Experimental Study On Resistance To Clogging Of Pervious Concrete By Saturated Slurry Method

As the rapid development of urbanization in China,there is more and more ground being over hardened,and impermeable pavement makes it difficult for precipition sinking down into earth,which may casue negative impact about city Water Recycling.At the same time,the government issued policies to accelerate the construction of "sponge city",which also put forward more urgent requirements about permeable pavement.The pervious concrete pavement is easily blocked,so functional maintenance of permeability is the essential factor.Studying resistance to clogging through the preparation of pervious concrete with different water permeability.In order to find out the clogging law of pervious concrete which also provide theoretical basis for the subsequent pavement maintenance and cleaning.The samples with different strength were prepared by using 5?10 mm single size primary coarse aggregate,controlling apparent paste-to-void ratio in pervious concrete and the saturated slurry made of silt in Yellow River Flood Area as clogging medium.To measure the permeable parameters of samples after the scheduled clogging cycles(slurry sprinkling-air drying),to evaluate the effect of saturated slurry on resistance of pervious concrete to clogging.We could get the vertical two-dimensional pore parameters after cutting the pervious concrete with same continuous porosity and different permeable,and analysis the influence of pore area and inclination on water permeability.The result shows that the reasonable water-to-cement ratio of primary coarse aggregate pervious concrete with particle size of 5?10mm is 0.29(no superplasticizer),and the reasonable water-to-cement ratio is about 0.24.The pervious concrete with the highest strength(28.3 MPa)when permeability coefficient is 1.58mm/s which prepared in water-to-cement ratio of 0.241 and 0.35% dosage of superplasticizer in apparent paste-to-void ratio of approximate 0.69.The silt content(suspended particles)of silt in the Yellow River flood area is 31.0%,the saturated slurry concentration prepared by silt is 5.17g/L.The result shows the number of the projected area in the vertical pores of the pervious concrete samples without superplasticizer and with superplasticizer is the highest in the range of 0.21?5mm2/dm2.The number of vertical porosity dip of the sample without superplasticizer is higher than that of the sample with superplasticizer in the range of 60?90°.Under the condition of the same water-to-cement ratio and no superplasticizer,the continuous porosity and strength of pervious concrete are obvious negative correlation.The permeability is positive correlation with continuous porosity,and there is the exponential function quantitative relationship.The result shows that the strength of pervious concrete does not meet the regular of boromi formula,and there is an optimal water-to-cement ratio.The larger size of coarse aggregate,the smaller bonding area between paste and aggregate,and the lower compressive strength.It is suitable to prepare saturated slurry with local topsoil as clogging medium to carry out plugging test of pervious concrete,which is more easily in engineering practice.After the predetermined number of clogging cycles(such as 7 times),the permeability index is tested once,and the test is finished when the minimum permeability index is reached.The anti-blocking property of pervious concrete is evaluated by the number of blocking cycles.The permeability of pervious concrete obviously reduced after clogging cycles.The permeability of pervious concrete samples without superplasticizer generally lost faster than that of samples with superplasticizer.For the pervious concrete with initial continuous porosity of 10.5%,which coefficient of permeability lowered to less than minimum value defined by related specification after about 30 clogging cycles.The more pores in the main facade,the more tortuous the pore morphology,the longer the water flow path,the greater the water resistance,and the lower the water permeability.The more the pervious concrete facade with the pore angle between 45° and 90°,the better the permeability.Taking the apparent paste-to-void ratio as the main control index,the preparation of pervious concrete improves the strength under the premise of meeting the requirements,which is conducive to the application and promotion of pervious concrete pavement.The maintenance of water permeability function affects the service life of pervious concrete to the certain extent,and the saturated slurry test method is used to explore the anti-blocking law of pervious concrete,which is beneficial to the preliminary engineering design,post-use and maintance.