Recycling of air pollution control residues in low-carbon supersulfated cement: Effect of lime treatment

This study explored the feasible use of sulfate-rich air pollution control residues (APCR) to prepare supersulfated cement (SSC). The APCR was pre-treated and poste-treated with 0%, 1%, 2%, 3%, and 5% lime. The physical, hydration, and mechanical properties of SSC as well as the immobilization of soluble salts were investigated. Results showed that post-treated APCR accelerated the hydration of SSC due to its higher pH values, and SO42− and Ca2+ concentrations than pre-treated APCR. The compressive strength of SSC with post-treated APCR was significantly increased because of its high hydration degree, fine pore structure, and dense microstructure. In contrast, the pre-treated APCR with less lime deteriorated the compressive strength and initial absorption of SSC. The addition of more lime induced higher compressive strength of SSC in the air curing but reduced in the water curing. Sulfate and chloride ions were successfully immobilized in the SSC. This work provided a novel route for producing low-carbon supersulfated cement using APCR with high compressive strength, good water resistance, and high-efficiency immobilization of soluble salts.