Experimental Study On Road Performance Of Basalt Fiber Permeable Concrete

In the construction of sponge city,permeable concrete is widely used in parks,sidewalks,garden roads,squares and other pavements.Increasing the strength of pervious concrete usually reduces its porosity and leads to a decrease in its permeability coefficient.At the same water-cement ratio,with the increase of porosity,the frost resistance becomes worse and worse.In other words,when permeable concrete meets the requirement of permeable water,its strength and frost resistance are often insufficient.Strength and frost resistance limit the extensive application of permeable concrete in pavement engineering.Aiming at the key problem of the difficult coordination of pervious concrete's pervious coefficient,strength and freeze-thaw resistance,this paper conducted an experiment on the preparation of ecological pervious concrete by adding basalt fiber.The main research contents and results are as follows:(1)Conduct single-factor variable test on concrete mixed with basalt fiber,and analyze the influence of basalt fiber diameter,length,content and mixing mode on compressive strength,splitting tensile strength,porosity,permeability coefficient and frost and thaw resistance of permeable concrete.1)With the increase of basalt fiber diameter,the compressive strength of pervious concrete decreases,the splitting tensile strength first decreases significantly and then increases slightly,porosity increases slightly,permeability coefficient increases,mass loss rate and compressive strength loss rate after freezing-thawing increases.This is mainly because with the increase of diameter,the effect of fiber on the adhesion between aggregate and cement increases,and water is more likely to leak through the fiber into concrete.2)With the application of longer basalt fiber,the compressive strength of pervious concrete increases,the splitting tensile strength decreases slightly first and then increases significantly,porosity increases,permeability coefficient increases,mass loss rate increases after freezing-thawing,and compressive strength loss rate decreases.The analysis shows that,with the increase of the length,when the permeable concrete specimen is destroyed,the fiber can bear greater tensile stress and restrain the destruction of concrete.Longer fiber is more likely to form a network structure in permeable concrete,and water is more likely to exude concrete through the fiber.3)With the addition of more basalt fibers,the compressive strength of pervious concrete decreases,splitting tensile strength increases,porosity decreases,permeability coefficient decreases,mass loss rate and compressive strength loss rate after freezing-thawing decreases.Reason is that if the amount of mixed with basalt fiber is too much,does not favor the fiber mixing in concrete,can produce cluster,the accumulation of situation,not only make cement can't completely package fiber,but also affect the bonding effect between aggregate and cement,the mixing of concrete become illiquid,gelled material is not fully homogeneous wrapped in aggregate.4)For three mixing ways,primary feeding method,premixed cement net slurry method and cement coated stone method,the first mode of mixing a charging method of porous concrete has the highest compressive strength,and the third way of mixing cement stone coating method of the permeable concrete splitting tensile strength,the second largest net ready-mixed cement slurry mixing way method of permeable concrete porosity and permeable coefficient,the third largest mixing way measured permeable loss rate of mass loss and the compressive strength of concrete specimen is minimal.After comprehensive analysis of the three stirring modes,the third stirring mode can make the mixing between the mixtures the most even and the cohesion between the aggregates the best.The second stirring mode is prone to the phenomenon of fiber agglomeration,cement accumulation and uneven stirring,and the cohesion between the aggregates is the worst.The first stirring mode is moderate.(2)Using the orthogonal experiment method to basalt fiber permeable concrete composite factor variable test,choose four factors three levels orthogonal design table,taking into account the four factors:the diameter of the basalt fiber length,content,and the way of mixing,analyzing the four factors are very poor,to analyze its influence on permeable concrete strength and water permeability,and analyze the influence to primary and secondary factors.After the above test and analysis,the results show that:The main and secondary order of factors affecting the compressive strength of basalt fiber permeable concrete are length,content,diameter and mixing mode.The main and secondary order of factors affecting the permeability of basalt fiber permeable concrete are:content,length,mixing mode and diameter.(3)By analyzing the freeze-thaw resistance of concrete prepared by orthogonal test method,it was found that after 50 freeze-thaw cycles,the mass loss rate of the specimen was 0.59%at most,the compressive strength loss rate was 7.37%at most,and the relative dynamic elastic modulus was 71.45%at least,all of which met the standards in the code.(4)The orthogonal test results of the combination of four factors were comprehensively analyzed to obtain the optimal combination.The final parameters of permeable concrete in this paper are as follows:basalt fiber diameter 14um,length 18mm,content 2kg/m~3,mixing mode is the third mixing mode.