Q: What does the term “saturated surface dry” mean in relation to concrete aggregates?

A: The term is one of four used to describe the moisture content of the aggregate prior to mixing, and refers to a condition where all pores in each particle of aggregate are filled with water, but no excess water appears on the surface of the particle. The other terms are “ovendry” for aggregate that contains no moisture, “air dry” for aggregate that has absorbed some moisture but less than its potential absorption, and “wet” for aggregate that has collected more water than it can absorb. It’s important to determine the moisture content of aggregate prior to mixing, because it affects the proportion of mix water needed to achieve the desired water/cementitious materials ratio.