'Thermal cracking' in mass concrete (like dam and raft foundations) is controlled by:
Choose the correct answer
Using rapid-setting cement
Low-heat cement, pre-cooling, post-cooling pipes, and pour size limits — reduce temperature rise and gradient during hydration
Adding more water to concrete
Heating the concrete externally
Correct Answer
B. Low-heat cement, pre-cooling, post-cooling pipes, and pour size limits — reduce temperature rise and gradient during hydration
Why is this the answer?
Mass concrete: heat of hydration causes temperature rise (peak at 2–3 days); subsequent cooling → tensile stress → cracking if ΔT > 20°C (thermal gradient). Control: (1) Low heat cement (LHC/SRC/fly ash blends); (2) Pre-cooling aggregate and mixing water (chilled water, ice); (3) Post-cooling with embedded water pipes; (4) Limiting pour depth/width; (5) Insulation of formwork. IS 7861 covers hot weather concreting.
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