Solid-Waste Valorization in Cementitious Binders: Feedstocks, Reaction Pathways, Performance, and Remaining Barriers — A Civil Engineering Review

Abstract

Industrial by-products and post-consumer mineral residues are increasingly engineered into supplementary cementitious materials (SCMs) or precursors for alkali-activated materials (AAMs), aiming to reduce clinker demand while addressing large-volume waste disposal. This review synthesizes the civil-engineering evidence base for solid-waste-derived binders with an emphasis on (i) feedstock chemistry and reactivity (fly ash, ground granulated blast-furnace slag, steel slags, red mud, phosphogypsum, municipal solid waste incineration residues, waste glass, rice husk ash, and construction–demolition fines), (ii) reaction pathways governing hydrate/gel formation in Portland-cement blends, LC3-type systems, and AAM/geopolymer binders, and (iii) structural performance and durability under service exposures (shrinkage cracking, carbonation, chloride ingress, sulfate/acid attack, leaching, and fire). A unified framework is proposed linking precursor composition, activator/SCM selection, curing, and microstructural development to measurable engineering properties and code-relevant indicators. Key barriers remain: variability of waste streams, activator footprint and safety, standardization gaps, and the limited number of long-term field validations. Practical strategies are highlighted, including feedstock classification and blending, accelerated carbonation of steel slags, low-hazard one-part activation routes, and performance-based specifications supported by life-cycle assessment. The review concludes with research needs for scalable quality control, durability models in cracked states, and harmonized testing routes to accelerate adoption of solid-waste valorization in sustainable infrastructure.