The influence of the hydration procedure of MgO expansive agent on the expansive behavior of shrinkage-compensating mortar

摘要

The objective of this paper is to evaluate the influence of the hydration process of MgO expansive agent in binder on the expansion of shrinkage-compensating mortar. The variation of MgO and Mg(OH)(2) content in binder at certain curing ages was examined quantitatively through X-ray diffraction (XRD) Rietveld analysis. Expansive behavior of shrinkage-compensating mortars containing MgO expansive agent was also investigated as a comparison with the hydration process. Results indicated that the hydration speed of MgO is determined by its reactivity, highly reactive MgO results to a fast hydration and expansion speed. The curing condition (sealed or saturated) hardly influences the hydration speed of MgO, but largely influences the expansion rate of mortars. The expansion effect due to MgO hydration lags behind its reaction in the binder paste. Sufficient pore water contributes to the recrystallization of Mg(OH)(2), which thus causes high crystal growth pressure and promotes the expansion of mortars. (C) 2019 Elsevier Ltd. All rights reserved.