Study On Bond Behavior Between Rebar And Waste Fiber Recycled Concrete Under Freeze-Thaw Conditions

Due to the rapid development of economy,in order to meet the needs of people's life and social,a large number of old buildings were demolished,which also brought a lot of construction garbage.At present,the way to deal with those construction garbage is simply landfill.This treatment not only causes serious damage to the environment,but also wastes a lot of land resources.At the same time,a large number of waste textiles that are difficult to deal with also casue serious damage to the environment.The main research object of the paper-"Waste Fiber Recycled Concrete" is the green environmental protection concrete which comes into being after the combination of the waste concrete in the construction garbage and the waste fiber in the waste textile.It can solve the environmental problems brought by the construction garbage and the waste textile in a great extent.Through the freeze-thaw cycle test of 7 groups and 84 specimens to be tested in the center pull-out test,found that the freeze-thaw damage of all specimens has a similar process:from the occurrence of pockmarks on the surface of concrete,to the different degree of mortar peeling off on the surface,to the exposure of coarse aggregate;then to the mortar peeling off around the aggregate,the coarse aggregate peeling off.Finally,the internal structure of concrete damaged.At the same time,the failure process of specimens with high replacement rate of recycled aggregate can be shortened.Adding waste fiber can improve the frost resistance of recycled concrete,but not the larger the volume of waste fiber,the higher the frost resistance of recycled concrete.Then the center pull-out test is carried out on the test piece of freeze-thaw cycle test.According to the analysis of the test results,it is concluded that when the volume of waste fiber is fixed the higher the replacement rate of recycled aggregate,the degradation rate is faster with the increase of the number of freeze-thaw cycles.When the replacement rate of recycled aggregate is certain,the addition of waste fiber has little influence on the ultimate bond strength,interface bond strength and initial bond slip modulus,but it can improve the frost resistance of recycled concrete,so as to retain the bond and anchorage ability as much as possible.According to the test of bond stress distribution,find that the bond stress distribution of ordinary concrete and recycled fiber reinforced concrete have the same essence.The obvious difference between both of them is that there are two peak points in the bond stress distribution curve of ordinary concrete,but there is only one peak point in the bond stress distribution curve of recycled aggregate which replacement rate of recycled aggregate is 50%and 100%.And the number of peak points is independent of freeze-thaw times.In the last chapter of this paper,the BP neural network model of bond performance prediction between rebar and waste fiber recycled concrete under freeze-thaw condition is established by using MATLAB,and the model is trained by 234 groups of effective data.After simulating the test parameters in this paper by the model,it is proved that the model can meet the requirements in terms of accuracy.