National Seminar on Engineered Building Materials and their ...

1DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

CEL 774 CONSTRUCTION PRACTISES

Concrete: Production (Curing )

B. Bhattacharjee

CIVIL ENGINEERING DEPARTMENTIIT DELHI

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General OutlineGeneral Outline

Concrete Production.Concrete Production.CuringCuring

NeedNeedMethods & detailsMethods & details

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

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Curing NeedsCuring Needs

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

–– Hydration Reaction of cement with water Hydration Reaction of cement with water takes time.takes time.

–– Hydration takes place at 100% R.H . Hydration takes place at 100% R.H . –– Loss of water by evaporation shall be Loss of water by evaporation shall be

prevented and replenishedprevented and replenished..–– SelfSelf--desiccation cause internal water loss desiccation cause internal water loss

and needs replenishing. and needs replenishing. –– Maintain conducive temperature.Maintain conducive temperature.–– Needed for capillary segmentationNeeded for capillary segmentation

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Results of Poor curingResults of Poor curing

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

–– Poor strength development.Poor strength development.

–– Drying shrinkage and resultant cracks, may Drying shrinkage and resultant cracks, may be aggravated by high ambient temperature be aggravated by high ambient temperature and low Relative Humidityand low Relative Humidity..

–– Poorly segmented capillaries resulting in Poorly segmented capillaries resulting in lower durability of concrete.lower durability of concrete.

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Effect of moist Curing on strengthEffect of moist Curing on strength

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

w/c =0.5Concrete

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Methods of curingMethods of curing

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

–– Moist (water) Curing.Moist (water) Curing.– Ponding.– Spraying.– Covering with wet sand, wetted Hessian or absorbent covering.

–– Form retention and covering concrete Form retention and covering concrete prior to settingprior to setting..

–– Membrane curing Membrane curing (spray/ hand applied resins (spray/ hand applied resins and waxes).and waxes).

–– Water proof plastic sheeting.Water proof plastic sheeting.–– Steam curingSteam curing

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Moist curingMoist curing

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

Cylinder Compressive

strength

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Curing by other methods

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

o Curing by form work, covering, membrane stops evaporation losses but do not replenish the moisture loss due to self desiccation.

o Minimum days of curing required for segmentation of capillary depends on w/c for w/c=0.4 it is 3 days and w/c= 0.7 it is 1 year.

Pozzolana blended cement or concretes with pozzolana requires more number of curing days for strength development.

IS 456 recommendations: at least, 7 days for OPC and 10 days for Blended cement/ concrete with mineral admixture

For dry and hot condition these periods are 10 &14

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High temperatureHigh temperature

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

ConcreteCast & cured at the indicated temperature

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Temperature effect Temperature effect

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

M=ΣT.ΔtT measuredAbove -11 ̊ C

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Steam CuringSteam Curing

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

Steam cured concrete w/c=0.5, curing applied immediately after casting

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Steam CuringSteam Curing

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

TypicalSteam curing Cycle

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DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

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