Axial compressive performance of CFRP-confined concrete columns with magnesium phosphate cement-based adhesives

This study evaluates the effectiveness of magnesium phosphate-based carbon-fiber-reinforced inorganic polymer (CFRiP) composites for confining reinforced concrete columns. Seven nearly full-scale reinforced concrete columns are prepared for uniaxial compression tests, with each type of confined specimen having different carbon fiber sheet strip spacings. Three specimens are confined with magnesium phosphate-based carbon-fiber-reinforced inorganic polymer (CFRiP) composites, three specimens are confined with epoxy-based CFRP composites, and one unconfined specimen is used as a control. The specimen failure modes, bearing capacity and ductility gains, and development of rebar and fiber strains are analyzed. In particular, the evolution of the hoop strain field is monitored using a digital image correlation (DIC) system. Subsequently, theoretical calculations of the bearing capacity of reinforced concrete columns confined with magnesium phosphate-based CFRiP composites are performed. The experimental results and analyses show that the magnesium phosphate-based CFRiP composites significantly improves the bearing capacity and ductility of reinforced concrete columns, and the confined specimens gain peak load and ultimate axial strain enhancements of 28.6–47.1 % and 77–110 %, respectively. The bearing capacity prediction results are aligned with the test results, and the maximum error between the two does not exceed 6 %.