Powder gradation effect on the fresh, mechanical, and early-age shrinkage properties of UHPC

Particle sizes and proportions of powders (e.g., cement and mineral admixtures) may play an important role in determining the early-age performance of ultrahigh-performance concrete (UHPC). Therefore, in this study, the effects of powder gradation on the fresh state, mechanical properties, and early-age shrinkage of UHPC were investigated. The results show the effects of dense powder gradation on fluidity and early-age strength, which could be related to the variation of hydration processes. Moreover, considering the effect of the dry environment on the autoge-nous shrinkage, accurate assessments of the shrinkage components were available, which further revealed that drying shrinkage may dominate the total shrinkage of UHPC at an early age. Be-sides, as the evaporation was combined with the pore structure, the critical pore diameters were calculated and employed to theoretically clarify the development of drying shrinkage.