Novel insights into the amorphous feature of granulated blast furnace slag-supplemented magnesium potassium phosphate cement and its effect on bulk properties

This paper reports the effects of MgO:PO₄ (3, 9, and 15) ratio and granulated blast furnace slag dosage (0 wt%, 40 wt%, and 80 wt%) on the phase formation, microstructure, and bulk properties of magnesium potassium phosphate cement (MKPC). Results show that the supplementary of slag and the increment in MgO:PO₄ inhibit the formation of K-struvite via X-ray diffraction. While the detections of ²⁹Si magic-angle spinning nuclear magnetic resonance spectroscopy and scanning electron microscope-energy dispersion spectrum further unveil the dissolution of slag and the formation of Q₄ amorphous structure in slag supplemented MKPCs. Although the Q₄ structure increases the interplanar spacing of K-struvite even leads to its amorphization in MKPCs with high MgO:PO₄ (>9), the optimum coexisting of K-struvite and Q₄ structure minimizes the porosity and maximizes the compressive strength of MKPCs with MgO:PO₄=3 and 40 wt% slag. These results are crucial to developing optimal mixture formulations of MKPC with superior mechanical performance and lower costs associated with their production.