Concrete technology slides all.pdf

Benefits and limitation of Concrete
There are numerous positive aspects of concrete:
 It is a relatively cheap material and has a relatively long life with few
maintenance requirements.
 It is strong in compression.
 Before hardening it is a very pliable substance that can easily be
shaped.
 It is non-combustible. ( Good Resistance to heat)
The limitations of concrete include:
 Relatively low tensile strength when compared to other building
materials.
 Low ductability.
 Low strength-to-weight ratio.
 It is susceptible to cracking.

Concrete Strength
 Concrete strength is determined by the force required to crush it and
is measured in pounds per square inch or kilograms per square
centimetre or N/mm2.
 Concrete quality is directly related to the amount and properties of the
materials used, and the way that it is placed, finished, and cured.
 With proper materials and techniques, it can withstand many acids,
silage, milk, manure, fertilizers, water, fire, and abrasion.
 Concrete has substantial strength in compression, but is weak in
tension. Most structural uses, such as beams, and other flexure
members, involve reinforced concrete, which depends on concrete's
strength in compression and steel's strength in tension.
 The tensile strength of concrete can be improved with the addition of
metal rods, wires, cables or mesh.

Components of Modern Concrete
Constituent of Concrete
1. Air
(0-3% by volume)
2. Aggregate
(60-70% by volume)-
Inert Filler
3. Hydrated
cement paste (20-
40% by Volume)
4.Admixture (Optional)
Impart the properties of
concrete
Entrapped
Air
(Un-
intentional)
Entrained
Air
(Intentional)
Coarse
Aggregate
(Gravel)
Fine
Aggregate
(Sand)
Binding
Medium
(14-
21%)
Water
(7-
15%)
Chemical
Admixture
Mineral
or
Pozzolanic
Admixture
• Air
Entrapped Air (Un-intentional)- Void present due to insufficient compaction.
Entrained Air (Intentional)- Made by mixing a small quantity of air entraining
agent or by using air entraining cement. It will modify the properties of plastic
concrete regarding workability, segregation, bleeding and finishing quality etc.
as well as the properties of hardened concrete regarding its resistant to frost action
and permeability

Components of Modern Concrete
o Binding Medium- Cement (generally OPC), Lime
 Aggregate
 Water i. For Mixing ii. For Curing iii. ForWashing aggregate
 Admixture: -Admixture is defined as materials other than aggregate, cement and
water, which are added to the concrete batch immediately before or during mixing. It
imparts the properties of concrete.
Aggregate
Fine aggregate (sand) less than 4.75 mm size but larger than 75
(microns)
Coarse aggregate (gravel)  Larger than 4.75 mm and up to 75 mm (above
is boulder or Cyclopean aggregate)
Chemical Admixture Mineral or Pozzolanic Admixture
i. Accelerators ii. Retarders
iii. Air Entraining Admixture
iv. Plasticizer (water reducer)
v. Super plasticizer (High range water reducer)
i. Fly ash ii. Silica Fume
iii. Rice Husk Ash iv.Metakaolin
v Ground granulated blast furnace slag
vi Surkhi

Types of Concrete
Based on unit weight: -
•Normal Wt. Concrete = 2400 Kg/m3 (4000lb/yd3)
•Light Wt. Concrete (less than 1800kg/m3 = 3000 lb/y3)
•Heavy Wt. Concrete (more than 3200 Kg/m3 = 5300
lb/y3)
Based on strength: -
•Ordinary Concrete M10-M20
•Standard Concrete: M25-M60
•High Strength Concrete M65 and above
Based on materials used
•Cement Concrete
•Lime Concrete

Types of Concrete
Other types are: -
•Plain Cement concrete, Reinforced concrete, Pre-stressed concrete
•Lean concrete: - A plain concrete with a large aggregate to cement
ratio. It is used for filling and non-structural duties
•Structural concrete: - light wt. concrete of such a quality that, it is
suitable for load bearing members of structure.
•Cast in situ/cast in place concrete &Pre-cast concrete
•Pumpable / Vacuum concrete: which includes high water content to
allow enough workability to enable it to be placed into complicated
mould or around extensive reinforcement
•Ready mix concrete: concrete which is made at a mixing plant and
delivered to the site in special transport vehicle ( eg :Panchakanya)

Aggregate
 Aggregate is one of the main constituent of concrete which
occupy around 60 – 75% of the body of concrete
 Variation in aggregate property directly affects the property of
concrete (Strength, workability & durability).
 Chemically inert, inexpensive material distributed throughout
the concrete so as to produce large volume
 Acts as an economical space filler
 Provides rigidity, stability, durability and strength to concrete i.e.
Aggregate properties greatly influence performance of the
concrete.
 Depending upon its Origin
a. Natural aggregate
b. Artificial aggregate

SOURCE AND CLASSIFICATION:
Natural aggregate: Aggregate derived from natural source (eg,
quarries or river) by blasting, crushing or screening. Can be further
classified into:
i. Igneous: Normally all type of aggregate from igneous rock source
is considered suitable for concreting. Hard , tough , dense in
nature , e.g. Basalt Granite
ii. Metamorphic: As aggregate from metamorphic rock source
shows weak plane of foliation is not considered very suitable but
aggregate like quartzite & gneiss still produce good concrete of
its class.
iii. Sedimentary: The quality of aggregate from sedimentary rock
source varies considerably depending upon the pressure in
which original rock is compacted & cementing material in it.
Normally limestone, siliceous sandstone can produce good
quality concrete.

Igneous Metamorphic
Sedimentary

Artificial aggregate: Artificially made aggregate for special
concrete or industrial byproducts.
 Clean broken bricks: Obtained by cleaning broken bricks.
Not suitable for wear & tear surface & can be used in low to
medium strength concreting.
 Blast furnace slag: This is the byproduct of pig iron in blast
furnace.
 Steel shots: Steel aggregate made for high density concrete.
Used in nuclear plants.

II) Depending upon its Unit wt.:
 Light wt.: Aggregate with sp. gravity< 2.5. Used to produce
light weight concrete
 Medium wt.: Aggregate with sp gr. 2.5-2.7. Commonly used
in construction. Produce concrete with unit wt. 2300-
2600kg/m3.
 Heavy wt.: Aggregate with sp gr. >2.7. Normally used in
radiation shield. Eg, ferro-phosphorus 5.8-6.8, magnetite
4.2-5.2, iron shots 6.2 - 7.8 sp gr.

III) According to its Size:
 Fine Aggregate: Normally aggregate passing through 4.75mm sieve is
considered as fine aggregate. IS383:1970 further classified this into
various zone depending upon its fineness.
 Coarse Aggregate: Normally aggregate retained on 4.75mm sieve is
considered as coarse aggregate. Coarse aggregate is normally
represented by is nominal max size.

IV) According to its Shape:
 Round: Aggregate with round particles, directly obtained from river or
quarries without any processing. Fully formed by attrition e.g. water rock , sea
sand etc
 Angular: Aggregate with angular particles, obtained by manual or machine
crushing.
 Irregular: Aggregate comprising irregular aggregate type (between round &
angular aggregate).Partly formed by attrition e.g. Pit sand , shore gravel etc
 Flaky: Aggregate having its least dimension less than 0.6 times its mean
dimension.
 Elongated: Aggregate having its larger dimension greater than 1.8 times its
mean dimension.

 V) According to its Surface texture:
 Glossy: Aggregate having glossy surface:black flint, seashell
 Smooth: Aggregate with smooth surface texture. Eg, chert,
slate, marble etc
 Crystalline: Aggregate with crystalline surface texture. Eg,
basalt, dolerite, granite etc
 Granular: Aggregate formed essentially with granular
material. Eg, sand stone, oolite etc
 Honeycombed : Surface shows lumpy cavities
 Porous aggregate : Surface is made of numerous small pores
Eg, pumice

Vi) According to surface moisture:
 Very-very dry-which do not contains any moisture either in pores or
on the surface it is obtained by drying aggregate 24 h hrs. at -1100c
 Dry-aggregate: - which contains some moisture in pores but having
their surface dry.
 Saturated surface dry aggregate -all the pores are filled with
moisture but having their surface just dry.
 Wet or moist aggregate: - all the pores are filled with moisture and
also having their surface wet.
 Vii) According to mineralogical composition: According to
this classification aggregate may be siliceous calcareous etc. the
minerals in aggregate may be silica minerals, silicate minerals,
carbonate minerals, sulfide and sulphate minerals.

Grading of Aggregate:
Particle size distribution of aggregate is also termed as grading of aggregate.
Fine Aggregate:
Aggregate passing through 4.75mm sieve is considered as fine aggregate.
IS383:1970 further classified this into various zone depending upon its fineness.
Zone I represents the coarse while Zone IV represents the finer sand.

Grading of Aggregate:
 Coarse Aggregate:
 Normally aggregate retained on 4.75mm sieve is considered as coarse
aggregate.
 Gradation of aggregate
 Gradation of the method of keeping the aggregate in such a way that max.
density is achieved
 No- ideal grading
 There is two types of grading as per IS IS383:1970.
i. Single sized &
ii. Graded coarse aggregate

Grading of Aggregate: Sieve Analysis
Gap-grading
 Gap grading indicated by st. line in the grading curve.
 Gap graded aggregates are easier for compaction as small sized practices can fill the
gap.
 Gap grading is recommended for the low workable concrete.
 One dis-advantage is higher chances of segregation. So care should be taken during
handling.

Grading of Aggregate: Fineness Modulus
 FM is index no. used to indicate the average size of particles in the aggregate.
 It does not define the grading of aggregate because different grading can give the
same fineness modulus
 It is an empirical factor obtained by adding the cumulative percentage of the aggregate
retained on Set of sieves: 80mm, 40mm, 20mm, 10mm, 4.765m 2.36mm, 1.18mm,
600 microns, 300 microns and 150 microns and dividing the sum by 100. The larger
the figure, the coarser the material is.
FM =
∑ %
Aggregate (sand) FM It is recommended that FM of the
sand should not be less than 2.5
and not more than 3.0
Fine 2.2-2.6
Medium 2.6-2.9
Coarse 2.9-3.2

MCqs
 1. The fineness modulus of good sand shall be in the range of
a. 2-2.25 b. 2.5-3 c. 2-2.5 d. 3-3.2
2. The value of fineness modulus of fine sand ranges between
 a. 1.1 to 1.3 b. 1.3 to 1.6 c. 1.6 to 2.2 d. 2.2 to 2.6
3. Sand requiring high water cement ratio belongs to
 a. Zone I b. Zone II c. Zone III d. Zone IV
 (Surface texture of aggregate- Total surface of rough textured aggregate is
more than the surface area of smooth rounded aggregate of same volume i.e.
rough textured aggregate will show poor workability) This is the logic which
we use for this and ans is consistent with many books.. And that is different
for coarse aggregate where greater nominal size require less water
4. The fineness modulus of fine aggregates is between
 a. 2-3.5 b. 3.5-5 c. 5-6 d. 6-7.5
Answer 1.B 2.D 3.A 4.A

AGGREGATE PROPERTIES & METHOD OF TESTING:
 Sp. Gravity. (Picnometer method)
 Bulk Density. (Weight/Volume Test)
 Water absorption / Moisture content. (Absorption Test)

 Angularity Number (AN):
 It is measured in terms of % of void in excess of voids in perfectly rounded
aggregate (33%). The more angular the aggregate is, the more is the AN.
 The normal aggregate suitable for making concrete have angularity
number lying between 0 and 10. The rounded aggregate has Angularity
Number zero.
 When rounded aggregate is filled in a vessel, it leaves about 33% void in it.
If a well compacted Aggregate in the same vessel of rounded aggregate
leaves 43% voids then its Angularity Number is 10.
 This test is not applied for the aggregates which gets crushed during
compaction of this test.
Angularity number = 67-W*100/w*G
Where, W= weight of aggregate filled in cylinder
w= weight of water filled in the cylinder
G = specific gravity of aggregate
 Irregualr : 35 % to 37 % and Angular : 38 to 45% (D prasad)

 FLAKYNESS INDEX: can be define as percentages by weight of particle
with least dimension (thickness) less than 0.6 times its mean
dimension. (Not applicable for particle size less than 6.3mm)
 ELONGATION INDEX: can be define as percentages by weight of
particle with largest dimension (length) more than 1.8 times its mean
dimension.

 BULKING OF SAND:
 Free moisture content in aggregate results in the increase in
volume of aggregate also termed as bulking of aggregate.

MECHANICAL PROPERTIES
 Crushing strength (Compressive strength)- Resistance of
aggregate against crushing under gradually applied load -
Aggregate Crushing Test.
 Toughness (Impact Strength)- Resistance of aggregate
against impact load- Aggregate Impact Test.
 Hardness (Wearing Strength)- Resistance of aggregate
against wear - Aggregate Abrasion Test.

 Crushing strength (Compressive strength)
Resistance of aggregate against crushing under
gradually applied load - Aggregate Crushing Test.
The test specimen is cylindrical in shape of size 152 mm
internal diameter and 125 mm height.
Aggregate passing 12.5mm Sieve & retained 10mm sieve.
Aggregate placed on cylinderical mould & load of 40ton
is applied through plunger .
Aggregate finer than 2.36mm is separated & expressed
as Crushing Value. (Max. Limit = 30-45% )
30% for concrete used for roads and pavements and 45%
may be permitted for other structures.

Toughness (Impact Strength)/AGGREGATE
IMPACT VALUE (AIV)
Resistance of aggregate against impact load-
Aggregate Impact Test.
Aggregate passing 12.5mm Sieve & retained 10mm
sieve.
Weight of aggregate taken – 5 to 10 kg
Aggregate placed on cylinderical mould & load of
14Kg falling from 38CM ht. 15 Blow.
Aggregate finer than 2.36mm is separated &
expressed as Impact Value. (Max. Limit = 30-45% )
AIV – ratio of the weight of the fines formed to the
weight of the total sample taken

Hardness (Wearing Strength) /
LOS ANGELES ABRASION VALUE TEST
(LAAVT)
Resistance of aggregate against wear - Aggregate
Abrasion Test.
5 to 10 kg of aggregate is placed in a cylindrical
drum mounted horizontally with a shelf inside.
11 /12 sphere of 47/48 mm dia
The drum is rotated for about 500 cycles.
The tumbling and dropping of the aggregate and of
the balls result abrasion and attrition of the
aggregate.
Aggregate finer than 1.7mm is separated &
expressed as Abrasion Value. (Max. Limit = 30-50% )

 CHEMICAL PROPERTIES
 Normally aggregates are considered chemically inert material but some
aggregates shows active character toward various chemical reaction.
a) ALKALI AGGREGATE REACTION: Aggregates are normally inert material but some
aggregate may contain reactive silica which reacts with alkalis (Sodium /
Potassium oxide) present in cement called alkali aggregate reaction.

 Cement is considered as one of the most important constituent
of concrete as it acts as binding agent to whole concrete mass.
 Property of cement greatly affects the property of concrete; in
harden stage as well as in green stage.
CEMENT
Primary constituent of
Portland cement are:
1) Calcareous material
(Lime Stone, Chalk)
2) Argillaceous/
Siliceous material
(Clay, Shale etc)

 Process of manufacture of cement consists:
1) Proportioning of raw material
2) Grinding & intimate Mixing
3) Burning in kiln , with temperature upto 1500 deg C (which
form fused nodular shape clinker, which after cooling is
ground as fine powder mixing 3-5% gypsum)
Production of cement

Raw material of cement primarily consists of:
 Calcareous material (Lime Stone, Chalk)
 Argillaceous/Siliceous material (Clay, Shale etc)
Oxide Composition of which can be represented as:
Composition of cement

 After fusion the compound composition of Cement/Clinker
mainly consists of:
Composition of cement

 As identification of major compound in cement largely based on RH
Bogue’s work its also called Bogue’s compound & equation to
determine quantity of these compound from oxide composition of raw
material is called Bogue’s equation.
Set of Bogue’s equations:
1) %C3S (Alite) = 4.071 C – 7.600 S – 6.718 A – 1.430 F – 2.850 Ŝ
2) %C2S (Belite) = 2.867 S – 0.754 C3S
3) %C3A (Celite) = 2.650 A – 1.692 F
4) %C4AF (Felite) = 3.043 F
Here, C – CaO
S - SiO2
A – Al2O3
F – Fe2O3
Ŝ– SO3
Bogue's equations to find the composition

Influence of Various compound in Cement:
(Tri-calcium silicate C3S: )
 Mainly contributes the early strength of cement.
 Produce high heat of hydration.
 Quality/density of C-S-H gel produce from this
compound is slightly inferior than from C2S.
 This compound produce more Ca(OH)2 than C2S.
Microstructure of cement

Influence of Various compound in Cement
(Di-calcium silicate C2S)
 Mainly contributes the later strength of cement.
 Produce low heat of hydration.
 C-S-H gel produce from this compound is dense and with
high sp. surface.
 This compound produce less Ca(OH)2 than C3S.
 More durable than C3S in acidic & sulphur environment.

(Tri-calcium Aluminate C3A)
 Strength contribution of this compound is negligible.
 Very high heat of hydration.
 This compound is characterized by its very fast reaction
leading flash set of concrete; to control its fast setting
character gypsum is added to cement.
 Produce C3AH6 cubical compound after hydration.
 Harmful for durability as is likely to attack by sulphur.

(Tetra-calcium alumino ferrite C4AF)
 Strength contribution of this compound is negligible.
 Produce high heat of hydration.
 Produce C3FH6 after hydration.
 Show more resistance to sulphate attack than C3A.

 Chemical reaction of cement with water is termed as hydration
of cement which turns cement into the binding material with
strong adhesive property.
 Various compound present in cement reacts individually with
water to produce various hydration products. The major
compounds of hydration are C-S-H gel & Ca (OH)2.
 Calcium Silicate Hydrate (C-S-H gel) : C-S-H gel is the most
important & major product obtained from hydration. It covers
around 50-60% solid volume in completely hydrated paste.
 It shows poorly crystalline fibrous mass. It exhibits the strength
& binding property to concrete.
Hydration of cement

Hydration C3S & C2S produce C-S-H gel & Ca(OH)2
Hydration of cement
C – CaO / S- SiO2 / A – Al2O3 / F – Fe2O3 / H – H2O / CH- Ca(OH)2
C-S-H gel – C3S2H3 – 3Cao.SiO2.3H2O
C-S-H gel
C-S-H gel

 Calcium Hydroxide (Ca(OH)2): Ca(OH)2 is not a desirable product in
concrete mass but it also covers around 20-25% solid volume. It shows
distinctive hexagonal prism morphology.
 It reacts with sulphate present in environment/water to form calcium
sulphate which reacts with C3A causing detoriation in concrete (also
called Sulphate Attack).
 Ca(OH)2 is alkaline in nature which maintain PH value of concrete
around 13 & resists corrosion of reinforcement.
Sulphate attack chemistry:
 Ca(OH)2+ Sulphur compound = CaSO4
 C3A+32H + 3CaSO4 = C6AS3H32 (tri-sulphate hydrate - “ettringite” – cause
large volume change & detoriation in harden concrete)
Hydration of cement

Hydration of C3A & C4AF
 2C3A+6H = 2C3AH6
 C4AF + 2CH + 10H = C3AH6 + C3FH6
Hydration of C3A in presence of gypsum:
 C3A+32H + 3CaSO4 = C6AS3H32 (tri-sulphate hydrate - ettringite”)
 C3A+ 18H + CaSO4 = C4ASH18 (mono-sulphate hydrate)
Hydration of cement

Hydration of cement
Rate of Hydration of various Compound Rate of Strength gain of various Compound

Types of Cement
 ASTM Classification:
(American Society of Testing Material)
 Type I: Normal Cement Type (OPC): Also called general purpose
cement Used in general construction type where corrosive
environment/ sulphur is not present & the special property of cement
is not required. C3A shall not exceed 15%. This is the most used type of
cement in all type of general construction.
 Type II: Sulphate Resistance Cement(Moderate) This type of
cement is manufactured to have moderate sulphate resistance.
Normally used where moderate sulphate attack / moderate corrosive
environment is present. Used in underground concrete work & in
presence of ground water where sulphate may present. C3A content is
limited to < 8% to control the sulphate attack.

Types of Cement
 TypeIII: High early strength (Rapid Hardening Cement):
This cement is similar to Type I, but ground finer. In some case
C3S and C3A content is also increased to achieve early strength.
This gives the concrete using this type of cement a three day
compressive strength equal to the seven day compressive
strength types I. It may be used in emergency construction and
repairs and precast concrete job.
 TypeIV: Low heat of hydration(Low heat Cement)The
percentages of (C2S) and (C4AF) are kept relatively high and
(C3S) and (C3A) are relatively low. This type of cement gives low
heat of hydration & rate of strength gain is also low. Suitable for
mass concreting such as dam where low heat of hydration is
desirable.

Types of Cement
 TypeV: High Sulphate Resistance: This cement is manufactured
with very low (C3A). The maximum content of (C3A) allowed is 5%.
Normally used where sulphate & alkali content is high which react
with (C3A) causing detoriation of concrete.
 TypeIS: (Type I + Slag): Manufactured with (Type I cement + blast
furnance slag). Slag content may varies from 25-70%. This type of
cement gives low heat of hydration & better corrosion resistance. But
its strength gain is also slower.
 Type IP: (Type I + Pozzolona): Manufactured with intimate
blending of Type I cement & fine pozzolona.
Pozzolona content may varies from 15-40%. This type of cement gives
low heat of hydration & better corrosion resistance. But its strength gain
is also slower. Flyash, Silica fume is common pozzolona material used to
produce this type of cement.

Types of Cement
 TypeIA/IIA/IIIA: (Types I or II or III + air-entraining agent): Have
the same composition as types I, II, and III + air-entraining agent is
ground into the mix. They introduce the fine air bubble in concrete &
increase workability / improve resistance to freezing under low
temperatures.
 Types II(MH) and II(MH)a: have recently been added with a similar
composition as types II and IIa but with a mild heat.

Types of Cement
 BIS Classification:
(Bureau of Indian Standard)
Ordinary Portland Cement (OPC):
 Extensively being used in general construction where corrosive environment/ sulphur is
not present & the special property of cement is not required.
 Normally available in three different grade – 33grade, 43grade & 53grade.
Sulphate Resisting Cement:
 Manufactured with low C3A content (<5%) & comparatively low C4AF to prevent the
sulphate attack reaction.
 Used where environment (ground water/soil ) is corrosive & sulphur attack is present.
 Normally used in foundation, buried pipeline & marine environment.
Rapid Hardening Cement:
 Similar to OPC, but ground finer.
 High C3S and low C2S content is maintained to achieve early strength.
 Produce more heat of hydration, creates problem in mass concreting.
 Can be used where high early strength is desirable Eg, Prefabrication, road repair, cold
weather.

Types of Cement
Extra Rapid hardening Cement:
 Manufactured with inter grinding Rapid hardening cement with calcium chloride
(CaCl2) < 2%.
 Produce very high heat of hydration.
 Can be used where very fast hardening is desirable.
 In concreting mixing, transportation, placing & finishing needs to be done within 20min.
 Storage of this type of cement shall not be greater than 1 month.
Low heat Cement:
 Manufactured with low C3A & C3S and increased C2S.
 Ideal for mass concreting where low heat is desirable.
 Heat of hydration for 7days<65Cal/gm and for 28days< 75Cal/gm.
Super-sulphate Cement:
 Manufactured with granulated slag (80-85%) + hard burnt gypsum (10-15%) + OPC
clinker (5%)
 Used where high sulphate resistance is desirable.
 Produce low heat of hydration.
 Used where environment (ground water/soil ) is highly corrosive & sever Sulphur attack
is present.

Types of Cement
Portland Slag Cement:
 Manufacture intergrinding OPC clinker + gypsum + blast furnance slag (25-65%).
 Slag need to be the ground granulated blast furnance slag (GGBS), presence crystalline
slag cause low quality cement.
 Produce low heat of hydration, making ideal for mass concreting.
 Better corrosion resistance.
 But have slow strength development.
Portland Pozzolana Cement.
 Manufactured with intimate blending of OPC cement & fine pozzolona.
 Pozzolona content may varies from 15-35%.
 This type of cement gives low heat of hydration & better corrosion resistance.
 But strength gain is also slower & requires more curing. Ideal for hydraulic structure.
 Flyash, Silica fume is common pozzolona material used.
Coloured Cement
 Manufactured with high quality limestone (96% CaCO3 & Fe2O3<0.07%) with very low
iron oxide content.
 5-10% pigment is groung together with OPC clinker to produce colour cement.
 To preserve colour due to environmental change pigment are selected accordingly.

Types of Cement
Hydrophobic Cement:
 Manufactured with OPC Clinker + water repellent film forming
substance (Oleic acid / Stearic acid / Calcium Oleate).
 Prevent the cement to react with environmental moisture thus
can be used with long storage & poor storage condition.
 The preventive film broken out in mixing process of concreting,
allowing cement particle for hydration.
Mortar Cement
 Manufactured to overcome the drawback of OPC interms of
workability & water retainability for masonry construction.
 Air entraining agent and/or admixtures are mixed with cement
to achive better workability & water retainability.
 Ideal for all type of mortar work.

Types of Cement
High Alumina Cement:
 Manufactured with Limestone (CaCO3) + Bauxite (High alumina) heating at
1550-1600 deg C. & casing in mould (pig).
 Characterized by very high alumina content & rapid strength gain.
 Produce very high heat of hydration.
 Used in high temperature application: Furnace, combustion chamber, boiler
etc.
Air Entraining Cement:
 OPC Cement + Air entraining agent mixed together.
 Increase workability & resistance to freezing & thawing.
Quick Setting Cement:
 Manufactured mixing less gypsum in cement & sometime
high C3A thus causing fastest.
 Used where fast setting is desirable Eg underwater
concreting.

Tests on cement
FINENESS test
 Affects rate of hydration / Setting time / hardening /
Heat of hydration / Durability also.
 Particle Size normally ranges from 1 - 100μ.
 Roles of size in strentgh
 1day strength is provided basically by cement
particles< 3 μ
 28 days strength – 3 to 25 μ
 Difficult to hydrate completely - >45 μ
 Never hydrate completely - >75 μ

Tests on cement
 FINENESS TEST:
1) Dry Sieving
2) Air-permeability test
i) Blaine air-permeability test.
ii) Lea & Nurse air-permeability test.
- Specific surface area per unit weight (cm2/gm)

Setting Vs Hardening
 Setting – Solidification of the plastic cement paste
• Initial set – beginning of solidification – Paste
become unworkable – loss in consistency
• Final set – Time taken to solidify completely
 Hardening – Strength gain with time – after final
set

Consistency/ Setting Time
 Consistency indicates the relative mobility or
flow of freshly mixed cement paste.
 Standard consistency of cement paste is
defined as the percentage of water required to
prepare the paste of consistency that allows
standard Vicat plunger to penetrate the depth
of 33-35mm.
 This percentage is usually indicates by P
 Test is performed at standard temperature
of (27±2)0C & constant humidity of 90%.
 Test needs to be performed within
3 – 5min after addition of water to cement.

Tests on cement
Setting Time
Initial Setting Time: Time at which the paste of standard
consistency began to lose its plasticity.
 Cement (500gm) + Water (0.85P%)
 Time Required by paste to allow penetration of Needle –
33 to 35mm. (>30min for OPC)
Final Setting Time: Time at which the paste of standard
consistency completely lose its plasticity.
 Cement (500gm) + Water (0.85P%)
 Time Required by paste to allow penetration of Needle –
0.5mm. (<600min for OPC)

Tests on cement
Strength Test
 Compressive strength of cement is one of the most
important properties among all.
 Three cube of size 7.06cm2
 Cement: Sand = 1:3
 Water= (P/4+3)% of combine mass.
 2min Vibration with 2000vibration/min
 After 24hour of placing curing shall be carried out.
 After Specified time - Compressive test of loading
rate 35Mpa/min.

2.6 Tests on cement
Soundness Test
Measure of Expansion of Cement.
Due to Free lime
Due to excess Gypsum
Due to magnesia / Sulphates
 Le Chatlier Test:

WATER
 Water is needed in concrete for chemical process (hydration). It is also acts as
lubricant during mixing of concrete.
 Water is the one of the main ingredient of concrete which react with cement
particle to convert into C-S-H gel.
 The other purpose of use of water in concrete is
i. For Mixing of concrete
ii. For curing of concrete
iii. For washing of aggregate
 Parameter affecting quality of concrete:
i) Quantity of water.
ii) Quality of water.

 Increase in the quantity
of water per unit cement
- increase the workability.
- decrease the strength of
harden concrete.
- decrease the durability of
concrete.
Quantity of Water in concrete

 Water used for mixing & curing shall be free from any reactive
substances that can harm the concrete in any way.
 Quality of both mixing & curing water affects the concrete
properties in green as well as in harden stage.
Quantity of Water in concrete

 Normally potable water is considered satisfactory with maximum permissible value
as given:
(d) PH value of water shall not be less than 6..
Quality of Water in concrete

 Sodium & potassium carbonate / bicarbonate affects the setting time of
concrete. Higher concentration may affects the 28days strength also.
(Limit – 1000 ppm)
 Sodium sulphide reduce the strength. (Limit– 100 ppm)
 Chloride / Sulphate very little harm to concrete (Limit – 2000 ppm)
 Silt / Suspended particle – reduce bond strength. (Limit – 2000ppm)
 Sugar – Elongate the setting time. Greater than 0.2% also affects the
28days strength.
Sea Water:
 Mixing & curing of concrete with sea water is not recommended.
But under unavoidable condition sea water may be used in plain
concrete without embedded steel, and taking due consideration of
negative effect of water & using suitable cement system.
Quality of Water in concrete

 Admixture can be define as the ingredient added to concrete in
order to achieve desired property of concrete as required.
 Can also be define as the additives added to concrete so as to
obtained the specific requirement of concrete.
 Admixtures are mainly classified into two types:
a) Chemical Admixture
b) Mineral Admixture
ADMIXTURE

 These are the admixture containing basic ingredient as various
chemicals. Normally available in liquid / powder form. Use relatively low
dosage normally 0.04% to 5% by wt. of cement.
 Normally used to increase the workability, to retard or accelerate the
setting time/hardening process, for air entraining & water proofing etc.
TYPES:
a) Water Reducing Admixture (Plasticizer)
b) High Range Water Reducing (Super-plasticizer).
c) Retarding Admixture.
d) Accelerating Admixture.
e) Air-entraining admixture.
f) Waterproofing Admixture.
g) Mix type:
 Water Reducing & Retarding admixture.
 Water Reducing & Accelerating admixture.
 High Range Water Reducer & Retarding Admixture
CHEMICALADMIXTURE

a) Water Reducing Admixture (Plasticizer)
 Increase the workability of fresh concrete/mortar without
increasing water content or maintain workability with reduced
water. By Lubrication, Electrostatic repulsion,& Dispersion
 Can reduce water requirement by 5-15%
 Dosage based on cement per 100kg (Eg, 200ml per 100kg
 High dose may cause excessive retardation in setting time.
 Eg: (Various lignosulphonate normally derived from wood product),
(synthetic raw materials), (polyglycol esters) etc.
CHEMICALADMIXTURE

b) High Range Water Reducing (Super-plasticizer).
 Similar to plasticizing admixture with high water reducing capacity.
 Normally used when high degree of water reduction is desirable.
 Depending upon its type can reduce water content more than 30%.
 Due to their powerful dispersing & fluidifying effect facilitates to work
with very low W/C ratio also.
 HRWR normally available in market are:
i. Sulphonated melanie-formaldehyde (SMF),
ii. Sulphonated napthalene-formaldehyde (SNF),
iii. Carboxylate acrylic easter,
 Out of above listed HRWR Carboxylate polymer based superplasticisers
are found more effective & powerful.
ADMIXTURE

b) Super-plasticizer – Optimum Dose - Marsh cone test
 2kg Cement
 W/C – 0.5
 Variable admixture dose
 Note: Flow time of 1lit slurry
ADMIXTURE

c) Retarding Admixture.
 Retarding Admixture delay the setting time of concrete /
mortar.
 Keep concrete workable for long period giving additional
time for mixing, placing, compacting & finishing.
 Normally used to overcome unwanted effect of high
temperature & to reduce slump-loss.
 Facilitates finishing in hot weather.
 Eg: Calcium sulphate (gypsum), starch/sugar, cellulose,
lignosulphonic-acid etc.
ADMIXTURE

d) Accelerating Admixture.
 Accelerating Admixture when added increase rate of
hydration of hydraulic cement, shorten setting time &
increase hardening process.
 Normally used when fast setting & early strength gain is
desirable (Eg, Urgent repair work, road pavement
construction etc)
 Can be used in cold climate region for rapid strength gain.
 Chloride is one of the economic/effective accelerating
admixture but due to its action on corrosion of steel its use
is limited to 0.15% of Cement for RCC & 0.06% for
prestressed concrete.
 Eg; Soluble carbonates, silicates & flurosilicates, Organic
compound – triethenolamine etc.
ADMIXTURE

e) Air-entraining admixture.
 Induce micro-air bubble (5 to 80 µ) to concrete.
 Used to produce air entrained concrete.
 Air entraining admixture induce millions of fine uniformly
distributed air bubble to concrete.
 These micro-air bubble acts as flexible ball bearing thus
increase workability, reduce segregation & bleeding, also
the harden concrete have better resistance to freezing &
thawing.
 Eg; Natural wood resin. Water soluble soap of resin acid,
hydrogen petroxide, aluminium power, Animal & vegetable
oil etc.
ADMIXTURE

f) Waterproofing Admixture.
Normally used where water impermeability is desirable.
Mainly two types:
 Pore-filler: Reduce permeability by its pore-filling action.
Normally used materials are Chalk, Talc, Silicates,
Aluminium power.
 Water repellent: Prevent water penetration by its water
repellent action. Normally used materials are: Resin,
vegetable oil, waxes, calcium soap, soda etc.
 Mineral admixture like silica-fume, fly-ash & air entraining
admixture can also used to improve impermeability of
concrete.
ADMIXTURE

MINERAL ADMIXTURE:
 These are the admixture basically obtained from various
natural or artificial minerals.
 Normally available in finely divided power form. Its dose is
relatively higher than chemical admixture ranging from 5 –
80% by wt of cement.
 Eg: Fly ash, blast furnace slag, silica fume, brick dust, stone
dust etc. In many case used as cement replacement ingredient
due to its pozzolana property.
Ca(OH)2 in hydrated paste + POZZOLANA = C-S-H gel
 Fly ash
 Blast furnace slag
 Silica fume
 Rice husk ash
 Calcined clay pozzolana (Brick dust / Burned clay dust)
 Stone dust
ADMIXTURE

 Fly ash: Finely divided residue from combustion of powdered coal
 Fly ash, a principal byproduct of coal burning power plants, is an
industrial waste product containing large amounts of silica, alumina and
small amount of unburned carbon, which pollutes environment. This fly ash
has real disposal problems, and should hence be utilized effectively for
various purposes.
 Fly ash, being primarily pozzolanic, can actually replace a percentage of
the Portland cement, to produce a stronger, more durable and more
environment friendly concrete.
 The cement production process releases a lot of carbon-di-oxide in
atmosphere, which is the primary green house gas that causes global
warming. Hence replacement of a considerable portion of cement by fly
ash, can make a major contribution toward solving the global warming
problem
ADMIXTURE

ADMIXTURE
 For similar cementations material content and similar
range of slump, the use of fly ash (0 to 50 %) decreased the
water-to-cementitious-material ratio in general.
 The long term strength of the concrete containing fly ash is
higher than that of control concrete without fly ash.
 Abrasion resistance of fly ash concrete is less than
corresponding samples without fly ash both at early and
longer ages, in general. The loss of thickness due to
abrasion increases with percentage of fly ash in concrete.
 The fly ash concrete shows lower water permeability
compared to that of control concrete.
 The depth of carbonation is increased with the increase in
percentage replacement of fly ash in concrete.

ADMIXTURE
BLAST FURNANCE SLAG
Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained by
quenching molten iron slag (a by-product of iron and steel-making)
from a blast furnace in water or steam, to produce a glassy, granular
product that is then dried and ground into a fine powder.
The chemical composition of a slag varies considerably depending on the
composition of the raw materials in the iron production process.

ADMIXTURE
SILICA FUME
Silica fume is a byproduct of producing silicon metal or ferrosilicon
alloys.
Because of its chemical and physical properties, it is a very reactive
pozzolan.
Concrete containing silica fume can have very high strength and can
be very durable.

ADMIXTURE
Silica fume consists primarily of amorphous (non-crystalline)
silicon dioxide (SiO2).
The individual particles are extremely small, approximately
1/100th the size of an average cement particle.
Because of its fine particles, large surface area, and the high
SiO2 content, silica fume is a very reactive pozzolan when used in
concrete.

Concrete and Steel: Matching
 Concrete and steel possess similar coefficient of
thermal expansion (steel 1.2 x 10-5; concrete 1.0-1.5 x 10-
5).
 Concrete also provides good protection to steel.
Therefore, while steel bars provide the necessary
tensile strength, concrete provides a perfect
environment for the steel, acting as a physical barrier
to the ingress of aggressive species and preventing
steel corrosion by providing a highly alkaline
environment with pH about 13.5, passivating the steel.
 No coating or painting is needed as for steel
structures.

 It is a method of selecting the suitable ingredient and it’s proportioning
with the objective of getting as economical as possible concrete of certain
minimum strength, workability and durability. The main purpose of
concrete design is to economize the cost of concrete and gain a desired
strength.
General steps of mix design
i. Required grade of concrete is found according to structure and strength
(Grade of concrete depends upon the type of structure and its functional
requirements. High grade of concrete is required to construct for ex:
hydropower dam, bridge, tunnel as compared to the other non
important structures)
ii. Mean target strength is fixed using the relation as fmean = fck + Kσck
where k = 1.65 (95 % level of confidence or 5 % level of significance)
i.e. fmean = fck + 1.65σck
Concrete Mix Design

Where,
fmean= Target strength of concrete
fck=characteristics strength of concrete
σck= standard deviation =
σ 𝑥−𝑥𝑚𝑒𝑎𝑛
2
𝑛−1
x= strength of cube test
n= number of test
k= Him worth constant =1.65 (for 95%confidence level or 5% level
of significance)
Note: 5% level of significance means strength below which not more
than 5% of the test results are expected to fall
iii. Select a type of cement and its amount considering both the w/c ratio
and durability criteria
Concrete Mix Design
Grade Assumed σck
M10, M15 3.5
M20, M25 4.0
M30-M50 5.0
refer code

iv. Fixed nominal size, shape and type of aggregate and determine its
amount
v. Mixed ingredient in desired proportions
vi. The strength of concrete proportion is found out which must be equal to
target strength of concrete. If not then re-proportioning is required to
achieve the target strength
Concrete Mix Design

Mix Design : Information to be collected
 Required Information
i. Zoning of sand- Natural sand is divided into four groups
 Or Fineness Modulus
ii. Characteristics strength of concrete (fck)
iii. Workability of concrete-Workability of concrete measures the
ability and easiness to work. It can be measured by slump test,
compaction factor test, Flow test, and Vee-Bee consistometer test
Zone Passing through 600 micron sieve
I 15-34 %
II 35-59%
III 60-79%
IV 80-100% -not suitable for reinforced
concrete

Mix Design : Information to be collected
iv. Water cement ratio-Water cement ratio (W/C ratio) is defined as
relative weight of water to the cement in a mixture. W/C ratio controls
two factors i.e. strength and workability
V. Exposure condition of concrete- Mild, moderate, severe, very severe
and extreme
Vi. Durability of concrete-Durability of the concrete is defined as ability
of concrete to resist weathering action, chemical attack, abrasion or any
other process of deterioration. Therefore durable concrete will remains its
original forms, quality and serviceability when exposed to its
environmental

Mix Design Step for IS Code
Go through this website if you
want more details . Their youtube
video will be helpful for subjective
part too.
https://dcbaonline.com/online-
concrete-mix-design-calculator-
10262-2019/

Workability and Its Test
Workability and consistency
➢ Workability is the amount of useful internal work
necessary to produce full compaction. The useful internal
work is a physical property of concrete alone and is the
work or energy required to overcome the internal friction
between the individual particles in the concrete. Also
additional energy is required to overcome the surface
friction between the formwork and the reinforcement.
➢ Consistency is a general term to indicate the degree of
fluidity or degree of mobility.
Measurement of workability - Workability is determined in the
laboratory by
a. Slump test
b. Compaction factor test
c. Vee-bee consistometer test

Workability and Its Test
Factors affecting the workability
i. Water content- workability is directly proportional to water
content
ii. Mix proportioning- workability is inversely proportional to the
aggregate cement ratio
iii. Size of aggregate-workability is directly proportional to size of
aggregate up to certain limit
iv. Shape of aggregates- workability is high for rounded shaped
aggregate rather than other shapes
v. Surface texture of aggregate- Total surface of rough textured
aggregate is more than the surface area of smooth rounded
aggregate of same volume i.e. rough textured aggregate will
show poor workability
vi. Grading of aggregate- workability is high for well graded
aggregate
vii. Use of admixture- admixture increases the workability of the
concrete

Slump Test
 Slump test is a most commonly used
method of measuring the consistency
of the concrete which can be
employed either in laboratory or at
site of work. This method is not
suitable for very dry and very wet
concrete.
 The apparatus for conducting the
slump test essentially consist of
metallic mould in the form of a
frustum of a cone have the internal
dimensions as below:
Bottom dia.: 20 cm Top dia.: 10 cm
Height =30 cm
 For temping the concrete, a steel
tamping rod of 16 mm dia, 0.6m long
along with bullet end is used
 Concrete is filled in four layers and
tamping each layer 25 times

Compaction factor test
 It is more precise and sensitive than slump test
 This test works on the principal of determining the degree
of compaction achieved by a standard amount of work
done by allowing the concrete to fall through a standard
height. The degree of compaction, called the compaction
factor is measured by the density ratio i.e. the ratio of the
density actually achieve in the test to density of same
concrete fully compacted.
 Compaction factor= wt of partially compacted concrete /
wt of fully compacted concrete
Where,
 Wt. of partially compacted concrete: - concrete filled from
conical hopper to cylinder during test
 Wt of fully compacted concrete: – concrete filled to
cylinder manually and compacted

Compaction Factor Test
➢ It is more precise and sensitive than slump test
➢ This test works on the principal of determining the degree of compaction
achieved by a standard amount of work done by allowing the concrete to fall
through a standard height. The degree of compaction, called the
compaction factor is measured by the density ratio i.e. the ratio of the
density actually achieve in the test to density of same concrete fully
compacted.
➢ Compaction factor= Wt. of partially compacted concrete / Wt. of fully
compacted concrete
Where,
Wt. of partially compacted
concrete: - concrete filled from
conical hopper to cylinder during
test
Wt. of fully compacted concrete: –
concrete filled to cylinder
manually and compacted

Vee-Bee Consistometer Test
➢ This test consists of a vibrating table, a
metal pot, a sheet metal, cone, a standard
iron rod. The apparatus is shown in figure
below
➢ Concrete is placed at top pot and vibrator is
then switched on and simultaneously a stop
watch started
➢ The vibrator is continued till such a time as
the conical shape of the concrete disappears
and the concrete is assumes a cylindrical
shape

However according to Foreword of IS 456: 2000,

W/C ratio in Concrete
➢ Strength of concrete is primarily depends upon the
strength of cement paste and the strength of cement
paste depends upon the dilution of paste. In other
word, the strength of paste increases with cement
content and decreases with air and water content.
➢ In 1918 Abrams presented his classical law in the
form: S=
𝐴
𝐵𝑥 where, x= water cement ratio by volume
and for 28 days result constants A and B are
14000lbs/sq. inch and 7 respectively
➢ Abrams water/ cement ratio law stated that the
strength of concrete is only dependent upon
water/cement ratio provided the mix is workable.
➢ The formula for concrete strength in terms of volume
fractions of the constituents by the equation:
S=K(
𝑐
𝑐+𝑒+𝑎
)2
➢ Where K= a constant, S= strength of concrete c, e
and a= volume of cement, water and air respectively

Concrete Mix Design
Concrete mix design can be done by the two ways namely
 Nominal concrete mix
 Designed concrete mix
1. Nominal Concrete Mix
➢ Nominal concrete mix are low grade concrete mixes (below M20) which
are used for small and unimportant works. In this method, fine
aggregate quantity is fixed irrespective of cement and coarse aggregate
proportions. Hence, the quality of concrete mix will be varied and
required strength may not be obtained.
➢ In Nominal mix design water-cement ratio also not specified. Grades of
concrete M20 and below are prepared by the Nominal mix design. For
higher grade designed concrete mix is preferred.

Concrete Mix Design
2. Designed concrete mix
➢ The designed concrete mix does not contain any specified ranges in proportions. The
design is done according to the requirements of concrete strength. So, we can achieve
the desirable properties of concrete either it is in fresh stage or in hardened stage.
➢ The fresh concrete properties like workability, setting time and hardened concrete
properties like compressive strength, durability etc. are attained surely by this
method. Use of additives like admixtures, retarders etc. other than basic ingredients
are used to improve the properties of mix.
➢ Using design concrete mix, one can design various grades of concrete from as low as
M10 grade to higher grades such as M80, M100 can also be prepared. The workability
requirements of each mix can also meet using this method from zero slump to the 150
mm slump. Each mix prepared is tested in laboratory after hardening to verify
whether it meet the requirement or not.
Advantages of Mix Design- The advantages of concrete mix design are as follows
 Required Proportions of Each ingredient
 Quality Concrete Mix and Economical Concrete Mix
 Best Use of Locally Available Material and Desired Properties of Mix

Quality control in site : Batching, Mixing,
handling, placing, compaction and curing
a) Batching
Batching is the process of measuring concrete mix ingredients either by volume or
by mass and introducing them into the mixture. Traditionally batching is done by
volume but most specifications require that batching be done by mass rather than
volume.
1) Volume Batching 2) Weight Batching
b) Mixing
The mixing operation consists of rotation or stirring, the objective being to coat
the surface the all aggregate particles with cement paste, and to blind all the
ingredients of the concrete into a uniform mass; this uniformity must not be
disturbed by the process of discharging from the mixer.
1)Hand Mixing 2) Machine Mixing

Quality control in site : Batching, Mixing, handling,
placing, compaction and curing
c)Transporting/Handling
Concrete can be transported by a variety of methods and equipments. The
Precaution to be taken is that the homogeneity obtained at the time of
mixing should be maintained while being transported to the final place of
deposition. Eg: Wheel Barrow, Mortar pan, Crane and Bucket, Chute, Skip
and Hoist.
d) Placing
It is of utmost importance that the concrete must be placed in systematic
manner to yield optimum results.The aim of good concrete placing can be
stated quite simply.
 It is to get the concrete into position at a speed, and in a condition, that
allow it to be compacted properly.

e) Compaction
 Compaction is the process adopted for expelling the entrapped air from the concrete. In
the process of mixing, transporting and placing of concrete air is likely to get entrapped
in concrete.
 Stiff concrete mix( concrete with Low workability) has high percentage of entrapped air
and therefore, would need higher compacting efforts than high workable mixes.
 If air is not removed fully, concrete loses strength considerably. 5% voids & 10% void
reduces strength by 30% & 50%
 Hand Compaction, Needle vibrator,
 Formwork vibrator

Curing
 Concrete derives its strength by the hydration of
cement particles which is a long process.
 It is the process of hardening the concrete mixes by
keeping its surface moist for a certain period, in order
to enable the concrete to gain more strength.
 The objective of curing is to prevent the loss of water
by evaporation, to reduce the shrinkage of concrete
and to preserve the properties of concrete.
 Water Curing, Membrane Curing

Segregation and Bleeding
Segregation: Segregation can be defined as the separation of the constituent
materials of concrete. In case of concrete, there is differences in the size of
particles and in the specific gravity. Therefore, it is natural that the materials
show a tendency to fall apart. Segregation may be of three types
➢ The coarse aggregate separating out or setting down from the rest of the
matrix
➢ The paste or matrix separating away from coarse aggregate
➢ Water separating out from rest of the material
The extent of segregation can be controlled by the choice of suitable grading
and by care handling.
Bleeding: Bleeding is sometimes referred as water gain. It is a particular form
of segregation, in which some of the water from the concrete comes out to the
surface of the concrete, being of the lowest specific gravity among all the
ingredient of concrete. Bleeding is predominantly observed in a highly wet mix,
badly proportioned and insufficiently mixed concrete. In thin member like roof
slab, road slab and when concrete is placed in sunny weather show excessive
bleeding.

Concreting in extreme weather
temperature
Concreting in extreme weather temperature
a) Concreting in hot weather
b) Concreting in cold weather
 Concreting in hot weather
➢ It is difficult to define what hot weather condition is. However just for
convenience, it is regarded that the concrete placed at an atmospheric
temperature above 40 degree centigrade is considered as hot weather
concreting
 Problems
➢ Rapid rate of hydration of cement, quick setting and early stiffening.
➢ Rapid evaporation of mixing water
➢ Greater plastic shrinkage
➢ Reduce relative humidity ( this point is positive from corrosion point of view
but required more curing)

Concreting in extreme weather
temperature-Concreting in hot weather
 Problems
➢ Absorption of water from the concrete by the sub grade and formwork
➢ Difficult in continuous curing due to being more hot in less time
➢ Difficult in incorporation of air entrainment
 Precautions
➢ Kept temperature as low as possible by shading the aggregate piles and the
mixture
➢ Reduce the temperature of aggregate by sprinkling water on it. The
evaporation of sprinkled water will cool the aggregate
➢ Keep water supply cool by insulating or shading pipes and tanks
➢ Use crushed ice with mixing water
➢ Effect of hot weathering can also be reduced by working at night time
➢ For curing, covering with wet burlap (jut bag) or by sprinkling or by other
moisture retaining materials has been found better as it has a definite cooling
value.

Concreting in extreme weather temperature-
Concreting in cold weather
 Concreting in cold weather
➢ The Temperature generally freezing temperature is considered as cold
weather for concreting
 Problems
➢ Delay in setting and hardening
➢ Freezing of concrete at early age
➢ Freezing and thawing: setting of concrete is suspended if concrete freezes
immediately after it has been placed. If concrete freezes after it has sets but
before it has attained sufficient strength, the expansion due to the
formation of ice causes disruption and loss of strength. If freezing takes
place when concrete has developed sufficient strength ,it can resist freezing
effect without damage not only by virtue of the higher resistance to the
pressure of ice but also due to the fact that large parts of the mixing water
will have combined with the cement or located in the gel pores and thus
would not freeze.

Concreting in extreme weather temperature-
Concreting in cold weather
 Precaution
➢ Heat mixing water, to increase temperature of fresh concrete
➢ Heat aggregate, if water (hot water) alone does not raise the temperature of concrete
➢ Use of cement of high rate of heat generation (i.e. cement having high C3S and C3A
produced high heat during reaction)

C
1.C
2. A ( C and B is not
correct they either
have zero missing or
zero extra

 Stress-strain curve of concrete shows its distinct non
linear behavior even at lower stress level.
 The fig below also indicates that the properties of
concrete is not equal to sum of properties of its
components.
Stress-Strain relationship of concrete

 Due to its non-linear behavior there exists different E value
at different stress level. Different types of modulus of
elasticity, depending upon its mode of determination
Modulus of elasticity

 The modulus of elasticity found out from the actual loading
of the structure or specimen is called the static modulus of
elasticity.
 It can be determined by subjecting a cube or cylinder
specimen to uniaxial compression and measuring the
deformations by means of a dial gauge.
 From the stress strain curve of the concrete, it is seen that
concrete does not behave as an elastic material even under
the short term loading. For higher stresses, the stress strain
relationship will be greatly curved and as such it will be
inaccurate.
 However, up to 10-15 % of the ultimate strength of the
concrete, the stress strain graph is not very much curve and
hence can give more accurate values.
Static modulus of elasticity

1. Initial tangent modulus : If the E – value is
determined by drawing tangent at beginning of
curve, is termed as Initial tangent modulus. This is
only suitable for low stress level.
2. Tangent modulus: If modulus of elasticity is
determined by drawing tangent at any point in curve,
is termed as tangent modulus. This is only suitable
for stress level near to that point.
3. Secant Modulus: If modulus of elasticity is
determined by joining any point in curve to origin, is
termed as secant modulus. This is one of the widely
used method for determination of E.
Types of Static modulus of elasticity

4. Chord modulus: If modulus of elasticity is determined by
joining any two point in curve, is termed as chord modulus.
This is mainly used for typical research purpose only.
Factor affecting E:
 Strength of concrete (Directly proportional)
E=5000 (𝑭𝒄𝒌)1/2 𝒂𝒔 𝒈𝒊𝒗𝒆𝒏 𝒃𝒚 𝑰𝑺𝟒𝟓𝟔: 𝟐𝟎𝟎𝟎)
 Moisture condition (Ewet > Edry)
Aggregate has significant effect on the modulus of elasticity.
 (1/E = Vol. of paste/E paste+ Vol. of Agg/E agg)
Since Volume of aggregate is highest, its affect is
pronounced.
Cont.

 Creep can be defined as the gradual increase in strain
with time even at sustained loading condition(without
increase in stress)
 Cement paste plays important role in creep
phenomenon.
Shrinkage and Creep

 Creep is partially reversible & partially irreversible phenomenon.
 The permanent deformation due to creep is also called residual
deformation.
 One of the explanations given to the mechanics of creep to the concrete is
based on the theory that the colloidal particles slide against each other to
readjust their position displacing the water held in gel pores and capillary
cavities.
 This flow of gel and consequent displacement of water is responsible for
complex deformation behavior and creep of concrete.
Factors affecting creep:
1. Aggregate properties : light weight aggregates shows substantially higher
creep.
2. Mix Proportion
3. Age/Time : Value of creep is higher at early age.
26% of 20 years creep in 2 weeks
55 % of 20 years creep in 3 month
76 % of 20 years creep in 1 year

 Change in volume of concrete by various phenomenon(autogenous or induced) is
called shrinkage.
 Shrinkage in concrete is mainly due to the loss of moisture from concrete at its various
stages.
 Various types (as well as cause) of shrinkage can be listed as;
1. Plastic Shrinkage: Shrinkage due to the loss of moisture of concrete at its plastic stage
(green stage) is called plastic shrinkage. high water cement ratio, badly proportioned
concrete, rapid drying, greater bleeding, unintended vibrations etc. are the reasons for
plastic shrinkage.
2. Drying Shrinkage: Shrinkage due to the loss of moisture of harden concrete is called
drying shrinkage. The loss of free water contained in the hardened concrete does not
result in any appreciable dimension change. It is the loss of water held in the gel pores
that causes the change in volume and shrinkage.
3. Autogeneous Shrinkage: Shrinkage due to without moisture movement from or to
concrete system can be termed as Autogeneous shrinkage.It is of minor importance and
is not applicable in practice to many situations except that of mass concrete in the interior
of the concrete dam.
4. Carbonation Shrinkage: CO2 present in environment react with Ca(OH)2 in concrete
producing CaCO3. As the new product is less in volume than the product replaced,
shrinkage takes place.
Shrinkage

Effect of Aggregate Shape /size /strength:
Aggregate shape / size / strength also shows some effect on concrete strength.

Effect Of Time On Concrete:
As we know the hydration of cement continues for long course of time,
provided the moisture available for hydration process; strength of
concrete also increases in similar pattern with time. In general,
strength of concrete increases with time.
 ACI -209 recommends the following relationship to determine compressive
strength at any time ,
 fcm (t) = fc28*

Effect of Temperature
High mixing temperature, higher
early strenghth but lower ultimate
strength
Low mixing temperature, Lower
early strength
Temperature around 20 degree,
higher ultimate strength

Effect of Curing:
 Various research/test data shows that the continuously moist cured
concrete gives almost 2 to 3 times greater ultimate strength than entire
air cured concrete. The decrease in strength of air cured concrete is due
to loss of moisture, which ultimately interrupt the hydration process of
cement.

Effect of W/C ratio: Most important parameter to control strength.

Also expressed as strength porosity or Gel Space
ratio.
 Abrams presented his W/C rule in 1918 as:
 S= A/B x
 Where, x = w/c ratio; A=96 N/mm2; B= 7 for 28
days compressive strength.

Gel Space Ratio
• The gel/Space ratio is the ratio of the solid products of hydration to
the space available for these hydration products.
• A higher gel/space ratio reduces the porosity and therefore
increases the strength of concrete.
• Many research has shown that the strength parameter can be
related more accurately to the gel-space ratio than the w/c ratio.
• The gel/space ratio , which governs the porosity of concrete
affecting its strength , is affected by water/ cement ratio of concrete

Gel/space Ratio
 A higher water/cement ratio decreases the
gel/space ratio increasing the porosity
thereby decreasing the strength of concrete.
 Power & Brownyard presented that the
gel-space ratio (ratio of volume of
hydrated cement paste to sum of volume
of hydrated paste & capillary pores.)
 They found the relationship to be 240 x^3,
where x is the gel/space ratio
And 240 represents the intrinsic strength of
the gel in Mpa for the type of cement and
specimen used.

 TO DETERMINE THE QUALITY OF CONCRETE.
 Testing of hardened concrete
 Destructive testing
 Non destructive testing
TESTING OF CONCRETE

Compressive Strength
 Compressive strength is taken as the one of the most
important parameter of concrete. As most of its other
properties are also related to the compressive strength
 Concrete is commonly employed to resist the compressive
strength.
Cube compressive strength:
 Compressive strength of standard cube (normally taken as
150x150x150mm). It shows that the smaller size cube give
relatively higher strength value than bigger size. Typical test
result is given below:
TESTING OF CONCRETE

Cylinder compressive strength:
 Compressive strength of standard cylinder (normally
150mm dia. X 300mm ht – ht. to dia. ratio = 2).
 It is found that the ratio of ht. to dia. other than 2
(standard size) affect the cylinder strength as given
below:
 BS 1881:1970 ; Cylinder strength = (4/5)*
Cube Strength
 L Hermite; Cylinder strength =
0.76+0.2*log(fcm/2840) Here, fcm =cube
strength lbs/sqin
TESTING OF CONCRETE

Tensile Strength: Being weak in tension, tensile strength of concrete is
normally neglected in design. Various test method / tensile strengths are
given below:
 Direct tension: If tensile strength of concrete is determined applying
direct (Pure) tension to concrete specimen.
Tensile Strength (fct) = Tensile Force (P)/Area
 IS456:2000 relates direct tensile strength to compressive strength as:
TESTING OF CONCRETE

Flexural Test
Tensile Strength:
Flexural tension: Flexural tension is the tensile force developed
in concrete in bending.

Poisson Ratio
Poission ratio
0.11-0.2
Mostly 0.15
Modular ratio
=280/ (3ø cbc)
For Fck =20, ø cbc =7
Fck =15, ø cbc =5
Fck =25, ø cbc =8.5
Fck =30, ø cbc =10

Tensile Strength:
 Splitting tension: This is one of the popular indirect tensile
test method also known as Brazilian test.
 Horizontal Tensile Stress = 2P/π LD
TESTING OF CONCRETE

Shear Strength:
 Shear can be defined as the action of equal & opposite
parallel force acting in plane short distance apart.
 Direct determination of shear force is difficult, can be taken
as 12% of compressive strength.
Bearing strength:
 Concentrated loading on concrete surface tends to punch
the surface inside, resistance to which can be termed as
bearing strength. Normally, bearing stress is significant at
the base of the steel/concrete column in foundation
 IS 456:2000 recommends,
 Bearing Strength = 0.25*Fck for Working stress design
method.
 Bearing Strength = 0.45*Fck for Limit State design method.
TESTING OF CONCRETE

Bond strength:
 Bond between cement & aggregate: Bond between hydrated
cement & aggregate affects the overall strength of concrete.
Lower W/C ratio & use of mineral admixture significantly
enhance the bond strength by reducing porosity &
enhancing characteristics of transition zone.
 Bond between steel & concrete:
 This bond is primarily due to the friction & adhesion
between steel & concrete surface. Mainly depends upon the
strength of concrete & surface and mechanical property of
steel.
 Higher specific surface of gel also found to give higher bond
strength (C-S-H gel from C2S gives more sp. surface than
from C3S compound).
 Taken as 30-50% of compressive strength.
TESTING OF CONCRETE

NON Destructive test
Rebar detector / Cover meter
Corrosion Analyser

Non destructive / Partial destructive testing
 Rebound Hammer Test
 This is a simple, handy tool, which can be used to provide a convenient and
rapid indication of the compressive strength of concrete. It consists of a
spring controlled mass that slides on a plunger within a tubular housing.
TESTING OF CONCRETE

 Rebound Hammer Test
TESTING OF CONCRETE

 Windsore Probe Test
 Penetration resistance methods are based on the
determination of the depth of penetration of probes
(steel rods or pins) into concrete. This provides a measure
of the hardness or penetration resistance of the material
that can be related to its strength.
TESTING OF CONCRETE

 Core test
 Fixing the drilling machine on the ground.
 Cores are available in different sizes (mainly 7 cm and 10cm).
 The cores were obtained at different locations from the unreinforced
concrete slabs.
TESTING OF CONCRETE

 PULL OFF TEST
 Pull off tester is microprocessor based, portable hand
operated mechanical unit used for measuring the tensile
strength of in situ concrete. The tensile strength obtained
can be correlated with the compressive strength using
previously established empirical correlation charts.
TESTING OF CONCRETE

 Ultrasonic pulse - velocity test
 Ultrasonic instrument is a handy, battery operated and
portable instrument used for assessing elastic properties
or concrete quality.
 Determine concrete quality depending upon velocity of
wave through concrete.
TESTING OF CONCRETE

 Ultrasonic pulse - velocity test
Ultrasonic pulse velocity

Non destructive / Partial
destructive testing
 Rebar detector / Cover
meter
 To detect rebar dia. / Cover
in concrete.
 Magnetic field theory
TESTING OF CONCRETE
Corrosion Analyser
Half Cell Potentiometer
Eddy Current Technique

VARIABILITY OF CONCRETE STRENGTH AND
ACCEPTANCE CRITERIA
 The strength of concrete varies from batch to batch and within the same batch so it is
difficult to assess the strength of the concrete.
 Strength test of concrete from random sampling of a mix exhibit variations due to various
operations involved in making and testing of concrete.
 Also it is observed that the strength of a sample varies with the variation in shape and
size of the sample as well as the type of testing method used.

Acceptance criteria IS 456:1978

Pre stress Concrete
 Prestressed concrete is a
system into which internal
stresses are deliberately
induced without any form of
external loads to improve its
performance. The internal
stresses induced in the
concrete structure is used to
counteract the stresses
coming from the external
load application.

Pre tensioning method
In the pre tensioning method, the stress
is induced by initially tensioning the steel
tendons. These are wires or strands that
are tensioned between the end
anchorages. After this tensioning process,
the concrete casting is performed. Once
the casted concrete has hardened
sufficiently, the end anchorages arranged
are released. This releasing transfers the
prestress force to the concrete. The bond
between the concrete and the steel
tendons facilitates this stress transfer.

Post tensioning method
 Here, the steel is prestressed only
after the beam is cast, cured and
attain strength to take the prestress.
Within the sheathing, the concrete is
cast. For the passage of steel cables,
ducts are formed in the concrete.
Further divided in to
a) Bonded post-tensioning
b) Unbonded post-tensioning

. For the pre-stressed concrete to be feasible
the total loss in the system shall not exceed
a. 15%
b. 20%
c. 25%
d. 30% Answer : C

Thank You
follow the link if you want more
https://www.sanfoundry.com/1000-concrete-technology-questions-
answers/
Also
https://mcqmate.com/topic/306/concrete-technology-and-design-set-1

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