Research On Paste-coating Method Mix Proportion Design Of Permeable Concrete

With the continuous improvement of China's urbanization rate,the urban surface is covered by more and more impermeable materials.This makes the connection between surface water and underground water cut off,and causes the continuous decline of urban underground water table and the continuous intensification of urban heat island effect.It is difficult for impermeable materials to quickly infiltrate the rainwater that should penetrate into the ground,but it flows into the river along with the urban sewage system,resulting in the increasing urban waterlogging phenomenon and increasing river flood peaks.However,pervious concrete,which can effectively solve the above problems,is relatively backward in domestic research.Therefore,this study will study the relationship between compressive strength,permeability coefficient,paste-coating thickness and water-cement ratio of pervious concrete,and put forward the design scheme of mixing ratio.In this study,the specific surface area of coarse aggregate was analyzed.In this study,the paste-coating thickness method was used to measure the specific surface area of coarse aggregate,and then to prepare pervious concrete.The actual coating thickness was measured and compared with the designed one to verify the accuracy of the specific surface area measured by the paste-coating thickness method.A formula for calculating the specific surface area of coarse aggregate by fractal theory is presented.It is found that the cement paste in pervious concrete is not wrapped around coarse aggregate as well as ideal.Moreover,the increase of water-cement ratio and slurry thickness will make the paste-coating thickness uneven.Based on the specific surface area of coarse aggregate,the paste-coating thickness,watercement ratio on compressive strength and permeability coefficient of pervious concrete were studied.The compressive strength and permeability of pervious concrete have a good correlation with the paste-coating thickness,but not with the water-cement ratio.The influence of water-cement ratio on compressive strength and permeability coefficient of pervious concrete is much less than that of paste-coating thickness.It is found that there is a strong correlation between compressive strength and permeability coefficient of pervious concrete.The correlation coefficients among the paste-coating thickness,water-cement ratio,compressive strength and permeability coefficient are analyzed,so as to determine that the paste-coating thickness plays a certain role in determining the properties of pervious concrete.The regression analysis of compressive strength and permeability coefficient of pervious concrete shows that the best fitting effect of surface regression equation.Based on this,the formula of calculating the paste-coating thickness by compressive strength and permeability coefficient is put forward.Finally,the design scheme of the mixing ratio of pervious concrete with compressive strength and permeability coefficient as main target parameters,paste-coating thickness as main design parameters and water-cement ratio as secondary design parameters is put forward.