Research On Deterioration Mechanism Of Sulfate Solution Corrosion Resistance And Creep Law Of Recycled Plastic Concrete

In the long-term use of concrete,there are some problems,such as excessive selfweight,insufficient tensile strength,insufficient sulfate solution corrosion resistance and creep deformation.Some scholars at home and abroad have studied the short-term performance of recycled plastic concrete by replacing the coarse and fine aggregates in concrete with recycled plastic particles.Although the problems such as excessive self-weight and insufficient tensile strength of concrete have been solved to a certain extent,the research on the long-term performance such as sulfate solution corrosion resistance and creep characteristics is still insufficient,these long-term properties have an important impact on the application of recycled plastic concrete.Therefore,it is of great theoretical and engineering significance to study the sulfate resistance and creep behavior of recycled plastic concrete.Based on the 4 factors and 4 horizontal orthogonal experiments,the optimal proportion and the main physical and mechanical properties of recycled plastic concrete are systematically studied.On this basis,the strength degradation mechanism,sulfate solution corrosion resistance and creep characteristics were studied by means of microstructure test,sulfate solution corrosion resistance test,creep test and theoretical analysis.The main conclusions are as follows:(1)Based on the orthogonal test and microstructure test,the slump,apparent density,compressive strength and splitting tensile strength of recycled plastic concrete were systematically analyzed.The optimal ratio of recycled plastic concrete was obtained,and the strength degradation mechanism of recycled plastic concrete was revealed.Through ICP-OES equipment testing,the leaching solution of recycled plastic concrete was analyzed systematically,and it was proved that the leaching solution of recycled plastic concrete had little impact on the environment.The suitable temperature range of recycled plastic concrete was obtained through heat resistance test.(2)Based on the corrosion test of sulfate solution(sodium sulfate,magnesium sulfate and ammonium sulfate),the change rules of appearance,quality,ultrasonic speed and compressive strength of recycled plastic concrete corroded by sulfate solution were obtained,and the damage degree model with compressive strength as damage parameter was established.By means of SEM-EDS,XRD and FT-IR,the phase composition and microstructure of recycled plastic concrete corroded by sulfate solution were analyzed,and the degradation mechanism of recycled plastic concrete was revealed.(3)Based on particle swarm optimization(PSO)and BP neural network,the prediction model of DT-PSO-BP neural network was established,which was applied to predict the compressive strength of recycled plastic concrete corroded by sulfate solution.The neural network prediction model of compressive strength changing with erosion time,erosion solution concentration and solution type was established.And the corresponding DT-PSO-BP neural network program was compiled in MATLAB.By comparing with BP and PSO-BP neural network,it was proved that DT-PSO-BP neural network had better prediction effect,so the prediction model can be better applied to the strength prediction of recycled plastic concrete corroded by sulfate solution.(4)The creep test of concrete under the combined action of axial pressure and water pressure was carried out.The total creep strain,creep rate,creep coefficient and creep degree of recycled plastic concrete and ordinary concrete were compared and analyzed,and the creep characteristics of the two kinds of concrete were obtained.Based on the creep test results,the burgers creep model was improved,and the RCBurgers creep model which can better describe the creep characteristics of recycled plastic concrete was constructed,and the accuracy of the model was verified.