Sustainable Utilization of Construction and Demolition Waste as a Subgrade Material Using the Process of Geopolymerization

The present study examines the potential use of recycled fine aggregates (RFA) generated from construction and demolition waste as a principal component in geopolymer binder systems as a subgrade material, when paired with fly ash (FA) and ground granulated blast furnace slag (GGBS). Various samples were prepared to assess and identify the ideal binder composition that meets the necessary mechanical and durability specifications for subgrade applications. Geopolymer samples activated only with NaOH demonstrated a higher unconfined compressive strength (UCS) compared to those activated with a sodium silicate and a mixture of sodium hydroxide and sodium silicate in the ratio of 1. The UCS values of the RFA-FA-GGBS geopolymers cured at 60\(\:^\circ\:\)C show a slight increase compared to ambient cured samples. The result showed that all geopolymer samples met the minimum strength criteria for application as a subgrade, sub-base, and base layers. Similarly, the soaked CBR values of the geopolymer-treated recycled fine aggregates met the minimum criteria for cement-stabilised subgrade or subbase material as stipulated by the Indian standard. The toxicity characteristic leaching procedure (TCLP) test results demonstrated that the concentration of the heavy metals in the leachate generated from the samples was within the limits set by the US Environmental Protection Agency.