Effect of mechanical activation on hydration properties of natural volcanic rock towards partially replacing cement in composite cementitious materials

Abstract

With the rapid increase in the consumption of various mineral admixtures, using regional distinctive raw materials to prepare cement mineral admixtures is an effective approach to achieve green and sustainable development. In this paper, the natural volcanic rocks (NVR) in Western Sichuan are mechanically activated at different times, subsequently, the ion dissolution characteristics of NVR powder at different activation times and the hydration mechanism of NVR powder composite cementitious material are studied. In a simulated alkaline environment of cementitious liquid phase, based on the dissolution behavior of Si4+, Al3+, and Ca2+ ions in NVR powder and the morphological analysis of NVR powder before and after dissolution, it is indicated that SiO2 and Al2O3 are the primary sources of reactivity in NVR powder and the reduction in particle size promotes the breakage of Si–O and Al–O bonds in NVR powder. Analysis of the hydration process, mineral composition of hydration products, and their microscopic morphology reveals that an appropriate amount (15 %) of NVR powder, after 45 min of mechanical activation, can promote the generation of hydration products and denser mortar structure, enhancing the strength of the composite cementitious material. Mainly attributed to the increased volcanic ash activity of NVR powder through mechanical activation, as well as the nucleation induction and filling effects of NVR powder. This study provides theoretical and technical supports for the efficient use of raw materials with regional characteristics to prepare mineral admixtures.