The test specimens are three specimens with the same size and the concrete strength of the bending specimen is C40. The net span of the test piece is 4.0m, the cross-sectional area is 250mm×400mm, and the length of the pure bending section is 1.1m.

L-1 is a reinforced concrete structure with unprestressed carbon fiber strip; CL-1, CL-2 are both reinforced concrete structures with prestressed carbon fiber strip applied with 960 MPa

Analysis of the load-bearing performance of the specimen

After CL-1 and CL-2 are reinforced with carbon fiber strip, the self-cracking load is significantly increased. Compared with the unreinforced L-1, the yield load and ultimate load are significantly improved.

Specimen deformation analysis

The technical points of prestressing technology to reduce the deformation degree of reinforced concrete structures are as follows. The pre-stress technology can make the structure reverse deflection, and the pre-stress effectively enhances the cracking load and yield load capacity of the structure, so as to achieve the purpose of extending the service life in these two periods. The change of the deflection in the middle of the span is an important basis for evaluating the prestressed carbon fiber reinforcement technology to reduce the deformation of the specimen.

Although the specimen L-1 was severely cracked before reinforcement, the cross-sectional area was greatly reduced, but the relevant test data at each stage of the test was close to CL-1. This strongly proves that the structure can still be reinforced by using carbon fiber strip when the structure is severely damaged due to force majeure factors. Tests have proved that the performance of the reinforced structure is not inferior to the related performance of the original structure.

Carbon fiber strip efficiency analysis

Through the analysis of the relevant data obtained from the test, it can be known that the performance of the specimens reinforced with non-prestressed reinforcement technology has not been significantly improved, and the tensile strength of the carbon fiber strip has not been fully reflected. Demonstrate the waste of carbon fiber high-strength materials used in non-prestressed reinforcement technology. The specimens reinforced with prestressed carbon fiber strips can not only strongly repair the structure and restore the structural strength, but also give full play to the superior performance of carbon fiber high-strength materials, showing the superiority of the prestressed carbon fiber reinforcement technology.

Concluding remarks

In the case that the size of the material selected in the test is large and the reinforcement range of the carbon fiber strip is small, the prestressed carbon fiber reinforcement technology still shows excellent results in the test. Effectively improve the basic structural properties such as the structural strength, compressive capacity, and rigidity of the test piece. Compared with the traditional non-prestressed reinforcement technology, it greatly improves the use efficiency of the high-strength material carbon fiber.

During the test, after the test piece has been loaded and loaded until the longitudinally stressed steel bar yields, the test piece is reinforced. The load-bearing performance of the specimen is still similar to that of the non-prestressed reinforced specimen, that is, the reinforced specimen without loading history. When the section is severely damaged, the stiffness of the section is greatly reduced. The degree of deformation of the specimen is similar to that of the comparison specimen, indicating that the specimen with prestressed carbon fiber reinforcement technology can still restore the structure with severe cracking to a level similar to the performance of the undamaged specimen.