Durability of autoclaved construction materials of sewage sludge–cement–fly ash–furnace slag

Abstract

In the present work, we demonstrate an alternative for the final disposal of sewage sludge by using it as an additive in a mixture with cement, fly ash and furnace slag, which can potentially be used to develop newly promising construction materials by autoclave curing. The dewatered sewage sludge is obtained with fly ash and lime. These physical conditioners contribute to both dewatering process and solidifying/stabilizing of sludge.Various mechanical properties such as flexural strength, compressive strength and the toxicity characteristic leaching procedure (TCLP) were evaluated. To evaluate long-term performance, different types of accelerated attacks, i.e. freezing–thawing cycles, accelerated carbonation, wet–dry cycles, and heat–cool cycles were also determined. The obtained test results were indicated that the autoclaved samples exhibit good long-term performance after evaluations of different durability tests. XRD patterns show that the hydration products of autoclaved samples are katoite and C–S–H phases, which mainly contribute to strength of autoclaved products. Morphologies of autoclaved samples also demonstrate the existence of the gel-like and honeycomb-like hydrated products. The results show that this new construction material could be applied as many construction and building materials, i.e. landfill liners and building blocks.