Experimental Study On Properties Of Pervious Concrete With Recycled Aggregate And The Relationship Between Ultrasonic Pulse Velocity And Properties Of Pervious Concrete

As an ecological and environment-friendly pavement material,pervious concrete has the characteristics of water permeability,air permeability and porosity,which plays an obvious role in reducing urban waterlogging,improving the safety and comfort of vehicle driving,alleviating urban heat island effect and maintaining ecological balance.The use of recycled aggregate made of construction waste in pervious concrete has achieved the goal of environmental protection and resource recycling.But at present,the research results on the properties of pervious concrete with recycled aggregate have not reached a consistent conclusion.Moreover,Jilin province is located in the cold region,freeze-thaw damage phenomenon is serious,which puts forward higher requirements for the strength and freeze-thaw durability of pervious concrete.Therefore,it is of great significance to study the properties of pervious concrete with recycled aggregate.In addition,since the mechanical properties and durability of pervious concrete are lower than that of normal concrete,more frequent testing is needed to ensure that it meets the requirements for normal use,so a convenient and effective testing method for pervious concrete is particularly important.Ultrasound testing technology is one of the most widely used non-destructive testing technologies.Many scholars use ultrasonic pulse velocity to measured the strength,porosity and freeze-thaw durability of normal concrete.However,there is little introduction of application of ultrasonic pulse velocity in testing the properties of pervious concrete materials.Therefore,it has important guiding significance to study the relationship between ultrasonic pulse velocity and pervious concrete properties.This article relies on the key scientific research and development project of Jilin Province Science and Technology Department“Research and Application of Ecological Green Permeable Pavement Materials in Severe Cold Area”to study pervious cement concrete material,analyzed the influence of different aggregate size,water-binder ratio and target porosity on its properties,obtained the optimum mix proportion of pervious concrete.On this basis,recycled aggregate is used to replace natural aggregate partially or totally,and the effects of different recycled aggregate replacement rates on the properties of pervious concrete are studied.The relationships between the ultrasonic pulse velocity and the properties of pervious concrete were studied,and the ultrasonic testing technology is applied to evaluate the freeze-thaw durability of pervious concrete,which provides basic data and theoretical reference for the application of ultrasonic testing technology in the properties evaluation of pervious concrete materials.The specific work carried out is as follows:（1）Pervious concrete mix proportion was designed with orthogonal test mothed.The orthogonal design table L₉（3⁴）is selected.Three factors including aggregate size,water-binder ratio and target porosity were considered respectively,and three different levels were set for each factor.The total porosity,effective porosity,dry density,permeability coefficient,compressive strength,flexural strength and freeze-thaw durability of pervious concrete were tested.Range analysis and variance analysis were carried out on the test results.The influence laws of three factors on the properties of the pervious concrete were studied.The optimum base mixture proportions considering the combination of the above three factors is obtained,of which aggregate size is 4.75 to 9.5mm,water-binder ratio is 0.30 and target porosity is 15%.Finally,the property test results were fitted and analyzed,and the relationship between the properties indexes was established.（2）The abandoned concrete bricks were mechanically crushed and artificially sieved to obtain the recycled aggregate required for the test.Based on the optimum basic mix proportion,the properties of recycled aggregates and the properties of pervious concrete with recycled aggregate with different replacement rates were studied.The best replacement rate of recycled aggregate is 25%.Under this replacement rate,the properties of pervious concrete with recycled aggregate meet the requirements of relevant standards.（3）Ultrasonic pulse velocity of pervious concrete was measured by ultrasonic testing technology.The relationship between ultrasonic pulse velocity and total porosity,dry density,permeability coefficient,compressive strength and flexural strength were studied.In the freezing-thawing durability test,degree of freezing-thawing damage based on ultrasonic pulse velocity,rate of ultrasonic pulse velocity loss and rate of mass loss were used to evaluate degree of freezing-thawing damage of pervious concrete.