| Road dust has become an important source of air pollution in recent years.Based on the principle of improving road functionality,our research team developed porous adsorption asphalt pavement and polar adsorption asphalt pavement in the early stage.However,there are still some problems with the two types of adsorption asphalt pavement.One is the uneven distribution of pores in natural zeolite powder and the uneven water retention performance caused by many impurities;The second problem is that polar adsorbent exhibits agglomeration and precipitation on asphalt pavement.In response to this phenomenon,this study has developed a modified porous adsorption type material,which optimizes the pore structure to some extent while conducting ion exchange to greatly improve the moisture absorption ability of natural zeolite powder.However,its modification effect and improvement of dust suppression ability,as well as its specific road performance,durability,and humidification and dust suppression mechanism,still need to be further studied.Firstly,in order to clarify the effect of salt solutions with different concentrations on the moisture absorption of natural zeolite powder,the adsorption characteristics of zeolite powder were analyzed.Four inorganic salts(NH4Cl,NaCl,MgCl2,and CaCl2)were selected and fully immersed in three different concentrations(15%,20%,and 25%)at a liquid solid ratio of 5:1 for 72 hours,and their moisture absorption ratios were compared.The method of modifying with 20%CaCl2 was determined,The pore parameter increment after modification was determined by nitrogen adsorption BET method and BJH method.Secondly,the mix proportion design of the modified zeolite based dust suppression asphalt mixture was carried out to determine the gradation and optimal asphalt content by replacing mineral powder with 40%,60%,and 80% of the same volume,respectively.The changes in the mixing interface and functional groups between the modified zeolite based material and asphalt were studied by scanning electron microscopy and Fourier transform infrared spectroscopy.Then,the hightemperature stability and low-temperature stability of the modified zeolite based asphalt mixture were carried out in accordance with the specifications The test of water stability and skid resistance shows that the road performance with the addition of modified zeolite powder can meet the needs of road driving.Thirdly,through the design of moisture absorption and weight gain tests,evaporation and water retention tests,and through self-developed laboratory dust concentration detection equipment,a detailed study was conducted on the dust suppression ability of modified zeolite based materials.According to the principle of controlling variables,experimental research was conducted on the dust suppression effect at different temperatures and humidity.When the content of modified zeolite powder reaches 80%,its moisture absorption ability can reach 8-9 times of that of ordinary mineral powder samples,and the evaporation and water retention time can be extended to more than 4 times;Design test conditions for rainfall erosion and freeze-thaw cycles to simulate the impact of natural factors on the durability of dust suppression asphalt mixtures.The dust suppression coefficient decreases by less than4%,and still has a good dust suppression effect.Finally,through nitrogen adsorption experiments and contact angle experiments,the variation amplitude of the three humidifying parameters of modified zeolite based asphalt mixture,namely,adsorption pore volume,specific surface area,and surface free energy,was determined.The degree of their impact on the three dust suppression indicators,namely,the quality of moisture absorption and weight gain,the time of evaporation and water retention,and the dust suppression coefficient,was determined through gray correlation analysis. |
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