| Pervious concrete as porous cement-based material is composed of aggregate,cement,water,additive and admixture.Compared to the ordinary pavement materials,pervious concrete can channel the rainwater into the underground and avoid the “urban waterlogging”.Pervious concrete can effectively replenish groundwater resources and avoid the sharp decline in groundwater level.The main characteristics of pervious concrete include reducing road noise,improving road safety and mitigating heat island effect.Pervious concrete with the porous-structure can maintain the ecological balance of the city.The study of pervious concrete is beneficial to the construction of sponge cities in China.In this paper,the forming method,workability,mechanical properties and water permeability of pervious concrete are studied.The research results are as follows:(1)The effects of different forming processes(insert ramming forming,pressure forming,vibration forming and vibration-pressure forming)on mechanics performance and workability of pervious concrete were compared.Compared to the other three forming methods,the sample prepared by pressure forming has better performance.The compressive strength and permeability coefficient of pervious concrete prepared was～28.5MPa and ～4.39 mm/s respectively curing for 28 days.The influences of four curing methods on mechanical properties of pervious concrete were outstanding,while on the permeability of pervious concrete were not obvious.(2)The working property of fresh pervious concrete was quantitatively evaluated by using the subsidence rate and subsidence area rate respectively,and the evaluation index was set.The experimental data showed that the reasonable range of subsidence rate was 3% ～ 6%,and the reasonable range of subsidence area rate was 60% ～ 70%.The influences of water-cement ratio,silica fume content and admixture content on the workability of fresh pervious concrete are studied respectively.With the increase of water-cement ratio and admixture content,the subsidence rate and the subsidence area ratio increase.With the increase of silica fume content,the subsidence rate and subsidence area rate are decreasing gradually.(3)Based on the porosity results of pervious concrete,the porosity decreases first and then increases with the increase of water-cement ratio,silica fume content and admixture content.When the water-cement ratio is 0.26,the silica fume content is 4%and the admixture content is 0.75%,the porosity is at the lowest value(14.5%,12.6%and 13.4%).When the diameter of coarse aggregate increases gradually,the porosity increases.(4)Based on the compressive strength results of pervious concrete,the compressive strength increases first and then decreases with the increase of water-cement ratio,silica fume content and admixture content.When the water-cement ratio is 0.26,the silica fume content is 4%,and the admixture content is 0.75%,the compressive strength reaches the highest value(25.3MPa,27.3MPa,and 26.4MPa).When the aggregate particle size increases gradually,the compressive strength decreases.(5)Based on the permeability coefficient results of pervious concrete,the permeability coefficient decreased gradually with the increase of water-cement ratio.When the water-cement ratio was 0.20,the permeability coefficient was 5.02mm/s.When the water-cement ratio was 0.30,the permeability coefficient was 1.28mm/s.With the increase of silica fume content,the permeability coefficient increased gradually.When the dosage of silica fume was 0%,the permeability coefficient was 1.28mm/s,.When the dosage of silica fume was 8%,the permeability coefficient was 3.29mm/s.The permeability coefficient increased with the increase of aggregate size.(6)The relationship between porosity,compressive strength and permeation coefficient was studied.The results showed that the variation trend of porosity was positively correlated with permeability coefficient.The fitting relationship was y=0.94x+0.66.There was a negative correlation between porosity and compressive strength.The fitting relationship was y=-0.86x+36.59.There was an indirect negative correlation between permeability coefficient and compressive strength. |
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