Clarifying the confinement mechanism of basalt <scp>TRM</scp> using a low‐strength mortar matrix: Experimental and modeling insights

Abstract This study investigates the confinement behavior of textile‐reinforced mortar (TRM)‐confined concrete by eliminating the axial load‐bearing interference commonly observed in conventional TRM systems. Basalt TRM with low‐strength mortar was applied to high‐strength concrete to suppress axial load sharing and isolate confinement action. Thirty‐six concrete cylinders with varying textile layers were tested under axial compression. Following a systematic examination of existing analytical approaches, a representative analysis‐oriented model was selected and subsequently refined using a confinement stiffness reduction coefficient. Test results revealed that BTRM functioned strictly as a passive confinement system, becoming effective only after noticeable lateral dilation of the concrete core. The actual hoop rupture strains were substantially lower than coupon‐based tensile values, demonstrating that reliance on uniaxial tensile rupture strains severely overestimates confinement capacity. A minimum confinement stiffness ratio of 0.00118 was identified as necessary for meaningful enhancement. Existing design‐oriented models failed to capture rupture behavior because they assume idealized rupture strains. In contrast, accurate prediction was achieved by considering only the linear tensile response of the embedded fiber yarns and introducing a mortar‐dependent reduction coefficient in the confining pressure equation of an analysis‐oriented model. The refined model provides satisfactory accuracy and offers a clearer interpretation of passive confinement development in BTRM systems, contributing both experimental evidence and analytical guidance for TRM‐confined concrete applications.