Experimental Research On Key Mechanical Properties Of Pervious Concrete Modified With Fly Ash And Silica Fume

Pervious concrete refers to concrete with continuous pore structure formed by mixing coarse aggregate and cement-based cement.Because of its high porosity,pervious concrete has good permeability.If the traditional hardened road used in urban construction is replaced with pervious concrete pavement,it can partly reduce the amount of road area water and urban heat island effect and a series of environmental issues after rain.Using fly ash and silica fume to replace part of the cement in the pervious concrete can not only promote the recycling of industrial waste,but also improve some performance of pervious concrete.In China,which has a positive effect on promoting the industrialization of pervious concrete,and it is corresponds to the strategic requirements for sustainable development.In this paper,ordinary pervious concrete is used as the benchmark,through the use of fly ash,silica fume equally instead of cement to produce pervious concrete,study of axial compression mechanical properties and bending mechanical properties and permeabilities of pervious concrete affect by different fly ash and silica fume dosages.The main research results of this paper are as follows:(1)The compressive strength of pervious concrete mixed with fly ash is higher than the benchmark pervious concrete when the fly ash content is in the range of 5 to 25%,and the compressive strength gradually decreases with the addition of fly ash.The flexural strength of pervious concrete mixed with fly ash is lower than the benchmark pervious concrete,and the flexural strength gradually decreases with the addition of fly ash.Single-doped silica fume can improve the compressive strength of pervious concrete but cannot improve it's flexural strength,when silica fume content in the range of 30%,25% of the amount of silica fume is the optimal mix of pervious concrete's compressive strength and flexural strength;(2)The elastic modulus of pervious concrete mixed with silica fume is higher than the benchmark pervious concrete,but the effect of silica fume incorporation on the elastic modulus is small.The elastic modulus of pervious concrete with mixed fly ash gradually decreases with the addition of fly ash;(3)Through SEM electron microscopy,it was found that the effect of fly ash on pervious concrete is mainly a pozzolanic effect,and the gel corresponding to the cemented area is more dense.The effect of silica fume on pervious concrete is mainly reflected by the effect of micro-aggregate filling,and the gel corresponding to the cemented area is more compacted;(4)The connected porosity and permeability coefficient of pervious concrete mixed with silica fume increase with the addition of silica fume.For the pervious concrete mixed with fly ash,25% of fly ash content is it's optimal content of porosity(Connected porosity and total porosity)and permeability coefficient.The incorporation of silica fume and fly ash reduces the segregation and bleeding of pervious concrete.