Chemical erosion resistance and sustainability of cement containing incinerated sludge ash

Recycling incinerated sludge ash (ISA) as a supplementary cementitious material is one of the main disposals of sewage sludge. In this study, the long-term durability properties of ISA-contained samples are comprehensively evaluated to reveal the failure mechanisms of ISA-contained samples under various chemical attack. The results demonstrate that the low reactivity of ISA and its inhibition effect on cement hydration exhibit an adverse impact on the strength development of mortars. The incorporation of ISA increases the drying shrinkage of ISA-contained samples due to its porous structure. The carbonation degree of mortars increases with the dosage of ISA due to the reduction in cement clinker content and the consumption of portlandite from the pozzolanic reaction of ISA. Aluminates dissolved from ISA generate a large amount of ettringite under the sulfate attack. In the early stage of attack, ettringite refines the pore structure of the matrix in ISA-contained samples, promoting strength development. However, the matrix eventually undergoes expansion failure due to the continuous formation of crystal products. ISA-contained mortars exhibit enormous environmental benefits. The carbon emissions and fossil fuel depletion of mortars are greatly reduced by the replacement of cement with ISA. The multi-criteria evaluation results reveal that the optimum dosage of ISA is 10 wt% under the comprehensive consideration of strength development, durability and environmental impacts.