Experimental Study On Flexural Behavior Of Polypropylene Fiber Recycled Concrete Beams

Using recycled coarse aggregate concrete instead of natural aggregate concrete preparation can save resources and reduce pollution, also form recyclable resources and have positive impact on social development. However, recycled concrete because of the natural defects of recycled aggregate concrete resulted the internal renewable micro cracks and more voids, and degradation of the concrete compressive strength, tensile strength and other performances, restricted the wide application of recycled concrete. In recycled concrete adding polypropylene fiber to study the properties of polypropylene fibers on recycled concrete beam flexural.First of all, prepare size, with the ratio of recycled aggregate and fiber content the same ordinary concrete, polypropylene fiber reinforced concrete, recycled concrete and recycled polypropylene fiber concrete, the standard test cubes of these four groups test the compressive strength for28days. The results showed that the polypropylene fiber concrete compressive strength test cubes increase of3%compared with ordinary concrete, recycled concrete compressive strength test cubes decreased9.7%compared with ordinary concrete, polypropylene fiber recycled concrete compressive strength test cubes increase of5.2%compared with recycled concrete. Scan electron microscope microscopic observation on recycled polypropylene fiber concrete interface failure, as can be seen in polypropylene fiber recycled concrete, the crack width of the recycled aggregate and mortar bond interface is small compared with recycled concrete, and fewer micro cracks and voids in mortar, Fiber and mortar damage is the state fiber pull-type damage, fiber crack resistance effect is very obvious.Prepare Parameters and concrete cube standard test block of the concrete beams from the same four categories, test their flexural performance, comparative analysis their cracking load, bearing capacity limit state load, deflection changes, crack propagation state to detect polypropylene fibers on Recycled Concrete Beams performance. Theoretical calculate on four groups of concrete beams cracking load and ultimate load of to explore the current formula for the reliability of the calculation of polypropylene fiber recycled concrete beams. Through the analysis of test results obtained recycled concrete beams cracking moment is lower8.2%than ordinary concrete beams, polypropylene fiber reinforced concrete beams cracking moment is larger9.1%than ordinary concrete beams, polypropylene fiber recycled concrete beams cracking moment increase14.1%than the recycled concrete beams; when achieve ultimate limit state, recycled concrete beam maximum crack width is higher16.1%than ordinary concrete beams, and higher23.2%than the polypropylene fiber recycled concrete beams, fiber crack resistance effect is obvious; under the loads of the same plastic phase, incorporate polypropylene fiber reinforced concrete beam deflection, compared with ordinary concrete beams and recycled concrete beams overall stiffness is better, and ultimately destroy completely lost when the carrying capacity of ordinary concrete beam deflection values above15%than recycled concrete beams, polypropylene fiber reinforced concrete beam deflection value is higher15.5%than normal concrete beams, recycled polypropylene fiber concrete beam deflection values above16%than recycled concrete beams, after the incorporation of polypropylene fiber concrete beams significantly improved the overall stiffness and ductility; four groups of specimens reach the ultimate limit state, recycled concrete bearer force measurement is less6.9%than ordinary concrete beams, polypropylene fiber reinforced concrete beams bearing capacity test values higher4.5%than ordinary concrete beams polypropylene fiber reinforced concrete beams bearing capacity of recycled concrete beams measured value is higher4.5%than ordinary concrete beams, it also can be mixed with polypropylene fibers increase the carrying capacity of concrete beams bearing capacity limit state.At last, apply ANSYS software to nonlinear numerical simulation analysis concrete beam flexural, further comparative analysis the flexural properties of the polypropylene fiber on recycled concrete beam, simulation results and actual test results are close, under the ultimate limit state, recycled concrete beam deflection is6.351mm, polypropylene fiber recycled concrete beam deflection is6.09mm; polypropylene fiber recycled concrete beams simulate the load bearing capacity limit state is144.53kN, it increased3.2%that compared with recycled concrete beam load simulation value.