Investigation on the preparation of low carbon cement materials from industrial solid waste phosphogypsum: Clinker preparation, cement properties, and hydration mechanism

Abstract

Low-carbon calcium sulfoaluminate (CSA) cement can be prepared with industrial by-product phosphogypsum (PG). This paper uses PG to replace natural gypsum in preparing PG-based CSA (PGCSA) cement as a raw material and mineral admixture, and the mechanical properties and hydration mechanism of PGCSA cement are explored. The results showed that the clinker with ye'elimite mineral content of 67.23% was fired at 1250 °C by mixing 19.52% PG into the raw materials. The participation of PG in hydration can accelerate the hardening of paste and improve the compressive strength of cement. The optimum dosage of PG as a mineral admixture was 20%, and the compressive strength reached 88.4 MPa at 28 days. Added PG promoted the early hydration of ye'elimite, and reaching 60% hydration within 1 day. The hydration mechanism was believed that a large amount of Ca2+ released by PG dissolution increased the ion concentration and promoted the hydration of ye'elimite. The PGCSA cement prepared in this study at 1250 °C had low carbon emission and PG utilization was higher than 40%. In addition, the pH and exothermic hydration of PGCSA cement were reduced about 2 and 100 J/g compared to that of CSA cement. This paper provides a feasible solution for PG resource utilization and carbon reduction.