Examining the “time-zero” of autogenous shrinkage in high/ultra-high performance cement pastes

There is a general agreement about the existence of a relationship between autogenous shrinkage and RH changes in hardening cement paste. An improved hygrometer method was developed for monitoring the change of internal RH in cement pastes 1 h after casting. This provides immediate experimental results of RH change for determining the “time-zero”. It indicates that the internal RH of cement pastes does not decrease immediately after the final setting time. A new “time-zero” is defined as the onset of internal RH drop, which is more reasonable for estimating the cracking potential of cement-based materials, compared to the “time-zero” represented by the final setting time.