Analytical modeling and numerical analysis of FRP-confined low strength engineered geopolymer composites

As the demand for sustainable materials grows, geopolymer concrete (GC) has emerged as a low-carbon alternative to Portland cement concrete. However, its long-term compressive strength (CS) remains a limitation. While unconfined GC has been widely studied, limited research exists on carbon fiber reinforced polymer (CFRP)-confined GC. This study evaluates the axial performance of red mud-based geopolymer concrete (RMGC) confined with CFRP. Thirty-six cylindrical RMGC specimens (15 MPa and 30 MPa) were tested under axial loading with one or two CFRP layers. Finite element analysis (FEA), incorporating an enhanced concrete damaged plasticity model, was used to predict structural responses, and a parametric study assessed key confinement effects. Experimental results showed that CFRP confinement significantly improved CS, with increases of 91.77% and 153.85% for 15 MPa RMGC, and 52.28% and 99.33% for 30 MPa RMGC with single and double CFRP layers, respectively. Lower-strength RMGC benefited more in terms of strength, strain capacity, and ductility. The FEA model aligned well with experiments, with discrepancies of 9.1% for CS and 6.6% for strain. A new analytical equation, achieving an R2 of 0.96 and a minimal 4.48% deviation, provided improved predictive accuracy. These findings underscore the potential of CFRP confinement in enhancing RMGC's mechanical properties and offer a reliable analytical tool for FRP-confined GC systems.