Cement testing — purpose of the soundness test The soundness test of cement primarily assesses which aspect of cement quality?

Introduction / Context:
Unsound cement expands excessively after setting, leading to cracking and failure in concrete. The soundness test is designed to detect potential late expansion due to undesirable constituents, protecting long-term durability.

Given Data / Assumptions:

• Problematic constituents: excess free CaO and MgO that hydrate slowly and expand.
• Common test methods: Le Chatelier and autoclave expansion tests.
• Objective: ensure volume stability of hardened cement paste.

Concept / Approach:
Free lime and periclase (MgO) can hydrate after setting, causing volumetric instability. Soundness tests accelerate conditions to reveal such expansion risk. They do not measure strength or set times; those are separate standardized tests.

Step-by-Step Solution:
Recognize the property measured: freedom from excessive expansion.Link expansion to free CaO/MgO content and their late hydration.Therefore, soundness testing primarily assesses the presence/effect of these expansive components.

Verification / Alternative check:
Compare acceptable expansion limits in standards; cements failing soundness often show higher free CaO or MgO in chemical analysis.

Why Other Options Are Wrong:
Ultimate strength, setting time, and fresh workability are measured by different tests (compressive strength cubes, Vicat, and slump/flow tests), not by soundness procedures.

Common Pitfalls:
Assuming sulfate resistance equals soundness; confusing autoclave expansion (soundness) with sulfate expansion tests on mortar bars.

Final Answer:
quality of free lime (and magnesia) causing excessive expansion