Frost resistance and sustainability of seawater-mixed sintered sludge cement paste

Abstract

Due to a loose and porous structure, the addition of sintered sludge ash (SSA) in large amounts often leads to a decrease in durability. To address the issue, a systematic investigation is conducted into the combined effects of seawater and SSA (0∼50%) on cement paste. The mixing of seawater enhances the improvement effect of 10% SSA on frost resistance and capillary water absorption. Meanwhile, the seawater-mixed cement paste containing 30% SSA withstands 125 freeze-thaw cycles, superior to PC. After seawater mixing, SSA performs better in terms of the generation of high-density C–S–H gel. The promoting effect of SSA on the transformation of capillary pores into gel pores in cement paste and its content threshold are amplified. The chemical binding of Cl− and SO42− with amorphous Al2O3 in SSA promotes the conversion of AFt to AFm. Additionally, based on multi-criteria analysis, the seawater-mixed sintered sludge cement is more competitive.

Keywords

• Seawater mixing
• Sintered sludge ash
• Pore structure
• Frost resistance
• Multi-criteria analysis