Characterization of Magnesium Phosphate Cement Incorporating Waste Glass Powder as Mineral Admixture

This article utilized waste glass in the form of glass powder (GP) and researched its effects on the properties of magnesium phosphate cement (MPC), which were investigated via working properties, mechanical properties, microstructures, and hydration products. The results showed that successive additions of GP to MPC led to a cumulative decrease in setting time and fluidity. A suitable dosage of GP (within 15%) as magnesia replacement improved the mechanical properties of hardened MPC mortar, but it decreased upon more additions. The sample blended with 10% GP exhibited a fluidity of 242 mm and a setting time of 20 min, with a 28-day compressive strength of 78.2 MPa, which was the highest among all the groups, and it met the requirements for applying in field construction. The XRD, SEM-EDS, TGA-DTG, and NMR tests showed that GP accelerated the hydration rate and promoted the crystallization process of hydrates. More gels were produced in MPC after incorporating GP, where some calcium-phosphate and sodium-phosphate gels were formed by the alkali components with phosphate. However, activating the silicate glassy phases content in GP was difficult. The microstructure observed via SEM and the pore structure measured by an optical microscope with MIP illustrated that GP compacted the microstructure, reduced the total porosity, and improved the pore size distribution of MPC by the pore-filling effect. The research indicated that GP could be regarded as a mineral admixture in MPC, making MPC more eco-friendly and suitable for use as a rapid repair material.