Hydration mechanisms and mechanical properties of pumice substituted cementitious binder

Abstract

This paper reports the hydration production, micro structuring, and compressive strength results of Portland cement-pumice systems. The compressive strengths of cement mortars examined on the 2nd, 7th, 28th, and 90th days in the first stage. In the second step, hydration mechanisms of cement paste samples containing 0%, 10%, and 20% pumice at the 2nd, 7th, 28th, and 90th ages were determined by SEM, FT-IR, XRD, and DTA/TGA. In addition, the chemical, physical, molecular, mineralogical characterizations of the pumice and Portland cement were detected. Water demand, setting time, and volume expansion of paste samples with standard cement tests were determined. The XRD and TGA results prove that the pumice-containing cement displays a high hydration degree on the 90th day and will continue to hydrate. Furthermore, on the 90th day, the chemically bound water content in 10P paste is the same as that in Portland cement. Moreover, SEM images reveal that the usage of pumice results in a much denser microstructure as the hydration age increases. The results showed that pumice has lower pozzolanic activity in the early period and yet the compressive strength increases with time.