Synergy of tests and finite element analysis for predicting axial structural behavior of CFRP-confined activated red mud-based geopolymer composites

As sustainability gains prominence, the demand for eco-friendly materials is increasing, particularly those with minimal carbon footprints. Geopolymer concrete (GC), utilizing waste materials and by-products, is emerging as a promising low-carbon alternative to traditional Portland cement concrete. Despite its potential, GC’s long-term compressive strength (CS) remains relatively low, necessitating ongoing research to enhance its mechanical properties. While substantial research has explored the mechanical behavior of unconfined GC, there is a notable gap in understanding the structural performance of carbon fiber reinforced polymer (CFRP)-confined GC, crucial for material selection and application. This study addresses this gap by investigating the impact of CFRP sheet confinement on the axial performance of activated red mud-based geopolymer concrete composite (RMGCC). A total of 36 cylindrical RMGCC samples, with strengths of 15 MPa and 30 MPa, were tested, using either one or two layers of CFRP sheets. Finite element analysis (FEA) was employed to predict the structural behavior of CFRP-confined RMGCC samples under axial compression, utilizing an enhanced concrete damaged plasticity model. A detailed parametric study was also performed using proposed FEA model to investigate the effect of various parameters of confined concrete. The study also included a theoretical assessment of compressive strength using various existing models and proposed a new theoretical equation for more accurate prediction of axial strength in CFRP-confined RMGCC. The results demonstrated significant improvements in strength with CFRP confinement. For 15 MPa RMGCC, single and double CFRP layers increased compressive strength by 90.96% and 151.89%, respectively. For 30 MPa RMGCC, the enhancements were 51.37% and 98.78% with single and double CFRP layers, respectively. CFRP confinement proved more effective in enhancing the strength, strain, and ductility of low-strength (15 MPa) RMGCC compared to higher-strength (30 MPa) samples. The average discrepancies between the experimental and FEM results for the axial compressive strength and corresding strains were 9.1% and 6.6%, respectively. The newly proposed theoretical model achieved a close match with the experimental results of compressive strength for low-strength FRP-confined RMGCC samples, demonstrating a high correlation with an R² value of 0.96%. The model showed a minor deviation of just 4.45% from the observed outcomes.