Bogue's Compounds MCQ with answer and solution

Concept

Bogue compounds in cement hydration and their respective heat generation characteristics.

Step-by-step solution

Step 1: Identify the main Bogue's compounds in ordinary Portland cement: C₃S, C₂S, C₃A, and C₄AF. Step 2: Recall the heat of hydration values for each compound: C₃A (~865 J/g), C₃S (~502 J/g), C₂S (~260 J/g), and C₄AF (~418 J/g). Step 3: Compare the values to find that C₃A has the highest heat of hydration.

Explanation

Tricalcium aluminate (C₃A) hydrates the fastest and releases the maximum amount of heat of hydration during the early stages of cement setting. Although C₃S also contributes significantly to early strength and heat, C₃A has the highest heat of hydration per unit mass (~865 J/g).

Why the other options are wrong

A: C₃S has high heat of hydration and early strength, but lower than C₃A. B: C₂S has the lowest heat of hydration and hydrates slowly, contributing to ultimate strength. D: C₄AF has an intermediate heat of hydration, lower than C₃A.

Shortcut

Remember the order of heat of hydration from highest to lowest: C₃A > C₃S > C₄AF > C₂S.

Common mistake

Confusing C₃S (which has the highest contribution to early strength and substantial heat) with C₃A, which actually has the highest heat of hydration per gram.