Mechanisms of autogenous shrinkage for Ultra-High Performance Concrete (UHPC) prepared with pre-wet porous fine aggregate (PFA)

Here, the intrinsic driving mechanisms of autogenous shrinkage for Ultra-High Performance Concrete (UHPC) incorporating porous internal curing (IC) medium are detailly investigated, including characterization and monitoring of UHPC hydration kinetics, internal relative humidity (IRH) and internal temperature (IT) fields. The results show that the autogenous shrinkage evolution of UHPC prepared with pre-wet porous fine aggregate (PFA) undergoes multiple stages. The potential expansion drivers of UHPC with IC at super early hardening period are identified as the extra liquid volume compensation and the effect of thermal expansion. Furthermore, the rapid shrinkage growth stage of the UHPC matrix is governed by the hydration dynamic, while the sustained shrinkage growth stage is managed by cold shrinkage, chemical shrinkage and capillary pressure. Finally, the feasibility of the Powers model in the design of UHPC incorporating wet PFA is carefully revealed, and the key parameters for obtaining UHPC with advanced volumetric stability are elucidated. The strategy in terms of the autogenous shrinkage for the UHPC designed with PFA is revealed.