Building stones — purpose of Smith’s test In traditional stone testing for civil engineering works, Smith’s test is performed mainly to determine which characteristic of a stone sample?

Introduction / Context:
Before selecting building stones for masonry, engineers carry out several field and laboratory tests. Among these, Smith’s test is a simple procedure aimed at identifying deleterious soluble substances that may cause efflorescence, staining, or durability issues.

Given Data / Assumptions:

• Hand specimen or small fragments of the stone are available.
• Basic chemicals and water are used to reveal the presence of soluble impurities.
• Goal is rapid screening, not full mechanical characterization.

Concept / Approach:
Soluble salts such as sulfates, chlorides, and other alkalis can migrate with moisture, crystallize on surfaces, and produce efflorescence or internal stresses. Smith’s test targets such soluble matter qualitatively, alerting the engineer to potential service problems.

Step-by-Step Solution:

Verification / Alternative check:
Complementary tests include water absorption, efflorescence checks on masonry panels, and sulfate soundness tests, which together give a more complete picture of durability risk.

Why Other Options Are Wrong:

• Compressive strength (B): measured by compression testing machine, not by Smith’s test.
• Hardness (C) and toughness (D): evaluated via abrasion/impact tests (e.g., Los Angeles, Deval, impact value), not Smith’s.
• Specific gravity (E): found by density/volume measurements; unrelated to Smith’s qualitative soluble-matter check.

Common Pitfalls:
Relying solely on Smith’s test to approve stone; it is indicative, not definitive. Always corroborate with mechanical and durability tests per project requirements.

Final Answer: