Compressive Behavior Of PET FRP-Confined Rubberized Concrete

As a kind of solid waste,the waste tire,which is harmful to the environment,is increasing year by year.Therefore,the domestic and foreign countries have already started to recycle the waste tires,but the amount of recycled waste tires is small.Therefore,in the early years,some scholars proposed to use rubber to replace some aggregate in concrete to make rubber concrete?the resulted concrete is referred to as rubberized concrete?.This method not only recycles a large number of waste tires,but also saves natural sand resources,which is conducive to the sustainable development of the environment.The results show that the compressive strength/elastic modulus of rubberized concrete is low,its workability is poor,but its ductility is good,so it is suitable for seismic materials.In recent years,the green large rupture strain fiber-reinforced polymer?LRS FRP?,which is mainly made of polyethylene terephthalate?PET?fiber-reinforced polymer as fiber material,has attracted attention because of its good deformation ability,and its fracture strain is up to 7%.When FRP with large strain is used to restrain rubberized concrete,its lateral restraint has greatly improved the strength and ultimate axial strain of rubberized concrete.The combination of the two materials has great significance in saving resources and protecting the environment.In this paper,three kinds of rubberized concrete with different rubber replacement rate?0,25%,50%?are constrained by large strain FRP to study the monotonic and cyclic axial compression properties of large strain FRP.The main contents showed that:?1?In order to study the effects of FRP confined stiffness and rubber content on the mechanical properties of concrete,monotonic axial compression tests were conducted on 15uncofined-rubberized concrete and 16 PET FRP-confined rubberized concrete.The results show that the failure mode of PET FRP confined specimenss is central fiber ruptured,the strength of the confined rubberized concrete is greatly improved,which is better than that of the ordinary concrete,and the ductility of the confined concrete is increased by more than 10times.?2?Through the cyclic axial compression test of 24 PET FRP-confined rubberized concrete,the effects of FRP confined stiffness,loading rules and rubber content on mechanical properties were studied.The results show that the failure mode of the specimens under cyclic axial compression is similar to that of the specimens under monotonic axial compression;Under two different cyclic loading rules,the envelope curve agrees well with the stress-strain curve of constrained rubber concrete under monotonic axial compression;compared with the ultimate axial strain under monotonic axial compression test,the performance of the specimens under cyclic loading have better axial deformation capacity;the axial strain-hoop strain curve of most specimenss under multiple cycles is lower than that of single cycle;different loading rules have little influence on the linear rule of plastic strain unloading strain curve.The plastic strain and stress damage coefficients of this experiment were compared with the predicted values of the Lam and Teng's cyclic model,and the plastic strain calculation formula and stress damage formula were modified by fitting experimental data.?3?Comparing with four monotonic models,it is found that Zeng's design-oriented model can predict the test value better.Matching with the Lam and Teng cycle model,it is found that the model can predict the cumulative change of plastic strain and the law of stress damage coefficient₉),but the predicted value has larger error compared with the test value.