Hydration evolution mechanisms of magnesium ammonium phosphate cement within three days of curing

Abstract

This study systematically investigated the hydration evolution mechanisms of magnesium ammonium phosphate cement (MAPC) within 3 d of curing. The effects of magnesia-to-phosphate (M/P) ratios were mainly focused. The results showed that the samples with a high M/P ratio generated more struvite within 1 h of curing, which led to a faster initial heat release rate supported by microscopic analyses of hydration process and products. The lower M/P ratio group exhibited better performance after curing 3 h, and the amorphous intermediate phases continuously transferred and crystallized into struvite. The pore structure and electrical impedance evolution characterized by low-filed nuclear magnetic resonance and alternating current impedance spectroscopy further indicated that the attenuation amplitude of signal intensity and the increase rate of resistance were both inversely proportional to M/P ratio of MAPC within 3d. Considering both microstructure and performance, M/P ratios in the range of 3/1–3.5/1 were suggested for filed construction.