Research on the Bending Behavior of Concrete Beams Reinforced with CFRP Sheets Bonded Using BMSC

To improve the construction performance of inorganic adhesives used for bonding fiber-reinforced polymer (FRP) sheets to reinforce concrete structures, make rational use of resources, and reduce carbon emissions, double-shear tests on the interface bonding performance between bonded FRP sheets and cement mortar test blocks, as well as four-point bending tests on bonded carbon fiber-reinforced polymers (CFRPs) to reinforce concrete beams, were conducted using basic magnesium sulfate cement (BMSC) as the adhesive. The influence laws of parameters, such as the type of FRP sheet and the number of FRP sheet bonding layers on the shear performance of the bonding interface between BMSC and cement mortar test blocks, were investigated, as well as the influence laws of the number of CFRP sheet bonding layers and the type of binder on the bending performance of CFRP sheet-reinforced beams. The test results show that the ultimate load of CFRP-reinforced beams bonded with BMSC as the binder increased by 17.4% to 44.4% compared with the unreinforced beams and simultaneously improved the flexural stiffness and crack-limiting ability of the reinforced beams. The failure of the reinforced beam begins with the separation of the CFRP sheet from the concrete at the middle and bottom of the beam span. When the CFRP sheet of the reinforced beam is one layer and two layers, the flexural bearing capacity reaches 91.4% and 96%, respectively, of the reinforced beam, with epoxy resin as the binder under the same conditions. With the increase in the number of CFRP layers, the flexural bearing capacity of the reinforced beam improves, but the increased flexural bearing capacity does not increase proportionally with the increase in the number of sheet layers. By introducing the influence coefficient of BMSC on the flexural bearing capacity (FBC) of reinforced beams, based on the test results, the formula for calculating the FBC of concrete beams, which are reinforced with CFRP sheets bonded by BMSC, was developed. After verification, the calculation formulas established in this paper have high accuracy and can provide theoretical references for similar engineering applications.