Development of chemical admixtures for green and environmentally friendly concrete: A review

Chemical admixtures are indispensable functional ingredients in modern construction, and their raw materials for synthesis are mainly sourced from petrochemical products, leading to petrochemical resource consumption and environmental damage. Using biomass as a raw material for preparing chemical admixtures for concrete is an effective and environmentally friendly method that holds great promise for overcoming these environment problems and obtaining exceptional application properties. This work systematically addresses the recent research advances in chemical admixtures using polysaccharide, polyphenol biomass and biorefineries, including their preparation methods, application effects and environmental impact assessment. The results show that the molecular structures of polysaccharide and polyphenol biomass contain a large number of active functional groups, which help bio-based chemical admixtures to be prepared by acylation, sulfonation and/or graft copolymerization, significantly improving the dispersibility, water retention, retardation, anti-adhesion and durability of cement-based materials. Also, the use of biorefinery technology endows chemical admixtures with superior environmental performance. In addition, this review addresses the importance of the life cycle assessment (LCA) method in evaluating the environmental impacts of bio-based chemical admixtures and establishes that environmental pollution can be substantially minimized by optimizing the preparation process (e.g., use of renewable raw materials, adoption of biorefineries, etc.). This article gives an overview on bio-based chemical admixtures and their high-value utilization and ecological development that provide a theoretical basis for the design of energy-saving and low-cost bio-based chemical admixtures.