Exploring the use of mixed waste materials (MWM) in concrete for sustainable Construction: A review

This review presents an in-depth examination of the usage of six major waste materials in mixed waste materials (MWM) concrete: recycled coarse aggregates (RCA), fly ash (FA), waste glass (WG), waste rubber (WR), steel waste (SW), and waste plastic (WP). The review assesses the impact of these waste materials on the mechanical performance of concrete, and the article highlights the rising interest in this area among scholars and practitioners. The review paper provides recommendations on the appropriate replacement levels for various combinations of waste materials in concrete mixes to ensure optimal mechanical properties. It advises against exceeding replacement levels of 25% for both recycled coarse aggregates (RCA) as a substitute for natural coarse aggregates (Cagg) and fly ash (FA) as a replacement for cement (C). When utilizing a combination of RCA and waste glass (WG) as replacements, the suggested replacement levels are 50% RCA and 20% WG. Similarly, when using RCA and waste rubber (WR) as replacements, it is advised to limit the replacement levels to 25% RCA and 10% WR. The study also recommends replacement amounts of 50% FA and 5% WG, and identifies 80% steel slag (SS) as a suitable replacement for fine aggregate (Fagg) and 20% WG as a replacement for cement. Additionally, it highlights the potential to enhance concrete compressive strength by combining waste glass (WG) with granite powder (GrP) as replacements, with a recommended replacement level of 30% WG and 15% GrP. While MWM concrete has shown promising results, there is still a study gap in the structural behavior of MWM concrete reinforced concrete (RC) elements, particularly under various loading scenarios. As a result, more research in the future is required to examine the structural behavior of MWM concrete in RC members and to establish the possibility of employing MWM concrete in full-scale applications.

Automated summary

This review provides a comprehensive examination of the usage and impact of various waste materials in MWM concrete. It offers recommendations on replacement levels to optimize mechanical properties and highlights the potential to enhance concrete compressive strength through certain combinations of waste materials. However, further research is needed to study the structural behavior of MWM concrete in RC members and its application in full-scale scenarios.