Select the cements from the following that may be used in mass concrete construction. 1. Low heat Portland cement, 2. Portland blast furnace slag cement, 3. Portland pozzolana cement, 4. Rapid hardening Portland cement.

A. Only 1

B. 1 and 2

C. 1, 2 and 3

D. All

Correct Answer: C. 1, 2 and 3

🏛️ Suitable Cements for Mass Concrete

Mass concrete generates significant heat of hydration. If temperatures rise too high, differential cooling causes thermal cracking. Cements must therefore produce low heat of hydration:

1. Low heat Portland cement (IS 12600) — specifically formulated with less C₃A and C₃S to minimise heat. ✔

2. Portland blast furnace slag cement (IS 455) — slag replaces clinker, generating less heat over a longer period. ✔

3. Portland pozzolana cement (IS 1489) — fly ash or calcined clay replaces clinker, reducing heat. ✔

4. Rapid hardening Portland cement — gains strength quickly by generating high heat. Unsuitable for mass concrete. ✘

Cements 1, 2 and 3 are suitable — option C.

Key takeaway

Mass concrete needs low-heat cement. Rapid hardening = high heat = thermal cracking risk. Avoid it in large pours.

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