The Use of Recycled Aggregate Concrete

Abstract

In Australia’s transition to a low-carbon economy, there is much work still to be done in the area of reducing the environmental footprint of industrial operations. Currently, Australia reports low recycling rates among developed nations and lags in implementing best practices to repurpose waste to secondary markets. Among many of the research and development needs which contribute to make the above transition faster and more effective, the ability to conduct holistic, integrated assessments to evaluate alternative practices, materials, technologies and business models is of great importance.

Often the evaluation conducted in comparing an alternative assesses the effect on a single interested party and looks at a single or two dimensions. However, this does not provide sufficient or complete information to evaluate an important industrial alternative and hence to promote it as a best practice. Therefore, there is a need to combine multiple criteria into the decision making process and to obtain a representative answer. More importantly, the outcome of such an assessment should provide clarity on the impact on the alternative concerning general public, evaluating the net benefit to society rather than on a single concerned party.

This study presents application of such a holistic assessment methodology on the use of recycled concrete aggregate obtained from demolition waste in structural concrete, replacing its traditional alternative – natural coarse aggregate. The evaluation is conducted using cost-benefit analysis, leading to a representative outcome integrating all relevant different dimensions, which includes a financial assessment, direct and indirect environmental impact assessment including externalities, on a simulated industrial production environment of recycled aggregate concrete. The methodology adopted is considered comprehensive and systematic and can be used to evaluate a sustainable material, technology or industry practice, especially to compare potential waste-derived products at design stage.

The results of the study show that the use of recycled aggregate concrete, if manufactured at industrial scale would be more expensive to purchase as a concrete product, compared to natural aggregate. The embodied emissions associated with the production processes does not differ much when the traditional and the alternative product is compared. However, when the external cost associated with the avoided demolished concrete disposal through landfills and natural aggregate extraction is considered, the production and use of recycled aggregate concrete results in a significant net benefit to society.

The findings of this study highlight the key decision-making points to act upon by industry bodies and policy makers, including how economic instruments can be devised to initiate demand for recycled aggregate concrete, by internalising the externalities. Therefore, this case study provides insights as to how holistic assessments on sustainable alternatives can be conducted and how the findings can be used to unravel the strategies for implementation to promote industry uptake.