A Review on Experimental Investigations on the Suitability of Recycled Fine Aggregates and Ground Granulated Blast Furnace Slag for Structural Applications

The growing volumes of construction and demolition (C&D) debris combined with cement manufacturing’s heavy carbon burden has led researchers to seek greener alternatives within structural concrete production. The paper reviews 37 experimental investigations of two such alternatives - Recycled Fine Aggregates (RFA) from crushed concrete waste and Ground Granulated Blast Furnace Slag (GGBS), a glassy by-product of iron smelting that can partially replace binders. The research comes from investigators located across the globe - from India, Portugal, Hong Kong, Argentina, Spain, the United Kingdom and Australia - including many of the noted contributions of Evangelista and de Brito (2007, 2014), Zega and Di Maio (2011), Kou and Poon (2009, 2012), de Brito and Saikia (2013), Corinaldesi and Moriconi (2009), Silva et al. (2021), Oner and Akyuz (2007) and Mehta and Monteiro (2014). Concrete grades from M20 through M50 are covered, with attention to workability, compressive and tensile strength, flexural performance, water absorption, sorptivity, and chloride ingress resistance. The evidence summarized in this paper demonstrates that up to 25–30% of natural sand can be substituted by pre-treated RFA in all structural grades without an unacceptable strength loss. Replacing 30–40% of cement with GGBS reliably increases the long-term strength, reduces permeability, with an unavoidable early-strength cost. Their combination results in an additive effect – notably beyond 28 days – because hydration products from GGBS can densify the porous zone around RFA particles. The behavior of Portland Pozzolana Cement (PPC) as the base binder, the microstructural mechanisms responsible for the observed trends, the environmental/cost evaluation and research areas remaining to be adequately explored are investigated.