Effect of phosphogypsum on the properties of magnesium phosphate cement paste with low magnesium-to-phosphate ratio

The incorporation of phosphogypsum (PG) in magnesium potassium phosphate cement (MPPC) can promote the utilization of PG not only by utilising the phosphate impurity in PG, but also by immobilising the heavy metals with MPPC. This paper investigates the feasibility of the incorporation of PG in preparing MPPC. Both early age properties, including workability and setting time, and hardened properties of compressive strength and microstructure, of PG-incorporated MPPC paste were investigated, and the hydration mechanism was explored. The results indicated that the addition of PG increased the workability of MPPC and extended the setting time of MPPC. However, incorporation of 20% PG slightly reduced the compressive strength because higher PG content led to the loose microstructure. Moreover, the addition of PG did not change the formation of hydration product, while it only reduced the hydration heat. Finally, compared to PG, the concentration of leached heavy metals of MPPC with PG was significantly reduced after 28 days curing. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigates the feasibility of incorporating phosphogypsum in magnesium potassium phosphate cement, showing that phosphogypsum addition can improve workability and extend setting time, while slightly reducing compressive strength at higher content due to loose microstructure. The addition of phosphogypsum does not alter hydration product formation, but decreases hydration heat, and significantly reduces leached heavy metal concentration compared to phosphogypsum after 28 days curing.