| Pervious concrete is a kind of porous concrete mixed by fixed gradation aggregate,water,cement and reinforcing agent in a certain proportion.As a kind of ecological concrete,it is not only widely used in areas such as residential pavement,square and parking lot,but also widely used in water conservancy projects,urban roads and other fields with the gradual promotion of sponge city concept.Due to the many pores of pervious concrete,the pavement paved with it has the functions of water permeability,air permeability,sound absorption and noise reduction,etc.,which play an important role in improving traffic safety,slowing down urban "heat island effect" and maintaining ecological balance.Based on the research on the basis of the extensive experimental research,by consulting relevant literature,the permeable concrete understanding of the current domestic and foreign research present situation,research progress and research method,to determine the need to study the influence factors of waterproof concrete,for low permeable concrete mechanics performance of existing,permeable performance problems are studied,such as difference of success by different particle size of coarse aggregate and cement was prepared,and blend plus material permeable concrete frost resistance,to select optimal mixture ratio the layered color cast-in-situ,provide technical support for engineering application.The specific research conclusions are as follows:(1)The effects of target porosity,water-cement ratio,polyacrylonitrile fiber and plastic steel fiber on porosity,permeability coefficient,compressive strength and flexural strength of concrete with coarse aggregate of different particle sizes of 5-10 mm and 10-15 mm were studied through single factor test.The test results show that: under different target porosity,the 28 d compressive strength of 5-10 mm and 10-15 mm coarse aggregate pervious concrete with different particle sizes reaches the maximum value when the water-cement ratio is 0.35 and 0.37,respectively.The compressive strength of polyacrylonitrile fibers with volume fraction of 0.10% and 0.15% was increased by 29.34% and 39.02%,respectively.The 28 d flexural strength of the plastic steel fiber increased by 58.30% and 41.62%,respectively,by adding 0.30% and 0.20% of the volume fraction.(2)For two kinds of coarse aggregate pervious concrete with different particle sizes of5-10 mm and 10-15 mm respectively,orthogonal tests of four factors and three levels weredesigned and range analysis was carried out.The test results show that the factors affecting the compressive strength of pervious concrete are the target porosity > water-cement ratio >polyacrylonitrile fiber > plastic steel fiber.The factors that affect the flexural strength of pervious concrete are plastic steel fiber >,water-cement ratio >,target porosity >polyacrylonitrile fiber.The factors affecting the porosity of pervious concrete are as follows:target porosity > plastic steel fiber > water-cement ratio = polyacrylonitrile fiber;The factors affecting the pervious coefficient of pervious concrete are the target porosity >polyacrylonitrile fiber > water-cement ratio > plastic steel fiber in turn.On the basis of range analysis,the optimal mix ratio was determined: the optimal mix ratio of coarse aggregate with5-10 mm particle size was selected as A3B2C2D3.A3B2C2D2 is the optimal proportion of coarse aggregate with particle size of 10-15 mm.(3)Two kinds of coarse aggregate pervious concrete with different particle sizes were layered cast-in-situ with the optimized mix ratio.The structure was divided into two layers during cast-in-situ: C20 ordinary pervious concrete was adopted for the base layer,and the coarse aggregate particle size was 10-15 mm.C20 color pervious concrete is adopted for the surface layer,and the coarse aggregate particle size is 5-10 mm.After cast-in-place concrete slab is de-moulded and cured for 28 d,the measured compressive strength of pervious concrete is 24.06 mpa,the flexural strength is 3.40 mpa,the pervious coefficient is 9.69mm/s,and the frost resistance level reaches F150.The measured indexes meet the standard requirements and can be used in cold areas in north China.(4)On the basis of a large number of preliminary experimental studies,the research group cooperated with shandong water pipe co.,ltd.to select a site within the water pipe factory and build a standard parking space for family cars with a size of 2.5m 5.5m.In the process of engineering application,rainwater collection can be used in the surrounding green irrigation and flushing of the parking space,realize the recycling of the rain,100 ?antifreeze permeable concrete floor,can collect rainwater about 40 m after a year,during the term of use,can save about 1200-1700 yuan,has the good ecological benefits.The project has accumulated construction experience for the popularization and application of anti-freezing pervious concrete in cold regions of China. |
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