Research On Mechanical Properties And Durability Of Crumb Rubber And Silica Fume Composite Modified Pervious Concrete In Seasonal Frozen Area

With the rapid advancement of urbanization,the urban surface has been covered by dense concrete materials,which causes many urban problems,such as urban waterlog,decline of groundwater,noise pollution,urban heat island phenomenon,etc.Therefore,sustainable urban development has become a global concern.In recent years,China has put forward the sponge city development strategy.The first batch of pilot city has been laid out sponge city construction.As an important part of sponge city construction,pervious concrete is of great significance to the construction of sponge city.However,the research on pervious concrete started late in China,and the mechanical properties and durability of pervious concrete are poor due to its own structural characteristics,which makes its engineering application scope and scale relatively small.In particular,the influence of freeze-thaw on the pavement structure in seasonal frozen zone has seriously restricted its development and application.Therefore,it is of great practical significance to study the pervious concrete performance in seasonal frozen zone.Waste crumb rubber,as the waste of industrial development,is usually disposed by means of burial and incineration,causing serious environmental pollution.Due to the high elasticity,abrasion resistance and durability of crumb rubber,its application in concrete pavement materials can greatly improve the deformation property and durability of concrete materials.Silica fume,as a by-product of smelting industry,is rich in Si O2,making it a cementitious material with superior performance.Its application in concrete material can not only realize the reuse of industrial waste,but also effectively improve the mechanical properties and durability of concrete.Funded by the Science Technology Development Program of Jilin Province “Research and application of ecological green pervious pavement materials in cold region”,considering the requirements of pavement material in seasonal frozen area,the mixture ratio design,basic mechanical properties,freeze-thaw resistance and fatigue performance of crumb rubber and silica fume composite modified pervious concrete are researched.The aim is to develop a pervious concrete in accordance with pavement material requirements in seasonal frozen area with high mechanical properties and durability.The main research contents of this paper are as follows:(1)Based on three factors and three levels orthogonal experiment,the coarse aggregate size,water-binder ratio and porosity were selected as the orthogonal factors,the effective porosity,permeablity coefficient,compressive strength,flexural strength and freeze-thaw resistance of pervious concrete were chosen as evaluation indexes.The influences of various factors on pervious concrete performance were analyzed by range analysis and variance analysis of orthogonal experiment.Considering the permeability,strength performance and freeze-thaw resistance of pervious concrete at different levels,the mix ratio of pervious concrete with optimal strength and freeze-thaw resistance was determined under the condition of the requirement of permeability.(2)Based on the mix ratio design of pervious concrete,the permeability,mechanical properties and freeze-thaw resistance of crumb rubber modified pervious concrete were studied.The permeability coefficient,compressive strength,flexural strength,failure strain,flexural elastic modulus and freeze-thaw resistance of pervious concrete with different particle sizes and incorporation levels were tested.In addition,with the replacement of cement by equal volume method,the permeability,mechanical properties and freeze-thaw resistance of silica fume modified pervious concrete were studied.Silica fume modified pervious concrete with excellent strength and freeze-thaw resistance was obtained.Considering the strength,deformation property and freeze-thaw resistance of crumb rubber and silica fume single modified pervious concrete,the properties of pervious concrete mixed with silica fume and crumb rubber were researched.(3)The flexural fatigue performance of ordinary pervious concrete,crumb rubber and silica fume composite modified pervious concrete was studied.The fatigue life of the two kinds of pervious concrete under different stress levels was measured.Based on K-M survival analysis,the influence of stress level and modifier on fatigue performance of pervious concrete was studied.The two parameter Weibull distribution model was used to analyze the fatigue life.The linear regression method,the moment estimate method and the maximum likelihood method were used to solve the shape parameter and scale parameter of Weibull distribution.The K-S test was adopted to test the goodness of fit.By the analysis of Weibull distribution function,probability density function and failure rate function,the effects of the stress level and the modifier on the fatigue properties of pervious concrete were studied.Based on the established Weibull distribution model,the fatigue equations of pervious concrete with different reliability probabilities were established,and the influence of modifier on the fatigue equation was analyzed.(4)Considering the shortcomings of traditional methods in dealing with the fatigue damage,based on the fatigue mechanics and the atomic thermal perturbation motion,the fatigue damage mechanism was obtained from deformation of the cycle of the atom.Based on the proposed fatigue mechanism,a general form stress fatigue damage evolution law was established.In addition,the uniaxial stress fatigue theory under alternating ground state load and damage evolution during fatigue cycle life cycle was researched.The fatigue damage evolution laws of common pervious concrete and composite modified pervious concrete were analyzed.Taking the freeze-thaw damage of composite modified pervious concrete after different freeze-thaw cycles as the initial damage of the material,the influence of the initial damage on the fatigue characteristics of pervious concrete was analyzed,and the evolution law of the fatigue damage of pervious concrete under different initial damage was established.