Author(s)

S. Bethanis

Abstract

Over the last few decades there has been an immense demand for aggregate materials for use in construction. These are currently obtained from primary rock and gravel resources. However, such resources are finite and material extraction is associated with significant environmental costs. In addition, the significant quantities of residues generated by Waste-to-Energy incineration and coal combustion have emphasized the need to find practical reuse applications for these high-volume wastes. These, together with the economic burden of waste disposal and associated adverse environmental impacts, have made it imperative to develop alternative techniques for converting wastes into high-added value products. This paper describes the process used to produce a lightweight aggregate using incinerator bottom ash from municipal solid waste incineration and pulverized fuel ash from coal-fired power plants. The method involves wet milling of the IBA/PFA mixes, pelletisation of the powder mixes and firing in a rotary kiln at high temperatures to produce sintered aggregates. Lightweight aggregates with particle densities between 1.5 and 1.8 g/cm3, bulk densities between 0.8 and 0.9 g/cm3 and water absorptions between 16 and 19% by dry weight have been produced. The manufactured lightweight aggregates achieved compressive strengths of approximately 58 N/mm2 at 28 days when cast in concrete. Corresponding properties of commercial aggregates Lytag and LECA have been determined for comparison. The leaching characteristics of the IBA-derived aggregates were similar to Lytag and showed low heavy metal leachability under non-highly acidic leachate pH conditions. The results confirm the feasibility of producing a lightweight aggregate using 100% by weight combustion ashes. Keywords: incinerator bottom ash, pulverized fuel ash, clay, Lytag, Leca, aggregate, concrete, leaching.

Keywords

incinerator bottom ash, pulverized fuel ash, clay, Lytag, Leca, aggregate, concrete, leaching.