Experimental Study on Flexural Capacity of PP-ECC Beam

To study the difference of mechanical properties between PP-ECC (polypropylene fiber cement-based composite) beam and ordinary reinforced concrete beam under bending load, the bending performance of PP-ECC beam was tested through four point bending load. Firstly, the bending failure process of PP-ECC beam was divided into stages. Secondly, the theoretical critical loads of each stage of PP-ECC beam were derived based on the calculation assumption and simplified PP-ECC constitutive model. Finally, the calculation model was verified by the test results, the differences of flexural capacity, fracture development, maximum mid-span deformation, and ductility between PP-ECC beam and ordinary reinforced concrete beam were compared under the same reinforcement ratio. The results show that PP-ECC material in the tensile zone does not quit working after cracking, but cooperates with the tensile reinforcement to participate in the full section stress. The accuracy of the theoretical bending capacity calculation model of PP-ECC beam calculated by the simplified constitutive model reaches 0.83～1.17, which has a good accuracy. When PP-ECC beam reaches the ultimate state, the tensile zone presents the steady development of multiple cracks, when the ultimate bearing capacity reaches 80%, the maximum crack width is less than 0.2 mm. With the same reinforcement ratio, the deformation, maximum deformation, and displacement ductility coefficient of PP-ECC beam at each loading level are higher than those of ordinary reinforced concrete beam (the average increase of the maximum deformation and displacement ductility coefficient is 71.39% and 42.84%), and with the increase of reinforcement ratio, the maximum deformation and displacement ductility coefficient in the middle of span decrease. With the same reinforcement ratio, the ultimate bending capacity of PP-ECC beam is 6.09% higher than that of ordinary reinforced concrete beam.