Comparative Assessment of Crushed Glass Aggregate, Fly Ash, and Mining Tailings in Cementitious Composites and Shotcrete Applications.

Waste-derived materials are increasingly being investigated as aggregate replacements and supplementary cementitious materials (SCMs) in cementitious composites due to their potential to improve resource efficiency while maintaining engineering performance. This review critically evaluates waste-derived materials used as aggregate replacements and SCMs, with particular emphasis on crushed glass aggregate (CGA), fly ash (FA), and mining tailings. Unlike previous reviews that focus primarily on individual waste streams, this study provides a comparative and mechanism-based assessment of these materials within a unified framework relevant to cementitious composites and shotcrete applications. Their influence on mechanical performance, durability, rheology, and microstructural development is assessed through the review of 78 publications, together with the governing mechanisms of packing effects, pozzolanic reactivity, and interfacial transition zone (ITZ) modification. Across the reviewed studies, CGA generally demonstrated favourable performance at moderate aggregate replacement levels (approximately 15-30%), FA commonly improved workability and durability at cement replacement levels of 10-20%, while mining tailings exhibited highly source-dependent behaviour, with performance strongly influenced by tailing type, mineralogy, processing history, and functional role within the cementitious system. Variability in physicochemical properties and processing methods contributed to inconsistent behaviour and limited direct comparison between studies. Critical knowledge gaps are identified, including long-term durability and hybrid CGA-FA and FBMT-FA systems. A comparative framework and research roadmap are proposed to support the development of durable and resource-efficient cementitious composites.