling and erection capabilities.
• General performance criteria, including concrete strength requirements for
loading, deflection requirements, temperature considerations, and any toler-
ance or clearance requirements for proper interfacing with other parts of the
structure.
• The order of priority in which the project contract, specifications, or drawings
prevail in the event of conflict.
• All aesthetic, functional, and structural requirements that impact the precast
concrete fabrication.
To delineate responsibility for all interfaces of precast concrete components with
other materials, the architect also should define:
• Precast concrete components to be designed by the precaster, stating who
takes responsibility for conditions at interfaces with other parts of the structure.
• Details or concepts of supports, connections, and clearances that are
part of the structure designed by the architect and that will interface with the
precast concrete components.
• Permissible load transfer points with generic connection types indicated so
the precaster does not make assumptions during bidding.
The architect and engineer of record should review submitted designs, calcu-
lations, and shop drawings to ensure they conform to design criteria, loading
requirements, and design concepts as specified in the contract documents. This
review does not relieve the precaster and the precast concrete engineer of their
design responsibilities (see Reference 4).
The format and extent of information supplied by the architect will impact the
precaster’s responsibility. The accompanying chart indicates three ways in which
contract information can be supplied by the architect and the activities for which
the precaster is thereby responsible.

Design Responsibilities
Source: Table 4.1.1: Design Responsibilities; Chapter 4, Section 4.1.2, “Responsibilities of the Architect,” PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
Contract Information Supplied
by Design Team
Responsibility of the Precaster
OPTION I
Provide complete drawings and
specifications detailing all aesthetic,
functional, and structural requirements
including design criteria, plus
dimensions.
The precaster should make shop drawings (erection and production drawings),
as required, with details as shown by the designer. Modifications may be
suggested that, in precaster’s estimation, would improve the economics,
structural soundness, or performance of the precast concrete installation.
The precaster should obtain specific approval for such modifications. Full
responsibility for the precast concrete design, including such modifications,
remains with the designer. Alternative proposals from a precaster should
match the required quality and remain within the parameters established for
the project. It is particularly advisable to give favorable consideration to such
proposals if the modifications are suggested so as to conform to the precaster’s
normal and proven procedures.
OPTION II
Detail all aesthetic and functional
requirements but specify only the
required structural performance
of the precast concrete units.
Specified performance should
include all limiting combinations of
loads together with their points of
application. This information should
be supplied in such a way that all
details of the unit can be designed
without reference to the behavior
of other parts of the structure. The
division of responsibility for the
design should be clearly stated in the
contract documents.
The precaster has two alternatives:
(a) Submit erection and shape drawings with all necessary details and design
information for the approval and ultimate responsibility of the designer.
(b) Submit erection and shape drawings and design information for approval
and assume responsibility for the structural design; that is, the individual
units, but not their effect on the building. Precasters accepting this practice
may either stamp (seal) drawings themselves or commission engineering
firms to perform the design and stamp the drawings.
The choice between the alternatives (a) and (b) should be decided between
the designer and the precaster prior to bidding with either approach clearly
stated in the specifications for proper allocation of design responsibility.
Experience has shown that divided design responsibility can create contractual
problems. It is essential that the allocation of design responsibility is
understood and clearly e×pressed in the contract documents.
OPTION III
Cover general aesthetic and
performance requirements only and
provide sufficient detail to define the
scope of the precast concrete work.
The precaster should participate in the preliminary design stage and the
development of the final details and specifications for the precast concrete
units and should work with the design team to provide an efficient design.
The precaster provides the engineering design of the precast concrete units
and their connections to the structure and should work with the design team
to coordinate the interfacing work. The precaster should submit shop design
information for approval and drawings at various stages of completion for
coordination with other work.

Logan International Airport Central Parking Garage Expansion, Boston; Architect; TAMS/Fennick/McCredie Architecture
Ltd.; Photo: Blakeslee Prestress Inc. (top right), ©PhotoDisc (bottom right).
Key Architectural Design Issues
The architect should make sure that the contract documents address the issues
that affect a precaster’s bid. The drawings should provide a clear interpretation of
the configurations and dimensions of individual units and their relationship to the
structure and to other materials. Contract documents that lack detail may extend
shop-drawing time and could lead to confusion over the scope of work and
impact schedule.
The contract documents should supply the following data:
• Elevations, sections, and dimensions necessary to define the sizes and
shapes (profiles) of each type of precast concrete component.
• Locations of joints real (functional) and false (aesthetic).
• Required materials, color, and finish treatment for all surfaces with a clear
indication of which surfaces are to be exposed to view when in place.
• Corner details.
• Details for jointing and interfacing with other materials (coordinated with the
general contractor) including windows, roofing, and other wall systems.
• Openings for services and equipment with their approximate size and
location.
• Details for special or unusual conditions, including fire-endurance
requirements.
• Governing building codes, design loads, and deflection limitations.
• Specified dimensional tolerances for the precast concrete and the supporting
structure, location tolerances for the contractor’s hardware, clearance
requirements and erection tolerances for the precast concrete.
• Support locations for gravity and lateral loads.
• Building location and site access.
• Delineation of any unusual erection
sequence requirements.

The precaster will use this information from the contract drawings and docu-
ments to generate shop (erection) drawings and design calculations. The shop
drawings should detail elevations showing panel sizes, surface features and
panel relationships. Detail sheets should show panel cross-sections, special edge
conditions and feature details, and they should specify connections showing
mechanisms and locations of load transfers to the supporting structure.
Greater economy and flexibility will be achieved by allowing the precaster to
suggest configurations and select which joints are false and which are real in the
panelization. The architect should then review all shop drawings to ensure they
conform to the contract documents.
Small mockups are encouraged, as they help verify the appearance of the com-
pleted façade and help clarify actual field-construction techniques and material
interface issues. When the units have returns, the same size return should appear
in the mockup panels. It is the architect’s responsibility to determine the standards
of acceptability for surface finish, color range, and remedial procedures for defects
and damage.
After the project is erected and detailed, the architect should immediately prepare
a punch list setting forth, in accurate detail, any items that are not in accordance
with the contract documents so the proper corrective action can be taken. All
repairs should conform to the architect’s requirements for matching the original
finish and should be structurally sound.
When advised by the precaster that the listed items have been completed, the
general contractor, construction manager, architect, and engineer should check
the corrections as needed. After the precast concrete components have been
accepted, subsequent responsibility and liability for their condition rests with the
general contractor (GC)/construction manager (CM). (For more on these responsi-
bilities, see Reference 5.)
The bid Process
When selection of the precaster cannot be negotiated or controlled by the
owner or architect but is governed by an open-bid situation, these steps should
be followed:
1. Verification of architects concepts and systems. A review of the proposed
precast concrete assumptions during the early design development stage of
the architectural contract documents should be arranged with at least one
local precaster. Items to be reviewed include:
• Panelization, form families, piece sizes, weights, and reveals.
• Potential shipping and erection issues.
• Architectural concepts for structural supports or connections for the precast
concrete so that the architect can communicate to the engineer of record
about any support requirements.

• Desired aesthetic issues relative to mixture(s) and finish(es) and the sample
process.
• The architect’s intent for any interfaces with adjacent systems, such as win-
dows, roofing, or building entrances.
• Mockups or other special testing requirements.
2. The prebid conference. A meeting with all precasters planning to bid on the
project should be held at least three weeks prior to the bid date. Items to
be discussed include:
• Specifications and any special provisions.
• Design responsibilities and lines of communication.
• The architect’s approved finish samples with information on the mixture
design, where applicable.
• Prebid submittal requirements, such as proposal drawings and finish
samples.
• Project schedule, shop-drawing submittal requirements, and architectural-
review turnaround times.
• Panelization.
• Mockups, if applicable.
• Potential problems, discrepancies, or both found in the contract documents.
• How and where the project’s precast concrete will be structurally attached
to the building frame.
• Interfacing with other trades.
• Responsibility for designing, providing and installing embedded items,
connection hardware attached to the structural steel, bracing, and other
structural items.
• Hardware and reinforcement finishes.
• Special erection needs, such as access, crane limitations, and sequences,
as well as logistics.
• Responsibility for caulking.

3. The post-bid scope review. A final meeting allows the architect and general
contractor to review the precaster’s proposal and confirm the company’s ability
to satisfactorily produce the project and conform to the design concepts and
finish requirements. This review should include:
• Proposal drawings that express the architectural precast concrete
panelization and structural attachment concepts.
• Finish samples.
• The history of the precaster’s company and confirmation of the plant’s PCI
certification.
• A list of comparable projects, references, and financial capability.
• Key schedule items such as mockup panels, shop drawings and design
submittals, mold production, production start and duration, and erection
start and duration.
• Qualifications to the bid that can be listed and reviewed.
If the project allows a negotiated precast concrete contract, and the precaster
is brought on board during the initial stages of development, prebid and bid
submittal information can be minimized.
4. Construction coordination. This meeting should be held at the jobsite after
the precast concrete and erection contracts have been awarded. The general
contractor should conduct frequent jobsite meetings to coordinate precast
concrete design and erection with the work of other trades and general build-
ing construction. These meetings should include the subcontractors whose
work is impacted by the precast concrete design and erection.
The coordinating meetings should consider a variety of details, including:
• Loading, delivery sequence, and schedules.
• Types of transportation.
• Routes of ingress and egress for delivery trucks and erection cranes.
• Handling techniques and devices.
• Connections.
• Erection methods and sequences.
• The effects of temporary bracing on other trades.
• Offsite storage and protection.
Additional questions about site access, street use, sidewalk permits, oversized
loads, lighting, or unusual working hours should be addressed at this time. (For
more on the prebid process, see Reference 6.)

The Precaster’s Responsibilities
The precaster will perform component design of the members when this task is
required by the contract. The precaster normally accepts responsibility for design
of the connections when the forces acting on the connections are defined by the
engineer. Precast concrete reinforcement is determined by code and industry-
standard design, unless otherwise defined by the contract documents.
The precaster’s responsibilities include:
• Value engineering to improve construction economics, structural efficiency,
and precast concrete performance.
• Panelization (panel sizing and joints), which is typically designed first.
• Connection details.
• Detailed shop drawings and design calculations, showing all design criteria,
identifying all materials and illustrating panel interfaces with each other, the
structure, and adjacent materials.
• Designing panel and connection hardware for the specified loads.
• Selecting, designing, and locating hardware for the specified loads and panel
reinforcement.
• Items associated with the precaster’s methods of handling, storing, shipping,
and erecting the precast concrete components.
• If necessary, creation of an erection and bracing sequence, developed in
conjunction with the erector, engineer, and general contractor, to maintain the
stability of the structure during erection.
The extent of additional design responsibility vested with the precaster should
be clearly defined in the project documents prepared by the architect.
Quality control for product manufacturing is supplied by the precaster accord-
ing to provisions contained in a comprehensive quality system manual developed
by the precaster, in addition to requirements contained in PCI MNL-117, Manual
for Quality Control for Plants and Production of Architectural Precast Concrete
Products. Quality assurance is provided through the precaster’s participation in
the PCI Plant Certification Program. Additional inspection at the owner’s expense
may be required by specification through the owner’s quality-assurance agency
(see Reference 7).

Resources:
DN-13-03: Designer’s Notebook: Specification Guidance.
PCI MNL-117: Manual for Quality Control for Plants and Production of Architectural Precast Concrete Products.
PCI MNL-120-04: PCI Design Handbook, Sixth Edition.
PCI MNL-122-07: Architectural Precast Concrete, Third Edition.
PCI MNL-126-98: Manual for the Design of Hollow-Core Slabs, Second Edition.
1. Chapter 4, Section 4.1, “Design Construction
Responsibility,” PCI MNL-122-07: Architectural
2. Chapter 2, “Design Approach,” MNL-126-98:
Manual for the Design of Hollow-Core Slabs,
Second Edition.
3. Chapter 10.4.3, “Design Practices,” MNL-120-
04: PCI Design Handbook, Sixth Edition.
4. Chapter 4, Section 4.1.2, “Responsibilities of
the Architect,” PCI MNL-122-07: Architectural
the Architect,” PCI MNL-122-07: Architectural
the General Contractor/Construction Manager,”
PCI MNL-122-07: Architectural Precast Con-
crete, Third Edition.
the Precaster (Manufacturer),” PCI MNL-122-07:
Architectural Precast Concrete, Third Edition.
8. Chapter 10.4.3, “Design Practices,” MNL-120-
04: PCI Design Handbook, Sixth Edition.
References:
Value Engineering and Design-Build Applications
Owners may allow, or even encourage, considerations of alternative construction
schemes on a project. In such cases, the design drawings frequently are not as de-
finitive as in fully developed designs. When such alternatives use precast concrete
as the primary structural system, the precast engineer or another qualified consult-
ing engineer may be designated as the engineer of record.
If a fully developed design is included in the contract documents, a contractor
proposing an alternative for some part of the structure should consider the effect of
the alternative on all other parts of the structure and provide all necessary design
changes.
Owners also may directly seek proposals from general contractors who are
willing to prepare design-build proposals. The general contractor may employ
a professional engineer or subcontract the design to a firm that serves as the
engineer of record. Typically, the precaster serves as a subcontractor of the
general contractor, and he or she accepts responsibility for component design
of the produced member.
Local regulatory authorities may approve design documents for starting construc-
tion without final design of the precast concrete members. In some cases, the
design can be performed and submitted at a later time, often in conjunction with
preparation of shop drawings. The engineer of record may require that a registered
engineer seal the documents that depict the precast design.
PCI is keenly aware of the competitiveness in the marketplace for building sys-
tems. Along with high quality, it is essential that a structure have structural integrity
and performs as intended. Because the construction process involves many par-
ties, it is essential that work assignments and responsibilities be clearly defined in
the contractual arrangements, whatever form they take (see Reference 8).

Joe Serna Jr. California EPA Headquarters;
Sacramento, Calif.; Architect: A.C. Martin Partners;
Photo: Walters and Wolf Precast.
d•
Initial Life-Cycle Costs
A variety of cost calculations is required on every project to determine what
design approaches will reap the most advantages for the owner and allow bud-
gets to be allocated most efficiently. Initial, in-ground costs are the most obvious
expenses, but hidden and longer-term costs are becoming more significant as
owners and designers study the budget impact of various specifications.
The primary philosophy that has come to the fore looks at the project holistically,
understanding that every system and decision impacts others. The goal is to
ensure that all products and systems work together to enhance each other without
creating redundancy or inefficiencies.
Added insulation and other energy efficiencies, for instance, may allow the
installation of smaller HVAC equipment than would be needed otherwise. Siting
the building certain ways and using more glass may allow fewer light fixtures to
be installed. Using products that can enclose the building quickly avoids winter
slow downs and gets crews inside quicker, bringing the project online faster so
revenues can be generated quicker.
Maintenance needs throughout the building’s life must also be considered.
These expenses come from the operating budget rather than the construction
budget, and so they often were overlooked in the past when designing the build-
ing. Today, owners and designers are acknowledging that all budgets must be
considered, and labor and material costs that keep a building operating efficiently
through its life are part of the equation at the design phase.
Durability, such that a building does not need to have its exterior refurbished
or possibly replaced in 20 years, has also become more of a consideration. The
entire life-cycle costs of a project are being calculated, and each material choice
must justify its value today, tomorrow, and many years from now.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3D-1

Day 1 — Foundation ready. Day 7 — Building begins taking shape.
NBSC Headquarters Building, Greenville, S.C.;
Architect: Neal + Prince Partners; Photos: Metromont
Corporation.
In-Ground Costs
Initial or in-ground costs are the most obvious and most significant when deter-
mining budgets and where to allocate funds for the construction of a building.
Precast concrete components provide a variety of savings to a project in ways
that are not always considered when looking at upfront costing versus other
materials, including masonry and curtain wall. These savings include:
Speed. Precast concrete components provide a variety of ways to speed the
construction process, from design through fabrication and erection. These ef-
ficiencies can shave as much as one-third of the time needed for construction,
meeting tight deadlines and generating revenues quicker. Time can be saved
through:
• The design process. It takes less time to design a precast concrete building
than one built of other materials, due to the lessened detail required in precast
concrete’s panelized system and the ability to quickly replicate components on
each floor or wing.
• The fabrication process. Precast concrete components can be fabricated
while permitting and foundation work progress, so they are ready to begin
erection as soon as foundations are complete. As a single-source supplier for
a large portion of the structural system, precasters help maintain the critical-
path scheduling.
• The erection process. Foundations can be placed one day and precast
concrete loadbearing or non-loadbearing panels can be erected as soon as
the foundations have cured sufficiently. Wall panels, double tees, and hollow-
core planking also erect quickly, often cutting weeks or months from the
schedule. This speed allows construction to get into the dry quicker. The fast
enclosure also lessens concern for weather or material damage during erection,
reducing the contractor’s risks and costs.
• The finishing process. Precast concrete insulated sandwich panels create
a finished interior wall that avoids the time and cost of furring and drywalling.
Architectural panels can have a variety of colors and textures cast into them,
including several in one panel, eliminating the need to field-set trim pieces
or paint the façade after the structure is built. (For more on this aspect, see
Reference 1.)
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3D-2

Day 15 — Interior shear walls. Day 44 — Structurally and architecturally dry.Day 25 — Shear structure.
Design Economy. The custom, sculptured designs that are possible with pre-
cast concrete may be achieved within a limited budget by selecting economical
aggregates and textures combined with repetitive units and effective production
and erection details. The key factors in designing economically with architectural
precast are:
• Repetition. By reusing the same dimensions for components, the same molds
can be used, minimizing the total number needed and the changes between
casting. Efficiency is created by making it possible for similar, if not identical,
shapes to be produced from the same basic (master) mold and by minimizing
the time required to disassemble a mold and reassemble it for the next piece.
Mold costs range from hundreds to thousands of dollars per mold, depending
on size, complexity, and materials used.
Number of Reuses Panel Size (square feet)) Mold Cost Cost per Square Foot
1 200 $5,000 $25.00
10 200 $5,000 $2.50
20 200 $5,000 $1.25
30 200 $5,000 $0.83
Effect of Repetition on Panel, Square-Foot Cost
Source: PCI MNL-122-07: Architectural Precast Concrete, Third Edition. Art. 2.2.2 Mold Costs.
Note: This table reflects a typical cladding application of precast concrete architectural panels. The same
or a similar process can be used for a total-precast concrete structure.

• Average piece size. Precast concrete pricing is primarily determined by the
size of the pieces and piece repetition. Pricing depends more on the number
of pieces than the size of the project. A 100-piece project of large panels
can be less expensive per square foot than a 1000-piece project of much
smaller panels on the same size building. Labor functions drive pricing more
than material cost, and each new piece, particularly different shapes or sizes,
drives up the amount of labor needed to create and erect a component. It is
most economical to cover a larger portion of the building’s exterior with fewer
precast concrete panels.
During a project’s preliminary design, a precast concrete project can be budget
“guesstimated” on a square-foot basis. Although this provides a good starting
point, it is not recommended that designers rely on this method alone. A square-
foot take-off can differ depending on the precaster, general contractor, and
architects involved and on the procedures used. Work-scope criteria typically isn’t
known, and it impacts the final budget. Erection access and crane requirements
also are not defined, and back-forming and other details cannot be predicted
(see Reference 2).
Panel Size
(Square Feet)
Erection Cost per Piece, $/Square Foot
$500 $1,000 $1,500 $2,000
50 10.00 20.00 30.00 40.00
100 5.00 10.00 15.00 20.00
150 3.33 6.67 10.00 13.33
200 2.50 5.00 7.50 10.00
250 2.00 4.00 6.00 8.00
300 1.67 3.33 5.00 6.67
Effect of Panel Size on Erection Cost, per Square Foot
(based on a minimum erection time of one month)
Source: PCI MNL-122-07: Architectural Precast Concrete, Third Edition. Art. 2.2.4 Panel Size/Panelization.
Note: This table reflects a typical cladding application of precast concrete
architectural panels. The same or a similar process can be used for a total-
precast structure.

Resources:
CD/IGS-8-02: Commercial Building CD-ROM.
DN-12-02: Designer’s Notebook: Benefits Advantages.
MK-21-98: Parking Structures: Team Solutions Timeline.
MK-22-98: The Precast Prestressed Advantages for Owners and Developers.
MK-35-03: Precast Concrete Panels: Tilt-up Doesn’t Measure Up.
1. MK-34-03: Precast Concrete Makes the Grade
For K-12 School Facilities, p. 4: “Meeting
Deadlines.”
2. Chapter 2, Section 2.2, “Design Economy,”
MNL-122-07: PCI Architectural Precast
Concrete Manual, Third Edition.
For K-12 School Facilities, p. 2, “Total Precast
Concrete Systems Meet Schools’ Total Lifetime
Needs.”
4. DN-11-02: Designer’s Notebook: Design
Economy.
5. MK-34-03: Precast Concrete Makes the
Grade For K-12 School Facilities, p .3:
“Cost Effectiveness.”
6. MK-34-03: Precast Concrete Makes The
Grade For K-12 School Facilities, p.3:
“Cost Effectiveness.”
References:
Material Efficiency. Precast concrete saves money by replicating the look of
more expensive materials, such as natural stone (granite, marble, limestone, sand-
stone, or slate). Veneers of these materials also can be cast into the face of the
precast concrete components, saving the expense of full-thickness pieces. Brick-
faced precast concrete also eliminates labor costs and speeds up
construction.
Precast concrete components can save money by using single components to
serve several functions. Hollow-core planking and double tees, for instance, can
be used as a combined ceiling/flooring unit, saving material costs and speeding
construction further due to less labor. This is enhanced with total-precast concrete
systems, which can combine architectural and structural functions into one piece
(see Reference 3).
In parking structures, precast concrete spandrel panels are used as a vehicle-im-
pact restraint in addition to providing a perimeter design feature. This eliminates the
need for an upturned cast-in-place concrete beam or cable system (see Reference
4).
Construction Efficiency. Because precast components are fabricated under
factory-controlled conditions at a plant, harsh winter weather does not impact the
production schedule or product quality. This approach means they can be erected
through the winter months to meet a tight schedule, cutting overhead costs, and
opening the building for occupancy faster.
Producing the components in a plant also ensures tight tolerances, which will
facilitate erection and require fewer field adjustments that other methods may need
to complete the structure.
Precast concrete panels inset with thin bricks or cast using formliners to resemble
stone require only one trade, eliminating costly and time-consuming masonry as
well as other trades from the site. (For more on this aspect, see Reference 5.)
Hidden Costs. Precast concrete’s speed of construction can reduce the con-
struction time frame by several months. This results in less time to carry financial
bonds, lower contractor overhead costs and risk, elimination of expenses for
nonprecast-related equipment, and reduced subcontractor costs by giving more
responsibility to a single-source supplier (see Reference 6).

Hull Street Parking Structure, Athens, Ga.;
Architect: Smallwood, Reynolds, Stewart,
Stewart Associates Inc.;
Photo: Jim Roof.
Maintenance Costs
Generally, precast concrete components, even architectural precast concrete
panels exposed to weather, require little maintenance. A regular inspection and
routine recaulking of cladding panels every 15 to 20 years are all that may typi-
cally be required. Panels can be washed with strong chemicals and cleaners
without losing their color, and UV rays will not cause them to fade, as will happen
with paint.
Parking structures, more than any other building type, require routine mainte-
nance. Unlike other buildings, the structural components are exposed directly to
weather and other environmental conditions. Extreme temperature changes, rain,
snow, deicing salts, road grime, and dampness directly influence the durability of
parking structures and have the potential to create performance problems. The
severity of these problems will depend on the structure’s location, environmental
conditions, and maintenance schedule.
Based on national surveys, precast concrete parking structures offer superior
resistance to deterioration. Components produced by PCI-certified plants in
particular offer a controlled environment where durable concrete with specialty
curing can be created that cannot be achieved in the field. However, without
proper maintenance, any structure’s life will be compromised.
Besides increasing service life and reducing long-term structural repairs, a com-
prehensive maintenance program for a parking structure will produce a cleaner,
safer, and more user-friendly atmosphere that encourages repeat business and
discourages littering and loitering. It is essential that a maintenance program be
a major part of the operation of all parking structures. A routine maintenance pro-
gram should be set up immediately upon turnover of the parking structure, and
the precaster can help in preparing a schedule of activities (see Reference 1).

Resources:
CD/IGS-8-02: Commercial Building CD-ROM.
DN-12-02: Designer’s Notebook: Benefits
Advantages.
MK-21-98: Parking Structures: Team Solutions
Timeline.
MK-22-98: The Precast Prestressed Advantages for
Owners and Developers.
MK-35-03: Precast Concrete Panels: Tilt-up
Doesn’t Measure Up.
1. Chapter 1.0, “Introduction,” MNL-136-04: Main-
tenance Manual for Precast Parking Structures.
2. Chapter 2.1, “Housekeeping,” MNL-136-04:
Maintenance Manual for Precast Parking
Structures.
3. Chapter 2.3, “Prevention Maintenance,”
MNL-136-04: Maintenance Manual for
Precast Parking Structures.
4. Chapter 2.4, “Structural Repairs,”
5. Chapter 2.5, “Periodic Structural Audit,”
References:
Union Plaza Transit Terminal and Parking Garage, El Paso, Tex. The use of an all-precast concrete strucure, including double tees,
beams, columns, and shear walls speeded construction and maximized interior layout space.
In general, there are three types of maintenance:
1. Housekeeping. This includes general cleaning, floor washing, cleaning of
debris from expansion joints, touchup of painted surfaces, upkeep of land-
scaping, repainting stripes and graphics, cleaning lighting fixtures, removing
graffiti, etc. (see Reference 2).
2. Prevention Maintenance. This focuses on periodic checkup, cleaning, and
restoration of all components, including structural, architectural, and mechani-
cal elements, as well as equipment maintenance and safety systems. Such
activities will prevent premature deterioration of the structure and unexpected
failure of mechanical components (see Reference 3).
3. Structural Repairs. Even the best maintained parking structure may occasion-
ally require some structural repairs. Repairs may be needed to fix scaling,
spalling, cracking, or delamination. In addition, flange connections should
be checked for weld failures or corrosion damage. An experienced engineer
should examine these conditions to determine the best course of action
(see Reference 4).
Having an engineer experienced in this type of construction perform a periodic
structural audit will ensure that any conditions are caught before they become a
major expense. Performing such an audit every three to four years with experienced
personnel using the proper testing equipment is recommended. The first audit
should take place immediately after construction is completed so a basis for
future audits is established (see Reference 5).

Life-Cycle Costs
Determining life-cycle costs, or all of the expenditures incurred over the lifetime
of a particular structure, has gained a higher profile as owners and architects
realize the impact of long-term expense on the operating cost of a building and its
effect on the structure’s overall return on investment. The focus on sustainable de-
sign in particular has made owners and designers examine the long-term benefits
and costs of various decisions.
Performing a life-cycle analysis, however, requires a variety of assumptions and
complexities. Many types of life-cycle analyses can be created, and the best one
to meet the owner’s needs will vary based on the project, the owner, and the goals.
Economic versus Environmental
A life-cycle analysis can be done in terms of the economic or environmental life-
cycle cost impact. Although the two approaches are different, they each consider
the impacts of the building design over the life of the building, an essential part of
sustainable design.
When the energy and resource impacts of sustainable design are considered
over the life of the building, a sustainable design often becomes cost-effective.
Conversely, when the energy-consuming impacts of a low, first-cost design are
considered over the life of the building, the building may not be as attractive of
an investment (see Reference 1).
A life-cycle cost analysis is a powerful tool used to make economically sound
decisions for selection of materials. Costs at any given time are discounted back
to a fixed date, based on assumed rates of inflation and the time-value of money.
A life-cycle cost is given in terms of dollars and represents the construction cost
plus the present value of future utility, maintenance, and replacement costs over
the life of the building.
Using the widely accepted life-cycle cost analysis, it is possible to compare,
in a fair way, the economics of alternatives that may have different cash-flow
factors but provide a similar standard of service. The result is financial information
for decision making, which can be used to balance capital costs and future repair
or maintenance costs.
Quite often, those designs with the least first cost for new construction will
require higher costs during the building life. Because they avoid a high first cost,
they require more maintenance over time and thus have a higher life-cycle cost.
As a very durable material, precast concrete may have somewhat higher initial
costs but lower life-cycle costs because they require little maintenance after they
are fabricated and erected.
The Building Life-Cycle Cost software from the National Institute of Standards
and Technology (NIST) provides economic analysis of capital investments, en-

ergy and operating costs of buildings, systems, and components. The software
includes the means to evaluate costs and benefits of energy conservation. It
complies with ASTM standards related to building economics and Federal Energy
Management Program requirements.
Accepted methods of performing life-cycle cost analyses of buildings assume
a 20-year life, with the building maintaining 80% of its residual value at the end of
this period. However, buildings actually last hundreds of years if they are not torn
down due to functional obsolescence.
Sustainability practitioners advocate that the building’s foundation and shell
should be designed to last for 200 to 300 years. The building’s long-term flexibility
can be increased by allowing extra capacity in the columns for extra floors and
floor loads as well as extra capacity in roofs for roof-top gardens.
Speculative-building developers often design for a return on investment in
seven years and generally do not buy into the life-cycle cost approach. Similarly,
minimum code requirements for energy-conserving measures in the building shell
are generally calculated for five years, meaning initial insulation levels should pay
for themselves in that time. Since it is difficult and costly to add more insulation to
the building shell after it has been constructed, the 5-year payback for insulation
is not consistent with a 100-year building use.
Advanced building-design guidelines from the New Buildings Institute (www.
NewBuildings.org) and others specify insulation levels for those who want to
build cost-effective buildings above minimum code level. Alternatively, thermal
mass and insulation can be included in the life-cycle cost analysis to determine
cost-effective levels. However, this requires whole-building energy analyses, to
determine annual costs to heat and cool the building. Economic levels of insula-
tion depend on the climate, location, and building type. (See Reference 2.)
Creating a Life-Cycle Assessment
A life-cycle assessment (LCA) is an environmental assessment of the life cycle
of a product. An LCA looks at all aspects of a product life cycle, from the first
stages of harvesting and extracting raw materials from nature to transforming and
processing these raw materials into a product, using the product and ultimately
recycling or disposing of it back to nature. An LCA consists of four phases:

A life-cycle assessment of a building is necessary to evaluate the environmental
impact of a building over its life. It includes impacts due to:
• Extraction of materials and fuel used for energy.
• Manufacture of building components.
• Transportation of materials and components.
• Assembly and construction.
• Operation, including energy consumption, maintenance, repair, and renova-
tions.
• Demolition, disposal, recycling, and reuse of the building at the end of its
functional or useful life.
A full set of impacts includes land use, resource use, climate change, health
effects, acidification, and toxicity.
A life-cycle assessment involves a time-consuming manipulation of large
quantities of data. A model such as Simapro provides data for common building
materials and options for selecting LCA impacts. The Portland Cement Association
(www.cement.org) publishes reports with life-cycle inventory data on cement and
concrete. All models require a separate analysis of annual heating, cooling, and
other occupant loads using a program such as DOE2.1e.
Creating an LCI
A life-cycle inventory (LCI) is the first stage of a life-cycle assessment. An LCI
is an accounting of all the individual environmental flows to and from a product
throughout its life cycle. It consists of the materials and energy needed to make
and use a product and the emissions to air, land, and water associated with mak-
ing and using that product.
Several organizations have proposed how an LCA should be conducted.
Organizations such as the International Organization for Standardization (ISO,
www.ISO.org), the Society of Environmental Toxicology and Chemistry (SETAC,
www.SETAC.org), and the United States Environmental Protection Agency
(www.EPA.gov) have documented standard procedures for conducting an LCA.
These procedures are generally consistent with each other. What these standards
have in common is that they are scientific, explained in detail, and repeatable.
The usefulness of an LCA or LCI depends on where the boundaries of a product
are drawn. A common approach is to consider all of the environmental flows from
cradle-to-grave. A system boundary for a precast concrete operation would look
like the diagram on the next page.
Note that the boundary does not include upstream profiles of fuel, electricity,
water, or supplementary cementitious materials. It also does not include form
preparation, placing the concrete in the formwork, curing, and stripping. A
complete precast concrete LCI would include these steps.

An upstream profile can be considered as a separate LCI that is itself an ingre-
dient to a product. For example, the upstream profile of cement is essentially an
LCI of cement, which can be imported into an LCI of concrete. The LCI of concrete
can then be imported into an LCI of a product, such as an office building.
To obtain the most useful information from an LCI, precast concrete should be
considered in the context of its end use. For example, in a building, the environmental
impact of the building materials is usually dwarfed by the environmental impacts
associated with building operations such as heating, ventilating, cooling, and lighting.
Life-cycle inventories of materials generally do not consider embodied energy
and emissions associated with construction of manufacturing-plant equipment and
buildings, nor the heating and cooling of such buildings. This is generally accept-
able if their materials, embodied energy, and associated emissions account for
less than 1% of those in the process being studied. Guidelines established by the
Society of Environmental Toxicology and Chemistry indicate that inputs to a process
do not need to be included in an LCI if:
• They are less than 1% of the total mass of the processed materials or product.
• They do not contribute significantly to a toxic emission.
• They do not have a significant associated energy consumption.
(For more on this aspect, see Reference 3.)

Resources:
MNL-122-07: PCI Architectural Precast Concrete
Manual, Third Edition.
1. Chapter 5, Section 5.4.3, “Life Cycle,” MNL-122-
07: PCI Architectural Precast Concrete Manual,
Third Edition.
2.Chapter 5, Section 5.4.3.1, “Life Cycle Cost and
Service Life,” MNL-122-07: PCI Architectural
Precast Concrete Manual, Third Edition.
3. Chapter 5, Section 5.4.3.2, “Environmental Life
Cycle Inventory and Life Cycle Assessment,”
MNL-122-07: PCI Architectural Precast Concrete
Manual, Third Edition.
4. Chapter 5, Section 5.4.3.3, “Concrete and
Concrete Products LCI,” MNL-122-07: PCI
Architectural Precast Concrete Manual, Third
Edition.
References:
Precast Concrete LCI
The data gathered in an LCI is voluminous by nature and does not lend itself
well to concise summaries; that is the function of the LCA. The data in typical
LCI reports often are grouped into three broad categories: materials, energy, and
emissions. These LCI data do not include the upstream profiles of supplementary
cementitious materials (such as fly ash, silica fume, etc.) or energy sources (such
as fuel and electricity).
The embodied energy of concrete increases in direct proportion to its cement
content. Therefore, the embodied energy of concrete is sensitive to the cement
content of the mix and to the assumptions about LCI energy data in cement
manufacturing.
Replacing cement with supplementary cementitious materials, such as slag
cement or silica fume, has the effect of lowering the embodied energy of the
concrete. Fly ash, slag cement, and silica fume do not contribute to the energy
and emissions embodied in the concrete (except for the small energy contribu-
tions due to slag granulation/grinding, which is included). These products are
recovered materials from industrial processes (also called post-industrial recycled
materials) and, if not used in concrete, would use up valuable landfill space.
For instance, with a 20% replacement of fly ash for portland cement in a 3000-
psi (20 MPa) mixture, embodied energy changes from 1.2 to 1.1 MBtu/yd3
(1.7 to
1.5 GJ/m3
), a 10% reduction. With a 50% slag-cement replace-ment for portland
cement in a 5,000-psi (35 MPa) mixture, embodied energy changes from 2.3 to 1.5
GJ/m3
(1.7 to 1.1 MBtu/yd3
), a 34% reduction.
Fly ash or slag cement replacement of portland cement also can significantly
reduce embodied emissions. For instance, a 20% substitution of fly ash for port-
land cement in a 3000-psi (20 MPa) mixture results in a 17% reduction in carbon
dioxide emissions. A 45% carbon-dioxide-emissions reduction is achievable
with 50% substitution of slag for portland cement in a 7500-psi (50 MPa) precast
concrete mixture.
Embodied energy of reinforcing steel used in concrete is relatively small be-
cause it represents only about 1% of the weight in a unit of concrete, and it is
manufactured mostly from recycled scrap metal. Reinforcing steel has over 90%
recycled content, according to the Concrete Reinforcing Steel Institute (www.
crsi.org) The process for manufacturing reinforcing bar from recycled steel uses
significant energy and should be considered if the reinforcing bar content is more
than 1% of the weight of the concrete.
It is assumed that, at a typical site and in a precast concrete plant, concrete-
production formwork is reused a number of times through the repetitious nature of
work, so its contribution to an LCI or LCA is negligible. Steel and wood formwork
is generally recycled at the end of its useful life (see Reference 4).

e•
Sustainability LEED Considerations
Precast concrete components can aid designers in achieving sustainable
designs and in meeting standardized requirements for environmentally friendly
designs. Sustainability has become a watchword for owners and architects when
designing new buildings, intermingled with terms such as “environmental friendli-
ness” and “green building.”
In general, sustainability is considered to mean development that meets present
needs without compromising the ability to meet the needs of future generations.
The goal is to use building materials and energy resources in ways that will mini-
mize their depletion or not restrict their ability to be used by future generations.
Today’s approach extends beyond the ability to renew or recycle resources to
examine the embodied energy required to make use of that material. This ac-
counting practice encompasses all the energy necessary to manufacture, deliver,
and install the product, including fuel to extract materials, finish them, and trans-
port them to the site. Even so, the concept also balances environmental impact
with cost-effectiveness.
While other building materials may have to alter their configurations or properties
to be applicable to sustainable structures, precast concrete’s inherent composi-
tion allows it to naturally achieve sustainability. It contributes by incorporating
integrated design, using materials efficiently, and reducing construction waste,
site disturbance, and noise.
The information in this chapter, which discusses sustainable concepts as they
apply to precast concrete, is condensed and edited from Chapter 5, Section 5.4,
“Sustainability,” in PCI’s Architectural Precast Concrete Manual, Third Edition
(MNL-122-07). Additional resources pertaining to precast’s role in designing a
sustainable building can be found at the end of the chapter.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3E-1

The U.S. Department of Transportation facility in
Lakewood, Colo., used an all-precast concrete structure
to help it achieve LEED Silver Certification.
Design Architect: Oz Architecture; Architect/engineer:
Opus Architects Engineers Inc.; Photo: Oz
Architecture.
Integrated Design
Precast concrete components play a key role in maximizing benefits from
integrated-design strategies. Integrated design, also called the holistic or whole-
building approach, focuses on all of the building’s materials, systems, and design
from the perspective of all project team members and tenants.
Decisions are based on the combination of energy efficiency, cost, durability (or
service life), space flexibility, environmental impact, and quality of life. Choices in
one area impact other areas, requiring all systems to be considered together to
maximize efficiency and minimize redundancies or interference.
Integrated design requires coordinating the architectural, structural, and mechani-
cal designs early in the schematic-design phases to evaluate system interactions
and decide which beneficial interactions are essential for project success. For
example, a well-insulated building with minimal windows facing east and west
requires less heating and air-conditioning. That reduction, in turn, could result in
fewer ducts or the elimination of registers along the building’s perimeter.
Integrated design consists of eight key components. Requests for proposals
and contracts should clearly describe sustainability requirements and project
documentation. The eight components are:
1. Emphasize the integrated process.
2. Consider the building as a whole—often interactive, often multi-functional.
3. Focus on the life cycle.
4. Have disciplines work together as a team from the start.
5. Conduct relevant assessments to help determine requirements and set goals.
6. Develop tailored solutions that yield multiple benefits while meeting require-
ments and goals.
7. Evaluate solutions.
8. Ensure requirements and goals are met.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3E-2

Some of the primary ways that precast concrete components can help include:
• Precast concrete walls act as thermal storage to delay and reduce peak
thermal loads.
• Precast concrete walls used with insulation provide energy benefits that
exceed the benefits of mass or insulation used alone in most climates.
• Precast concrete sandwich wall panels used as an interior surface can save
material by eliminating the need for framing and drywall.
• Hollow-core panels used as ducts can save material and energy by eliminating
ductwork and charging the thermal mass of the panel.
• Precast concrete walls can be designed to be disassembled for building-
function changes, saving material and extending the service life of the panels.
• Precast concrete’s durability creates a long life cycle and low maintenance,
which creates less need for replacement and maintenance during the build-
ing’s life.
• As a plant-cast product manufactured under tight quality controls, precast
concrete eliminates any construction waste and minimizes transportation
and disposal costs.
In addition, a major tenet of an integrated-design strategy embracing sustainable
concepts is to focus on three ways to minimize the material used in the project:
1. Reduce the amount of material used and the toxicity of waste
materials. Precast concrete can be designed to optimize or lessen the
amount of concrete used. Industrial wastes such as fly ash, slag cement, and
silica fume can be incorporated into the mix, reducing the amount of cement.
As a manufactured product created under controlled conditions in the plant,
precast concrete generates low amounts of waste, and the waste generated
has low toxicity. It is generally assumed that 2% of the concrete at the plant
is waste, but because it is generated at the plant, 95% of the waste is used
beneficially elsewhere.
2. Reuse and repair products. Precast concrete panels can be reused when
buildings are expanded. Concrete pieces from demolished structures also
can be reused, such as protection for shorelines. Because the precast
process is self-contained, formwork and finishing materials are reused.
Wood or fiberglass forms can generally be used 40 to 50 times without
major maintenance, while concrete and steel forms have practically
unlimited service lives.
3. Recycle and use products with recycled content. Concrete can be
recycled as fill or road base. Wood and steel forms are recycled when they
become worn or obsolete. Virtually all reinforcing steel is made from recycled
steel. Many cement plants burn waste-derived fuels such as spent solvents,
used oils, and tires.

Total-precast concrete structure aids office design by
offering “green” qualities, including close proximity,
energy efficiency, reliability, and minimal construction
waste.
CH2M Hill World Headquarters, Englewood, Colo.; Architect: Barber Architecture, Denver, Colo.; Photos: Rocky Mountain Prestress.
LEED Rating System
Precast concrete can help buildings in a variety of ways to achieve the stan-
dards created by the LEED building-rating system. LEED is a voluntary, con-
sensus-based national standard for developing high-performance, sustainable
buildings. Administered by the U.S. Green Building Council, LEED-NC applies
to new construction and major renovation projects and covers commercial and
institutional projects as well as high-rise residential new construction and major
renovation projects.
The system uses points to create a framework for assessing building perfor-
mance and meeting sustainability goals. Points are awarded when a specific
intent is met, and a building is LEED certified if it obtains at least 26 points.
Additional silver, gold, and platinum levels of ratings are awarded for at least 33,
39, and 52 points, respectively. The points are grouped into five categories:
1. Sustainable Sites
2. Water Efficiency
3. Energy Atmosphere
4. Materials Resources
5. Indoor Environmental Quality
Appropriate use of precast concrete components can help a building earn up
to 27 points, one more than is required for LEED certification. Precast concrete
can help meet minimum energy requirements, optimize energy performance, and
increase the life of a building. The constituents of concrete can be made from
recycled materials, and concrete itself can also be recycled. The materials are
usually available locally.
These attributes of concrete, recognized in the LEED rating system, can help
lessen a building’s impact on the natural environment. Points applicable to precast
concrete are summarized in the accompanying table. The USGBC website (www.
usgbc.org) contains a downloadable “letter template” that greatly simplifies
documentation requirements

LEED CATEGORY CREDIT OR PREREQUISITE
POINTS
AVAILABLE
Sustainable Sites Credit 5.1: Site Development, Protect or Restore Habitat 1
Sustainable Sites Credit 5.2: Site Development, Maximize Open Space 1
Sustainable Sites Credit 7.1: Heat Island Effect, Non-Roof 1
Energy and Atmosphere Prerequisite 2: Minimum Energy Performance —
Energy and Atmosphere Credit 1: Optimize Energy Performance 1-10
Materials and Resources Credit 1.1: Building Reuse, Maintain 75% of Existing Shell 1
Materials and Resources Credit 1.2: Building Reuse, Maintain 95% of Existing Shell 1
Materials and Resources Credit 2.1: Construction Waste Management, divert 50% by weight or
volume
1
Materials and Resources Credit 2.2: Construction Waste Management, divert 75% by weight or
volume
1
Materials and Resources Credit 4.1: Recycled Content, the post-consumer recycled content plus one-
half of the pre-consumer content constitutes at least 10% (based on cost) of
the total value of the materials in the project
1
Materials and Resources Credit 4.2: Recycled Content, the post-consumer recycled content plus one-
half of the pre-consumer content constitutes at least 20% (based on cost) of
the total value of the materials in the project
1
Materials and Resources Credit 5.1: Local/Regional Materials, Use a minimum of 10% (based on cost)
of the total materials value
1
Materials and Resources Credit 5.2: Local/Regional Materials, Use a minimum of 20% (based on cost)
of the total materials value
1
Indoor Environmental
Quality
Credit 3.1: Construction Indoor Air Quality Management Plan, during
construction
1
Innovation and Design
Process
Credit 1.1: Use of high volume supplementary cementitious materials. Apply
for other credits demonstrating exceptional performance
1†
Process
Credits 1.2: Apply for other credits demonstrating exceptional performance 1†
Process
Process
Process
Credit 2.1: LEED Accredited Professional 1
PROJECT TOTALS 23
LEED* Project Checklist: Precast Concrete Potential Points
*LEED: Leadership in Energy and Environmental Design.
†
Up to 4 additional points can be earned, must be submitted and approved (not included in total).
Note: Scoring System: Certified, 26-32 points; Silver, 33-38 points; Gold, 39-51 points; and Platinum, 52-69 points.

Precast Concrete Attributes Applied To LEED Certification
The attributes and capabilities of precast concrete that help meet LEED certi-
fication vary by the intent of each category. The key applications center on the
following attributes:
Durability
Durability of the original structure represents a key factor in building reuse.
Precast concrete panels provide a long service life due to their durable and
low-maintenance concrete surfaces. A precast concrete shell can be left in
place when the building interior is renovated. Yearly maintenance should include
inspection and, if necessary, repair of joint material.
Modular and sandwich-panel construction with precast concrete exterior and
interior walls provides long-term durability inside and out. Precast concrete
construction creates the opportunity to refurbish the building if its use or function
changes rather than tearing it down to start anew.
These characteristics of precast concrete make it sustainable in two ways:
1. It avoids contributing solid waste to landfills.
2. It reduces the depletion of natural resources and production of air and water
pollution caused by new construction.
Mitigating the Urban Heat-Island Effect
Precast concrete provides reflective surfaces that minimize the urban heat-
island effect. Cities and urban areas are 3 °F to 8 °F warmer than surrounding
areas due to buildings and pavements taking the place of vegetation. Trees
provide shade that reduce temperatures at the surface and also create
transpiration and evaporation that cool the surfaces and air surrounding them.
Urban heat islands result primarily from solar radiation being absorbed by hori-
zontal surfaces such as roofs, pavements, parking lots, driveways, and walkways.
Vertical surfaces, such as the sides of buildings, also contribute. The ability of a
material to reflect solar heat is called albedo, and the higher the material’s albedo,
the better it reflects. High albedo can reduce the heat-island effect, save energy
by reducing the demand for air conditioning, and improve air quality.
Concrete has a relatively high albedo. Traditional portland-cement concrete
generally has an albedo or solar reflectance of approximately 0.4. The solar
reflectance of new concrete is greater when the surface reflectance of the
sand and cementitious materials in the concrete are greater. Surface finishing
techniques also have an effect, with smoother surfaces generally having a
higher albedo. Lighter or white colors also increase solar reflectance.

Moisture in concrete helps to cool the surface by evaporation, too. Concrete,
when placed, has a moisture content of 100% relative humidity. The concrete sur-
face gradually dries over a period of one to two years, until it reaches equilibrium
with its surroundings. Concrete surfaces exposed to rain and snow will continue
to become wet and dry. This moisture helps cool the concrete by evaporation
whenever the temperature and relative humidity of the air are greater than that
just beneath the concrete surface.
The thermal mass of concrete delays the time it takes for a surface to heat up,
but it also delays the time to cool off. For example, a white roof will get warm
faster than concrete during the day, but will also cool off faster at night. Concrete
surfaces are often warmer than air temperatures in the evening hours.
Concrete’s albedo and thermal mass will help mitigate heat-island effects during
the day but may contribute to the nocturnal heat island effect. Designers should
try to use concrete to mitigate heat islands while keeping evening temperatures
as cool as possible.
Precast Concrete Production
The production of precast concrete has many environmental benefits, including:
• Less material is required because precise mixture proportions and tighter
tolerances are achieved.
• Optimal insulation levels can be incorporated into precast concrete sandwich
wall panels.
• Waste materials are more likely to be recycled because concrete production is
in one location.
• Gray water is often recycled into future mixtures.
Material Albedo Range
Alphalt .05-.20
Roofing tile .10-.35
Stone .20-.35
New concrete .35-.40
Colored metal roofs .55-.66
Cool roofs (with reflective membrane) .85
Snow .75-.95
Source: U.S. Environmental Protection Agency (www.epa.gov) and ESPERE-ENC (Environmental Science Published for
Everybody Round the Earth-Educational Network on Climate)
Typical Albedos for Selected Building Products

• Hardened concrete is recycled (about 5% to 20% of aggregate in precast
concrete can be recycled concrete).
• Steel forms and other materials are reused.
• Less dust and waste are created at the construction site because only needed
precast concrete elements are delivered.
• There is no debris from formwork and associated fasteners.
• Fewer trucks and less time are required for construction because concrete is
made offsite, which is particularly beneficial in urban areas where minimal
traffic disruption is critical.
• Precast concrete units are normally large components, so greater portions of
the building are completed with each activity.
• Less noise is generated at the construction site because concrete is made
offsite.
• Less concrete generally is used in precast buildings compared with other con-
crete buildings because of the optimization of materials. A properly designed
precast concrete system will result in smaller structural members, longer spans,
and less material used onsite. This creates economic and environmental savings.
Precast concrete components can provide the building structure as well as the
interior and exterior finishes. Structurally efficient columns, beams, and slabs can
be left exposed with natural finishes. Interior and exterior concrete walls offer a
wide range of profile, texture, and color options that require little or no additional
treatment to achieve aesthetically pleasing results.
Constituent Materials
Concrete contributes to a sustainable environment because it does not use
scarce resources. It consists of only a few ingredients, primarily cement, water,
large and small aggregates, and admixtures, all of which are abundant locally.
Portland cement is made by heating common minerals (primarily crushed
limestone, clay, iron ore, and sand) to a white-hot mixture to form clinker. This
intermediate product is ground with a small amount of gypsum to form a fine,
gray powder. To trigger the necessary chemical reactions in the kiln, these raw
materials must reach a temperature of about 2700 °F, the temperature of molten
iron. Although portland cement is energy intensive, the U.S. cement industry has
reduced energy usage per ton of cement by 35% since 1972.
Aggregates, which comprise about 85% of concrete, generally consist of materi-
als that require low levels of energy to produce, comprising local, naturally occur-
ring sand and stone. Limestone and clay needed to manufacture cement also are
prevalent. Limestone and aggregate quarries often are reused. While quarrying is
intense, it is closely contained and temporary.

Three types of industrial by-products, or pozzolans, are used to replace portland
cement in concrete to reduce the energy and CO2
impacts of cement in concrete.
If not used in concrete, these pozzolans would use valuable landfill space. These
admixtures are:
1. Fly ash, a by-product of the combustion of pulverized coal in electric power
generating plants. It can replace up to 25% of the cement used in precast
concrete.
2. Slag cement, made from iron blast-furnace slag. It can replace up to 60% of
the cement used in precast concrete.
3. Silica fume, a by-product from the electric arc furnace used in the production
of silicon or ferrosilicon alloy. It can replace up to 7% of the cement used in
precast concrete.
Because the cementitious content of concrete accounts for only about 15% of
the material’s total, these pozzolans typically comprise only 2% to 5% of the over-
all concrete material in buildings. However, their use can have a significant effect
on the environmental impact of concrete: When slag cement replaces 50% of the
portland cement in a 7500-psi concrete, greenhouse-gas emissions per cubic
yard of concrete are reduced by 45%.
The environmental attributes of concrete can be further improved by using
aggregates derived from industrial waste or using recycled concrete as aggre-
gates. Blast-furnace slag is a lightweight aggregate with a long history of use in
the concrete industry. Recycled concrete also can be used as aggregate in new
concrete, particularly the coarse portion.
Admixtures provide enhancing qualities in concrete but are used in such small
quantities that they do not adversely affect the environment. Likewise, color
pigments used to provide decorative colors in precast concrete generally do not
contribute to environmental calculations, although some may contain trace amounts
of heavy-metals.
The use of local materials reduces the transportation needs for heavy building
materials, along with the associated energy and emissions. Most precast
concrete plants are within 200 miles of a building site. The cement, aggregates,
and reinforcing steel used to fabricate precast concrete components, along with
the raw materials used to manufacture cement, are usually obtained or extracted
from sources within 200 miles of the precast concrete plant.
Precast concrete elements are usually shipped efficiently because of their large,
often repetitive sizes and the ability to plan their shipment during the normal
course of the project.
Energy Conservation
Energy conservation is a key tenet of sustainability. About 90% of the energy
used during a building’s life is attributed to heating, cooling, and other utilities.
The remaining 10% is attributed to manufacturing materials, construction,
maintenance, replacement of components, and demolition.

Precast concrete’s inherent capabilities to provide energy efficiency rely on
the high thermal mass of the material, which benefits exterior wall applications.
Precast concrete walls provide benefits because they:
• Delay or reduce peak loads.
• Reduce total loads in many climates and locations.
• Work well regardless of the placement of mass.
Precast’s thermal mass works best in commercial applications by delaying the
peak summer load, which generally occurs around 3:00 p.m. The high mass also
can be applied to smaller residential applications. The approach works most ef-
ficiently when mass is exposed on the inside surface.
Precast concrete’s high thermal mass may help shift the peak hour of electric
demand for air conditioning to a later hour and help reduce time-of-use charges.
Nighttime ventilation can be used to cool thermal mass that has been warmed
during the day. Local outdoor humidity levels influence the effectiveness of night-
time ventilation strategies. These strategies can help to reduce the overall load in
many climates.
Mass works well on the inside surfaces by absorbing the heat gains generated
by people and equipment indoors. Interior mass from interior walls, floors, and
ceilings will help moderate room temperatures and reduce peak energy use.
Thermal mass is most effective in locations and seasons where the daily outdoor
temperature rises above and falls below the building’s balance-point temperature.
The balance-point temperature is the outdoor temperature below which heating
will be required. It is less than room temperature, generally between 50 °F and
60 °F, at the point where internal heat gains approximately equal the heat losses
through the building envelope. In many climates, buildings with thermal mass
have lower energy consumption than non-massive buildings with walls of similar
thermal resistance; heating and cooling needs can be met with smaller equipment
sizes.
Light-colored precast concrete will reduce energy costs associated with indoor
and outdoor lighting. The more reflective surfaces will reduce the amount of fixtures
and lighting required.
To maximize the effectiveness of the insulation used with precast concrete
panels, thermal bridges (disruptions of insulation between two layers of concrete)
should be minimized or avoided. Fiberglass or epoxy-coated, carbon fiber com-
posite fasteners or thermal breaks offer the best approach, as they will minimize
thermal bridges. Concrete thermal bridges may occur at the bottom and the top
of concrete panels. Metal thermal bridges may occur as fasteners that penetrate
insulation to connect concrete layers.

Chapter 5, Section 5.4, “Sustainability,” MNL-122-
07: PCI Architectural Precast Concrete Manual,
Third Edition.
References:
Resources:
DN-15 Designer’s Notebook: Energy Conservation Condensation Control.
Ascent:
“Best Justice Facility: Fresno Courthouse Federal Building,” Ascent, Fall 2006, p. 30.
“DOT Project Shows LEEDership,” Ascent, Winter 2006, pp. 32-35.
“Precast Helps Attain LEED Certification,” Ascent; Winter 2005, pp. 18-23.
“Precast Helps Projects Attain LEED Certification,” Ascent; Summer 2004, pp. 18-22.
PCI Journal:
“Achieving Sustainability with Precast Concrete,” PCI Journal, January-February 2006, pp. 42-61.
“Analytical Investigation of Thermal Performance of Precast Concrete Three-Wythe Sandwich Wall Panels,” PCI
Journal; July-August 2004, pp. 88-101.
“Some Aspects of Sustainability,” PCI Journal, January-February 2006, p. 75.
“State-of-the-Art of Precast/Prestressed Sandwich Wall Panels,” PCI Journal; March-April 1997, pp. 92-134.
“U.S. Department of Transportation Facility, Lakewood, Colo.,” PCI Journal, January-February 2006, pp. 76-81.
Concrete contains low to negligible volatile organic compounds (VOC). These
compounds degrade indoor air quality when they off gas from new products such
as interior finishings, carpet ,and furniture. Manufactured wood products such
as laminate, particleboard, hardboard siding, and treated wood can also lead
to off gassing. In addition, VOCs combine with other chemicals in the air to form
ground-level ozone.
Polished concrete floors do not require carpeting. Exposed concrete walls
do not require finishing materials. The VOCs in concrete construction can be
reduced further by using low-VOC materials for form-release agents, curing
compounds, damp-proofing materials, wall and floor coatings and primers, mem-
branes, sealers, and water repellants.
Precast concrete components can further help meet LEED standards for indoor
air quality because they are delivered to the site in modules that do not require
fabrication, processing, or cutting at the construction site, thereby reducing dust
and airborne contaminants on site. Concrete is not damaged by moisture and
does not provide nutrients for mold growth.
Precast concrete panels can be reused when buildings are expanded, and
precast concrete can be recycled as road base or fill at the end of its useful life.
Concrete pieces from demolished structures can be reused to protect shorelines.
Most concrete from demolition in urban areas is recycled and not placed in land-
fills.
The concrete industry has LEED-experienced professionals available to assist
teams with concrete applications and help maximize points for concrete. An ad-
ditional point is available if a principal participant of the project team is a LEED-
accredited professional.

Orville L. Freeman Office Building and Laboratory,
St. Paul, Minn.; Architect: HGA.
f•
Health Indoor Air Quality
Building users have growing concerns about having a healthy environment in
which to work, shop, play, and live. The damage that can be wrought by mold
and the lack of fresh air within a structure continues to gain awareness, making
designers place more emphasis on controlling these factors in their structures.
Mold damage has ruined countless projects and has been directly or indirectly
linked to severe illness and harm to individuals.
A side aspect to this problem for designers is that mold problems have clogged
the court system with more than $300 million annually in litigation as well as
produced a 300% increase each year in the number of lawsuits filed nationwide.
Remediating mold growth also requires expensive treatments that disrupt the
building’s operation and pose burdens on operating budgets.
Proper design and production techniques can help prevent mold proliferation as
well as reduce moisture damage and water migration. The proper design of build-
ing envelopes with the correct construction materials is a key way to reduce the
presence and potential damage from mold (see Reference 1).
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3F-1

Mold requires four conditions to thrive: mold spores, organic matter for food,
moisture, and optimal temperatures (40 to 100 °F).
There is no way to eliminate all mold in the interior environment, as it exists
throughout the natural world. Treatment of materials with chemicals may reduce
the potential for mold but can not eradicate it. The careful attention to the building
envelope, the choice of materials, and control of moisture penetration can reduce
harmful mold’s success in establishing itself and growing.
Precast concrete aids in controlling mold growth for a number of reasons:
• It is not an organic material. While concrete can accumulate dirt and debris,
which can breed mold, its durability allows it to be cleaned in place rather
than removed for remediation, as must happen with many other organic
construction materials.
• Its production is controlled away from moisture. Unless properly designed
and constructed, the building site can permit excessive moisture in either
surface, underground water, outside humid air, or rain into openings like doors,
windows, ventilation ducts, or shafts that pull outside air in the buildings.
Precast concrete is produced in a controlled and protected environment in
a process that resists moisture intrusion. By delivering the components to
the site as needed, they are exposed to the environment for a shorter period
of time (see Reference 2).
• Precast concrete’s speed provides interior protection quicker. The use
of precast concrete systems to construct building envelopes also allows the
structure to be completed faster, leaving it exposed to humidity and moisture
for a shorter time period. This is particularly vital for the installation of the HVAC
system, which is one of the more common entrance paths for mold formation.
During the “exposed” phase of the construction process, mold spores can
come to rest on building materials and components, whether installed or
simply stored. If water is added from any natural or other source, the spores
may be able to begin to grow.
• It can be cleaned easily. Concrete can be cleaned of mold and dust spores,
making them ideal substrates for controlling mold growth. The cleaning can be
accomplished on precast concrete components by pressure washing, which
rids the surface of any food source for mold that may have lodged there. In
addition, the site’s natural ventilation will normally dry out concrete and steel,
eliminating moisture as a source of growth (see Reference 3).
• Precast concrete provides fewer entry points. Because of its panelized
construction, fewer points of potential moisture penetration exist with precast
concrete panels. This helps control moisture and eliminate the possibility for
mold growth in water that penetrates the walls. Maintenance needs for precast
concrete panels are also minimal, with panels only requiring caulking every 15
to 20 years to maintain their reliability. This limits the need to budget for repairs
in annual maintenance budgets and reduces the potential for lapses to allow
problems to develop.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3F-2

Resources:
Chapter 5, Section 5.3.6, “Condensation Control,” MNL-122-07: PCI Architectural Precast Concrete Manual,
Third Edition.
Chapter 9.1.7.1, “Air Barriers,” PCI MNL-120-04: PCI Design Handbook, Sixth Edition.
Chapter 9.1.7.2, “Vapor Retarders,” PCI MNL-120-04: PCI Design Handbook, Sixth Edition.
“Mold White Paper,” produced for the Precast/Prestressed Concrete Institute; April 2005, p. 4.
MK-34-03: Precast Concrete Makes the Grade For K-12 School Facilities.
1. “Mold White Paper,” produced for the Precast/
Prestressed Concrete Institute; April 2005, p. 1.
For K-12 School Facilities (12 pp.).
5. Chapter 5, Section 5.3.6, “Condensation
Control,” MNL-122-07: PCI Architectural
Precast Concrete Manual, Third Edition.
References:
HeatTransmittance,U
Outside Temperature, °F
• It ensures mold growth isn’t exacerbated by changes in the interior
environment. Because precast concrete panels eliminate worries about
moisture penetration, administrators can reduce HVAC usage when a build-
ing, especially seasonal structures such as schools, are unoccupied for long
periods and not worry that they are risking mold growth or creating bad indoor
air quality (see Reference 4).
Air, Vapor Barriers Required
Controlling condensation in a building with a precast concrete façade, as with
any material, requires an air barrier and a vapor barrier, although they often
consist of a single material that can provide both functions. The principle function
of the air barrier is to stop outside air from entering the building through the walls,
windows, or roof, and inside air from exfiltrating through the building envelope to
the outside environment.
The principal function of a vapor retarder made of low-permeability materials is
to stop or retard the passage of moisture as it diffuses through the assembly of
materials in a wall. Vapor-diffusion control is easy to achieve and is primarily a
function of the water-vapor diffusion resistance of the chosen materials and their
position within the building-envelope assembly. The vapor retarder should be
clearly identified by the designer and be clearly identifiable by the general
contractor (see Reference 5).
Precast concrete construction supports the scientific community’s maxim to
prevent or inhibit mold formation rather than attempt remediation of fungi in indoor
environments.
In addition, precast concrete panels have no outgassing that can cause dete-
riorated air quality. This has become a critical component in recent years as the
need to enhance energy efficiency has tightened the “breathability” of buildings,
preventing air from infiltrating and exfiltrating, which retains existing particulates
in the air. Precast concrete will not add to this outgassing that comes from volatile
organic compounds and new materials brought into the structure (see Reference 6).
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3F-3

The Juanita K. Hammons Hall for the
Performing Arts, Springfield, Mo.;
Architect: Pelham-Phillips-Hagerman; and Butler,
Rosenbury Partners (joint venture);
Photos: Pelham-Phillips-Hagerman.
g•
Acoustics
Inhabited spaces should be acoustically designed to provide a satisfactory
environment in which desired sounds are heard clearly and unwanted sounds
are isolated or absorbed. Under most conditions, the architect or engineer can
determine the acoustical needs of the space and then design the building to
satisfy those needs.
Good acoustical design uses absorptive and reflective surfaces, sound barriers,
and vibration isolators. Sound is isolated from rooms where it is not wanted by
selected wall and floor-ceiling constructions. Vibration generated by mechanical
equipment must be isolated from the structural frame of the building.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3G-1

For buildings that require more sophisticated acoustical analysis, such as
churches, concert halls, or auditoriums, it may be desirable to review the needs
with an acoustical design consultant (see Reference 1).
The ability of a barrier to reduce the intensity of airborne sound is commonly
designated by its Sounds Transmission Class (STC). Precast concrete walls,
floors, and roofs usually do not need additional treatment to provide adequate
sound insulation (see Reference 2).
Even when airborne sounds are adequately controlled, there can be severe
impact noise problems. Footsteps, dropped objects, slammed doors, and plumb-
ing generate impact noise. For performance specifications, the Impact Insulation
Class (IIC) is used to measure this sound. In general, thickness or unit weight of
concrete does not greatly affect the transmission of impact sounds. Structural
concrete floors, combined with resilient materials such as carpeting, effectively
control impact sound (see Reference 3).
Often, acoustical control is specified as to the minimum insulation values of
the dividing partition system. Local building codes, lending institutions and the
Department of Housing Urban Development (HUD) list both airborne, STC and
IIC values for different living environments:
Other community ordinances can be more specific, listing the sound-insulation
criteria with relation to particular ambient environments. Once objectives are
established, the designer should refer to available data and select the system that
best meets the requirements. In general, concrete systems have superior properties
and can, with minimal effort, comply with these criteria (see Reference 4).
Sound Absorption vs. Sound Insulation
Designers must recognize that the basic mechanisms of sound absorption and
sound insulation are quite different. Designing for sound insulation is usually
considerably more complicated than designing for sound absorption. The former
involves reductions of sound levels, which are of greater orders of magnitude than
can be achieved by absorption. These large reductions of sound level from space
to space can be achieved only by continuous, impervious barriers. It also may be
necessary to introduce resilient layers of discontinuities into the barrier.
Sound-absorbing materials and sound-insulating materials are used for different
purposes. For instance, an 8-in. concrete wall will not provide much sound absorp-
tion, while a porous, lightweight material that may be applied for sound absorption
to room surfaces will not provide high sound insulation (see Reference 5).
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3G-2
Location STC IIC
Between living units 45 45
Between living units and public spaces 50 50
HUD Recommendations for STC and IIC
Source: Table 9.2.7.1, MNL-120-04: PCI Design Handbook, Sixth Edition

Fig. 1: Sound transmission class as a function of weight of floor or wall.
Sound-Transmission Loss And Sound Absorption
Sound-transmission loss measurements are made at 16 frequencies at one-
third octave intervals covering the range from 125 to 4000 Hz. Airborne sound
reaching a wall, floor, or ceiling produces vibrations in the wall that are radiated
with reduced intensity on the other side. Airborne sound-transmission loss in wall
assemblies is a function of their weight, stiffness, and vibration-damping charac-
teristics.
Weight is concrete’s best asset when it is used as a sound insulator. For sections
of similar design but different weights, the STC increases approximately 6 units for
each doubling of weight. This is shown in Fig. 1, which describes sound transmis-
sion class as a function of weight based on experimental data.
Precast concrete walls usually do not need additional treatments to provide ad-
equate sound insulation. If desired, greater sound insulation can be obtained by
using resiliently attached layers of gypsum board or other building materials. The
increased transmission loss occurs because the energy flow path is increased to
include a dissipative air column and additional mass (see Reference 6).
A dense, nonporous concrete surface typically absorbs 1% to 2% of incidental
sound. Where additional sound absorption is desired, a coating of acoustical
material can be spray applied, acoustical tile can be applied with adhesive, or
an acoustical ceiling can be suspended. Most of the spray-applied, fire-retardant
materials used to increase the fire resistance of precast concrete and other floor-
ceiling systems can also be used to absorb sound (see Reference 7).

Alberta Lea High School, Alberta Lea, Minn.; Photo: ©Don F. Wong.
Composite Wall Considerations
Windows and doors are often the weak link in an otherwise effective sound bar-
rier. Minimal effects on sound-transmission loss will be achieved in most cases
by proper selection of glass. The control of sound transmission through windows
requires large cavities between layers (multiple glazing), heavy layers (thicker
glass), and a reduction of the structural connection between layers (separate
frames and sashes for inner and outer layers).
These penetrations should be designed to be as airtight as possible. Fixed
windows usually provide much better sound-transmission control than operable
windows. The sound-transmission loss through a door depends on the material
and construction of the door as well as on the effectiveness of the seal between
the door and its frame.
There is a mass law dependence of STC on weight (psf) for both wood and steel
doors. The approximate relationships are:
• For steel doors: STC = 15 + 27 log W
• For wood doors: STC = 12 + 32 log W
In these relationships, W = weight of the door, psf. These relationships are purely
empirical, and a large deviation can be expected for any given door.
For best results, the distances between adjacent door and window openings
should be maximized, staggered when possible, and held to a minimum area.
Minimizing openings allows the wall to retain the acoustical properties of the
precast concrete. The design characteristics of the door or window systems
must be analyzed prior to writing the project specification.
Such qualities as frame design, door construction, and glazing thickness are
vital performance criteria. Installation procedures must be exact and care must
be given to the framing of each opening. Gaskets, weatherstripping, and raised
thresholds serve as both thermal and acoustical seals and are recommended
(see Reference 8).
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3G-4

Resources:
MNL-120-04: PCI Design Handbook, Sixth Edition.
MNL-122-07: PCI Architectural Precast Concrete Manual, Third Edition.
1. Chapter 9.2.2, “Acoustical Properties of Precast
Concrete: General,” MNL-120-04: PCI Design
2. Chapter 9.2.4, “Sound Transmission Loss,”
MNL-120-04: PCI Design Handbook, Sixth
Edition.
3. Chapter 9.2.5, “Impact Noise Reduction,” MNL-
4. Chapter 9.2.7, “Establishment of Noise Insula-
tion Objectives,” MNL-120-04: PCI Design
5. Chapter 9.2.3, “Acoustical Properties of Precast
Concrete: Dealing with Sound Levels,” MNL-
6. Chapter 5, Section 5.5.4, “Acoustical Properties:
Sound Transmission Loss,” MNL-122-07: PCI
Architectural Precast Concrete Manual, Third
Edition.
Absorption of Sound,” MNL-122-07: PCI Archi-
tectural Precast Concrete Manual, Second Edition.
Composite Wall Considerations,” MNL-122-07:
PCI Architectural Precast Concrete Manual,
Third Edition.
Leaks and Flanking,” MNL-122-07: PCI Archi-
tectural Precast Concrete Manual, Third Edition.
References:
Leaks and Flanking
A building section’s performance with an otherwise adequate STC can be seri-
ously reduced by a relatively small hole (or any other path) that allows sound to
bypass the acoustical barrier. All noise that reaches a space by paths other than
through the primary barrier is called flanking noise.
Common flanking paths are openings around doors or windows, electrical
outlets, telephone and television connections, and pipe and duct penetrations.
Suspended ceilings in rooms where walls do not extend from the ceiling to the
roof or floor above also allow sound to travel to adjacent rooms by flanking.
Anticipation and prevention of leaks begins at the design stage. Flanking paths
or gaps at the perimeters of interior precast concrete walls and floors are general-
ly sealed during construction with grout or drypack. All openings around penetra-
tions through walls or floors should be as small as possible and must be sealed
airtight. The higher the required STC of the barrier, the greater the importance of
sealing all openings.
Perimeter leakage commonly occurs at the intersection between an exterior
cladding panel and a floor slab. It is of vital importance to seal this gap to retain
the acoustical integrity of the system and provide the required fire stop between
floors. One way to seal the gap is to place a mineral-wool blanket covered by
sealant between the floor slab and the exterior wall.
Flanking paths can be minimized in three ways:
1. Interrupt the continuous flow of energy with dissimilar materials, such as with
expansion or control joints or air gaps.
2. Increase the resistance to energy flow with floating floor systems, full-height
or double partitions, and suspended ceilings.
3. Use primary barriers that are less subject to the creation of flanking paths.
Although not easily quantified, an inverse relationship exists between the
performance of an element as a primary barrier and its propensity to transmit
flanking sound. The probability of existing flanking paths in a concrete struc-
ture is much less than in one of steel or wood framing.
If the acoustical design is balanced, the maximum amount of acoustical energy
reaching a space via flanking should not equal the energy transmitted through
the primary barriers. In exterior walls, the proper application of sealant and
backup materials in the joints between units will not allow sound to flank the wall
(see Reference 9).

DESI GNING WIT H PRECAST PREST RESSED CONCRET E 3H-1
h•
Safety Security
Providing a safe and secure structure for owners and users provides key chal-
lenges for designers. Integrating these critical functional aspects while meeting
aesthetic goals and programmatic needs requires designers to remain up to date
on new techniques and systems that can minimize the intrusion of security and
safety elements in the overall plan. As security worries rise and Mother Nature
continues to show her power, these concerns become key drivers for more clients.
Precast concrete designs can offer protection against fires, earthquakes, hur-
ricanes, tornados, and explosive blasts when design and detailing are correctly
applied. The requirements for achieving these goals must be taken into account
as early in the design process as possible to maximize the effectiveness of pre-
cast concrete’s capabilities against each of these issues.
Photo: ©PhotoDisc
Photo: ©PhotoDisc

Photo: ©PhotoDisc.
DESI GNING WIT H PRECAST PREST RESSED CONCRET E3H-2
Fire Resistance
A key goal for the design team and the client is to protect the building from the
multiple risks and losses caused by fire. A common misconception is that fire
destroys by flames, which can be suppressed by sprinklers. In practice, this over-
simplification can leave both property and human life vulnerable during a fire.
Among the goals that must be achieved when designing for fire safety are the
following:
• Contain high heat, which can melt or ignite materials or kill in one breath.
• Contain smoke that can blind, choke, and ruin building components and
contents. Smoke is often generated by the sprinkler suppression process,
and it is unavoidable.
• Contain toxic gas, which is given off when plastics, synthetics, and chemicals
burn. They can be deadly at any temperature.
• Confine the fire event to its place of origin and prevent it from spreading.
• Reduce the fuel content of the building by using non-combustible building
materials whenever possible.
• Avoid the potential for structural collapse during the fire by protecting all
structural framing elements that support the building.
• Create a passive fire-protection strategy for the building that will enable
it to survive should arson, low water pressure, or a delayed fire-department
response occur.
• Divide the building into several noncombustible compartments that will
help achieve solutions for all the aforementioned hazards. This is the most
important aspect of all.
• Recognize that building codes provide the minimum protection allowable
and may not be enough to achieve the fire protection the building and its
occupants will need. Each risk exposure requires a defense.
Precast concrete provides noncombustible construction that can help contain
a fire within minimal boundaries. As a separation wall, precast concrete helps to
prevent a fire from spreading throughout a building or jumping between struc-
tures. During wildfires, precast concrete walls help provide protection to human
life and the occupant’s possessions. As an exterior wall, concrete that endures a
fire can often be reused when the building is retrofitted.
The fire endurance of concrete can be determined by its thickness and type
of aggregate. The American Society for Testing Materials (ASTM) E119 lists
procedures for determining fire endurance of building materials. Another good
resource is PCI’s MNL 124-89: Manual on Design for Fire Resistance of Precast,
Prestressed Concrete.
Fire endurance is defined as the period of resistance to a standard fire exposure
as defined by ASTM E119 that lapses before an “end point” is reached. Three
end points are critical:

Thickness of concrete slabs or wall panels faced
with 5/8 in. Type X gypsum wallboard to provide fire
endurances of 2 and 3 hours.
Thickness (in.) of Concrete Panel for Fire Endurance of
With no air
space
With 6 in. air
space
Aggregate 2 hr 3 hr 2 hr 3 hr
Sand-lightweight 2.5 3.6 2.0 2.5
Carbonate 2.8 4.0 2.0 2.7
Siliceous 2.9 4.2 2.0 2.8
1. Structural end point. Loadbearing components must sustain the applied
loading for the duration of the required fire endurance. Collapse prior to that
is an obvious end point.
2. Heat-transmission end point. When the temperature increase of the
unexposed surface of floors, roofs, or walls reaches an average temperature
of 250 °F or a maximum of 325 °F at any one point.
3. Flame-passage end point. Holes, cracks, or fissures allowing flames or
gases hot enough to ignite cotton waste to pass through must not form.
Structural End Points
Concrete generally fails by heat transmission long before structural failure,
whereas other construction materials fail by heat transmission when collapse
is imminent.
Heat-Transmission End Points
For single-course precast concrete slabs or wall panels, a two-hour fire endur-
ance means that thermocouples, measuring the passage of heat through the
thickness of the wall, are recording an average temperature rise of 250 °F or a
maximum temperature reading of 325 °F (see Reference 1).
Slabs or wall panels faced with protective materials can provide added
endurance. The accompanying table shows the fire endurance of concrete
slabs with 5
/8-in. gypsum wallboard (Type X) for two cases:
1. A 6-in. air space between the wallboard and slab.
2. No space between the wallboard and slab.
The specified materials and techniques for attaching wallboard should be
similar to those used in the test on which the data are based (see Reference 2).
Heat transmission through a ribbed or corrugated panel is influenced by the
thinnest portion of the panel and by the panel’s “equivalent thickness.” This term
is defined as the net cross-sectional area of the panel divided by the width of the
cross section. In calculating the net cross-sectional area of the panel, portions of
ribs that project beyond twice the minimum thickness should be ignored
(see Reference 3).

Fire endurance (heat transmission) of
concrete slabs or panels
Carbonate Aggregate
FireEndurance,hr
1
0
2
Slab or Panel Thickness, in.
*Interpolation for Different Concrete
Unit Weights is Reasonably Accurate
Siliceous Aggregate
2 3 4 5 6
Lightweight - 100 PCF
Sand-Lightweight - 115 PCF
3
4
5
70
Multi-course assemblies, such as floors and roofs, often consist of concrete
base slabs with overlays or undercoatings of other types of concrete or insulating
materials. In addition, roofs generally have built-up roofing. If the fire endurance
of the individual courses is known, the fire endurance of the composite assembly
can be estimated (see Reference 4).
Precast concrete insulated sandwich wall panels must conform to IBC require-
ments. Those regulations state that where noncombustible construction is speci-
fied, combustible elements in walls are limited to thermal and sound insulation
having a flame-spread index of 25 or less.
When the insulation is sandwiched between two layers of noncombustible mate-
rial such as concrete, the maximum flame-spread index allowed is 100, except
that it shall not exceed 75 for foam-plastic insulation. When insulation is not
installed in this manner, it is required to have a flame spread of not more than 25.
Data on flame-spread classifications are available from insulation manufacturers.
Cellular plastics melt and are consumed at about 400 to 600 °F. Thus, additional
thickness or changes in composition probably have only a minor effect on the fire
endurance of sandwich panels. The danger of toxic fumes caused by burning
cellular plastic is practically eliminated when the material is completely encased
within concrete sandwich panels. Until more definitive data are provided, PCI rec-
ommends that 5 minutes be considered as the value for R for any layer of cellular
plastic 1 in. or greater (see Reference 5), where R is the fire endurance rating of an
assembly.
Flame-Passage End Points
Joints between panels should be detailed so that passage of flame or hot gases
is prevented, and transmission of heat does not exceed the limits specified in
ASTM E119. Concrete wall panels expand when heated, so the joints tend to
close during fire exposure.
Noncombustible materials that are flexible, such as ceramic-fiber blankets,
provide thermal, flame, and smoke barriers. When used with caulking, they can
provide the necessary weather tightness while permitting normal volume-change
movements. Joints that do not move can be filled with mortar.
Where no openings are permitted, the fire endurance required for the wall
should be provided at the joints. Joints between adjacent precast floor or roof
elements may be ignored in calculating the slab thickness provided that a
concrete topping at least 11
/2 in. thick is used.

Where no concrete topping is used, joints should be grouted to a depth of
at least one-third the slab thickness at the joint, or the joints should be made
fire-resistive in a manner acceptable to the authority having jurisdiction. No joint
treatment is required for parking structures constructed with pretopped double
tees (see Reference 6).
Codes and Economics
An important aspect of dealing with fire endurance is to understand what the
benefits are to the owner of a building in the proper selection of materials incor-
porated in the structure. These benefits fall into two areas: codes and economics.
While code requirements must be met, designers typically have many options in
the specification of materials and assemblies that meet these regulations.
Economic benefits associated with increased fire endurance should be con-
sidered at the time decisions are made on the structural system. Proper consid-
eration of fire-resistive construction through a life-cycle cost analysis will show
the owner the amount of economic benefits that will accrue through the use of
different types of construction. These benefits can include lower insurance rates,
larger allowable gross area, fewer stairwells and exits, increased value for loan
purposes, longer mortgage terms, and better resale value (see Reference 7).
Several key areas of code compliance allow owners and designers to provide
effective fire protection at an economical cost. The three key areas are:
1. Minimum standards. A fire rating is not the same as fire safety. The IBC
includes a variety of compromises. Code trends generally emphasize sprinkler
installations by providing trade-offs that encourage their use. These active
systems offer valuable protection, but they also include trade-offs such as
more liberal fire-separation areas and other changes that decrease required
wall and floor performance.
2. Building materials. Wood and steel generally perform poorly in fires.
Both must be treated, coated, or covered to meet fire requirements, which
increases construction costs. Wood is a natural fuel source and steel begins
to fail at 1200 °F. Concrete begins to melt at 2200 °F.
3. Sprinklers. Automatic sprinklers are a desirable, active fire-suppression sys-
tem and can help control fire spread. But they should not replace passive fire-
suppression systems that are designed to inherently protect a building without
any mechanical activation required. Relying on active-suppression systems
alone can produce an inadequate response during a fire emergency.
A design approach that stresses compartmentalization offers a more funda-
mental method to protect lives and property. Compartmentalization uses passive,
noncombustible floors and walls, such as those made of precast concrete, to con-
struct sections of the building as separate modules that confine fire to a specific
area. Once constructed into the building, these passive protectors will protect the
building throughout its life.

Noncombustible compartmentalization, combined with an inherently fire-
resistant/tolerant structural frame, provide the best combination of economics and
protection that owners and users seek. When this passive design combines with
other safety measures, including sprinklers and early-warning detection systems,
a balanced design approach is achieved (see Reference 8).
A variety of precast concrete components can be used in creating a complete
passive-design system for a building. Foremost among these are:
• Hollow-core slabs, which serve as combined floor/ceiling systems and can
also be used as wall panels in either vertical or horizontal configurations.
• Wall panels, which offer high fire ratings and work with other components to
create a noncombustible envelope. Insulated sandwich wall panels can also
be used.
• Double tees, which can be used similar to hollow-core planks for roofs, ceilings,
floors, or wall panels.
• Columns and beams, which create a framework that will resist intense heat
and will not add fuel to a fire.
A total-precast concrete system provides an effective design for minimizing fire
damage and containing the effects within the smallest space possible for the
longest time.
The information above will provide for a structure with acceptable criteria for fire
resistance. The designer and owner should also consider the following factors
when designing for fire:
• Contain high heat, which can melt or ignite combustible materials.
• Contain smoke that can blind, choke, and ruin building contents. Smoke is often
generated by a sprinkler suppression process which may be unavoidable.
• Contain toxic gases that are given off by plastics, synthetics and chemicals
when they burn.
• Confine the fire event to its place of origin by using precast concrete
components to create compartments.
• Reduce the fuel content of the building by using noncombustible material
whenever possible.
• Create several noncombustible compartments in the building
• Understand that the local minimum code requirements may not be adequate
to achieve the fire protection that your building and its occupants should have.
A 2005 study sponsored by the Fire Safe Construction Advisory Council compared
construction costs among five building systems and found that a compartmentalized
construction approach using concrete-based methods costs generally less than
5% of the overall construction cost. The group noted that this amount was less
than the contingency budget typically recommended for the owner to carry for
unanticipated expenditures during the project.

The project evaluated the impact of building a fire-resistant, multifamily, residen-
tial structure using five separate building techniques, to meet requirements of the
2003 IBC. The five systems comprised:
• Conventional wood framing with a wood-floor system using Type 5A or 5B
construction;
• Light-gage steel framing with a cast-in-place concrete floor system on a metal
form deck;
• Loadbearing concrete masonry construction with a precast concrete plank
floor system or a cast-in-place concrete floor system;
• Precast concrete walls with a precast concrete floor system; and
• Insulated concrete form (ICF) walls or interior bearing walls made with
concrete masonry units (CMU) with a precast concrete plank floor system
or a cast-in-place concrete floor system.
In each case, except the conventional wood-frame system, it was assumed that
the partition walls within the building would be constructed using metal studs
finished with gypsum board.
The studied building was a four-story structure encompassing 25,000 ft2
of
space per floor. Two models were created, one with single-bedroom layouts and
another with a mix of one- and two-bedroom layouts to address the variety of
construction configurations commonly found in the multifamily dwelling market-
place. The team chose three specific locations in which to locate their projects
(Framingham, Mass.; Harrisburg, Pa.; and Towson, Md.) to provide diversity in
labor and material costs.
The study’s consensus was that the costs associated with using a compartmen-
talized construction method that took advantage of precast concrete’s benefits
required less than 2% more of the total construction cost.
In addition, although precast concrete’s initial in-ground cost was higher, the
design did not fully play to the advantages that a total-precast concrete design
would offer, as the designers created a layout that could be standardized for use
by all material options. Those general parameters would not be necessary if a
design intended to use precast concrete from the beginning, and the difference
in costs would be lower.
The costing parameters were also unable to take into consideration the
schedule advantages that precast concrete’s fast erection would provide.
Additional advantages, including longer span capability to reduce columns,
can provide sufficient cost effectiveness to eliminate the cost differential.
The use of concrete materials can also provide long-term benefits, the report
noted. Materials like concrete masonry, precast concrete, and cast-in-place
concrete offer advantages beyond their inherent fire performance, such as

Resources:
Executive Summary Report, “Fire Safe Construction Cost Study,” November 2, 2005, Commission Number 05119.
MK-33-03: Precast Concrete Fire Prevention: Setting the Record Straight.
MNL-124-05: Design for Fire Resistance of Precast Prestressed Concrete, Third Edition.
MNL-126-98: Manual for the Design of Hollow-Core Slabs, Second Edition.
PCI Journal:
“Are We Protected From Fire in Buildings?” PCI Journal, January-February 2005, pp. 118-123.
1. “Achieving Sustainability with Precast Con-
crete,” PCI Journal, January-February 2006,
pp. 42-61.
2. Chapter 9.3.6.1, “Fire Resistance: Single
Course Slabs or Wall Panels,” MNL-120-04:
3. Chapter 9.3.6.3, “Fire Resistance: Ribbed
Panels,” MNL-120-04: PCI Design Handbook,
Sixth Edition.
4. Chapter 9.3.6.4, “Fire Resistance: Multi-Course
Assemblies,” MNL-120-04: PCI Design Hand-
book, Sixth Edition.
5. Chapter 9.3.6.5, “Fire Resistance: Sandwich
Panels,” MNL-120-04: PCI Design Handbook,
Sixth Edition.
6. Chapter 9.3.6.6, “Fire Resistance: Treatment
of Joints between Wall Panels,” MNL-120-04:
7. Chapter 9.3.10, “Fire Resistance: Code and
Economic Considerations,” MNL-120-04:
8. MK-33-03: Precast Concrete Fire Prevention:
Setting the Record Straight.
9. Executive Summary Report, “Fire Safe
Construction Cost Study,” November 2, 2005,
Commission Number 05119.
References:
resistance to mold growth and damage from vandalism, as well as minimal
damage caused by water and fire in the event of a fire. Those attributes can
require reduced cleanup costs and quicker reoccupation of the structure (see
Reference 9).

Earthquake Resistance
Precast concrete can be designed to resist seismic events, and recent advance-
ments in connection approaches provide additional design options.
Earthquakes in Guam, the United States (Richter scale 8.1); Manila, the
Philippines (Richter scale 7.2); and Kobe, Japan (Richter scale 6.9), have subjected
precast concrete buildings, using both architectural cladding and structural com-
ponents, to some of nature’s deadliest forces. During the 1994 Northridge, Calif.,
earthquake (Richter scale 6.8), in which damage was estimated at $20 billion,
most engineered structures within the affected region performed well, including
structures with precast concrete components.
In particular, significant damage was not observed in precast concrete cladding
due to either inadequacies of those components or inadequacies of their con-
nections to the building’s structural systems, nor was damage observed in the
precast concrete components used for the first floor or first-floor support of resi-
dential housing. Parking structures with large plan areas, regardless of structural
system, did not perform as well as other types of buildings (see Reference 1).
The key reason designers have gravitated toward precast concrete components
is because they can span long distances between attachments to the main struc-
ture. Design methods and details have been developed to accommodate these
applications in seismic areas.
Earthquakes generate horizontal and vertical ground movement. When the
seismic waves pass beneath a structure, the foundation tends to move with the
ground, while the superstructure remains in position. The lag between founda-
tion and superstructure movement causes distortions and develops forces in the
structure. As the ground moves, distortions and forces are produced throughout
the height of the structure, varying with the ground acceleration and the reso-
nance of the building.
Ductility Needs
The current philosophy for the design of earthquake-resistant structures per-
mits minor damage for moderate earthquakes and major damage for severe
earthquakes, provided complete collapse is prevented. The design details often
require large, inelastic deformations to occur to dissipate energy and shed inertial
forces. This is achieved by providing member and connection ductility.
While this ductility helps resist total collapse, the resulting distortions may lead
to significant damage to mechanical, electrical, and architectural elements.
Seismic damage can be minimized by setting limitations on structural deflections,
usually considered as interstory drift.
The response of a structure to the ground motion of an earthquake depends
on the structural system’s dampening characteristics and on the distribution of
its mass. With mathematical idealization, a designer can determine the probable
response of the structure to an imposed earthquake.

The Paramount’s use of a precast hybrid, moment-
resisting frame as part of its structural system is that
it creates a restoring force provided by its elastic,
post-tensioned strands that rights the building
following a seismic event. Architect of Record: Kwan
Henmi, Architecture/Planning; Photo: David Wakely
Photography.
New Code Requirements
A number of changes have been made to existing codes in recent years based
on new research and observations. These include:
• Recognition of jointed-panel construction as an alternative to emulation of
monolithic construction.
• Achieving ductile structural behavior by using “strong” connections that
remain elastic while nonlinear action (plastic hinging) occurs in the member
away from the connection.
• Modification of drift computation and limiting drift.
• Deformation compatibility of structural elements and attached nonstructural
elements.
• Additional soil-type classifications.
• Special considerations for building sites located near seismic faults.
• Special considerations for structures possessing redundancy.
(See Reference 2.)
PCI has worked in several of these areas to help create new design solutions
that provide more effective responses to seismic events. A 10-year study by the
Precast Seismic Structural Systems (PRESSS) Research Program produced three
new approaches that have been or are in the process of being codified. These
three systems are:
1. A hybrid post-tensioned precast frame, which was codified in 1999.
Developed by the National Institute of Standards Technology (NIST), this
method has the precast concrete beams connected to multistory columns by
unbonded, post-tensioned strands that run through a duct in the center of the
beam and through the columns. Mild steel reinforcement is placed in ducts
at the top and bottom of the beam, which is sleeved through the column and
grouted.
The reinforcement yields alternately in tension and compression and pro-
vides energy dissipation, while the post-tensioning strands essentially act
as “rubber bands” that help right the structure after the seismic event ends.
There are no column corbels, with the vertical shear resistance provided by
the post-tensioning strand. The post-tensioning steel balances the mild steel
reinforcement so the frame re-centers after flexing during a seismic event (see
Reference 3).
2. A pretensioned precast frame, which is applied at locations where the most
economical connection method features one-story columns with multispan
beams. The multispan beams are cast with partially debonded pretensioning
strand set on the columns. The column’s reinforcing steel extends through the
sleeves inside the beams. Reinforcing-bar splices ensure continuity above the

Rigorous tests performed on an experimental structure
proved the success of the PRESSS program’s
connection technology.
A moment-frame beam form illustrates the center PVC
duct that holds the prestressing tendons and the six
corrugated tubes for the mild steel bars used in the
hybrid system.
beam. As the frame displaces laterally, the debonded strand remains elastic.
While the system dissipates relatively less energy than other systems, it re-
centers the structure after a major seismic event (see Reference 4).
Although this frame has performed satisfactorily in tests, it would not be
allowed to act as the sole seismic-force-resisting system in regions of high
seismic risk or for structures assigned to high seismic-performance or design
categories under Section 21.6.3 of ACI 318.
Such frames can be designed to satisfy all requirements for use as interme-
diate moment frames. These frames should also be acceptable for intermedi-
ate moment frames when designed using the same factors as those specified
in the governing building code for cast-in-place concrete construction.
Analyses are still being done to verify the applicability of this system to
various high seismic events. In the interim, the satisfactory performance of
the frames in the PRESSS tests can be used to seek building-department
approval for these designs in moderate seismic-risk zones and for structures
assigned to intermediate seismic performance or design categories (see
Reference 5).
3. A shear-wall system. The PRESSS shear-wall design used an innovative
approach for anchoring and connecting jointed walls to lengthen the struc-
tural period and reduce the design-based shear forces. Gravity loads were
mobilized to partially resist overturning from the lateral ground motions. The
system also considered the behavior of the jointed shear-wall system when
the wall lifts off and rocks, along with its effect on design forces. An important
level of hysteretic damping was added to the wall system through the connec-
tion devices located at the vertical joint between the wall panels.
U-shaped flexure plates were used for vertical joint-connection devices
where damping was achieved with flexural yielding of the plates. Unbonded
post-tensioning forces re-centered the wall system when the load was
removed, so there would be minimal residual drift after a design-level earth-
quake. Re-centering was ensured by relating the elastic capacity of the post-
tensioning system to the yield strength of the panel-to-panel connection.
The shear wall is expected to displace laterally to approximately 2% of story
drift under a design-level earthquake. This is consistent with the drift limits
specified by existing standards. Should the designer desire smaller design-
story drift or less energy dissipation, the balance of post-tensioning and
energy-dissipating connections could be altered (see Reference 6).
This shear-wall design and test has led to the adoption of an allowance for
nonemulative design of special precast concrete shear walls to be accepted
for the 2003 edition of the National Earthquake Hazard Reduction Program
(NEHRP) Provisions (see Reference 7).

Resources:
IBC-1-01: Impact of the Seismic Design Provisions of the International Building Code.
MNL-123-88: Design and Typical Details of Connections for Precast and Prestressed Concrete, Second Edition.
Ascent:
“Apartment Skyscraper Shows Precast’s Seismic Capabilities,” Ascent, Summer 2000, pp. 40-43.
“Newly Proven Seismic Connections Impact Designers and Owners,” Ascent, Spring 2000, pp. 38-40.
“The Paramount, Special Awards,” Ascent, Fall, 2002, p. 7.
“Precast Seismic Innovations Aid Designs Across Nation,” Ascent, Winter 2000, pp. 16-23.
“PRESSS Test Building, Building Awards,” Ascent, Fall 2001, p. 40.
PCI Journal:
“Behavior of Connections and Floor Diaphragms in Seismic-Resisting Precast Concrete Buildings,” PCI Journal, March-April 2005, pp. 56-75.
“Codification of Precast Seismic Structural Systems: An Update,” PCI Journal, May-June 2006, pp. 46-49.
“Design-Construction of The Paramount—A 39-Story Precast Prestressed Concrete Apartment Building,” PCI Journal, July-August 2002, pp. 56-71.
“Ductile Connections in Precast Concrete Moment Resisting Frames,” PCI Journal, May-June 2006, pp. 66-77.
“Hybrid Post-Tensioned Precast Concrete Walls for Use in Seismic Regions,” PCI Journal, September-October 2002, pp. 36-59.
“A Hybrid Reinforced Precast Frame for Seismic Regions,” PCI Journal, March-April pp. 20-33.
“Requirements for the Use of PRESSS Moment-Resisting Frame Systems,” PCI Journal, March-April 2004, pp. 98-103.
“Seismic Design of Lightly Reinforced Precast Concrete Rectangular Wall Panels,” PCI Journal, July-August 2002, pp. 104-121.
“Seismic Design of Partially Post-Tensioned Precast Concrete Walls,” PCI Journal; July-August 2005, pp. 100-125.
“Seismic Design Methodology for Precast Concrete Diaphragms Part 1: Design Framework,” PCI Journal, September-October 2005, pp. 68-83.
“Seismic Design Methodology for Precast Concrete Diaphragms Part 2: Research Program,” PCI Journal, November-December 2005, pp. 14-31.
“Seismic Design Provisions in U.S. Codes and Standards: A Look Back and Ahead,” PCI Journal, January-February 2002, pp. 94-99.
“Seismic Design Recommendations for Precast Concrete Diaphragms in Long Floor Span Construction,” PCI Journal, November-December 2003, pp. 46-64.
“Seismic Tests of Beam-to-Column Connections in a Precast Concrete Frame,” PCI Journal, May-June 2002, pp. 70-89.
“Structural and Economic Benefits of Precast/Prestressed Concrete Construction,” PCI Journal, July-August 2001, pp. 34-43.
“Trends in the Seismic Design Provisions of U.S. Building Codes,” PCI Journal, September-October 2001, pp. 98-103.
“Untopped Precast Concrete Diaphragms in High-Seismic Applications,” PCI Journal; November-December 2002, pp. 94-99.
1. “Achieving Sustainability with Precast Concrete,”
PCI Journal, January-February 2006, pp. 42-61.
2. Chapter 3.2.4, “Earthquake Loads,” MNL-120-04:
3. “Precast Seismic Innovations Aid Designs Across
Nation,” Ascent, Winter 2000, pp. 16-23.
5. “Codification of Precast Seismic Structural
Systems: An Update,” PCI Journal, May-June
2006, pp. 46-49.
7. “Codification of Precast Seismic Structural
Systems: An Update,” PCI Journal, May-June
2006, pp. 46-49.
References:
Contract Document Requirements
Many precast concrete buildings are designed by a team including the engineer
of record, the precast manufacturer’s engineer, and possibly a specialty engineer
retained by the manufacturer. It is the engineer of record’s responsibility to pro-
vide pertinent information on the contract documents so that others providing the
seismic design of the structure use the correct information for the location of the
project. The 2006 International Building Code indicates what these requirements
are in Section 1603.

Eight-four unit assisted-living facility built to withstand
an F-4 tornado. Photo: Dukane Precast Inc.
Wind Resistance (Tornados and Hurricanes)
In most areas of the United States using IBC 2003, the earthquake loading will
be more critical than wind. But wind loads should be checked, and more empha-
sis today is being put on designing structures to withstand tornado and hurricane
impacts, certainly in coastal areas where they are being addressed through
supplemental codes and other local requirements.
Precast concrete structural systems and architectural panels provide significant
benefits in meeting wind-resistance needs. A calculation for determining proper
windloads for precast concrete structures can be found in MNL-120-04: PCI
Design Handbook, Sixth Edition (see Reference 1).
Tornados
Single-family homes provide the greatest danger of destruction during a
tornado. In regions of the country where tornados can wreak havoc on single-
family homes, precast concrete designs can provide a durable, wind-resistant
structure. Several key elements are desired in designing a home to resist tornado
damage. These include:
• Connections that securely tie the house together from roof to foundation,
providing protection for winds up to 130 mph.
• Impact-resistant roof materials that better withstand high winds and fire.
• Windows and doors with higher wind- and water-design pressure ratings and
a garage door capable of withstanding impact from large objects.
• Construction materials and siting work that eliminate the threat of flood or
wildfire.
A number of designers and precasters have worked together to create precast
concrete housing designs across the country. These designs not only protect
homes from wind damage but also cut energy costs, are constructed quickly
and provide a range of aesthetic designs that can blend with any neighborhood
(see Reference 2).
A variety of precast concrete components are used to create tornado-resistant
housing. These include foundation walls, loadbearing precast concrete wall panels
with an architectural finish, and hollow-core plank for floors and roofing. Precast
concrete’s inorganic and noncombustible composition ensure the housing will not
generate mold or mildew following torrential rains, nor will they catch on fire should
sparks ignite flammables.
Hollow-core plank is a key component in housing. Typically, one thickness is
used as the lower level’s ceiling and the upper level’s floor. It is also used as the
roofing substructure, again serving as the ceiling of the lower level at the same
time. The long spans available with hollow-core planks are particularly useful for
opening up interiors while providing a safe room for protection from high winds.

The actual cannon used. Spectators
even got to touch the 2 x 4 to
confirm the authenticity. In the
distance are the panels ready to be
tested with the safety wall behind.
Photos: Susan Leader.
In test one, the 2 x 4 went through this vinyl
sided, wood-frame wall panel like a hot knife
through butter. Notice the entry, and the exit
holes. Not only are they clean holes, but it didn’t
even slow the projectile down.
Note as well the significant hole in the safety wall
behind the panel in the photo to the right.
Precast concrete panels offer several different uses in housing designed to with-
stand tornados, including façades and foundation walls. Insulated panels, typi-
cally 10 by 16 ft in size, are used as foundation walls, with an insulating board on
their back (interior) side. The walls offer more than twice the strength of concrete-
block walls (5000 psi compared to 2000-2400 psi) and minimize seams through
which moisture can penetrate.
Precast concrete homes provide significantly more protection from wind-borne
debris than other building materials, according to tests conducted by the Portland
Cement Association. The group tested various walls with the impact of a 2x4
wood stud traveling at 100 mph, the equivalent of wind-borne debris during a tor-
nado with 250-mph winds. About 90% of tornados have wind speeds of less 150
mph, the group says. Of all materials tested, only the concrete design stopped
the debris from penetrating the wall. All others suffered penetration
(see Reference 2).

Now for the real test: hurl a 2 x 4
at a precast wall panel at 112 mph.
The result: no damage visible, not even
a chip.
Test three smashed a 2 x 4 through a brick home with steel framing. This damage is still rather significant, but in this
test the projectile did not travel through the wall. Looking at the back side shows it would take only slightly more force
to push all the way through.
Test two shot the 2 x 4 through a brick wall with wood frame. Surprisingly, it’s not all that much safer then siding. What
you don’t see are the pieces of brick that went flying through the back side of the panel. This wall introduced even
more projectiles into the house.

Wall Type: Test Wall Description:
Speed of
Debris:
Results:
Wood frame:
5
/8-in. gypsum board interior finish, 2x4 wood
studs at 16 in. o.c., 31
/2-in. batt insulation,
3
/4-in. plywood sheathing, vinyl-sided exterior
finish
109 mph
The debris missile perforated
completely through the wall
assembly. Little damage to
missile.
5
studs at 16 inches o.c., 31
/2-in. batt insulation,
3
/4-in. plywood sheathing, 4-in. brick veneer
with 1-in. air space
69.4 mph
completely through the brick
veneer and the interior finish.
Minor damage to missile.
Steel frame:
5
/8-in. gypsum board interior finish, steel studs
at 16 in. o.c., 31
/2 in. batt insulation, 3
/4-in.
plywood sheathing, vinyl-sided exterior finish
103.5 mph
assembly. Little damage to
missile.
5
studs at 16 in. o.c., 31
/2-in. batt insulation, 5
/8-
in. gypsum board sheathing, synthetic stucco
exterior finish
50.9 mph
assembly. No damage to missile.
Concrete:
6-in.-thick reinforced concrete wall, #4 vertical
reinforcing bars, 12 in. o.c, no finishes
109 mph
No cracking, front-face scabbing,
or back-face spalling of concrete
seen.
6-in.-thick reinforced concrete wall, #4 vertical
reinforcing bars, 24 in. o.c, no finishes
102.4 mph
seen.
ICF:
Block ICF foam forms, 6-in.-thick flat concrete
wall, #4 vertical reinforcing bars, 12 in. o.c.,
vinyl siding (tested twice with similar results)
103.8 mph
Debris penetrated vinyl siding
and foam form. No cracking,
front-face scabbing, or back-face
spalling of concrete wall seen.
Block ICF foam forms, 6-in.-thick flat concrete
3-in. brick veneer with ties spaced 1 in. each
way
99 mph
Debris penetrated and cracked
brick veneer. Foam form dented.
wall seen.
Panel ICF foam forms, 4-in.-thick flat concrete
vinyl siding
96.7 mph
Debris penetrated vinyl siding
and foam form. No cracking,
front-face scabbing, or back-face
spalling of concrete wall seen.
Block ICF foam forms, variable thickness
“waffle” concrete wall, 6 in. maximum
thickness, and 2 in. minimum thickness,
#4 vertical reinforcing bars in each 6-in.
vertical core at 24 in. o.c, synthetic stucco
finish (tested twice with similar results)
100.2 mph
Debris penetrated synthetic
stucco finish and foam form.
Impact of wall at 2-in.- thick
section. No cracking, front-face
scabbing, or back-face spalling
of concrete wall seen.
Note: All concrete tested had 3000-psi compressive strength with a maximum aggregate size of 3/4 in. with a 6-in. slump.
Source: Portland Cement Association

Much of the damage done to precast concrete parking
structures along the Gulf Coast by Hurricane Katrina
was caused by the high storm surge, which flooded
the structures and caused double tees to be puched off
their supports. Otherwise, the material performed well.
(Three photos below).
Hurricanes
The devastating impact of recent hurricanes, notably Katrina and Rita, have put
a spotlight on designing to withstand the highest levels of these forces, which are
more complex than those associated with tornados. Hurricanes produce not only
high winds but also forces associated with the impact from high waves and im-
mense amounts of water overwhelming a structure.
Precast concrete components can help to withstand these forces if designers
take into account all of the actions involved and how the components must react
to them. The factors that designers must consider include:
1. High winds, which can be dealt with similarly to those in tornados and do not
pose a substantial risk for buildings built of precast concrete. Examination of
projects exposed to the high winds of Hurricane Katrina indicated that wind
loads for precast concrete buildings were well accounted for. Wind-borne
debris creates the largest problem and results in only chipping or cracking in
some instances at the high end of the wind speeds.
To be certain of withstanding wind loads in these high-risk areas, designers
should overcompensate for potential problems. Designing for a 200-mph wind
and using reinforcement to meet that level of force should protect the struc-
ture under any situation. Modifying designs to reduce surface area will also
help to ensure that wind loads do not create a problem.
2. Surge, in which large amounts of water rush over the land and up to build-
ings. Often, this water carries with it loose debris that can be substantial in
nature and can act as a battering ram against a building. In some cases, if
the surge is high enough, the debris can impact the building at a height that
was not designed to withstand such force. This can cause damage to the
stems on double tees, particularly on parking structures. Creating a precast
concrete soffit or other protective shield that prevents large debris from surg-
ing through the structure at such a height can mitigate this concern.
3. Scour, which results from water surging beneath a slab on grade. This action
loosens the soil beneath the concrete, causing it to deteriorate or break up,
resulting in the supported building tilting or becoming unstable. This can be
prevented by using precast concrete pilings or columns to create a stable soil
foundation on which the slab can be poured.
Photo: ©PhotoDisc.

Resources:
Chapter 3.2.2, “Wind Loads,” MNL-120-04: PCI
Design Handbook, Sixth Edition.
Ascent:
“All-Precast Concrete Residences Benefits
Developers, Homeowners,”Ascent, Summer 2002,
pp. 28-30.
“Archer Courts Townhouses, Building Awards,”
Ascent, Fall 2005, p. 32
“Designing for Hurricane Zones,” Ascent, Summer
2006, pp. 20-25.
“Precast Lofts Help Build Chicago Neighborhood,”
Ascent, Summer 2003, pp. 16-19.
“Precast Design Adds Safety To Residences,”
Ascent, Spring 2005, pp. 18-22.
“University Village Mid-Rise Condominiums,
Building Awards,” Ascent, Fall 2004, p. 34.
PCI Journal:
“NU Precast Concrete House Provides Spacious
and Energy-Efficient Solution for Residential Con-
struction,” PCI Journal, May-June 2005, pp. 26-39.
“Project Study: Archer Courts Townhouses,
Chicago, Illinois,” PCI Journal, November-
December 2005, pp. 96-101.
“University Village Mid-Rise Condominiums,
Chicago, Illinois,” PCI Journal, May-June 2005,
pp. 108-111.
1. Chapter 3.2.2, “Wind Loads,” MNL-120-04:
2. “Designing for Hurricane Zones,” Ascent,
Summer 2006, pp. 20-25.
3. “Achieving Sustainability with Precast
Concrete,” PCI Journal, January-February
2006, pp.42-61.
References:
4. Buoyancy, in which the water levels rise above the first floor of a structure,
such as a parking structure, where the levels are supported by double tees.
Designs typically do not account for tees being lifted from their position.
Connections must account for this possibility in the areas of the highest concern.
5. Structure orientation, which should provide the smallest exposure to the
likely direction of a hurricane in areas most likely to be hit. Interiors also
should take the concept of surging water into account. For instance, in park-
ing structures, ramps should be faced away from the ocean to allow water
to flow through the structure rather than be blocked by it. Creating fewer
obstacles for the likely path that water will follow during a hurricane will
minimize damage.
Salt-water damage, in the form of corrosion or deterioration of the components
after water recedes, should not create a long-term problem. In many instances,
precast concrete components produced for these marine environments already
include additives that hinder the potential for corrosion.
Home Designs
Designing homes for wind loads can follow the same concepts as expressed for
tornado designs, and these concepts are available throughout the country from
precasters. Meeting the needs for protecting against surging water requires ad-
ditional consideration.
With surges in New Orleans, La., of 12 ft or more, one design option is to use
precast concrete piles or columns to create a first-level garage on top of which
the living space can be created, using precast concrete panels to create the
shell.
The home still can have wood and drywall interior framing, although if the surge
or other water damage reaches the interior, all these materials may have to be
completely removed to remediate mold. Even then, the shell and structural integ-
rity remain intact, eliminating the need to start from scratch (see Reference 2).
Concrete is not damaged by water. In fact, concrete that does not dry out con-
tinues to gain strength in the presence of moisture. Concrete submerged in water
absorbs small amounts of water over long periods of time, and the water does
not damage the concrete. In flood-damaged areas, concrete buildings are often
salvageable.
Concrete will only contribute to moisture problems in buildings if it is enclosed in
a system that does not let it breathe or dry out, and moisture is trapped between
the concrete and other building materials. For instance, vinyl wallcoverings in
hot and humid climates will act as a vapor retarder, allowing moisture to become
trapped between the concrete and wall covering. For this reason, impermeable
wallcoverings (vinyl wallpaper) should not be used (see Reference 3).

Lloyd D. George Federal Courthouse, Las Vegas, Nev.;
Architect: Langdon Wilson; Photo: Langdon Wilson.
The first major federal courthouse built after the 1995
blast in Oklahoma City contains features intended to
avoid a catastrophic collapse in the event of a terrorist
attack. The precast concrete panels were designed to
be more ductile than conventional panels so they could
absorb as much of a bomb blast as possible without
destroying the connections that tie them to the main
structure. Note: Bollards used to increase the standoff
distance.
External Blast Resistance
In today’s environment of enhanced risk, some facilities require protective
design and the management of risk. There are many design options available to
reduce the risk to any building. Economically feasible design for antiterrorism/
force protection (AT/FP) requires an integrated approach encompassing many
aspects of the development, including siting, operation programming of interior
spaces, and the use of active and passive security measures using provisions of
both technology and human involvement.
The objective of blast-resistant design is to provide an acceptable level of safety
to building occupants in the event of an explosion. Considerable damage is usu-
ally acceptable as long as components remain attached to the building and the
building does not experience a progressive collapse.
Planning must include all involved members of the design team (owners,
architects, structural engineers, and blast consultants). They must agree upon
the blast forces to be withstood as well as the risk and vulnerability assessment
to the occupants and the protection levels that can be achieved within budget.
Probability Considerations
An awareness of a blast threat from the beginning of design helps to make deci-
sions early about what the priorities should be for the facility. Including protective
measures as part of the discussion regarding trade-offs early in the process helps
to clarify the issues.

The willingness to pay the additional cost for protection against blast hazards is
a function of the “probability of regrets” in the event that a sizable incident occurs.
In some situations, with some buildings, the small probability of an incident may
not be compelling enough to institute the design enhancements.
This logic will likely lead to a selection process in which buildings stratify into
two groups: those that incorporate no measures at all or only minimal provisions
and those that incorporate high levels of protection. It also leads to the conclusion
that it may not be appropriate to consider any but the most minimal measures for
most buildings.
Key Considerations
Unlike seismic and wind loads, blast loads have an extremely short duration
(i.e., milliseconds). Often, the large mass associated with the overall building
response provides enough inertia so the building’s framing does not need to be
strengthened to resist blast loads. The lateral force-resisting system on smaller
one- and two-story buildings generally needs to be designed to resist blast loads.
Conventional foundation systems are almost always adequate to resist the short-
duration reaction loads from building response to blast loads.
Quantifying blast events into overpressures and time durations is a science of
its own. Blast engineers should be consulted when explosion scenarios are to be
considered in the building’s design.
A key consideration will be designing the building’s façade, which is the struc-
ture’s first defense against an exterior explosion. How the façade responds to this
loading will significantly affect the structure’s behavior. The need for comprehen-
sive protection of occupants within the structure will likely cause window sizes to
decrease in height and width and increase in thickness. Attachments likewise will
become more substantial.
Architectural precast concrete can be designed to mitigate the effects of an
explosion and thereby satisfy requirements of the General Services Administration
(GSA) and the Department of Defense (DOD). Protecting the entire façade, how-
ever, will impose a great cost regardless of the material used. To provide the best
protection for occupants, designers should plan for the building and its cladding
to remain standing or attached long enough to protect occupants from injury or
death resulting from flying debris and to evacuate everyone safely (see Reference
1).
The shape of the building can affect the overall damage. A U- or an L-shaped
building can trap the shock wave, which may increase blast pressure locally
because of the complex reflections created. Large or gradual re-entrant corners
have less effect than small or sharp re-entrant corners. In general, convex rather
than concave shapes are preferred. The reflected pressure on the surface of a
circular building is less intense than on a flat building (see Reference 2).
Currently, no specific standards or guidelines exist for blast design from either
the American Concrete Institute (ACI) or the PCI.

All building components requiring blast resistance should meet the criteria
required for GSA or DOD facilities. They should be designed using established
methods and approaches for determining dynamic loads and dynamic structural
response. Design and analysis approaches should be consistent with the follow-
ing manuals:
• U.S. Departments of the Army, Navy and Air Force, “Structures to Resist
the Effects of Accidental Explosions,” Revision 1 (Department of the Army
Technical Manual TM 5-1300, Department of the Navy Publication NAVFAC
P-397, Department of the Air Force Manual AFM 88-22).
• DAHSCWEMAN, “Technical Manual – Design and Analysis of Hardened
Structures to Conventional Weapon Effects; PSADS (Protective Structures
Automated Design System), Version 1.0.” (It incorporates Army TM 5-855-1,
Air Force AF JMAN32-1055, Navy NAVFAC P-1080, and Defense Special
Weapons Agency DAHSCWEMAN-97).
• Unified Facilities Criteria, “Design and Analysis of Hardened Structures to
Conventional Weapons Effects,” U.S. Department of Defense, UFC 3-340-01,
June 2002.
• Hyde, D. “ConWep – Application of TM5-855-1,” U.S. Army Engineer
Waterways Experiment Station, Vicksburg, Miss., August 1992.
• U.S. Department of the Army, Security Engineering, TM 5-853 and Air Force
AFMAN 32-1071, Volumes 1-4, Washington, DC, Departments of the Army and
Air Force, 1994.
• Air Force Engineering Services Center, “Protective Construction Design
Manual,” ESL-TR-87-57, Prepared for Engineering Services Laboratory,
Tyndall Air Force Base, Fla., November 1989.
• U.S. Department of Energy, “A Manual for the Prediction of Blast Fragment
Loadings on Structures,” Revision 1, DOE/TIC 11268, Washington, DC,
Headquarters U.S. Department of Energy, July 1992.
• Unified Facilities Criteria, DOD Minimum Antiterrorism Standards for Buildings,
UFC 4-010-01, U.S. Department of Defense, July 2002.
• Interim Antiterrorism/Force Protection Construction Standards – Guidance on
Structural Requirements (Draft), U.S. Department of Defense, March 5, 2001.
Designing for blast resistance requires a comprehensive knowledge of explo-
sive effects and fortification sciences, as described in DAHSCWEMAN (1998), in
Technical Manual (TM) 5-855-1 (U.S. Department of the Army 1998), and in the
Tri-Service Manual (TM-5-1300, U.S. Department of the Army, Navy, and Air Force
1990). The electronic version of the DAHSCWEMAN manual will greatly assist in
applying blast-design concepts.
The report “Design for Physical Security—State of the Practice Report,” pre-
pared by the Structural Engineering Institute Task Committee, American Society of
Civil Engineers (1999), addresses the design of structures to resist the effects of
terrorist bombings and provides guidance for engineers (see Reference 3).

Nimitz-MacArchur Pacific Command Center, Oahu,
Hawaii; Architect: Wimberly Allison Tong Goo Design;
Photo: Gary Hofheimer Photography.
Creating Standoff Distance
Basic protection is produced by creating a minimum guaranteed distance
between the blast source and the target structure. The setback zone restricts
vehicular access by using dense components such as perimeter anti-ram bol-
lards, large planters, low-level walls, or fountains. Creating this standoff distance
helps minimize the design requirements for protecting the building cladding and
structural elements.
The blast pressure is inversely proportional to the cube of the distance from the
blast to the point in question. Current design standoff distances for blast protec-
tion vary from 33 ft to 148 ft, depending on the building’s function.
The four lowest stories of the building will be most impacted by a street-level
blast and must follow accepted blast criteria. Those criteria are described in
“Security Design Criteria for New Federal Office Buildings and Major Renovation
Projects,” issued May 28, 2001, by the Interagency Security Committee (ISC).
When designing with architectural precast concrete panels, designers should
combine these criteria with the applicable blast-analysis standards. This combina-
tion ensures that the architectural precast concrete cladding system will be suf-
ficiently sized, reinforced, detailed, and installed to resist the required blast-loading
criteria.
The panels should also be tested in accordance with “Standard Test Method for
Glazing and Window Systems Subject to Dynamic Overpressure Loadings (GSA-
TS01-2003), released by the General Services Administration.
In addition to safely transferring the blast pressures into the supporting struc-
ture, the panels must be checked for their capacity to transfer the additional load-
ing caused by the specified window framing and the blast-resistant glass units
(see Reference 4).
Preventing Progressive Collapse
Several significant factors must be considered when designing buildings for
blast resistance. These concepts include energy absorption, safety factors, limit
states, load combinations, resistance functions, structural-performance, and
structural redundancy to prevent progressive collapse of the building. This final
one is most important, as a design satisfying all required strength and performance
criteria would be unsatisfactory without redundancy.
To limit the extent of collapse of adjacent components requires five steps:
1. Highly redundant structural systems are designed.
2. The structure is analyzed to ensure it can withstand removal of one primary
exterior vertical or horizontal load-carrying element, such as a column, beam,
or portion of a loadbearing or shear-wall system without complete collapse of
the entire structure.
3. Connections are detailed to provide continuity across joints equal to the full
structural capacity of connected members.

The 6-in.-thick x 22-ft-tall panels were reinforced with
ribs spaced 6 ft apart.
4. Floors are designed to withstand load reversals due to explosive effects.
5. Exterior walls use one-way wall components spanning vertically to minimize
blast loads on columns.
Strength and ductility (energy-dissipating capacity) are necessary to achieve
high energy absorption. The structural materials and details must accommodate
relatively large deflections and rotation to provide redundancy in the load path.
Components with low ductility are undesirable for blast-resistant design.
Margins of safety against structural failure are achieved by using allowable
deformation criteria. Structures subjected to blast loads are typically allowed to
undergo permanent plastic deformation to absorb the explosion energy, whereas
response to conventional loads is normally required to remain in the elastic range.
The component’s response is determined by how much deformation it is able to
undergo before failure.
The more deformation the structure or member can provide, the more blast
energy it can absorb. As long as the calculated deformations do not exceed the
allowable values, a margin of safety against failure exists (see Reference 5).
Rigidity versus Ductility
A balance must be found between panel stiffness and the forces that the panel
connections must resist. The proper balance must be evaluated by the structural
engineer. Typically, the panels should have increased section thickness or ribs
and have additional reinforcement, which should be placed on both faces of the
panel to resist load reversals. However, the amount of flexural reinforcing should
be limited so that tensile reinforcing yields before concrete crushing can occur.
Shear steel can help increase shear resistance, confine the flexural reinforcing,
and prevent buckling of bars in compression. The mode of failure should be that
of the panel itself in flexure and not failure of the connections or a shear failure of
the panel.
A minimum panel thickness of 5 in., exclusive of reveals, should be designed.
The panels also should include two-way reinforcing bars spaced not greater than
the panel’s thickness to increase ductility and reduce the chance of flying concrete
fragments. The thinnest panel thickness acceptable for conventional loads should
be used. The objective is to reduce the loads transmitted into the connection,
which must resist the panel’s ultimate flexural resistance (see Reference 6).
The following features typically are incorporated into precast concrete panel
systems to accommodate blast loading:
• Panel sizes should be increased to two stories tall or one bay wide, at least,
to increase their ductility. Panels can then absorb a larger portion of the blast
energy and transfer less through connections to the main structure.
• Panels should be connected to floor diaphragms rather than to columns, to
prevent applying lateral loads to the columns.

Resources:
DN-14-04: Designer’s Notebook: Blast
Considerations.
1. DN-14-04: Designer’s Notebook: Blast
Considerations, Introduction, p. 2.
Considerations: Blast Basics, p. 3.
3. DN-14-04: Designer’s Notebook: Blast Consid-
erations: Blast Analysis Standards, pp. 5-6.
erations: Standoff Distance, pp. 13-14.
erations: Design Concepts, pp. 14-16.
Considerations: Architectural Precast Concrete
Cladding, pp. 19-20.
Considerations: Architectural Precast Concrete
Cladding, pp. 19-20.
8. DN-14-04: Designer’s Notebook: Blast Con-
siderations: Connection Concepts and Details,
pp. 21-24.
References:
• Panels may be designed with integrally cast and reinforced vertical pilasters
or ribs on the back to provide additional support and act as beams that span
floor-to-floor to take loads. This rib system makes the panels more ductile and
better able to withstand an external blast, but it also forces the window fenes-
tration into a punched-opening symmetry.
Loadbearing precast panels must be designed to span failed areas through
arching action, strengthened gravity connections, secondary support systems,
or other ways of providing an alternative load path (see Reference 7).
Connection Concepts
Precast concrete wall-panel connections for blast-loading conditions can be
designed as strengthened versions of conventional connections, with a likely sig-
nificant increase in connection hardware. They also may be designed as connec-
tion details that emulate cast-in-place concrete to provide building continuity.
For a panel to absorb blast energy and provide ductility while being structurally
efficient, it must develop its full plastic-flexural capacity, which assumes the de-
velopment of a collapse mechanism. The failure mode should result in yielding of
the steel, not the connection splitting, spalling, or pulling out of the concrete. This
means that structural steel connection material must be designed for 5% to 10%
more than tensile and yield strength. The connection’s shear capacity also should
be at least 20% higher than the member’s flexural capacity.
Steel-to-steel connections should be designed so the weld is never the weak
link in the connection. Where possible, connection details should provide redun-
dant load paths, since connections designed for blast may be stressed to near
their ultimate capacity, and the possibility of single-connection failures has to be
considered. The number of components in the load path and the consequences of
a failure of any one of them will also be a factor.
The key concept in the development of these details is to trace the load or
reaction through the connection. This is more critical in blast design than in
conventionally loaded structures. Connections to the structure should have as
direct a load path as practical, using as few connecting pieces as possible.
It is also important that connections for blast-loaded members have sufficient
rotational capacity. A connection may have sufficient strength to resist the applied
load, but when significant deformation of the member occurs, this capacity may
be reduced due to rotation of the connection. Both bolted and welded connections
can perform well in a blast environment if they can develop strength at least equal
to that of the connected components (see Reference 8).
(For details on key connections used in precast concrete designs, see Chapter
4C “Connections.”)

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