Waste-derived artificial aggregates for concrete applications

Abstract The depletion of natural coarse aggregates (NCAs) and rising environmental concerns have accelerated the demand for sustainable alternatives in concrete production. This study presents the development of cold-bonded alkali-activated artificial aggregates (AAAs) using fly ash (FA) and ground granulated blast furnace slag (GGBFS) as binders. AAAs were produced through disc pelletization, ambient curing, and surface treatment with an alkaline solution to improve aggregate quality. The produced AAAs exhibited a specific gravity of 1.83–2.02, bulk density of 1201–1241 kg m −3 , water absorption of 1.54%–1.03%, impact values of 21.65%–15.62%, and crushing values of 24%–20.06%. Concrete mixes were prepared by replacing NCAs with AAAs at 30%, 60%, and 100% replacement levels in M30-grade concrete. The compressive strength of the mixes ranged from 41.88 MPa (30% AAAs) to 38.21 MPa (100% AAAs), remaining within acceptable structural limits. Despite a slight reduction in density and mechanical strength with increasing AAAs content, all mixes showed satisfactory workability and ultrasonic pulse velocity. Scanning electron microscopy confirmed enhanced microstructural densification with higher GGBFS content. Environmental and cost assessments indicated that while AAAs involve higher production costs, they reduce CO 2 emissions significantly, supporting sustainable construction goals. A 60% replacement level offered an optimal trade-off between strength, environmental impact, and cost. The findings confirm that AAAs are a viable, eco-friendly substitute for NCAs in structural concrete applications.