Experimental Study On Permeability Coefficient And Mechanical And Frost Resistance Of Permeable Concrete

By using the volume method,a variety of permeable concrete with different void ratios,different particle sizes,different water-to-binder ratios and different admixtures were designed.The relationship between the permeability coefficient and the void ratio of the permeable concrete and its influence parameters were studied.The mechanical properties of pervious concrete with different void ratios,different aggregate sizes,different water-to-binder ratios and different admixtures were studied.The strength growth law of the permeable concrete and the ratio of compressive strength to flexural strength were analyzed.Relationship,and the effect of void ratio,aggregate particle size,water-to-binder ratio,and admixture.Based on the analysis of mechanical properties and its influencing factors,the freeze resistance test and the influencing factors of permeable concrete were studied by rapid freezing test.In addition,the effects of polypropylene fiber on the water permeability,mechanical properties and frost resistance of permeable concrete were studied.(1)A variety of permeable concrete was designed and manufactured by the volume method,and the number of test groups was 72 groups.The target porosity of the designed permeable concrete is 0%,11%,16%,21%,respectively;the aggregate particle size used is 4.75~9.50 mm,9.50~16.0mm,16.0~19.0mm,4.75~19.0mm;The water-binder ratio is 0.25,0.31,0.35;the blending amount is 20%,30%;the polypropylene fiber content is 0.1%,0.2%;the test results show that the error of the actual void ratio and the target void gap does not exceed 3.09%,and it is feasible to design the control parameters with the target void ratio as the mixture ratio.(2)Different void ratios,different aggregate particle sizes,different water-to-binder ratios,and the water permeability coefficient of the pervious concrete showed that the target void ratio of 11% can meet the specification requirement of 0.5 mm/s,and the aggregate particle size is larger.The larger the water-to-binder ratio,the smaller the water permeability coefficient,and the larger the blending amount,the smaller the water permeability coefficient.The results of section observation showed that the target void ratio,aggregate size,and water-to-binder ratio affected the number,size and shape of the connected voids and thus the permeability coefficient.(3)The larger the void ratio,the lower the compressive strength and flexural strength of the permeable concrete;the ratio of the flexural strength to the 28-day compressive strength is about 1/6 to 1/4,which is higher than that of ordinary concrete,and the influence of the gap against the compressive strength bigger.The early strength of permeable concrete mainly depends on the aggregate force of aggregate,and the later strength is also affected by the bond strength of the slurry.The main factors affecting the mechanical properties of permeable concrete are target void ratio and aggregate particle size.Adding fly ash reduces the strength of permeable concrete,while slag increases its strength.Double-mixed fly ash and slag have little effect on mechanical properties.(4)The freeze-thaw damage of permeable concrete is mainly caused by internal damage and dynamic elastic modulus,which is different from ordinary concrete.The main factors affecting the frost resistance of permeable concrete are target void ratio,aggregate granules,water-to-binder ratio;the larger the void ratio,the larger the aggregate granules,the larger the water-to-binder ratio,and the worse the frost resistance of permeable concrete.Adding fly ash reduces the anti-freezing grade of permeable concrete,the ore powder can improve its anti-freezing grade,and the double-mixed fly ash and ore powder have less influence on the freezing level change.(5)The viscous effect of polypropylene fiber leads to the decrease of the water permeability coefficient of the pervious concrete,and the link effect significantly improves its mechanical properties and frost resistance,but it is related to the blending amount,fiber length and maximum particle size ratio.