Study of Replacement of Sand with Electroplating Waste Sludge (EWS) in Manufacturing of Concrete Paver Blocks Using Different Binder Systems

Abstract

Electroplating waste sludge (EWS) is a hazardous industrial residue containing metal-bearing phases, while the growing demand for natural river sand creates a parallel resource-conservation challenge. This study evaluates processed EWS as a partial replacement of Zone II natural river sand in M40 concrete paver blocks manufactured with OPC 43 grade cement. Five mixes were investigated with 0, 5, 10, 15 and 20% sand replacement by mass. The experimental programme covered material characterization, dimensional tolerance, dry density, water absorption, compressive strength at 7, 14 and 28 days, 28- day splitting tensile strength, Böhme abrasion resistance, and heavy- metal leaching by Atomic Absorption Spectroscopy. A preliminary 50:50 EWS-waste-plastic thermal-fusion trial was also assessed. The 10% EWS mix achieved the highest 28-day compressive strength of 51.1 MPa, approximately 6.0% above the control, together with a splitting tensile strength of 4.05 MPa and water absorption of 4.88%. The 15% EWS mix retained a compressive strength of 42.8 MPa, water absorption of 5.65%, splitting tensile strength of 3.25 MPa and abrasion loss of 15,400 mm³/5,000 mm², and was identified in the source study as the maximum viable replacement level. At 20% replacement, strength and abrasion resistance decreased and water absorption increased to 6.72%. Leachate concentrations of Cr, Ni, Zn, Cu and Pb remained below the stated CPCB discharge limits up to 15% replacement, indicating effective immobilization in the hydrated cement matrix. The unformulated plastic-EWS thermal route produced a friable, non-cohesive material and was not carried forward. Overall, the results support low-to-moderate EWS utilization as a sand-conservation and hazardous-waste-management strategy for precast paver blocks.