Study On Effect Of Aggregate Size And Strength On Performance Of Pervious Concrete

The special skeleton pore structure in pervious concrete gives it a certain strength as well as the ability to pervious and store water.It can be used for pavement paving to achieve the effects of water recycling,sound absorption and noise reduction,anti-glare,etc,which can be an important material for the construction of "sponge city".Among them,aggregate,as the "soul" component of the internal structure of pervious concrete,has an extremely important influence on its permeability and mechanical properties.For this reason,the performance of pervious concrete with different particle size and aggregate strength is compared and studied in this paper,and then a method of mixture proportion design based on target strength and target permeability is proposed.Main research contents and conclusions include?1?Pervious concrete is prepared with 3-5 mm,5-10 mm and 10-15 mm gravel aggregate and its performance is compared.The results show that the compressive strength of pervious concrete increases with the decrease of porosity.The 28d strength of pervious concrete increases by 50%-60%for every 5%reduction of porosity.When the design porosity is the same,the compressive strength of pervious concrete with different particle sizes is basically the same.The permeability coefficient k of pervious concrete is mainly related to the porosity P,and the relation fitted:k=-25.334P2+15.076P-0.9179?2?Through mixing the above three kinds of single grade aggregate with different proportions,four series of mixed grade aggregate pervious concrete were prepared and tested By comparing their properties,the following results can be obtained:The permeability of single grade aggregate pervious concrete is higher than that of mixed grade aggregate pervious concrete when the compressive strength is the same?3?The pervious concrete was prepared by using aggregate with different strength and tested.The results showed that the compressive strength of pervious concrete increased linearly with the strength of slurry.For every 1MPa increase of slurry strength,the compressive strength increased by 0.24 MPa?0.28 MPa.For the pervious concrete with a slurry of strength of 112.7 MPa,the compressive strength can reach C40,C30 and C20 grades when the crushing indexes of aggregate are 3.2%,13.0%and 16.7%,respectively?4?Through the fitting of the above data,the expression of compressive strength of single grade pervious concrete is obtained:Fc=0.281?·f_c+?.Based on this,a mixture ratio design method was proposed:The crushing index of aggregate is determined by the target strength,and the aggregate is selected according to it.According to the proposed permeable coefficient k,determine the minimum porosity Pmin.The slurry content was determined by combining with the compact packing porosity of the aggregate.Finally,according to the expression of compressive strength of pervious concrete,the minimum value of slurry strength f_cmin is calculated,prepare the slurry,ensure that the strength of slurry f_c?f_cmin,determine the composition of slurry.