GATE Civil Engineering (CE) 2019 Shift 2 Solved Paper

As per IS-456, where freezing and thawing actions under wet conditions exit, inhance durability can be obtained by the use of suitable air entraining admixture. The entrained air percentage can vary from $4 \pm 1$ to $5 \pm 1$ (i.e. 3 to 6%) depending on size of aggregate. Hence, Assertion (1) is correct. Equivalent alkali content (in terms of $\mathrm{Na}_2\mathrm{O}$ equivalent) $=\mathrm{Na}_2\mathrm{O}+0.658 \times \mathrm{K}_2\mathrm{O}$ Molecular ratio of $\mathrm{Na}_2\mathrm{O}$ to $\mathrm{K}_2\mathrm{O}=0.658$ $=1\%+0.658 \times 0.6\%=1.39$ $\simeq 1.4$ (rounded to 1 decimal place).