Preparation and performance study of phosphogypsum slag based magnesium potassium phosphate cement

Abstract With the production of phosphate fertilizer or phosphoric acid, a large amount of phosphogypsum (PG) is generated as industrial waste and deposited in the open air, causing environmental pollution and occupying land resources. In this study, 0.00%~90.00% PG was used to replace the MgO at 10.00% intervals by the internal mixing method for preparing the magnesium potassium phosphate cement (MKPC). Finally, the physical and mechanical properties of MKPC were investigated. The results showed that with the increase of PG addition, the setting time and compressive strength of MKPC was prolonged and decreased, respectively. The effect of internal doping of PG was significantly better than the external doping for the MKPC preparation, with an optimal addition of internal doping of 50.00% PG. The results also showed that when the mass ratio of MgO, KH2PO4, and PG was 1:1:1, the setting time of the MKPC is 8 min, the compressive strength at 28 days reaches 46.2 MPa, which can still reach the strength of 42.5 grade Portland cement. The mechanism study showed that PG addition significantly slows down the hydration of MKPC and participates in the reaction to produce the hydration product, such as the physical phase of MKPC is MgKPO4·6H2O, CaSO4·2H2O, K2SO4 and unreacted MgO. This work is well help to reduce the burden of PG on the environment and contribute to the sustainability of the construction industry.