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GATE 2019 CE (CE2) – Question 41

Construction Materials · Cement: hydration, admixtures · 2 marks · Multiple choice

Assess durability assertions: (1) IS 456:2000 requires 3% to 6% air entrainment for concrete exposed to marine environment. (2) For cement containing 1% Na₂O and 0.6% K₂O, equivalent alkali content as Na₂O is approximately 1.4%, to one decimal place.

  1. 1 false and 2 true
  2. 1 true and 2 false
  3. both false
  4. both true

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Correct answer: (A) 1 false and 2 true

Explanation

The 3–6% air-entrainment provision concerns freezing/thawing exposure, not a general marine-environment requirement; assertion 1 is false. Alkali equivalent is $\mathrm{Na_2O}+0.658\mathrm{K_2O}=1+0.658(0.6)=1.3948\%$, rounded to 1.4%; assertion 2 is true. Answer **A**.