Hydration Process for Calcium-Aluminate Cement within EVA Emulsion by SPring-8 Synchrotron Radiation X-ray Diffraction Method

Abstract

Polymer-modified mortars which consist of a polymer emulsion and cement materials have been widely developed in the construction materials fields. Forming process of the polymer-modified cement membrane simultaneously involves evaporation of water within the polymer emulsion and hydration of cement. It is important for the polymer-modified cement paste that the hydrate crystal of cement is generating by the hydration during the setting process under existence of the polymer emulsion. In this study, hydration process for calcium-aluminate cement under existence of poly ethylene-vinyl acetate EVA emulsion polymer-cement ratio = 100% was investigated by X-ray diffraction method using synchrotron radiation SPring-8 . The diffraction peaks of calcium aluminate CA disappeared after the hardening, on the other hand, the peaks of hydrate crystals of calcium-aluminate cement C2AH8 and C3AH6 could be observed. This polymer-modified cement paste hydrated using the water within the polymer emulsion. The hydration of C2AH8 from CA started at around 300min, and then C3AH6 hydrate crystal increased after 700min at ambient temperature. This implies that the conversion from C2AH8 to C3AH6 occurred to be more stable phase. The setting temperature affected the reaction rate. In case of hydration at 35 , the start time of the hydration for calcium-aluminate cement was quicker than that in the ambient temperature four or more times.