Flexural behavior of RC beams strengthened with ultra-high ductility MPC-based composites and CFRP

This study investigates the flexural performance of reinforced concrete (RC) beams strengthened with ultra-high ductility magnesium phosphate cement-based composites (UHDMC) and carbon fiber reinforced polymer (CFRP). The experiment was designed with a total of seven beams, with the test variables comprising the number of CFRP layers, types of CFRP, and the combination method of UHDMC and CFRP. The experimental results showed that the combined UHDMC-CFRP strengthening system exhibited a preliminary synergistic strengthening effect in the investigated specimens, with the improvement in load-carrying capacity exceeding the sum of the improvements achieved by the individual strengthening measures. The UHDMC layer effectively redistributed tensile deformation and delayed premature CFRP debonding, thereby improving CFRP utilization. In addition, the strengthened beams exhibited reduced crack widths and more distributed cracking. A preliminary modified sectional analysis method was also developed to estimate the flexural capacity of flexure-governed UHDMC-CFRP strengthened beams.