Building materials

BRICKS Clay heated @ < 640 deg C --  only Physical change @ 700 -1100 deg C ---  chemical change, alumina & silica fuse together resulting in compound which is strong & stable  Brick @ > 1300 deg C --  above materials get vitrified (bricks lose shape) Brick size = 20 X 10 X 10 cm. – Nominal, Actual = 19 x 9 x 9 cm. Frog in a brick. Types of bricks (based on manufacturing process) : Wire-cut & Pressed brick Brick classification  General physical requirements  Class I, II, III (color, burnt, shape, water absorption 24 hrs in cold water by weight [20, 22, 25]), Efflorescence. I.S. Classification based on strength  10, 7.5, 5, 3.5. Test for bricks  compressive strength, water absorption [sat. coeff., IRA], Efflorescence,

Cement – process of manufacture

TriCalcium Silicate 3CaO.SiO 2 ~ C 3 S DiCalcium Silicate 2CaO.SiO 2 ~ C 2 S TriCalcium Aluminate 3CaO.Al 2 O 3 ~ C 3 A TetraCalcium Aluminoferrite 4CaO.Al 2 O 3 .Fe 2 O 3 ~ C 4 AF C 3 S + C 2 S constitute 65-75% by weight of cement and hydrate to form Ca(OH) 2 (~25%) and Calcium Silicate hydrate (~50%) (also called tobermorite gel). C 3 S ---- responsible for initial set and early strength C 2 S ---- increase in strength at ages beyond a week C 3 A ---- responsible for heat of hydration and also contributes slightly to early strength Reducing C 3 A increases sulfate resistance C 4 AF --- reduces clinkering temp. Hydrates rapidly but contributes very less to strength responsible for coloring effects. Type I ---- normal Type II --- moderate sulfate resistant Type III – high early strength Type IV – low heat of hydration Type V --- high sulfate resistant Type I,II,III A --- air-entraining variety

Type I ---- general use; where special properties are not required Type II --- general use; moderate sulfate resistance and heat of hydration Type III – when high strength required. Has similarity chemically with Type I but particles are ground finer. typical use cold or underwater structures Type IV – when low heat of hydration is required, typical use massive structures Type V --- when high sulfate resistance is required. Air-entraining materials --- improved resistance to freeze-thaw; scaling caused by chemicals applied for snow/ice removal White cement --- original color, grey comes in due to iron and manganese oxide, used for architectural purpose, curtain walls, tile grout and so on. Types of Ordinary portland cement used in India: grade 33, 43, 53 Fineness – greater cement fineness increases rate at which cement hydrates and accelerates strength development typically during the first week. Soundness – ability of the hardened paste to retain volume after set. (free lime and magnesia responsible for lack of soundness). More sound less shrinkage. Consistency – ability to flow. Depends on water-cement ratio. Setting time – affected by gypsum content, cement fineness, w/c ratio, admixtures Compressive strength – measured by 2 inch mortar cube. Compound composition and fineness of cement affects it. Heat of hydration – heat generated when cement and water react. Increase in w/c ratio, fineness of cement, curing temp increases heat of hydration. Specific gravity --- 3.15

Fineness measurement of cement (sq. cm per kg. of cement) Blaine’s air permeability test Wagner’s turbidimeter

Conduction calorimeter – Heat of hydration

Materials to supplement cement Contributes to the properties of hardened concrete through hydraulic or pozzolanic activity or both Pozzolan :- Sliciceous or aluminosiliceous material that in finely divided form and presence of moisture, chemically reacts with calcium hydroxide released by hydration of portland cement to form calcium silicate hydrate and other cementitious material Fly Ash Byproduct of combustion of pulverized coal in electric power generating plants During combustion, coal’s mineral impurities (clay, feldspar, quartz, shale) fuse in suspension and are carried away from combustion chamber by exhaust gas. The fused Materials cool and solidifies into spherical glassy particles. Silica, alumina, iron, calcium 1.9-2.8

Granulated blast-furnace slag Non-metallic hydraulic cement consisting essentially of silicates and aluminosilicates of calcium developed in a molten condition simultaneously with iron in blast-furnace. Molten slag rapidly chilled by quenching in water  glassy sandlike granulated material Silica Fume Byproduct obtained as a result of reduction of high purity quartz with coal in an electric-arc furnace in the manufacture of silicon or ferro-silicon alloy

Aggregates Natural sand/gravel deposits : deposited glacial formations, river deposits, or along beaches of lakes and seas. E.g. : limestone, granite, sandstone, etc. Crushed rock : Igneous rocks e.g. : basalt, granite. Sedimentary rocks e.g. : limestone, gypsum, shale, dolomite, sandstone Metamorphous rocks e.g. : slate, marble, quartzite, gneiss. Slag and mine refuse : Blast furnace slag , Industrial materials such as certain types of light volcanic rock, plastics used to produce lightweight concrete. Pulverized concrete and bituminous pavements substitute for natural aggregates which are costly; bituminous layers can be recycled and used in pavements. Other recycled and waste material : Crushed glass, rubber pellets, bricks, building rubble…

Fine aggregates- 4.75 mm (sieve No.4) to 75 microns (Sieve No.200) • Coarse aggregate- Greater than 4.75 mm (no.4) • Fines- Less than 75 microns (no.200) Classification

Grading of Aggregates ( Sieve analysis - ASTM C 136 ) Variation in grading can seriously affect the properties of concrete. The cement required for concrete is proportional to void content of combined agg. ASTM C33 grading for Fine-Aggregates (refer table in pg. 34) Fine agg. must not be more than 45% retained between any two consecutive standard sieves Fineness modulus 2.3 to 3.1 (do not vary between 0.2 from agg. source) (higher FM --- coarser aggregate) Fineness Modulus = 2.71 Average sieve size = No 30 Sieve # Sieve Size (mm) Weight Retained (g) Percent Retained (%) Percent Finer (cumulative percent passing) (%) Percent Coarser (cumulative % retained) (%) 3/8" 9.5 0 0 100 0 #4 4.75 60 2.84 97.16 2.84 #8 2.26 150 7.11 90.05 9.95 #16 1.18 400 18.96 71.09 28.91 #30 0.60 500 23.70 47.39 52.61 #50 0.30 510 24.17 23.22 76.78 #100 0.15 488 23.13 0.09 99.91 Pan - 2 0.09 0 100.00 Total 2110

Particle size distribution graph of fine aggregates Min. value Max value Sample

Absorption, Porosity and Permeability Absorption relates to the particle’s ability to absorb a liquid. Porosity is a ratio of the volume of the pores to the total volume of the particle. Permeability refers to the particle’s ability to allow liquids to pass through. Surface Texture The pattern and the relative roughness or smoothness of the aggregate particle. Plays a big role in developing the bond between an aggregate and a cementing material. A rough surface texture gives the cementing material something to grip, producing a stronger bond, and thus creating a stronger hot mix asphalt or Portland cement concrete. Strength and Elasticity Strength is the measure of ability of an aggregate particle to stand up to pulling or crushing forces. Elasticity measures the “stretch” in a particle. High strength and elasticity are desirable in aggregate Base and surface courses. These qualities minimize the rate of disintegration and maximize the stability of the compacted material.

Strength and Elasticity measure of ability of an aggregate particle to stand up to pulling or crushing forces. Elasticity measures the “stretch” in a particle. High strength and elasticity are desirable in aggregate base and surface courses. These qualities minimize the rate of disintegration and maximize the stability of the compacted material. Density and Specific Gravity Density is the weight per unit volume of a substance. Specific gravity is the ratio of the density of the substance to the density of water. Helps in determining the amount of asphalt needed in the hot mix asphalt. Aggregate voids There are aggregate particle voids and voids between aggregate particles. Most aggregate particles have voids, which are natural pores that are filled with air or water. It influence the specific gravity and absorption of the aggregate materials.

Specific gravity and water absorption Abrasion Resistance Soundness Impact Value Test Particle size and shape Aggregate voids Physical tests of Aggregates

Specific gravity (Relative density) ratio of the weight of the aggregate to the weight of an equal absolute volume of water (water displaced on immersion). These specific gravity of aggregates can be determined both at oven-dry state and at SSD state. Specific gravity at oven dry state --- Apparent SG Specific gravity at SSD state --- Bulk SG typically values range from 2.4-2.9 for natural aggregates Absorption capacity & Moisture content AC = (SSD weight – OD weight) * 100 / (OD weight) MC = (Sample weight – OD weight) * 100 / (OD weight) If MC of sample > AC  WET else DRY If WET then Surface Moisture = MC – AC Fine agg have higher surface moisture (surface tension) (2-6%) compared to Coarse agg (0.5-2%) Typically coarse agg. AC = 0.2-4% fine agg = 0.2-2% Bulking is increase in total volume of moist fine agg over same dry weight (due to surface tension). Finer the sand – higher bulking.

Concrete Concrete is itself a composite material. It is composed of aggregate and is chemically bound together by hydrated Portland cement . Aggregate = Sand + Gravel. Maximum size of gravel: Building construction = ¾ of an inch Bridge = 1 to 1 ½ inches Concrete = Sand + Gravel + Water + Cement

Workability Consistency Mobility Compactibility Workability depends on Proportion of aggregates Physical characteristics of aggregate and cement Equipment for mixing, transporting and compacting Size and shape of structure Workability increases with high cement content (not so sensitive) increased quantity of fine materials decrease in amount and surface area of coarse aggregates increase in water content Problems of workability Segregation Bleeding

Curing of fresh concrete to make hardened concrete Concrete curing should be done at 70 deg F for at least 7 days and kept continuously moist after initial set. (ACI 5.11). It gains 75% of its final strength In roughly 28 days. Moisture and Temp. => Influences process of concrete curing

Problems of improper curing: Shrinkage associated with loss of moisture from the gel particles of the paste Effects: if unrestrained, shortening of members => loss of prestress if restrained, induced tension, cracking. if asymmetric (eg. slabs on grade), curling and cracking

Reduction of shrinkage: low w/c ratio high aggregate content proper curing high pressure steam curing over normal curing (better results) water reducing admixtures decrease shrinkage retarding admixtures increase shrinkage strength durability modulus of elasticity creep shrinkage impermeability Mix proportions curing conditions environment Creep : Time dependant increase in deformation due to sustained loading. can occur in all types of loading : compression, tension, torsion The earlier the age at which loading is applied, the larger the creep creep higher in wet conditions than in dry conditions After load withdrawn : immediate recovery – elastic ; delayed recovery – creep recovery

Air entrained concrete Produced by using 1) air entraining cement or 2) air entraining agent. Air entraining agent enhances the incorporation of bubbles of various sizes by lowering surface tension of mixing water. Effects of increase in entrained air on concrete properties: Bleeding --- significantly reduced Bond to steel ---- reduced compressive strength --- reduced approx 2-6% per % point increase in air flexural strength --- reduced approx 2-4% per % point increase in air freeze-thaw resistance --- significantly improved modulus of elasticity --- decreases slump ---- increases sulfate resistance --- significantly improved unit weight --- decreases water demand --- decreases for same slump workability --- increases Factors affecting air-content: cement content, fineness increase --- decreases air content high alkali cements entrain more air than low alkali cements smaller aggregate size --- air content increases (no change beyond 1.5 in) more amount of fine aggregates ---- increases air content

Factors affecting air content mixing water increase ---- generates air bubbles --- more air content increase in vibration --- reduction in air content for constant amount of air-entraining admixture --- increase in slump increase air content up to about 6-7 in. concrete temp increase ---- less air entrained

Concrete admixtures Ingredients in concrete other than portland cement, water and aggregates which are added to the mixture immediately before or during mixing. Types of admixtures: Air entraining admixtures water reducing admixtures --- water/cement ratio reduced --- strength increase (plasticizer(8-15%), super-plasticizer (15-30%)) Retarding admixture --- retard rate of setting of concrete --- control heat of hydration --- hot weather application Accelerating admixtures --- accelerate strength development at early stage ---- cold weather applications and underwater applications Waterproofing admixtures --- cause capillary contraction resulting in impervious concrete (Aquaproof, cico, impermo) Mineral admixtures cementitous material --- granulated blast furnace slag, hydrated lime. pozzolonic material --- siliceous or aluminosiliceous material, in presence of water reacts with CaOH2 to form compound possessing cementitious properties -- fly ash, silica fume nominally inert materials --- raw quartz, dolomite, limestone

Lime Quicklime Hydrated lime / slaked lime Carbonation of hydrated lime results in calcium carbonate  cementing properties Sand added to lime  increase in bulk (leads to economy) to make mortar porous, so that air can circulate resulting in better carbonation Eminently hydraulic lime : structural work such as arch, dome Semi-hydraulic lime : constructing masonry Fat lime & Dolomite lime: finishing coat in plastering, white wash Kankar lime : masonry lime Siliceous Dolomite lime : undercoat and finishing coat of plaster Fibers in concrete

Mortar and Plaster Primary property : Bonding agent under different loading condition Masonry mortar Strength of mortar depends on strength of blocks it is binding. Should not be too off. Cement-sand mix ratio (Cement mortar) Damp-proof course -- 1:2 General brickwork -- 1:6 Stone masonry – 1:6 Brickwork below ground – 1:3 – 1:4 Cement plaster Brickwork plaster (inside + outside) – 1:5 R.C. Plaster – 1:4

Timber Hardwood Trees with broad leaves, enclosed nuts, and are found in high densities Mostly deciduous trees that drop their leaves annually Examples include Aspen, Birch, Elm, Maple Softwood Trees that are cone-bearing, leaves are needles Do not shed their needles annually Examples include Pine, Spruce, Cedar, Fir, and Douglas Fir

Knot Imperfection or defect that can be seen throughout in a board Caused from the branches or limbs that grow from the trunk Should not be placed in tension Green Timber Refers to lumber that has greater than a 15% absorption capacity Recently Harvested; “fresh” Resists splitting and cracking easily Air-Dry Timber Refers to lumber that has between 12%-15% absorption capacity Resists splitting easily as well Most desirable stage to work with Oven-Dry Timber Usually refers to timber with less that a 12% absorption capacity Splits easily

Seasoning of wood: Heat treatment as well as chemical treatment of wood to prevent its deterioration and restore strength Chemicals used include waterborne and oil-borne creosote.

Failure in timber structures shear Flexure Compression

Industrial timber products : Plywood Particle board (chipboard) Hardboard Fiberboard Blockboard Glulam

Bitumen, Asphalt & Tar Tar – dark colored product obtained from destructive distillation of organic substances like coal, wood and bituminious shales. Asphalt: A black or dark brown non-crystalline solid or viscous material, composed principally of high molecular weight hydrocarbons, having adhesive properties, derived from petroleum either by natural or refinery processes and substantially soluble in carbon disulphide. Asphalt = bitumen + inert mineral matter Bitumen is the binding material in asphalt

Asphalt is simply the residue left over from petroleum refining. Crude oil is heated in a large furnace to about 340° C (650° F) and partially vaporized. It is then fed into a distillation tower where the lighter components vaporize and are drawn off for further processing. The residue from this process (the asphalt) is usually fed into a vacuum distillation unit where heavier gas oils are drawn off. Asphalt cement grade is controlled by the amount of heavy gas oil remaining. Other techniques can then extract additional oils from the asphalt. Refining of Asphalt Depending upon the exact process and the crude oil source, different asphalt cements of different properties can be produced. Additional desirable properties can be obtained by blending crude oils before distillation or asphalt cements after distillation.

Types of Bitumen: Straight run Bitumen – bitumen distilled to a definite viscosity of penetration such that no further treatment like heating is required Blown bitumen – Liquid bitumen + pass air under pressure to remove volatile compoun Penetration grade – basic form, has to be heated before application Cutback bitumen – bitumen + petroleum distillates Bitumen Emulsion – product in liquid form formed in aqueous medium and stabilizing `agents Plastic Bitumen – bitumen thinner + suitable filler  plastic form Cutbacks – bituminious material in solvent Residual bitumen – solid substance at normal temp, obtd. as residue during distillation of high resin petoleum Modified bitumen – bitumen combined with plastic

Building materials

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