Integrated Durability Performance of Sustainable Geopolymer Concrete Incorporating Recycled Concrete Aggregates

Growing environmental concerns associated with Portland cement production, along with the continuous accumulation of construction and demolition waste, have intensified the need for sustainable construction materials and effective recycling strategies. This study experimentally investigates the performance of fly ash-based geopolymer concrete (GPC) incorporating recycled concrete aggregate (RCA) as a partial replacement for natural coarse aggregate, compared to conventional ordinary Portland cement concrete (OPC), with a particular focus on integrated durability performance. Ten mixtures were prepared, including five GPC and five OPC mixes with RCA replacement levels of 0–100% by volume. Mechanical properties were evaluated through compressive, splitting tensile, and flexural strength tests, while durability performance was assessed using water permeability, chloride penetration, acid resistance, elevated temperature exposure up to 1000 °C, and accelerated corrosion tests, supported by SEM–EDX analysis. Results show that GPC outperforms OPC across all replacement levels. Optimal performance was achieved at 20–40% RCA, while at 60% RCA a slight reduction in strength was observed; however, the values remained relatively high, particularly for GPC mixtures, indicating stable performance. A significant reduction occurred only at full replacement. GPC also exhibited lower permeability, enhanced corrosion resistance, improved thermal stability, and better resistance to acid attack. This study provides strong evidence that GPC can effectively compensate for the inherent limitations of RCA, offering a durable and eco-efficient alternative for structural and infrastructure applications.