| A considerable amount of construction waste will be generated in the process of demolition,maintenance,and reinforcement of buildings.The application and promotion of recycled concrete technology have alleviated the problem of construction waste reuse to a certain extent.In the process of preparing recycled coarse and fine aggregates,a kind of construction waste powder,namely recycled powder,will be produced,which accounts for about 20 % of the total amount of prepared aggregates.A large amount of recycled powder will cause great harm to the environment.Therefore,how to further solve the resource utilization of recycled powder is of great significance to ensure the realization of carbon peak and carbon neutrality,and to promote China’s green development to a new level.In this thesis,based on the design theory of Engineered Cementitious Composites(ECC),the recycled powder is used as a cementitious material to partially replace cement,and new green building material with excellent performance is prepared by mixing basalt fiber(BF)and polyvinyl alcohol fiber(PVA).That is Fiber Recycled Powder Concrete(FRPC).Reinforced concrete refers to concrete with reinforcement,and two different materials of steel bars and concrete can work together effectively,which is due to the bonding force between concrete and reinforcement after concrete hardening.In order to better promote the application of recycled powder concrete structure,it is necessary to study the bond-slip performance between fiber recycled powder concrete and reinforcement.According to the Concrete Structure Test Method Standard(GB/T 50152-2012),the central pull-out test was designed and carried out to explore the influence of water-binder ratio,sand-binder ratio,the replacement rate of recycled powder,fiber type and content on the bonding performance between FRPC and reinforcement.According to the test results,the mix ratio of High Ductility Recycled Powder Concrete was determined.The effects of anchorage length,reinforcement diameter,protective layer thickness,loading rate and fatigue cyclic load on the bonding performance of HDRPC were investigated.The main work contents and results are as follows:1)42 center pull-out specimens were designed and manufactured.Through the center pull-out test,the bond-slip curve and bond strength of FRPC were studied under the influence of water-binder ratio,sand-binder ratio,recycled powder content,fiber type and content.The bond-slip curve under different replacement rates of recycled powder was fitted,and its constitutive relationship was obtained.The test results show that the water-binder ratio has a significant effect on the bond performance of FRPC,while the sand-binder ratio has little effect on the bond strength.The hybrid fiber system can better improve the bonding performance of FRPC,and the performance is the best when the mixed ratio is 0.2 % BF +1.7 % PVA fiber.When the replacement rate of recycled powder exceeds 30 %,the effect of its change has little effect on bond strength;the bond-slip constitutive relationship under different replacement rates of recycled powder is proposed.2)According to the selection criteria of better bonding performance and better economic benefits,the HDRPC mix ratio is determined.A total of 72 center pull-out specimens were designed and manufactured.Through the center pull-out test,the change of HDRPC bonding performance under the influence of various factors was studied.The test results show that the long anchorage length weakens the HDRPC bonding strength,and the short anchorage specimens often show better bonding performance.With the increase of reinforcement diameter,the bond strength increases first and then decreases.Adequate protective layer thickness can effectively improve the bonding performance between HDRPC and reinforcement,but the continuous increase of protective layer thickness will weaken its bonding performance.The change in loading rate will affect the transmission along the direction of reinforcement and change the failure rate of the concrete interface.3)27 center pull-out specimens were designed and manufactured to explore the influence of fatigue load on the bonding performance of HDRPC.First,the fatigue cycle test was carried out on the specimens,and then the monotonic pull-out test was carried out.The test results show that the appropriate number of fatigue cycles can enhance the bonding performance of HDRPC,but the fatigue load will lead to accelerated bond degradation;with the increase of fatigue cycles,the fatigue damage of the specimen increases and the residual displacement increases.Lower fatigue load upper limit level can reduce the attenuation of bond performance.Based on the test results,the calculation formula of HDRPC bond strength after fatigue was proposed. |
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