Research On The Infiltration Performance And Pollutant Purification Efficiency Of Recycled Aggregate Permeable Concrete Pavemen

With the continuous development of urbanization,the proportion of impermeable pavement is getting higher and higher,which leads to the reduction of rainfall infiltration and the increase of runoff coefficient of rainwater,which wastes a lot of rainwater resources and is prone to urban waterlogging;Due to the destruction of the environment,there are more and more pollutants in the runoff rainwater.The long-term rainwater runoff has led to serious phenomena such as water deterioration,black and smelly river water.At the same time,in the process of urbanization,a large number of buildings have been upgraded,resulting in a lot of construction waste,further increasing the environmental pressure of the city.With the proposal of the national "sponge city" and "waste free city" ecological construction concept,various measures and policies have been implemented accordingly,making it possible to effectively control rainwater runoff and purify runoff pollutants,and recycle construction waste.In order to increase the ways of recycling construction waste and enrich the filler types of permeable concrete pavement system,this paper recycles the construction brick waste and construction concrete waste,which contain a large amount of construction waste,into recycled aggregate and applies them to the permeable concrete pavement system,using the method of combining physical test and numerical simulation,The infiltration performance and pollutant purification efficiency of various permeable concrete pavement systems under different conditions are studied.The main research contents and results are as follows:(1)Through consulting and analyzing the literature,the test materials were determined,the test device was improved,and the test scheme was improved.The permeable concrete pavement system of different structures was designed by recycling the building brick waste and building concrete waste into aggregates,namely,the permeable concrete pavement system of regenerated brick aggregate,the permeable concrete pavement system of recycled concrete aggregate,The ordinary permeable concrete pavement system is designed with natural aggregate as the control group;By changing the rainfall return period,the concentration of runoff pollutants and the slope of the surface layer of the system,the indoor columnar test scheme under various working conditions is designed,and the research contents of various aspects are designed for the rainwater infiltration performance of three kinds of permeable concrete pavement systems and the purification ability of the typical pollutants solid suspended solids concentration(SS),chemical oxygen demand(COD),total phosphorus(TP)and total nitrogen(TN).(2)The column tests under three conditions were carried out,namely,different rainfall return periods,different concentrations of runoff pollutants and different system surface slopes.The results showed that the infiltration performance and purification capacity of various permeable concrete pavement systems for typical pollutants decreased with the increase of rainfall return periods,Moreover,the infiltration performance and purification capacity of recycled aggregate pavement system are better than that of ordinary permeable concrete pavement system;With the increase of influent concentration of runoff pollutants,the infiltration and purification effects of various pavement systems are slightly reduced,and the high concentration of influent pollutants will cause blockage of the system and affect the infiltration capacity;With the change of the slope of the surface layer of each system,the impact of the pavement system on the purification capacity of typical pollutants is small,but the impact on the rainfall infiltration performance of each pavement system is large.With the increase of the slope of the surface layer of each system,the infiltration performance shows a downward trend.In short,the recycled brick aggregate permeable concrete pavement system has the best water storage capacity and purification capacity for typical pollutants SS,COD and TN,with the maximum purification rate of 98.95%,56.31% and 34.11% respectively.The permeable concrete pavement system of recycled concrete aggregate has the best infiltration capacity and purification capacity of pollutant TP,with the maximum purification rate of 76.50%.Moreover,the infiltration performance and pollutant purification capacity of recycled aggregate permeable concrete pavement system are better than that of ordinary permeable concrete pavement system under various conditions.(3)In order to further study the infiltration performance and pollutant purification efficiency of the permeable concrete pavement system,a numerical model was built using the software Hydras-1D to carry out a numerical simulation test.By comparing the simulated value with the measured value and calculating the Nash efficiency coefficient,the results show that the model has high reliability,which shows that the established model and the set parameters are reasonable.Then a permeable concrete pavement model with different thickness ratio of base course is constructed.According to the simulation results of Hydras-1D,the infiltration effect of model 1(thickness ratio of base course:1:2)is the best,and the pollutant purification effect of model 3(thickness ratio of base course: 2:1)is the best.The above research results have important application value for the research on the runoff permeability and pollutant purification capacity of pervious concrete pavement system,and the recycling of building brick waste and building concrete waste.