text: Among these four moisture condition of aggregates, saturated surface dry is the condition that has the most applications in laboratory experiments, researches and studies, especially these related to water absorption, composition ratio or shrinkage test in materials like concrete. For many related experiments, a saturated surface dry condition is a premise that must be realize before the experiment. In saturated surface dry condition, the aggregate's water content is in a relatively stable and static situation where it would not be affected by its environment. Therefore, in experiments and tests where aggregates are in saturated surface dry condition, there would be fewer disrupting factors than in other three conditions.