An investigation on hydration products of MKPC at low magnesium to phosphate ratio using XRD Rietveld Method

Abstract

Low pH environment provided by magnesium potassium phosphate cement (MKPC) with low M/P (magnesia to phosphate ratio) facilitates nuclear fuel waste solidification. Understanding development on hydration products of MKPC in low pH environment is of importance. This work studies the evolution of hydration products of MKPC pastes at quite low M/P (≤1) with ongoing time by isothermal conduction calorimetry and XRD Rietveld Method. The results show that, no k-struvite (MgKPO4·6H2O) were observed in the hydration products of MKPC at M/P = 0.2. MgHPO4·7H2O and Mg2KH(PO4)2·15H2O appeared firstly followed by destabilization of MgHPO4·7H2O in a short time. Low M/P promoted the formation of MgHPO4·7H2O and Mg2KH(PO4)2·15H2O while MgHPO4·7H2O and Mg2KH(PO4)2·15H2O are unstable at higher M/P.