| With the development of urbanization,dense asphalt pavement is widely used in urban roads,which blocks the natural infiltration of rainwater,and causes problems such as urban flood,groundwater level reduction and groundwater pollution.Permeable asphalt mixture,as a sustainable pavement material for cities,has been developed and applied to parking lots and light traffic pavement due to its potential for alleviating ‘‘urban syndrome’’.Compared with dense-gradation asphalt mixture,the high porosity(18%-25%)characteristics of Permeable asphalt mixture make it more competitive in reducing surface stormwater runoff,replenishing groundwater,absorbing traffic noise and improving wet-surface slip resistance.However,the mechanical properties,low temperature crack resistance and durability of permeable asphalt mixture are poor,which limits its wide application in seasonal frozen area.Therefore,how to improve the low-temperature cracking resistance and freeze-thaw durability of Permeable asphalt mixture for seasonal frozen regions without significantly compromising its permeability has become one of research hotspot in this field nowadays.Steel slag,as the waste of the steel industry,is traditionally disposed of by dumping landfills,occupying land resources and polluting the environment.Compared with natural aggregate,steel slag has superior physical properties,such as high specific gravity,rough surface,cube structure,high wear resistance and crushing resistance,which can significantly improve the mechanical properties of asphalt mixture.In addition,the utilization of steel slag can protect the environment,save natural aggregates,and promote the sustainable development of steel production and road construction industry.Fiber is the modifier commonly used in asphalt mixture,such as basalt fiber,lignin fiber,glass fiber and so on.Compared with other fibers,polyester fiber has the characteristics of high tensile strength and large specific surface area,which takes into account the mechanical properties and asphalt adsorption capacity,and can significantly improve the low temperature cracking and drain down resistance of the mixture.High viscosity additive can improve the viscosity of asphalt,improve the adhesion between asphalt and aggregate,and significantly improve the resistance to paeticle loss.Funded by the Science Technology Development Program of Jilin Province “Research and application of ecological green pervious pavement materials in cold region”,the optimum replacement level of steel slag was determined,the mixture ratio of polyester fiber-high viscosity additive compound modified permeable asphalt mixtures was optimized by the response surface method,and the feasibility of polyester fiber-high viscosity steel slag permeable asphalt mixture for seasonal frozen regions was verified by pavement performance test.The purpose of this paper is to develop a permeable asphalt mixture with high permeability,excellent mechanical properties,low-temperature crack resistance and durability to meet the strict environmental requirements for seasonal frozen regions.The main research contents of this paper are as follows:(1)Steel slag coarse aggregate was used to replace basalt coarse aggregate at four levels(25%,50%,75% and 100%)by equal volume.The volumetric property test,high temperature performance test,low temperature performance test,water stability test and expansion test were carried out.Based on the entropy weight method,the weight of each performance index was determined and the optimal replacement ratio of steel slag was obtained.The results showed that the permeability is slightly increased,the high temperature stability and low temperature cracking resistance were significantly improved,the water stability was improved and the expansion property was slightly increased,after adding 100%steel slag.Based on the experimental results,the complete replacement of basalt aggregate is advisable to obtain an optimal overall performance.(2)To study the fracture behavior of permeable asphalt mixtures with steel slag under low temperature,low temperature splitting test with low velocity was used to obtained stable crack propagation,acoustic emission instrument was used to obtained real-time acoustic emission signal.The relationship between the fracture energy and the accumulated acoustic emission energy was studied,the destruction stages were divided based on the acumulative RA and AF,the slope of the boundary line was determined by the method of minimum dispersion and the fracture mode was characterized.Finally,the relationship between b-value and load level was studied,and the characteristics of b-value for the critical failure of steel slag group and basalt group are given.(3)In order to reduce the Cantabro abrasion loss value and Draindown value of steel slag permeable asphalt mixture,polyester fiber and high viscosity additive were used for composite modification.The asphalt-aggregate ratio,the content of high viscosity additive and the content of polyester fiber were taken as factors,the range of factor levels was determined based the relevant studies and specification,and the volume of air voids,Marshall stability,Cantabro abrasion loss value and Draindown value were taken as response indexes.The response surface model between the response index and the factor index was established,and the influence of each factor,interaction and quadratic term on the index was analyzed,and the optimal mix ratio was determined by the target value optimization method.(4)Based on the optimal mix ratio design,the basalt group was used as the control group,and the steel slag group,polyester fiber steel slag group,high adhesive steel slag group and polyester fiber-high viscosity additive steel slag group were used as the test group.After20 freeze-thaw cycles of asphalt mixture,low-temperature splitting,Cantabro abrasion loss and creep tests were carried out to study the effects of freeze-thaw on low temperature crack resistance,abrasion resistance and viscoelasticity of different mixtures.The logistic model was used to fit the Cantabro abrasion loss curve to achieve quantitative damage analysis,and Burgers model was used to fit the creep curve to achieve quantitative viscoelastic analysis. |
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