Hydration study and characteristic analysis of a sulfoaluminate high-performance cementitious material made with industrial solid wastes

A sulfoaluminate high-performance cementitious material (SHCM) was prepared using flue gas desulfurization (FGD)-gypsum, coal gangue, limestone tailings, and aluminum ash as raw materials. The composition of the SHCM clinker, mechanics and hydration properties of the SHCM, and heavy metal leaching characteristics of the SHCM pastes were studied. The results showed that the mineral phases of the SHCM clinker were similar to that of ordinary sulfoaluminate cement (SAC) clinker, mainly including calcium sulfoaluminate and dicalcium silicate, and the key differences were that the SHCM clinker had an excessive content of calcination-formed anhydrite and contained some gehlenite. The 3-day and 28-day compressive strength of the SHCM mortars reached up to 45.7 MPa and 67.8 MPa, respectively, and a continuous strength gain was observed in the later age, unlike that in the case of ordinary SAC. The cumulative hydration heat during the first 3 days of the SHCM was 283 J/g, which is lower than that of ordinary SAC under the same conditions. Additionally, the SHCM pastes also showed good immobilization ability of heavy metals in the hydration process, with the leaching concentrations of Zn, Cr, As, and Cu much lower than the limits of Chinese National Standard, and with retention ratios of Zn, Cr, As, and Cu in SHCM pastes over 90%, at each hydration age. This work provides a practical and effective way to transform industrial solid wastes to value-added, high-performance and green sulfoaluminate cementitious material.