Effect of M/P and Borax on the Hydration Properties of Magnesium Potassium Phosphate Cement Blended with Large Volume of Fly Ash

Abstract

The effect of the borax content and magnesia to phosphate ratio (M/P) on the hydration properties of the magnesium potassium phosphate cement (MKPC) with large volume of fly ash was investigated, and a five-hydration-stage for MKPCs was proposed. The results show that MKPC sets rapidly with less than 8% of borax, which is unfavorable to the application of MKPC on construction. Adding more than 8% (including 8%) of borax results in a secondary hydration peak for MKPC, in which the process of hydration can be divided into five stages, namely, pre-induction period, induction period, acceleration period, deceleration period and stable period. M/P ratios could not change the multi-step reactive stages but higher M/P ratios could accelerate the hydration. Borax tends to impact the formation of Mg-containing hydrated products.