Interfacial interaction between phosphate tailings and cement matrix in foam concrete: enhancing pore structure and mechanical strength

Phosphate tailings were used as a partial substitute for cement in the preparation of foam concrete in this study to investigate its effect on the physical properties and pore structure of foam concrete. The results showed that Ca2+, Mg2+, and CO32- dissolved from phosphate tailings reacted with Al3+ in the aluminate cement to form MgAl2(OH)8 and Mg6Al2(CO)3(OH)16. The formation of this substance promoted cement hydration and shortened the setting time. The addition of phosphate tailings to foam concrete improved the pore structure, refining pore size, enhancing pore uniformity, and minimizing pore connectivity. When the phosphate tailings content was 10 wt.%, the foam concrete had fewer pores larger than 1000 μm in size and nearly no air holes on the pore wall, the compressive strength at 7 days of foam concrete reached a maximum value of 0.96 MPa, 2.3 times higher than the specimen without phosphate tailings.