Cement testing — which apparatus is specifically used to assess the soundness (volume stability on hydration) of cement? Choose the most appropriate option.

Introduction / Context:
Soundness is the ability of cement to retain its volume after setting without delayed expansion. Excessive unsoundness leads to cracking, disintegration, and loss of durability in concrete and mortar. This question checks whether you can correctly identify the standard laboratory apparatus dedicated to evaluating cement soundness (volume stability) rather than consistency, setting time, or strength.

Given Data / Assumptions:

• Ordinary Portland cement specimen is to be tested for excess free lime or magnesia that may cause late expansion.
• We must distinguish between instruments for consistency/setting, strength, and soundness.
• Standard laboratory conditions and procedures are assumed.

Concept / Approach:
Le-Chatelier apparatus measures the expansion of a cement specimen when exposed to boiling water after initial setting. The spread of the split cylinder’s pointers indicates potential unsoundness. By contrast, Vicat apparatus measures standard consistency and initial/final setting times, and a compression testing machine measures strength—not soundness.

Step-by-Step Solution:

Verification / Alternative check:
Reference procedures for soundness testing specify Le-Chatelier method for Portland cements susceptible to free lime and magnesia expansion. Autoclave expansion is another method for certain cements, but the named apparatus for routine soundness is Le-Chatelier.

Why Other Options Are Wrong:

• Vicat's apparatus: For standard consistency and setting time, not soundness.
• Compressive strength testing machine: Measures strength only.
• None of these: Incorrect because Le-Chatelier is correct.

Common Pitfalls:
Confusing consistency/setting (Vicat) with soundness; assuming high strength guarantees soundness—these are independent properties.

Final Answer:
Le-Chatelier apparatus