Alkali activation of lime kiln dust and fly ash blends for the stabilisation of demolition wastes

Chemical stabilisation has been extensively applied for improving the mechanical properties of the recycled construction and demolition (C&D) aggregates. To reduce the cost and carbon footprint of the stabilised C&D blends, alternative industrial by-products have been investigated to replace common binders, such as Portland cement and lime. This study presents the results of consuming lime kiln dust (LKD) along with Class F fly ash as an alternative precursor to be used for alkali-activation for stabilising C&D materials. The high-calcium content of LKD can be complimented by the alumina and silica contents of fly ash. A variety of LKD and FA mixtures were evaluated to optimise the impact of alkali-activation on amorphous and crystalised silica and calcium content in the binders for stabilisation of C&D aggregates. Alkali-activation was targeted to activate the precursors at room temperature for practical applications and increase the durability of C&D materials under repeated loads. Laboratory characterisation of unbound and stabilised C&D aggregates is presented to compare the improvement in strength characterisations. This research indicates that alkali-activation with an optimum of 15% LKD + 15% FA content for stabilisation of C&D aggregates is a viable replacement for road bases/subbases.