GATE CE 2015 Set 1 — Question 15

MCQ+1 / -0.33EasyWorkability of ConcreteConstruction MaterialsStructural EngineeringDurability of Concrete

Structural Engineering → Construction Materials → Durability of Concrete

Last updated 5 September 2026

Question

Consider the following statements for air-entrained concrete: (i) Air-entrainment reduces the water demand for a given level of workability (ii) Use of air-entrained concrete is required in environments where cyclic freezing and thawing is expected Which of the following is TRUE?

Correct answer (A) Both (i) and (ii) are True Solution Air-entrainment involves the intentional introduction of microscopic air bubbles into concrete. 1. Workability : The tiny air bubbles act like ball bearings, reducing internal friction between aggregate particles. This improves the workability of the mix, allowing for a reduction in the amount of water needed to achieve a specific workability level. Thus, statement (i) is True. 2. Durability : The primary purpose of air-entrainment is to improve resistance to freeze-thaw cycles. The air bubbles provide empty spaces where water can expand as it turns into ice, preventing internal pressure that would otherwise cause cracking and scaling. Thus, statement (ii) is True. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (A) Both (i) and (ii) are True Solution Air-entrainment involves the intentional introduction of microscopic air bubbles into concrete. 1. Workability : The tiny air bubbles act like ball bearings, reducing internal friction between aggregate particles. This improves the workability of the mix, allowing for a reduction in the amount of water needed to achieve a specific workability level. Thus, statement (i) is True. 2. Durability : The primary purpose of air-entrainment is to improve resistance to freeze-thaw cycles. The air bubbles provide empty spaces where water can expand as it turns into ice, preventing internal pressure that would otherwise cause cracking and scaling. Thus, statement (ii) is True.

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