Crystal morphology of calcium aluminates hydrated for 14 days

摘要

The active phases during early hydration of calcium aluminate cement are CA (C = CaO; A = Al2C>3) and C12A7, but CA2 seems to be fairly inactive before the massive precipitation [1]. The phenomenon of strength degradation of calcium aluminates as related to the phases transformation, i.e., conversion of metastable transition phase CAH10 (H = H2O) into unstable C2AH8 and finally stable C3AH6 phase [2-4]. Many researchers [5-7] have investigated the development of these hydrated phases by electron microscopy. The effects of crystal morphology on the hydration characteristics and setting time have also been studied by some workers [8-9]. The aim of the work reported here is to investigate exactly what the crystal habit and morphology are on the fourteenth day of hydration of calcium aluminates, and what their role is in the development of compressive strength of the hydrated samples.