Abstract
Australia and many other parts of the world face issues of contamination in groundwater and soils by per- and poly-fluoroalkyl substances (PFAS). While the pyrolytic treatment of contaminated soils can destroy PFAS, the resulting heat-treated soils currently have limited applications. The purpose of this study was to demonstrate the usefulness of remediated soils in concrete applications. Using heat-treated soil as a fine aggregate, with a composition and particle size distribution similar to that of traditional concrete sands, proved to be a straightforward process. In such situations, complete fine aggregate replacement could be achieved with minimal loss of compressive strength. At high fine aggregate replacement (≥ 60%), a wetting agent was required for maintaining adequate workability. When using the heat-treated soil as a supplementary cementitious material, the initial mineralogy, the temperature of the heat-treatment and the post-treatment storage (i.e., keeping the soil dry) were found to be key factors. For cement mortars where minimal strength loss is desired, up to 15% of cement can be replaced, but up to 45% replacement can be achieved if moderate strengths are acceptable. This study successfully demonstrates that commercially heat-treated remediated soils can serve as supplementary cementitious materials or to replace fine aggregates in concrete applications.
Highlights
On a global scale, concrete is the single most used man-made material, amounting to a usage of 3 tonnes per person per year [1,2,3]
An overview of trials is given where cement and fine aggregate replacements were sourced from heat-treated remediated soils that had been previously impacted by poly-fluoroalkyl substances (PFAS)
In this study we investigated the possibility of using remediated PFAS-contaminated soils, post pyrolysis treatment, in cement paste and mortar applications
Summary
Concrete is the single most used man-made material, amounting to a usage of 3 tonnes per person per year [1,2,3]. Numerous options are available to reduce the carbon footprint of the sector (e.g., avoid or limit concrete use where possible, substitute Portland cement with low CO2 supplementary cementitious materials (SCMs), improve efficiencies of cement manufacturing plants, use alternative fuels in kilns, substitute clinker/aggregate, improve concrete durability, etc.) [7,8]. All of these strategies, or combinations of them, are appropriate and should be utilised whenever possible. The heat-treatment, consisting of a two-phase pyrolytic process (the technology owned by Renex Op Co Pty Ltd., Dandenong South, Australia), both destroyed the PFAS and partially activated (i.e., calcined) the clay component of the soil
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