Reuse of quarry fines in production of secondary aggregates

Abstract

Large volumes of wastes are associated with the production of aggregates and dimension stone. Fine-grained wastes are particularly problematic and are deposited in settlement ponds or managed by stockpiling until backfill space becomes available. Although these fine materials have poor engineering properties, when they are mixed with hydraulic binders in a CO2-rich atmosphere, they can be bound together to form pellets suitable for use as aggregates. In the present work, a by-product called hassock, which originates from the quarrying of Kentish ragstone, is investigated for use as secondary aggregate. In excess of 200000 t of this poor-quality fine-grained material, originating from the Lower Greensand Formation of southern England, are disposed of each year. Hassock waste was blended with other solid waste products, namely cement kiln dust, ground granulated blast furnace slag and pulverised fuel ash, and was pelletised in a CO2-rich atmosphere. The pellets, produced by carbonate cementation; typically have a pH of 9–9·5 and aggregate impact values ranging from 14 to 19.