Hydration of ternary blended cements integrating Drinking Water Treatment Sludge as an artificial pozzolanic material

Abstract

One of the biggest challenges facing the cement industry is lowering clinker production without impacting product quality, requiring the investigation of sustainable supplementary cementitious materials (SCMs) in ternary cement system with clinker and limestone. The sludge was thermally treated for 2 h (120 min) at 500°C, 600°C, 700°C, 800°C and 900°C and its reactivity was assessed using R3 protocol through bound water and isothermal calorimetry. Hydration behavior, heat evolution, strength development, and microstructural characteristics were also investigated. Bound water reached its maximum at 600 °C (19.02 %), but this did not enhance strength because hydration was dominated by aluminum-based products rather than calcium silicate hydrate. The optimum activation occurred at 800 °C, where heat release peaked at 211.7 J/g after 7 days and structural changes generated a reactive amorphous phase. Mortars containing 30 % sludge calcined at 800 °C achieved compressive strengths of 47 MPa at 7 days and 65.47 MPa at 28 days. Hydration analysis confirmed the formation of ettringite, monosulfate, and portlandite, highlighting the role of alumino-silicates in strength development. • DWTS evaluated as a sustainable SCM in ternary cement systems. • Optimal calcination temperature of 800°C enhances pozzolanic reactivity. • DWTS-ternary blends achieved 65.47 MPa compressive strength at 28 days. • Hydration products characterized via combined XRD-TGA analysis. • DWTS enables eco-friendly, high-performance cement for carbon neutrality.