EFFECT OF NaCl SOLUTION ON PHASE STRUCTURE DEVELOPMENT OF MAGNESIUM PHOSPHATE CEMENT HYDRATION PRODUCTS

Abstract

Magnesium potassium phosphate cement (MKPC) and magnesium ammonium phosphate cement (MAPC) perform well as rapid repair materials, but the properties of their hydration products under NaCl attack (e.g., de-icing salt) are unknown. In this study, the synthesised magnesium phosphate cement (MPC) hydration products struvite and struvite-K were immersed in 5% and 15% NaCl solutions to study their phase and microstructural evolution. The results show that struvite partially dissolves in the pure water and NaCl solutions, without forming new crystalline hydrated products. However, in NaCl solutions, the morphology changes from scattered flakes to columnar structures. Struvite-K transforms into cattiite and hazenite (with higher strength) in the pure water and NaCl solutions, respectively, exhibiting flake-like morphology in pure water and clustered bloom morphology in NaCl solutions. The emergence of hazenite may contribute to MKPC displaying stronger resistance to NaCl corrosion compared to MAPC.

Keywords

• struvite
• struvite-k
• hazenite
• erosion