Water stability improvement and mechanism of magnesium phosphate cement modified by colloidal nano silica

Colloidal nano silica (CNS) demonstrated positive effects in enhancing the water stability of magnesium phosphate cement (MPC), and the underlying mechanism was investigated systematically in this paper. The experimental results showed that the nucleation effect of CNS accelerated the intermediate phase transition process and significantly enhanced the struvite early formation rate of MPC. Moreover, the addition of CNS led to a shift from macropore to gel pores observed from pore size distribution. Notably, the filling effect of CNS and the formation of novel hydration products were identified as critical factors in enhancing water stability and optimizing pore structure. Simulation experiments provided further validation that CNS could directly react with dead-burnt magnesium oxide to generate a novel gel phase-magnesium silicate hydrate (M-S-H) which confirmed a possible hydration reaction of silica in MPC.