Plain Concrete Prisms Externally Strengthened by CFRP Bonded with Graphene Oxide–Modified Magnesium Phosphate Cement

Abstract

Graphene oxide (GO)–modified magnesium phosphate cement (MPC) is used as an adhesive to bond carbon fiber–reinforced polymer (CFRP) composites in the formation of MPC-CFRP strengthening materials. The performance of GO-modified MPC paste and the mechanical performance of MPC-CFRP–strengthened concrete prisms are investigated in this paper. Workability and mechanical properties of MPC with different dosages of GO (0.035 wt% and 0.07 wt% by MgO) are tested. The results indicate that GO has negative effects on the fluidity and setting time of MPC. Mechanical properties of MPC are improved by a proper addition of GO. Compared with unstrengthened prisms, bearing capacity and stiffness of strengthened concrete prisms increase with the layers of MPC-CFRP: maximum bearing capacity increased by 372.08%, and stiffness increased by 130.15%, respectively. MPC with the optimal mechanical properties (MPC-GO1) is used as the adhesive to bond CFRP, which forms a new type of strengthening composite and greatly improves the bearing capacity and ductility of plain concrete prisms.