Does the hydration process of supplementary cementitious materials affect the aging creep of blended cement paste?

Abstract

In cementitious materials, continuous hydration of mineral phases and creep always coexist, making it difficult to decouple the effect of hydration on creep measurements, which are invariably time-dependent. This study compares a real hydration (aging) system with an equivalent hydration (non-aging) system. In the non-aging system, the unhydrated phase was replaced with inert quartz at specific ages (1, 7, 28, and 91 days) to uncover the mechanism of clinker and supplementary cementitious materials (SCMs) hydration on creep. The results show that the hydration process of SCMs and morphology of calcium-aluminate-silicate-hydrates (C-A-S-H) dominate the creep magnitude and kinetics. The ongoing pozzolanic reaction of fly ash (FA) significantly increases creep, whereas the formation of foil-like C-A-S-H in slag (SL) blends inhibits its creep, except for the significant early-age creep due to the steep reaction of SL at the corresponding period. The high calcium concentration in cement pore solution delays the further hydration of the clinker, thereby slightly inhibiting the development of creep. The hydration-triggered dissolution of SCM and clinker contributes to creep development, whereas the load-induced dissolution of C-A-S-H may account for aging creep.