Application of green agro-based nanoparticles in cement-based construction materials: A systematic review

Nanoparticles (NPs) based on agro-wastes and plant extracts have recently gained attention as supplementary cementitious materials (SCMs) in cement-based construction materials (CBMs) because they are environmentally friendly, low-energy consuming, and affordable. However, the sources, synthesis methods, characteristics, and effects of these materials on the performance of CBMs have not been thoroughly investigated. To address this gap, we comprehensively reviewed the research on agro-based NPs used in CBMs. We performed a scientometric analysis and a comprehensive review of publications in Scopus, Web of Science, and PubMed databases and gray literature from 2005 to 2023. Various agro-based NPs have been extracted for cementitious material application, and predominantly nano-silica particles hold great potential as SCMs. The pretreatment methods employed to produce agro-based NPs, and the physicochemical and morphological characteristics of NPs produced are presented. Moreover, the influence of agro-based NPs on fresh and hardened properties, microstructure, and durability properties of CBMs are discussed in detail. Our review established that agro-based NPs improve all performance properties of strength, microstructure, and durability of all the tested CBMs except for their rheological properties. The use of agro-based NPs is beneficial at low dosages of up to 5%, while detrimental at high proportions. We also discussed the environmental benefits of using agro-based NPs in CBMs and the challenges future research should focus on in this new research frontier. Our review findings will serve as an inventory of the theoretical and practical methods for processing agro-based NPs and their use in CBMs.