Sustainable Utilization of Tannery Waste Sludge in Cement concrete: Integrated Analysis of Strength, Durability, Microstructure, LCA, and Cost Efficiency

The disposal of tannery sludge (TS), a hazardous by-product of the leather industry, poses serious environmental concerns but also offers potential for sustainable cementitious applications. This study evaluates the use of TS as a partial replacement for cement in concrete production at substitution levels of 0%, 6%, 12%, 18%, 24%, and 30%. Experimental results reveal that a 12% TS replacement of cement in concrete provides optimal performance, achieving a 28-day compressive strength of 37.6 MPa compared to 31.4 MPa for the control mix. Durability assessments further demonstrate significant improvements at 12% replacement, including reduced sorptivity, enhanced resistance to chloride ion ingress, and higher acid resistance. These enhancements are may be the formation of additional C–S–H and C–A–H gels, which densify the matrix. Improved carbonation resistance and effective heavy-metal immobilization further confirm the environmental safety of the modified mix. Microstructural analyses (XRD, SEM-EDX, TGA-DTG, FTIR) support these findings, showing reduced porosity and improved C–S–H formation. Further life cycle assessment (LCA) was conducted whilerarely a notable reduction in CO₂ emissions and land-use impact at 12% replacement, aligning with sustainability targets. A Cost analysis further reveals a 7% reduction in material cost per cubic meter. Overall, the findings establish that the tannery sludge, when used in controlled proportions, can serve as a sustainable, safe, and economically viable alternative to ordinary Portland cement in concrete production.