Self-desiccation is one common phenomenon of high-performance cementitious materials characterized by low water to cementitious material ratio (w/c).Autogenous shrinkage is closely related to the internal relative humidity (RH) drop and capillary pressure induced by self-desiccation in the cement pastes.However, there is debate about the determination of time-zero, the time at which autogenous shrinkage begins to develop.The objective of this study is to provide an accurate determination of time-zero based on the relationship between the internal RH and autogenous shrinkage of low w/c ratio cement pastes.And according to the time-zero, cement pastes blended with zeolite were prepared to investigate the potential of zeolite as internal curing agent.