Experimental Study On Basic Mechanical Properties Of Pervious Concrete And Its Discrete Element Numerical Simulation

Pervious concrete pavement is an effective urban green infrastructure solution.Pervious concrete has good water permeability because of the existence of a lot of pores inside the pervious concrete,which can effectively reduce ground runoff and alleviate the problem of urban waterlogging.In addition,compared with ordinary concrete,pervious concrete significantly reduced the amount of cement and aggregates,which helps to reduce energy consumption and greenhouse gas emissions in the cement production process,as well as reduces the excessive consumption of natural sand and gravel resources.But at the same time,the existence of pores also affects the strength of pervious concrete.The main factors affecting pervious concrete are aggregate particle size and shape,cement paste and aggregate content,and the degree of compaction of the mixture.In this experiment,the single-factor test method was used to study the effects of aggregate particle size,slurry-to-aggregate ratio and loose paving coefficients on the basic mechanical properties and water permeability of pervious concrete.A numerical model based on the real aggregate shape of pervious concrete was established using the particle flow（PFC）discrete element modeling method,and the numerical simulation of compression and splitting tensile tests were carried out according to the test conditions,the numerical simulation was verified by the test results.The effects of different mixing ratios of coarse aggregate on the number of contacts of aggregates were studied by discrete element numerical model.The test results show that:（1）the permeability of 50% 5-10 mm + 50% 10-15 mm mixed particle size aggregate permeable concrete is slightly lower than that of the 5-10 mm and 10-15 mm single particle size aggregate,but has a higher compressive and splitting tensile strength;（2）With the increase of slurry-to-aggregate ratio,the permeability coefficient of pervious concrete showed a downward trend,while the compressive strength and splitting tensile strength showed an upward trend;（3）With the increase of the loose paving coefficient,the water permeability decreases and the compressive and tensile strength increases.Aggregate particle size has a great influence on the mechanical properties and water permeability of permeable concrete,and the loose paving coefficient and the ratio of slurry to aggregate can be used as control factors to guide the mix design and forming process of permeable concrete.The numerical simulation results shows that:（1）the modeling method of this test can accurately simulate the shape of the aggregate in the pervious concrete,and the numerical model can effectively simulate the crack development and failure form of the pervious concrete in the compression and splitting tensile tests;（2）Compared with the experimental results,under the condition that the loose paving coefficient is 1.10 and the ratio of slurry to aggregate is 0.5,the error of the numerical simulation results of the compressive test is within 3%,and the error of the numerical simulation results of the splitting tensile test is within 5%;（3）The numerical model using 70% 5-10 mm+30%10-15 mm mixed aggregate has the largest number of contacts,and the bonding between the aggregates is more sufficient,the experimental verification results show that the pervious concrete under this mixing ratio has better mechanical properties.