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

Abstract

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.

Keywords:

• lime kiln dust
• fly ash
• stabilisation
• alkali-activation
• recycling

Acknowledgements

The authors would like to thank Alex Fraser Group (Victoria, Australia) for providing the demolition aggregates used in this research.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was conducted by the Australian Research Council Industrial Transformation Training Centre for Advanced Technologies in Rail Track Infrastructure (IC170100006) and funded by the Australian Government. The last author is grateful to the financial support from the Thailand Research Fund under the TRF Senior Research Scholar programme Grant number RTA5980005 and Suranaree University of Technology.