Experimental Study On Reinforced Concrete Structure By Enhanced Coating

With the continuous growth of reinforced concrete consumption,its durability has been gradually concerned,and the lack of durability is often accompanied by the reduction of structural bearing capacity.Previous studies have shown that the bearing capacity and durability of reinforced concrete structures coated with polymer materials can be improved to a certain extent.The improvement of bearing capacity is not only related to the strength of the coating material itself,but also closely related to the bonding force of the concrete interface.In thesis paper,the mechanical properties of polymer materials were optimized by adding flexible fibers.The dumbbell direct tensile test was carried out on the polymer materials with flexible fibers,and the tensile failure mode of the polymer materials with flexible fibers was analyzed by SEM scanning test.Based on the dumbbell direct tensile test,the double-sided shear test of the interface between polymer fiber and concrete was carried out to explore the double-sided shear strength under different fiber types,concrete interface treatment methods and concrete strength to evaluate the interfacial bond strength.Based on the dumbbell direct tensile test and double-sided shear test,the flexural capacity of the normal section of the RC beam coated with polymer fiber materials was studied,and the cracking load and ultimate load of the test beam were theoretically deduced and calculated.The main work and conclusions are as follows:(1)Based on the dumbbell direct tensile test of polymer fiber materials,the tensile stress-strain curve of polymer fiber materials was drawn.When the volume fraction of 6mm PVA fiber in the matrix is 1.6%,the tensile strength reaches the maximum value of7.62 Mpa.Taking the fiber length and fiber volume content as the independent variables,and the tensile strength of the polymer fiber material as the dependent variable,the threedimensional surface fitting of the tensile strength of the polymer material doped with three kinds of fibers was carried out by using Table Curve 3D V4.0 software,and the tensile strength formulas of the three kinds of fibers were obtained.The goodness of fit of the three is greater than 0.86,and the fitting degree is good.The stress-strain curve of the dumbbell-shaped direct tension of the high polymer fiber material is simplified into a double broken line model,and the secant modulus of the high polymer fiber material is calculated.When the volume fraction of 6 mm PVA fiber is 1.6%,the secant modulus reaches the maximum value of 4.51 Gpa.(2)The failure modes of fiber reinforced composites were studied by scanning electron microscopy(SEM)at the interface between fiber and polymer matrix.The results show that the failure mode of the PVA-fiber reinforced group is mainly the slip of the fiber in the matrix,and the compactness between the fiber and the matrix is the best,and the integrity is the best.In the PPF fiber reinforced group,the compactness of fiber and polymer matrix is not as good as the PVA reinforced group,the integrity is not good enough,and the final tensile strength enhancement effect is not as good as the PVA fiber reinforced group.In the "E" type glass fiber reinforced group,the surface of the fiber is relatively smooth,the degree of compactness between the fiber and the polymer matrix is the worst,and the tensile strength enhancement effect is also the worst.(3)Based on the double-sided shear test of the interface between polymer fiber and concrete,the effects of concrete strength grade,interface treatment methods and fiber types on the double-sided shear strength were studied.Using SPSS software for statistical analysis,the significance of the other two factors on the double-sided shear strength was analyzed by two-factor variance analysis method under the condition of concrete strength grade C40,interface treatment for chiseling and fiber type for PVA fiber.(4)Flexural capacity tests were carried out on four strengthened beams and one control beam.The test results show that the polymer fiber coating can effectively improve the flexural capacity of the normal section of the RC beam and effectively inhibit the development of cracks.For the cracking load,the maximum increase is 47.9%;for the ultimate load,the maximum increase is 64.7%,and the strengthening effect is remarkable.(5)Based on the experimental study,the cracking load of two strengthened beams and one control beam in service stage was analyzed theoretically by using the conversion section method,and the calculation formula was derived.The calculation results of the ultimate flexural capacity of RC beams with different thicknesses of the strengthening layer show that the ultimate flexural capacity of the strengthened beams increases with the increase of the thickness of the strengthening layer.(6)According to the results of flexural failure mode analysis of the test beams,the calculation model of ultimate flexural capacity of RC beams is established,and the ultimate flexural capacity and ultimate load of the test beams are derived and calculated.The results show that the error between the theoretical calculation value and the test value is small.