What does soundness testing of aggregates primarily evaluate?

The soundness testing of aggregates primarily evaluates the durability of the aggregates against freeze-thaw cycles. This testing is crucial for determining how well aggregates can withstand conditions where they may be subjected to repeated freezing and thawing. In environments where temperature fluctuations occur, it is essential that aggregates do not suffer degradation or disintegration due to the formation of ice within their pores.

During the soundness test, aggregates are subjected to cycles of freezing and thawing, and their ability to maintain integrity without significant loss of mass or strength is assessed. This property is critical because failure in freeze-thaw conditions can lead to serious structural issues in concrete, affecting its longevity and overall performance.

The other options pertain to different aspects of aggregate evaluation: thermal resistance is related more to how aggregates manage heat, resistance to physical stress examines their mechanical properties under load, and moisture absorption capacity deals with how much water the aggregates can absorb. While all these factors are important for various applications, they do not specifically address the freeze-thaw durability that soundness testing focuses on.