| Water is one of the bases of the existence and development of human society.With the development of China's economy and urbanization,large area of natural ground becomes impermeable pavement,which has caused many problems,including poor drainage which leads to frequent occurrence of water logging disasters,scarcity of groundwater resources,and runoff rainwater pollution.Through the construction of permeable pavement in the sponge city,rainwater can penetrate through the road,floods can be reduced,groundwater resources can be supplemented;meanwhile,paving the road can also purify the rain and reduce water pollution.Therefore,the mix design of the permeable cement concrete surface layer and the permeable cement stabilized macadam base layer is carried out in this paper,and the road performance and water purification characteristics are studied.The main contents and achievements are as follows:1.The orthogonal experiment is used to calculate the mixing ratio of permeable cement concrete.The mixture is mixed through the cement wrapped stone mixing method.The specimen is molded by pounding method.The test results show that M4,M5 and M7 permeable cement concrete can meet the design requirements and can be used as a recommended mix.The optimum moisture content of the base layer was determined by compaction test.The specimens are formed by static pressure method,and the mix proportion design of pervious cement stabilized macadam base is carried out according to the relevant process The results show that the J5-8 can be used as the best mix ratio for permeable cement stabilized gravel.2.The three-factor and three-level orthogonal test design method was used to study the pavement performance and its influencing factors of permeable cement concrete surface layer.The test results show that the strength and permeability of the permeable cement concrete are affected by various factors,the influence degree of each factor is: design porosity> gradation> water-cement ratio.The increase in design porosity will reduce the strength,improve the permeability coefficient,and its anti-skid performance all can meet the specification requirements.The effective porosity P1 and the theoretical porosity P2 of the permeable cement concrete are determined by the combination of theoretical calculation and experiment.They show a good linear correlation with the designed porosity.The porosity is linearly negatively correlated with the intensity,and the porosity is exponentially positively correlated with the permeability coefficient,which can directly reflect the strength and the permeability coefficient.3.The road performance and influencing factors of the permeable cement stabilized macadam base were studied.The results show that the better the structure of the skeleton becomes,the higher the cement binder strength becomes and the more cement increases,the higher the compressive strength and compressive modulus of the specimen become.And the two are linearly positive correlated.The increase of cement dose will significantly reduce the permeability of the specimen.The effective porosity is exponentially positively correlated with the permeability coefficient,which can reflect the permeability of the specimen more intuitively.4.The water purification characteristics of the permeable cement concrete surface layer and the permeable cement stabilized macadam base layer were studied by simulated precipitation process.The results show that both can neutralize the partial acidity of the runoff rainwater and raise the pH value.The order of the removal rate of each pollutant is TP>TSS>TOC.There is a good linear correlation between the design porosity and the removal rate of each pollutant.The effect of water purification on cement pavement is better than that of permeable asphalt pavement.The water purification effect of the pavement structure combination layer is better than that of the two kinds of single layer structure. |
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