Axial Compressive Behavior of Concrete Confined by Sustainable Lightweight Fabric-Reinforced Cementitious Matrix

This study investigates the axial compressive behavior of concrete confined with a newly developed lightweight carbon fabric-reinforced cementitious matrix (FRCM) system, incorporating expanded glass (EG) aggregates and fly ash as partial cement replacements. The results indicate that the developed FRCM is a promising composite material for structural strengthening by significantly enhancing the compressive performance of concrete in both the prepeak and postpeak stages. Although the maximum EG aggregate sizes (0.5–1 mm), fly ash replacement content (20%–40%), and nylon fiber volume fractions (0.4%–1.2%) exhibited insignificant influence on the overall compressive performance of FRCM-confined concrete, the concrete grade, fabric reinforcement ratio, and mesh size of the carbon fabric had pronounced effects. Confinement efficacy depended on concrete grade, with lower strengths showing greater peak stress and strain improvements, while high-strength concrete exhibited the highest ductility index enhancement. Additionally, in the postpeak stage, larger mesh sizes reduced the ultimate strain, ductility index, and energy absorption compared with smaller mesh sizes. Furthermore, an analytical model was proposed to simulate the axial stress–strain curves of the FRCM-confined concrete based on the interactions between lateral strain–axial strain and axial stress–axial strain. The predictions of this model agreed reasonably well with the test results.