Influence of Geopolymer-Based Graphene Oxide Coating on Strength and Durability Characteristics of Recycled Aggregate Concrete

Construction and demolition waste (C&DW) constitutes a major environmental burden, and the utilization of recycled coarse aggregate (RCA) in structural concrete offers a viable pathway toward sustainable resource management. However, inherent deficiencies of RCA, including elevated water absorption, reduced bulk density, and higher crushing values, compromise the mechanical and durability performance of recycled aggregate concrete (RAC) relative to natural coarse aggregate (NCA) concrete. This study investigates the efficacy of a geopolymer-assisted graphene oxide (GO) pre-spraying treatment applied to RCA prior to concrete production as a means of mitigating these deficiencies. GO concentrations of 0, 0.15, 0.20, 0.25, 0.30, and 0.35% (by weight of RCA) were evaluated, with geopolymer solution applied at 10% of RCA weight to enhance GO adhesion. M35 grade concrete specimens were cast and tested for compressive strength, split tensile strength, sorptivity, rapid chloride permeability (RCPT), and rapid chloride migration (RCMT) at 7 and 28 days of curing. Results demonstrated that 0.30% GO treatment yielded the highest mechanical performance, achieving compressive and split tensile strengths of 49.33 MPa and 4.14 MPa at 28 days, respectively, closely approaching NCA concrete values. The sorptivity coefficient and chloride migration coefficient for the 0.30% mix were 0.0001 mm/min0.5 and 6.436 × 10−12 m2/s, comparable to NCA concrete. Beyond 0.30%, mechanical and durability properties deteriorated, indicating an optimal GO dosage threshold. These findings establish geopolymer-mediated GO surface treatment as an effective and promising strategy for enhancing RAC performance in structural applications.