Performance of Rice Husk Ash–Based One-Part Alkali-Activated Concrete Mixes Incorporating High Chloride Contaminated Recycled Aggregates

The growing demand for sustainable construction materials has led to increased research on alternative binders that reduce environmental impact. This study investigates the development and performance of one-part alkali-activated concrete (OPAA) incorporating pulverized rice husk ash (PRHA), ground granulated blast furnace slag (GGBFS), and high-chloride contaminated recycled coarse and fine aggregates (RCA, RFA). Using anhydrous sodium metasilicate (ASMS) as the activator, the research focuses on optimizing mechanical and durability properties through statistical analysis of variance (ANOVA). Experimental results demonstrate compressive strengths ranging from 52 to 67 MPa, flexural strengths between 4.13 and 5.25 MPa, and split tensile strengths of 3.19 MPa. The modulus of elasticity (MOE) achieved values between 30.91 and 31.83 GPa, with water absorption rates varying from 0.57% to 2.97%. Durability assessments, including sorptivity, high-temperature resistance, and microstructural analysis using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), confirmed the formation of dense C─ A─ S─ H and N─ A─ S─ H gels, contributing to enhanced mechanical strength and durability. Additionally, thermal stability tests demonstrated that OPAA concrete retains significant compressive strength even after exposure to 600°C, making it suitable for fire-resistant applications. Overall, this study provides a scalable and sustainable solution for reducing the carbon footprint of the construction industry while enhancing material performance. The findings support the adoption of alkali-activated concrete as a viable alternative to ordinary portland cement (OPC)-based concrete, contributing to the advancement of green building practices and sustainable infrastructure development. From a sustainability perspective, the study highlights the significant reduction in embodied energy (EE) and embodied carbon dioxide emissions (ECO2e) compared to OPC.