Experimental study reveals optimal mechanical strength in concrete with up to 10% sewage sludge ash replacement, suggesting a viable eco-friendly alternative to conventional cement.
Key Points
To evaluate the feasibility and mechanical performance of sewage sludge ash as a partial substitute for cement in structural concrete.
Sewage sludge from a wastewater treatment plant was incinerated, crushed, and screened to assess particle fineness and chemical composition in accordance with ASTM C618 standards.
Concrete specimens formulated with 5%, 10%, and 15% cement replacement were tested for compressive strength across 1, 3, 7, 14, and 28 curing days, with variance analyzed using a one-way ANOVA.
Chemical characterization showed total reactive oxides (SiO2 + Al2O3 + Fe2O3) exceeded the 70% threshold, meeting Class N pozzolan criteria.
Concrete mixes with 5% and 10% replacement reached 28-day compressive strengths of 296 kg/cm² and 271 kg/cm², respectively, outperforming the target design strength of 210 kg/cm².