Investigating the Combined Effects of Acid Pre-soaking, Slag/Metakaolin Replacement, and Three-Stage Mixing on Recycled Concrete Properties

Document Type : Original Article

Authors

1 M.Sc., Faculty of Engineering, University of Kashan, Kashan, Iran

2 Assistant professor, Faculty of Engineering, University of Kashan, Kashan, Iran

10.22065/jsce.2023.397843.3121

Abstract

The accumulation of demolition waste in landfills and high contamination of the cement industry are significant environmental hazards that can be mitigated by recycling concrete aggregates and using other binder materials, respectively. This study aimed to investigate the combined effects of corrective methods of the replacement of 40% supplementary materials (metakaolin and blast furnace slag powder), pre-soaking of recycled coarse aggregates in sulfuric acid, and a three-stage mixing approach on the recycled concrete properties. Different mixtures containing 0%, 33% and 66% recycled coarse aggregate were fabricated, and the specimens were divided into three categories: untreated, treated with two methods (using supplementary materials and three-stage mixing), and treated with three methods. The compressive strength, slump, and rapid chloride penetration of mixtures were then tested. The results showed that the second set of samples not only had better resistance against chloride ion penetration but also achieved a 91-day compressive strength comparable to non-recycled samples. However, the evidence from the interpretation of the compressive strength results, X-Ray diffraction analysis, and surface survey indicated that pre-soaking of coarse aggregates in acid had a negative effect on the performance of the slag/metakaolin replacement method. Overall, the findings of this study on the combined effects of treatment methods could be considered as a step towards the development of effective and sustainable recycling practices in the construction industry.

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Articles in Press, Accepted Manuscript
Available Online from 17 November 2023
  • Receive Date: 20 May 2023
  • Revise Date: 26 October 2023
  • Accept Date: 17 November 2023