Experimental Study On The Basic Mechanical Properties Of Pervious Concrete And Freeze-thaw And Dry-wet Cycles

Pervious concrete is favored by researchers because of its advantages of permeable and breathable and meeting the needs of urban development.Therefore a large number of experiments were carried out on permeable concrete.so the development of pervious concrete with high compressive stren gth and good water permeability has become the goal of researchers.Aiming at different porous concrete water-cement ratio,porosity,silica fume dosage,dosage slag powder,sand and steel fibers of various factors,Orthogonal test method and single optimization test method were used,With compressive strength and permeability coefficient as the target,the optimal mix ratio of permeable concrete is determined,And freeze-thaw and wet and dry durability testing pervious concrete is based on the best mix proportion.By recording the appearance,quality and compressive strength of the permeable concrete test block under different freeze-thaw and dry-wet cycles,The variation rules of mass and compressive strength of pervious concrete test blocks are analyzed,and the basic mechanical properties of pervious concrete are studied.It provides a basis for future research and engineering application of permeable concrete durability.The main research results of this article are as follows:(1)Orthogonal experiments were used to study the effects of water-binder ratio,porosity,silica fume,slag powder,sand rate and steel fiber on the compressive strength and permeability coefficient of permeable concrete.Through the analysis of range and variance,the key factors are determined,and each factor is sorted significantly.(2)Based on the determination of key factors in the orthogonal test,a single factor test is carried out.Through single control optimization test,it is concluded that when the optimal mix ratio of permeable concrete is 0.28 water-binder ratio,18%porosity,5%silica fume and 25%slag powder,the compressive strength of permeable concrete can reach more than 25MPa and the permeability coefficient of 3mm/s or more,to meet the permeability requirements of pervious concrete pavement.(3)The optimal mix ratio,benchmark,single doped silica fume and single doped slag powder were used to conduct 100 freeze-thaw cycles of permeable concrete in aqueous solution.The results show that with the increase of the freeze-thaw cycle,the four ratio pervious concrete compressive strength and quality are decreased;reduced degree:Complex of silica fume and slag powder group<group Silica Fume<slag powder group<reference group.At the end of 100 freeze-thaw cycles,except for the compound silica fume and slag powder group,the loss rate of compressive strength in the other three groups exceeds 25%.(4)Based on the optimal mix ratio,the permeable concrete was subjected to freeze-thaw cycle tests under three solutions of fresh water,chloride and sulfate.By analyzing the changes of the appearance,mass and compressive strength of the test blocks of pervious concrete under three solutions,it is concluded that the changes of pervious concrete under sulfate solution are the largest,while the changes of clean water are the smallest,and the chlorine salt is in between.(5)The permeable concrete test blocks were subjected to dry and wet cycle tests under different cycles in fresh water,5%,10%and saturated Na2SO4 solution to study the durability of permeable concrete in sulfate solutions of different concentrations.The test results show that the greater the sulfate concentration,the more obvious the damage of the test block.After 105 dry and wet cycles,the compressive strength and corrosion resistance coefficient of permeable concrete under different solutions were all below 75%,so the dry and wet cycle test was ended.The influence of different solutions on the durability of test block was as follows:saturated Na2SO4 solution>10%Na2SO4 solution>5%Na2SO4 solution>clear water.