Measurement And Analysis On Moisture Diffusion Characteristics Of Dense Asphalt Mixture

Water damage is one of the main forms of damage to asphalt pavement,and the prevention and control of road water damage is a worldwide problem.During the service of asphalt pavement,due to the driving load,natural precipitation and groundwater penetrate into the interface between asphalt and mineral material along the weak space of the pavement,resulting in weakened asphalt adhesion and reduced bearing capacity,which causes the asphalt pavement to be destroyed.In order to study the causes of water damage on asphalt pavement,this paper takes the mechanism of water transport in dense asphalt concrete as the research object,and explores the diffusion law of water in dense asphalt concrete under different conditions.Firstly,in order to detect the degree of water diffusion of asphalt concrete,a test method for observing the water diffusion depth of asphalt concrete by using the chemical properties of white anhydrous copper sulfate powder to water blue is proposed,and then the test temperature and pressure conditions are controlled for different types of asphalt.The concrete was subjected to water immersion treatment,and the internal and external factors affecting the degree of water diffusion were systematically analyzed.Secondly,the digital image processing technology is used to establish a two-dimensional mesoscopic numerical model of asphalt concrete.The water diffusion phenomenon is simulated and analyzed.The measured results are compared with the theoretical analysis results,and the reasons for the difference between the theoretical and measured results are studied.Finally,the splitting strength was used as a research index to characterize the deterioration of mechanical properties.The cracking test was carried out on the asphalt concrete specimen after water immersion,and the correlation between the water diffusion index and the degree of strength decay was analyzed.The research in this paper has the following results:(1)The depth of water diffusion tends to increase gradually during the immersion process,and its growth rate is first fast and then slow,increasing temperature and pressure,and its diffusion rate is correspondingly increased;the increase of oil-stone ratio leads to a decrease in void ratio,which hinders its The water diffusion process;the influence of the forming method on the water diffusion of different grades of asphaltconcrete is different: under the action of pressure and no pressure,the diffusion depth of water in the coMPacted SMA specimen is greater than that of the AC grade.Under the action of pressure,the diffusion depth of water in the rolled SMA specimen is slightly smaller than that of the AC grade.(2)There is a certain difference between the theoretical value and the measured value,but the growth rate of both diffusion depths is consistent with the first rapid and slow change law.When there is pressure,the water diffusion rate is greatly improved.(3)In the process of water immersion,the strength of asphalt concrete decreases with the increase of water absorption rate,and the temperature and pressure will accelerate the water damage of asphalt concrete;the larger the oil-stone ratio,the stronger the water damage resistance;The AC and SMA two-stage compacted specimens are more resistant to water damage than the compacted specimens.