Experimental Study On Mix Ratio And Material Properties Of High-replacement Recycled Aggregate Pervious Concrete

At present,many cities in China are exploring the construction of “sponge city”,and pervious concrete plays a very important role in the construction of “sponge city”.The porous nature of pervious concrete contributes to sound absorption and noise reduction,alleviates the urban “heat island effect”,maintains groundwater level balance,and accelerates surface drainage during the rainy season to alleviate urban guilt.Replacing natural aggregates with recycled aggregates to produce recycled aggregate pervious concrete can also reduce the use of natural aggregates,save natural resources,and also help consume part of construction waste.Therefore,recycled aggregate pervious concrete is an environmentally friendly pavement material.In order to respond to the requirements of the national construction of "sponge city",help solve construction waste disposal and promote the practical application of recycled aggregate pervious concrete.This project mainly studies the mixing ratio and performance of recycled aggregate pervious concrete,and analyzes the feasibility of high substitution rate recycled aggregate pervious concrete and large particle size recycled aggregate pervious concrete.The main research contents are as follows:(1)Design 5 factors(including an empty column)4 levels of orthogonal test,designed for the mix ratio of recycled aggregate pervious concrete.Analyze the compressive strength,flexural strength,effective porosity and water permeability coefficient of recycled aggregate pervious concrete under the influence of four factors including the replacement ratio of recycled aggregate,the amount of silica fume,the amount of polypropylene fiber and the amount of redispersible latex powder.Using the range analysis,analytic hierarchy process and analysis of variance,the test results were comprehensively analyzed to determine the primary and secondary factors affecting the performance of recycled aggregate pervious concrete.The optimal mixing ratio of recycled aggregate pervious concrete under orthogonal test conditions was obtained.(2)Based on the research conclusion of orthogonal experiment,the recycled aggregate pervious concrete with different substitution rates and different aggregate sizes was set,and the performance of recycled aggregate pervious concrete was optimized by blending fly ash.The compressive strength,flexural strength,effective porosity,water permeability coefficient and freeze-thaw resistance of the test piece were measured.(3)The relevant test results in the orthogonal test and the optimization test were respectively fitted to obtain the fitting relationship.(4)In combination with the relevant requirements of the industry standard CJJ/T 253-2016 "Technical specification for application of pervious recycled aggregate concrete ",feasible suggestions have been put forward in design and engineering construction.After experimental research,the reasonable mix ratio of recycled aggregate pervious concrete is:(1)when the aggregate particle size is 5 ~10 mm,the replacement ratio of recycled aggregate is 50%,the amount of silica fume is 4.7%,the amount of polypropylene fiber is 0.6%,the amount of redispersible latex powder is 7%,and the amount of fly ash is 10%;(2)when the aggregate particle size is 10 ~16 mm,the replacement ratio of recycled aggregate is 30%,the amount of silica fume is 4.7%,the amount of polypropylene fiber is 0.6%,the amount of redispersible latex powder is 7% and the amount of fly ash is 10%.The test results show that the high-volume recycled aggregate pervious concrete and the larger-size aggregate recycled aggregate pervious concrete have certain feasibility in engineering application.