Study On Pervious Concrete With Different Goal Porosity Based On Volume Method

In recent years,China is facing a serious "water crisis",and the proposal of "sponge city" has become an effective ecological way to solve this problem.As a green building material for "sponge city" construction,permeable concrete can not only solve the water problem in China,but also alleviate the "heat island effect" of the city,so it is widely concerned by many scholars.Due to the different requirements of pervious concrete in different areas and different uses,it is critical to design pervious concrete to meet the pervious demand.In addition,due to its porous structure,the mechanical properties of pervious concrete are generally lower than that of ordinary concrete,which leads to the current application of pervious concrete is not extensive.Therefore,it is worth paying attention to find the most effective method to improve the mechanical properties of pervious concrete on the premise of meeting different pervious needs.Based on the volume method,this paper studies the relationship between the volume method control parameters and the compressive strength and permeability coefficient of pervious concrete.Through the analysis of the failure section,it summarizes the failure forms of pervious concrete under different target porosity,and on this basis,studies the influence of aggregate and cementitious materials on the permeability of pervious concrete under different target porosity.In order to provide theoretical reference for the improvement of mechanical properties of pervious concrete and practical engineering application.The main research contents are as follows(1)The optimal method of volume method mix proportion is discussed through experiments.The water cement ratio of 0.25,0.28,0.30,0.33 and 0.35 is determined through trial mixing test and slurry fluidity test.Finally,the mix proportion used in the experiment is obtained.(2)The influence of volume method control parameters on the compressive strength and permeability coefficient of pervious concrete is studied,and the optimal water cement ratio is determined.On this basis,the test results are fitted,and the fitting relationship between the target porosity and compressive strength,permeability coefficient is obtained.Through the failure section produced by uniaxial compression test,the failure form and mechanism of permeable concrete under different target porosity are discussed.(3)Based on the discussion of the failure mode and mechanism of pervious concrete,the influence of cementitious materials on the performance of pervious concrete with different target porosity is studied.By adding NS and using fly ash to replace cement,the performance of permeable concrete cementitious material is changed,and its influence on the compressive strength and permeability coefficient of permeable concrete under different target porosity is studied.At the same time,an effective method to improve the compressive strength of permeable concrete with large target porosity is proposed.(4)Based on the discussion of the failure mode and mechanism of pervious concrete,the influence of aggregate on the performance of pervious concrete with different target porosity is studied.The whole strength of aggregate is improved by replacing crushed stone with steel slag,and the influence of steel slag on compressive strength and permeability coefficient of pervious concrete with different target porosity is studied.At the same time,an effective method to improve the compressive strength of permeable concrete with small target porosity is proposed.Through the experimental research,the target porosity has a good correlation with the compressive strength and permeability coefficient;when the target porosity changes,the failure form of permeable concrete also changes,with the increase of the target porosity,the failure form of permeable concrete gradually changes from aggregate failure to cement stone failure between adjacent aggregates;in the Research of cementitious materials,the main failure mode of permeable concrete is aggregate failure The findings are as follows: With the increase of the target porosity,the improvement effect of NS on the compressive strength of pervious concrete is gradually improved.The test results show that the method of improving the compressive strength of permeable concrete by improving the strength of cement paste is the most suitable for high permeable concrete with 25% target porosity.Considering the 28 d compressive strength and permeability coefficient of pervious concrete,when the target porosity is 15% and20%,it is recommended that the highest replacement rate of fly ash is 40% and 30%respectively;when the target porosity is 25%,it is not recommended to add fly ash;It is found that the improvement effect of steel slag replacing stone on the compressive strength of pervious concrete decreases with the increase of the target porosity.The test results show that the method of using higher strength aggregate instead of ordinary gravel to improve the compressive strength of pervious concrete is most suitable for the pervious concrete with 15% target porosity.