Study On The Clogging Performance Of Recycled Aggregate Pervious Concrete

In recent years,with the acceleration of urbanization in China,the annual output of construction waste is increasing year by year,and the pollution to the environment is also increasing year by year.Pervious concrete is a key component of sponge city.It is a kind of eco-green and environment-friendly functional pavement material,which can effectively absorb road surface rain water and reduce urban waterlogging.Recycled aggregate pervious concrete(RAPC)is prepared by replacing natural aggregate with recycled aggregate from broken construction waste,which can not only reduce the environmental pollution caused by construction waste,but also reduce the occurrence of urban flood,enhance the function of urban ecosystem and promote the sustainable development of construction industry.However,in the process of practical application,with the use of time,the sediment generated by human factors or natural settlement and other reasons tend to cause the internal pore clogging of RAPC,resulting in a significant reduction of its permeability,and even dissipate its function to become impervious pavement.Based on this,this paper takes RAPC with design porosity of 20%,25% and 30% as the research object,selects clogging materials from different areas(commercial area,traffic area,residential area and park),conducts continuous plugging and cyclic clogging-flushing tests to study the changes of permeability coefficient,permeability loss rate and permeability recovery rate of RAPC;studies its planar pore characteristics parameters based on Image method,the pore size and area distribution of RAPC are described by mathematical statistics;the influence of the ratio between the particle size of the clogging material and the characteristic pore size on the clogging performance of RAPC is studied,and the influence of different pore sizes on the compressive strength,permeability coefficient,permeability loss rate and permeability recovery rate of RAPC is analyzed based on gray correlation theory;finally,a continuous clogging model and a cyclic clogging-flushing model based on the pore structure parameters were established,it provides theoretical support for solving RAPC clogging problem and its engineering application.The results show that:(1)In terms of the relationship between permeability and pore structure parameters of RAPC,the initial permeability coefficient and effective porosity of RAPC are exponentially regular,the pore size distribution basically obeys Weber distribution,and the area distribution obeys lognormal distribution;the RAPC compressive strength,permeability coefficient and single plane pore characteristics such as plane porosity,perimeter,specific surface area and shape factor are exponentially and linearly related,respectively;there is a quadratic polynomial relationship between the permeability coefficient and composite pore structure parameters,and the correlation coefficient is above 0.95.(2)From the continuous clogging in different areas,the larger the design porosity,the more clogging the RAPC could sustain to maintain its permeable capacity,but the maximum number of plugs did not exceed 6;the rate of permeability loss in a residential area is relatively the largest and most prone to clogging;the ratio τ of clogged particle size to the average equivalent diameter is between 0.253 and 0.267,causing more serious clogging of RAPC;the continuous clogging model based on pore structure parameters can better predict the permeability coefficient after clogging.(3)During clogging-flushing,through the same number of cyclic clogging-flushing after the higher recovery coefficient is higher,the greater the porosity;and the permeability coefficient of RAPC did not drop below 0.5 mm/s after 10 cycles of clogging-flushing;the permeability recovery rate of the park was relatively the largest,and the flushing recovery effect was the best;different ranges of pore sizes had different effects on the compressive strength,permeability coefficient,permeability loss rate and permeability recovery rate of RAPC,among which holes of 2-4 mm and 4-6 mm have the greatest influence on the compressive strength;holes of 8-10 mm and >10 mm have the greatest influence on the permeability coefficient;the cyclic clogging-flushing model can better predict the permeability coefficient after flushing.