COMPARATIVE EVALUATION OF WTE RESIDUE: INCINERATION ASH AND PAG VITRIFIED SLAG AS SUSTAINABLE CONSTRUCTION AGGREGATES

Abstract

This study addresses the problem of managing hazardous incineration ash in Indian urban centres. Conventional grate-fired incineration reduces waste volume but generates ash that is chemically unstable, prone to leaching, and environmentally risky if dumped without proper treatment, creating a long-term waste-management and pollution challenge for urban local bodies. The research evaluates Plasma Arc Gasification (PAG) as a technology that can destroy residual organic matter, reduce waste volume further, and generate PAG-vitrified slag as a high-performance synthetic aggregate suitable for structural construction use. The objective is to compare incineration ash and PAG-vitrified slag across physicochemical, environmental, and mechanical parameters to demonstrate that the slag can safely replace natural river gravel and quarried stone in road sub-bases and other structural applications. A comparative secondary-data analysis is used, drawing on published studies of physicochemical composition, TCLP-based leaching behaviour, and mechanical performance of both materials, referenced against USEPA TCLP leaching limits and Indian Standards IS 383:2016 and IS 2386. Key parameters include LOI, glass content index (G%), immobilization efficiency (IE%) of heavy metals, compressive strength, LA abrasion value, 10% Fines Value, and flakiness index. Results show that PAG-vitrified slag is chemically and mechanically superior to incineration ash. LOI drops from 15.6% in ash to 0.5% in slag, indicating near-complete organic removal, while G% reaches 80.7%, confirming a predominantly amorphous glass-ceramic structure. TCLP tests show lead in ash (5.2 mg/L) exceeds the 5.0 mg/L limit, whereas PAG slag reduces lead to 0.04 mg/L (IE% = 99.23%), with similarly high IE% for cadmium and chromium. Mechanically, the slag shows 14.5 MPa compressive strength, 21.2% LA abrasion, 115 kN 10% Fines Value, and 12.4% flakiness index, all within or above IS 383 requirements. The study demonstrates that PAG-vitrified slag can replace natural river gravel and quarried stone in road sub-bases, embankments, and low-to-moderate-strength concrete, supporting waste reduction, landfill diversion, and a circular economy under India’s waste-management regulations. Future work should include life-cycle cost analyses, long-term field leaching and weathering studies under Indian climatic conditions, and multi-waste co-vitrification with industrial sludge.