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DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
CEL 774 CONSTRUCTION PRACTISESCONSTRUCTION PRACTISES
Hot & Cold weather Concreting
B. Bhattacharjee
CIVIL ENGINEERING DEPARTMENTIIT DELHI
General Outline
• Hot Weather problems• Concreting • Mass Concrete• Cold weather problem• Concreting in cold weather
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
Hot Weather problems
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
Rapid Hydration → accelerated setting→ Lower long term strength dueto less uniform frame work of gelRapid evaporation in lower humiditycauses loss of water → Plastic shrinkage& crazingIn mass concrete cracks due to thermalgradient is also experiencedAir entrainment is more difficult at highertemperature.
Affect of 28 days on strength of concrete
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
w/c=0.41Air content 4.5%
Hot Weather problems
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
Curing at high temperature posesadditional problem due to rapidevaporation → slower hydration
→ Inadequate development of strength &→may be cracking due to shrinkage
Hot weather concreting
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
Lower temperature of aggregate by sprinklingwater , shading, retarders tom prevent loss ofslump; Lower temperature of cement & water;May use iceHeat balance equation
T temperature of the mixtureSWW(T-TW)+SCC(T-TC)+SA(CA+FA)(T-TA)+SWWWA (T-TA)=0
Hot weather concreting
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
T=WTW+SCCTC/SW+SA(CA+FA)TA/SW+WWATA)/[W+SCC/SW+SA(CA+FA)+ WWA ]
T=WTW+0.22{CTC+(CA+FA)TA}+WWATA)/[W+0.22{C+(CA+FA)}+ WWA ]
When ice is added: all ice must melt beforemixingT=WTW+0.22{CTC+(CA+FA)TA}+WWATA-LWi)/[W+0.22{C+(CA+FA)}+ WWA +Wi]
Evaporation loss prevention
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
ACI 305.RLoss > 0.5 kg/m2
is to be avoided
Hot Weather problems
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
Temperature differentials cause thermalcracking
Creep relieves the stressWhen interior cools it would tend to contractstress in the exterior is relieved but furthercontraction may result in compression ofexterior and tensile stresses in interior, creepis now less, can result in crackingInsulation may reduce this effect whenwhole mass is not restrained
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
SummaryHot
Insitu testing
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
THANK YOU FOR HEARING
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