Study On Frost Resistance Durability Of Pervious Concrete

In recent years,the construction of "sponge city" has played a very good role in improving the ecological environment of the city.As an important part of "sponge city",the quality of permeable pavement materials has a direct impact on the development of "sponge city".The reason is that the porous structure of permeable concrete is relatively prominent,which leads to its poor freeze-thaw resistance,which limits its promotion and application in the "sponge city" in cold and frozen areas.In order to improve the freeze-thaw durability of pervious concrete,this paper analyzes the water permeability and mechanical properties of pervious concrete samples before and after freeze-thaw by adding different amounts of steel slag and slag,establishes the corresponding freezethaw damage model to carry out the law of freeze-thaw damage of pervious concrete,based on the propagation characteristics of shock elastic wave and multi index,and makes correlation The analysis provides an economic,effective and convenient means for engineering detection.The main achievements of this paper are as follows:(1)With the increase of steel slag and slag content,the permeability of pervious concrete increases first and then decreases.After several freeze-thaw cycles,the permeability coefficient of pervious concrete with steel slag,slag and steel slag slag has been increased in varying degrees.Adding steel slag and slag can inhibit the growth rate of permeability coefficient of pervious concrete in freeze-thaw cycle test.(2)Compared with the ordinary pervious concrete,the strength of the concrete can be increased by adding steel slag and slag.With the continuous freeze-thaw cycle test,the loss rate of compressive strength and the loss rate of flexural strength of each group showed almost a straight-line rise,in which the loss rate of strength of the double mixing combination was more serious.Through the quadratic function fitting of the loss rate of compressive strength and the growth rate of permeability coefficient,the correlation coefficients of each group are all above 0.96,which shows that the correlation is good.(3)With the increase of freeze-thaw cycles,the loss of mass and dynamic modulus of elasticity is significant.The continuous freeze-thaw damage aggravates the damage of the pore structure of the specimen,and the initial cracks formed in the specimen gradually expand and penetrate to the outside,which finally causes the concrete on the specimen surface to fall off and the aggregate to be exposed until the overall damage occurs.The combination of double admixtures has a certain restraining effect on the loss of mass and dynamic modulus.The overall anti freezing effect is not as good as that of single admixtures.The anti freezing perfor15% slag is better.(4)The damage evolution law of pervious concrete after freeze-thaw test is studied,and an index damage model of pervious concrete with relative dynamic modulus of elasticity as loss factor is established,which is in good agreement with the test data.In addition,based on the damage factors of water permeability coefficient and strength loss rate,the mechanical properties and water permeability of permafrost concrete after freezing and thawing are evaluated.The research shows that there is a linear correlation between the two damage factors.(5)After many freeze-thaw cycles,the wave velocity loss of each group of pervious concrete specimens increases.The fitting of the elastic wave velocity data measured by different freeze-thaw cycles with the quadratic function curve of multiple indexes shows a good correlation.Based on the dynamic elastic modulus calculated by shock wave method and resonance method,the error analysis is carried out.The maximum error of the two methods is no more than 10%,which shows that the dynamic elastic mold tested by the two methods has good consistency,so shock wave method can be used for penetration The non-destructive measurement of water concrete dynamic modulus.