A review of the advanced treatment techniques for enriching the recycled concrete aggregates for recycled-based concrete: economic, environmental and technical analysis

Abstract

PurposeThis study aimed to review various existing methods for improving the quality of recycled concrete aggregates (RCAs) as a possible substitution for natural aggregates (NAs) in concrete. It is vital as the old paste attached to the RCA weakens its structure. It is due to the porous structure of the RCA with cracks, weakening the interfacial transition zone (ITZ) between the RCA and binding material, negatively impacting the concrete's properties. To this end, various methods for reinforcement of the RCA, cleaning the RCA's old paste and enhancing the quality of the RCA-based concrete without RCA modification are studied in terms of environmental effects, cost and technical matters. Furthermore, this research sought to identify gaps in knowledge and future research directions.Design/methodology/approachThe review of the relevant journal papers revealed that various methods exist for improving the properties of RCAs and RCA-based concrete. A decision matrix was developed and implemented for ranking these techniques based on environmental, economic and technical criteria.FindingsThe identified methods for reinforcement of the RCA include accelerated carbonation, bio deposition, soaking in polymer emulsions, soaking in waterproofing admixture, soaking in sodium silicate, soaking in nanoparticles and coating with geopolymer slurry. Moreover, cleaning the RCA's old paste is possible using acid, water, heating, thermal and mechanical treatment, thermo-mechanical and electro-dynamic treatment. Added to these treatment techniques, using RCA in saturated surface dry (SSD) mixing approaches and adding fibres or pozzolana enhance the quality of the RCA-based concrete without RCA modification. The study ranked these techniques based on environmental, economic and technical criteria. Ultimately, adding fibres, pozzolana and coating RCA with geopolymer slurry were introduced as the best techniques based on the nominated criteria.Practical implicationsThe study supported the need for better knowledge regarding the existing treatment techniques for RCA improvement. The outcomes of this research offer an understanding of each RCA enrichment technique's importance in environmental, economic and technical criteria.Originality/valueThe practicality of the RCA treatment techniques is based on economic, environmental and technical specifications for rating the existing treatment techniques.

Developing a sustainable self-compacting geopolymer concrete with 100% geopolymer-coated recycled concrete aggregate replacement

“…RCA treatment techniques can be grouped into reinforcing RCA, removing attached paste to the RCA, and improving RCA-based concrete without RCA modifications (Nikmehr et al, 2023). RCA can be reinforced by soaking in some materials, such as polymer emulsions (Al-Baghdadi, 2021), waterproofing admixture (Wang et al, 2022), sodium silicate (Alqarni et al, 2022) and nanoparticles (Liang et al, 2022).…”

“…RCA treatment techniques can be grouped into reinforcing RCA, removing attached paste to the RCA, and improving RCA-based concrete without RCA modifications (Nikmehr et al. , 2023).…”

“…, 2018) can improve the quality of RCA-based concrete. So to evaluate various RCA treatment techniques, Nikmehr et al. (2023) conducted a review study on the existing RCA treatment techniques and assessed them based on the environmental, economic and technical criteria.…”

Editorial: Breaking the mold, circular construction for a greener and more efficient built environment

“…As per the European Commission, enhanced material efficiency would potentially result in an 80% reduction in these emissions (European Commission, 2022). Cement and steel, the most consumed materials in construction (Monteiro et al, 2017), constituting over 80% of the overall embodied GHG emissions, are the predominant materials responsible for this impact (Nikmehr et al, 2023;Zhong et al, 2021).The construction industry has gained significant importance in the shift towards circular construction (CC). Implementing a CC pattern can help the industry reduce overall consumption by keeping materials in use for longer and preserving their value at the highest possible level.…”

“…As per the European Commission, enhanced material efficiency would potentially result in an 80% reduction in these emissions (European Commission, 2022). Cement and steel, the most consumed materials in construction (Monteiro et al ., 2017), constituting over 80% of the overall embodied GHG emissions, are the predominant materials responsible for this impact (Nikmehr et al , 2023; Zhong et al , 2021).…”