Which statement about SSD conditioning is true?

• A. An SSD condition is one in which the aggregate contains only small amounts of free water on its surface.
• B. Shaking the basket to release any entrapped air as it is placed in the water bath is not recommended due to potential sample loss.
• C. When performing the cone test to check the condition of the sand, permit the tamper to fall freely from 50 mm over the top of the sand.
• D. The sample is covered with water either by complete immersion or by adding approximately 6 % moisture.

Answer: (D)

SSD conditioning means the aggregate is saturated in its pores with no free moisture on the surface, so tests see consistent absorption and compaction behavior. To reach this state, the sample is wetted until the pores are full and any surface water is removed, either by complete immersion with drainage or by bringing the moisture content to about 6% by weight. This ensures the material behaves predictably during testing.

The other statements don’t fit because one describes having a small amount of free water on the surface, which contradicts SSD; another emphasizes shaking to release entrapped air, which isn’t the standard approach for achieving SSD; and the remaining item relates to a cone test procedure for sand rather than SSD conditioning.