Geopolymer, a new low carbon green cementing binder, has widely been used as an alternative to Ordinary Portland cement (OPC), which effectively reduces carbon emissions and industrial solid waste stockpiles on land, also improving solid waste utilization. To raise the utilization of sulphate solid waste and decrease energy consumption, desulphurization gypsum (DG)-based binary cementitious materials were synthesized, and the effects of DG dosage and alkali exciter components on the compressive strength of binary cementitious materials were investigated. In addition, the improvement mechanism of the mechanical properties of binary cementitious materials was revealed by microstructure characterization tools. The results prove that the optimum compressive strength of 52.5 ± 0.5 MPa is achieved with a DG dosage of 20 %, SiO2/Na2O of 1, water glass dosage of 10 % and water-cement ratio of 0.5. Due to the continuous reaction of sulphate in DG with Ca2+ and reactive silicates/aluminosilicates during the curing process, the crystals of ettringite (AFt) are generated and filled the pores of binary cementitious materials and thus furtherly enhancing its compressive strength. And the gel products wrap the AFt that has been filled in the inter-vacancy space on the surface of aluminosilicates already formed at an earlier stage. In summary, ground granulated blast-furnace slag (GGBS) and DG work synergistically to reduce the negative effects of delayed AFt and increase the compressive strength of the geopolymer.

Investigation on the compressive strength of desulfurization gypsum binary cementitious materials with low energy consumption: The utilization enhancement of industrial wastes