Influence of granite on physico-chemical properties of pozzolanic cement pastes prepared from volcanic ash and lime

The main goal of this study is to investigate the effect of granite powder on the hydration characteristics of volcanic ash (85 %) - lime (15 %) cement pastes. The granite powders (10, 20 and 30 wt%) were added at the expanse of volcanic ash in the cement mixes. The casted cement cubes were cured under water (water-hydrated) or cured in air (air-hydrated with spraying of water every day), for 3, 7, and 28 days. XRD, FTIR, TG, and SEM, techniques were used to monitor the phase composition, thermal analysis and microstructure of the hydrated cement pastes. The chemically combined water, bulk density, apparent porosity, and compressive strength were also determined for the hydrated cement pastes. The results reveal that amorphous and crystalline hydrated phases as well as amorphous calcium-modified silica gel in addition to other minor phases were formed after curing in water or air. Generally, the pozzolanic cement pastes cured in air exhibited improved mechanical properties than that cured in water. Furthermore, the mechanical properties were improved with increasing curing time. Moreover, the substitution of volcanic ash by granite by up to 30 % did not affect the mechanical strength of cement pastes cured in water. On the other hand, the substitution of volcanic ash by granite in mixes cured in air exhibit slight reduction in compressive strength after addition granite. The granite granules act as nucleation sites on which the hydrated phases are deposited.