Study On Preparation And Properties Of Environmentally-friendly Pervious Concrete

Pervious concrete,as a new type of building material,contains a large number of connected pores inside,and has the functions of water permeability,ventilation,sound absorption and noise reduction.However,the strength and permeability of permeable concrete have contradictory opposition.In view of the existing permeable concrete technology,or the high water permeability but low mechanical properties,or high strength but poor water permeability,difficult to control quality during production,the paper uses more general materials,through the selection and adoption of materials.The special design method and preparation method make the prepared concrete have good water permeability and gas permeability while ensuring strength,and provide a preparation method of high-strength and high-permeable concrete.The permeability of concrete requires a large amount of interconnected voids inside,which requires the slurry to have suitable viscosity and fluidity.In this paper,the changes of slurry properties and properties of permeable concrete under different slurry fluidities were studied,and the reasonable range of slurry fluidity was explored.The results show that the plastic viscosity of the ordinary paste is between 2.4Pa·s and 3.1Pa·s when the fluidity is 174mm~185mm,and the thickness of the slurry layer on the surface of the coarse aggregate is 500~800?m.The plasticity of the polymer paste The viscosity is 3.4~7.1Pa,and the thickness of the slurry layer on the surface of the coarse aggregate is 600~900?m.Based on the reasonable film thickness,the theoretical analysis of the opening factor ?,the range of its value is modified,and the volume coefficient ? of the slurry is introduced for the design of the permeable concrete mix.It is recommended that the coarse aggregate of the particle size range of 4.5~9.5mm,the value of ? of ordinary permeable concrete is 0.84~0.90,the value of ? is between 0.39~0.46;the value of ? of polymer modified permeable concrete is 0.78~0.82 The value of ? is 0.49~0.60;when the particle size range of coarse aggregate is increased,? can be appropriately increased,and ? can be appropriately reduced.Reducing the aggregate particle size and a small amount of sanding contributes to the improvement of compressive strength,but reduces the water permeability coefficient.The aggregate with a particle size of 2.50~4.75 mm is added with 5% sand.When the compressive strength reaches 37.4MPa,the water permeability coefficient can still reach 3.14mm/s.The larger the film thickness of the coarse aggregate surface,the smaller the theoretical calculation of the distraction coefficient,the smaller the total porosity,the better the mechanical properties,and the worse the water permeability.Firstly,the VAE707 emulsion,styrene-acrylic emulsion,epoxy resin and PVA fiber four kinds of polymer modified slurry are optimized for the rheological,bonding and mechanical properties of the slurry.Then the preferred amount is used to prepare the permeable concrete.The mechanical properties and water permeability of permeable concrete were studied.The results show that the modification effect of various polymer blends on the slurry is 4% VAE + sand > 4% VAE > 1% PVA > 2% SAE ? 3% HY;the addition of sand can improve the bond between the pastes.Improve the tensile bond strength and mechanical properties of the slurry.Preferably,suitable polymers and dosages are prepared for the permeable concrete,and the effect of the properties is basically the same as that of the matrix;the permeable concrete blended with 4% VAE707 emulsion has a 28 d flexural and 28 compressive strength increased by about 13% and 13%,respectively.The water permeability coefficient is only reduced by about 8%;using the combination of polymer and sand,a water permeable concrete with a compressive strength of 40.7 MPa and a water permeability coefficient of 3.22 mm/s can be obtained.The pore structure characteristics were studied by X-CT,and the film thickness of the concrete aggregate slurry after hardening was measured by an optical microscope.Based on the analysis of the two,a reasonable mix ratio design method is used,and the connected pores in the prepared permeable concrete are about 95%.When the permeable concrete is prepared,the thickness of the slurry on the surface of the coarse aggregate is larger,and the porosity of the permeable concrete after hardening The smaller the smaller the internal equivalent pore diameter,the better the mechanical properties and the poorer the water permeability.Finally,the control points are proposed from the aspects of permeable pavement structure design,raw material control,mix design and construction,which provide guidance for the design and construction of permeable concrete.