Waste-treated waste: stabilization of colliery waste from South Wales (UK) using Wastepaper Sludge Ash (WSA)

Abstract

Sustainable construction requires a critical review of prevailing practices, techniques and sources of raw materials. Focus is turning to industrial wastes and by-products that have previously received little or no attention. One such waste is Colliery Spoil (CS) (minestone), a by-product of coal mining. Albeit its abundance in most parts of the world, its potential as a construction material has not been fully realized, as evidenced by the large piles of the waste, usually unrecognizable due to vegetation overgrowth. The major problems identified in attempts to utilize CS in construction include excessive wear, expansive behavior, leaching and radioactivity, reducing its use to merely backfilling of mines, quarries and other surface tips, or subjected to marine and other disposal options. The different options have environmental consequences of varying impact. This paper advances the scope of technological benefits of utilizing CS in construction, by utilizing waste-activated slag. The research was triggered by proximity of large supplies of both CS and slag in South Wales, UK, as well as the authors' interest in advances in sustainable construction. Two sulfate/sulfide-bearing colliery wastes were stabilized with a blended stabilizer comprising Wastepaper Sludge Ash (WSA) and Ground Granulated Blastfurnace Slag (GGBS), themselves industrial wastes or byproducts. Compressive strength of compacted cylinder specimens was monitored for a period of up to 180 days of curing and linear expansion for up to 50 days of soaking. Results indicate that the performance of systems incorporating WSA was generally superior to that of systems using Portland Cement (PC) or lime, the common traditional stabilizers.