Study on the mechanical properties of phosphogypsum composite cementing materials based on alkali excitation

In this research, phosphogypsum composite cementing material using phosphogypsum powder, slag powder, fly ash and cement were prepared as the main cementing materials, and sodium silicate was used as the activator. The influence of the cement content of 0 wt.%, 5 wt.%, 10 wt.%, 15 wt.% and the change of 0%, 2%, 4% alkali equivalent on the mechanical properties of cementing materials was studied, the types and content of admixtures suitable for phosphogypsum cementitious materials were also studied. The cost of the materials used was calculated and analyzed. The results showed the increase in cement content and alkali equivalent will improve the mechanical properties of the cementitious material, and the strength can reach 23.0 MPa; the change of alkali equivalent had a more obvious impact on the early (1 d) mechanical properties of the cementitious material than cement; when these two factors synergistically worked, the cement content should not exceed 10 wt.%, or the mechanical properties of the material would decline; the effect of using the naphthalene-based water-reducing agent was better than that of the polycarboxylic acid water-reducing agent, and when cement, sodium silicate and naphthalene water reducer were used together, the maximum compressive strength of 7 d reached 24.4 MPa, which was higher than 39.4% of the sample without water reducer. The ratio used in the experiment was relatively low cost, which had a great reference value for the comprehensive utilization of industrial by-product phosphogypsum.