Materials

Saturated Surface-Dry (SSD)

The aggregate moisture state with pores full of water but no water on the surface — the basis of mix design.

An aggregate in the saturated surface-dry condition has absorbed all the water its pores will hold but carries no free water on its surface. At SSD it neither adds water to a concrete mix nor takes any away, which is why mix proportions are written for SSD weights.

Real stockpiles are rarely at SSD. Drier aggregate soaks up mix water and wetter aggregate adds free water, so batch weights are corrected using the measured moisture content and the aggregate’s absorption.

How much of the FE Civil exam is Materials?