Improving the mechanical property and water resistance of β-hemihydrate phosphogypsum by incorporating ground blast-furnace slag and steel slag

•In comparison with the pure β-HPG system, the compressive strength was improved greatly, the softening coefficient was increased largely, and the water absorption rate was reduced in the β-HPG-GBFS-SS ternary system.•In β-HPG -GBFS-SS system, the 2 h strength value increased with the increasing content of β-HPG, and when fixing the content of β-HPG, the strength value increased with the decreasing GBFS/SS ratio. At 7 d and 28 d, the high-strength value in the system was greatly improved to be more than 30 MPa, and the high-strength range was distributed in the area where the β-HPG content was 60%-75% and the GBFS/SS ratio was about 3.•The hydration of SS could change the acidic environment brought by β-HPG in the system, and the GBFS hydrolyzed under the excitation to form AFt and C-S-H gels.•The new products of AFt and gels filled and wrapped in the hydration products of DG phases, making the structure of the system complete and compact, and thus greatly improving the strength and water resistance.