Design Of Pervious Concrete Mix Ratio And Experimental Study On Clogging

The rapid development of urbanisation and the frequent occurrence of extreme precipitation events have had a serious impact on the ecological environment and the production and living of the public.As an important part of the construction of "sponge cities",pervious concrete has been widely used to effectively alleviate urban flooding and urban heat islands,improve the ecological environment and provide a more comfortable living environment for the public.However,pervious concrete also suffers from poor mechanical properties and insufficient permeability,and clogging can occur during the use of pervious concrete pavements,which seriously affects the normal use of pervious concrete pavements.This thesis focuses on the optimisation of pervious concrete mix,clogging and recovery,and the characteristics of planar pore morphology through indoor tests and mechanism analysis,and provides certain suggestions and technical support for the application and later cleaning and maintenance of pervious concrete.The main work and results are as follows:(1)Based on the orthogonal experimental scheme of five factors and four levels,the effects of water cement ratio,target porosity,aggregate grading,and basalt fiber on working performance,mechanical performance,and permeability are obtained through range analysis and variance analysis.On the premise of satisfying the baseline compressive strength and water permeability coefficient,three types of mix ratio optimisation schemes are identified to meet the needs of different occasions,using the water permeability coefficient,water permeability coefficient and compressive strength and compressive strength as evaluation indicators respectively.(2)The three optimised solutions obtained from a comprehensive analysis of orthogonal tests were used to simulate the clogging of pore spaces by fully graded sand,clay and sand under both rainfall and rainfall and drying conditions.The results show that sand leads to the most serious clogging,clay has the least effect on clogging under rainfall,clay has a significantly higher effect on clogging under rainfall and drying,and drying treatment leads to clay slumping,thus increasing the degree of clogging.The clogging model developed can better explain the decay of the permeability coefficient.(3)Three methods,high-pressure water gun flushing+vacuum suction,high-pressure water gun flushing,and vacuum suction,were used to clean and maintain the clogged specimens.The results show that high-pressure water gun flushing+vacuum suction had the best effect on restoring the permeability coefficient,followed by high-pressure water gun flushing,with poor vacuum suction maintenance effect.For clogging caused by sand,the recovery rate of permeability coefficient is relatively low after cleaning and maintenance.Compared with the clay group under rainfall,the recovery rate of permeability coefficient of the clay group under rainfall and drying is significantly reduced,especially when using vacuum suction maintenance measures.(4)The number of planar pores,pore area and planar porosity can reflect the mechanism of pore influence on permeability and clogging.The planar pores of all three scenarios show complex and irregular morphology,and the pore morphology is relatively similar between the scenarios,with large differences in the morphology of each planar pore,most of the pore boundaries are relatively curved,and the pores are elongated and close to elliptical in shape.The larger pore size is the key to the permeability and degree of clogging.