Comparative axial compressive behavior of CFRPs-confined columns containing high-performance magnesium phosphate cement-based composites and epoxy resin

Magnesium phosphate cement-based composite (MPC) has been widely used to strengthen reinforced concrete (RC) elements based on its high early strength and strong adhesion; however, its effectiveness for strengthening RC columns has not been adequately evaluated. This study aims to investigate how carbon fiber-reinforced polymer sheet (CFRPs) utilizing high-performance MPC (HMPC) can enhance the mechanical performance of RC columns, thereby optimizing the application of HMPC as an adhesive in the CFRPs strengthening system. An experimental study was undertaken on the axial compressive behavior of 15 plain concrete cylinders and 23 square RC columns confined by CFRPs, which considered different adhesives (epoxy resin and HMPC), different sizes, stirrup ratios, and the number of confinement layers on the failure mode, ultimate capacity, axial stress-strain response, and axial stress-hoop strain behavior. The results show that specimens using HMPC as an adhesive can significantly improve the confined capacity compared to those using epoxy resin; however, their strain capacity was approximately 1.6-2.9 times lower than that of specimens using epoxy resin. Additionally, CFRPs-confined columns using HMPC can achieve a greater confining effect and deformation capacity compared to those using inorganic adhesives in the literature. Furthermore, a finite element model for CFRPs-confined RC columns using HMPC was developed and validated, showing a strong correlation with test results, and an extended parametric analysis was then performed.