Mechanical And Low Temperature Properties Of Diatomite Modified Permeable Asphalt Mixture Based On Acoustic Emission

With the development of urbanization,dense-graded asphalt pavement is widely used in urban roads,which blocks the natural infiltration process of rainwater and causes problems such as urban flooding,lowering of groundwater level and groundwater pollution.Pervious asphalt is a sustainable pavement material widely used in parking lots and light traffic load pavements.Compared with dense-grade asphalt mixtures,permeable asphalt mixtures have high porosity（18-25%）,which can reduce surface rainwater runoff,replenish groundwater,absorb traffic noise and improve pavement skid resistance.However,the low strength,poor crack resistance and poor durability of permeable asphalt mixture limit its wide application in seasonally frozen areas.Therefore,how to significantly improve the mechanical properties,low temperature crack resistance and freeze-thaw durability without significantly reducing the permeability of the mixture has become one of the current research hotspots in this field.Diatomite is an inorganic mineral formed by natural deposition.There are a lot of reserves in Changbai Mountain,Jilin,my country.In recent years,secondary diatomite products have been gradually used in the research of building construction materials.Compared with mineral powder,diatomite has a larger specific surface area and a porous structure,so it can absorb more free asphalt to form structured asphalt when used in asphalt mixtures,and the density of diatomite is lower than that of mineral powder.It has physical properties such as wear resistance,insulation,heat absorption and adsorption,and has better performance than mineral powder as a filler.In addition,diatomite is also a natural and environmentally friendly nonpolluting product,which can promote sustainable development.As an inorganic modifier,diatomite has a relatively simple preparation process,and the modified asphalt can increase the viscosity between the asphalt binders and improve the low-temperature crack resistance of the permeable asphalt mixture.Relying on the project of "Research and Application of Ecological Green Permeable Pavement Materials in Severe Cold Areas" of the Jilin Provincial Department of Science and Technology,and based on the pavement construction requirements of frozen land areas in the alpine season,the basic properties of diatomite modified asphalt and the mixture of diatomite modified permeable asphalt were studied.The mechanical properties and low-temperature properties of materials and the generation of micro-cracks and macro-fracture behavior in the process of low-temperature splitting based on acoustic emission.The purpose of this paper is to study the influence of the content change of diatomite on the mechanical properties and low-temperature properties of asphalt and permeable asphalt mixtures,and to develop a kind of diatomite with certain strength and low-temperature cracking resistance while ensuring that the permeability meets the requirements.diatomaceous earth permeable asphalt mixture.The main research contents of this paper are as follows:（1）The modified asphalt with 5%,10% and 15% diatomite content were prepared by using a high-speed shearing instrument,and the three indexes of penetration,softening point and ductility were measured.Asphalt elastic recovery properties,the rotational viscosity of the asphalt is also measured and the mixing and compaction temperatures during construction are given.Based on the ductility test,the low temperature dynamometric ductility test was carried out,and the low temperature performance of the diatomite modified asphalt with different contents was comprehensively evaluated by calculating the dynamometric ductility index.The results show that 10% diatomite modified asphalt has the best low temperature performance.（2）Determine the mix ratio design of the permeable asphalt mixture,replace the mineral powder with the same volume of diatomite,and form the Marshall standard specimen under the optimum oil-stone ratio.The Marshall specimens were then tested for volume characteristics,water stability and low temperature cracking resistance.The results show that10% diatomite modified asphalt has the best water stability,and 15% diatomite content permeable asphalt mixture has the best low temperature crack resistance.（3）Provide a stable load through low-speed displacement control,so that the microcracks in the specimen will expand stably at the initial stage of loading.Acoustic emission is used to collect various acoustic emission characteristic information during the loading process,and distinguish based on the relationship between RA and AF.Dominant change in fracture mode.And according to the research of b value,it is found that 15% diatomite modified permeable asphalt mixture is easy to form macro cracks,so the low temperature performance of asphalt mixture with 10% diatomite is the best.