Microscopic Characteristics Of Moisture Diffusion In Asphalt Concrete Under The Influence Of Pressure And Temperature

Asphalt pavement will be continuously affected by natural precipitation in the process of use.The dynamic water pressure causes a large amount of precipitation to quickly invade the pavement structure,and the change of environmental temperature causes the change of mechanical properties of asphalt concrete,which induces road damage such as water damage.Therefore,accurate analysis of water diffusion in asphalt concrete is of great practical significance to understand the water loss mechanism of dense asphalt concrete.Based on the micromechanical model of asphalt concrete,the finite element method is used to deeply analyze the characteristics of water diffusion.The main research work of this paper is as follows:(1)Using digital image technology and MATLAB software to realize programmed automatic modeling,the two-dimensional structure of real asphalt concrete is transformed into a microscopic numerical model for finite element calculation for the microscopic analysis of water diffusion.(2)The numerical models of asphalt mixtures with different diffusion coefficients and gradations are established and the internal water diffusion law is analyzed.The results show that the larger the diffusion coefficient is,the larger the diffusion rate of water in the corresponding asphalt concrete is,the deeper the diffusion depth is,and the greater the water concentration in the asphalt concrete is.Under the same conditions,AC-asphalt mixture is more advantageous than SMA-asphalt mixture in water diffusion to the interior.(3)The characteristics of water diffusion under the influence of temperature and hydrodynamic pressure are analyzed by mass diffusion and field variable update method(USDFLD).The results show that the higher the temperature and pressure are,the faster the water diffusion rate is;the equilibrium concentration of water diffusion under the influence of pressure and temperature will increase;the influence of pressure on water diffusion is higher than that of temperature,and the influence of temperature history on water diffusion is also significant.(4)A temperature history-wet-dry cycle water diffusion model was established to simulate the diffusion of water in asphalt concrete during the wet-dry cycle.The resultsshow that the diffusion coefficient of aggregate has little effect on the wet-dry cycle.Increasing the number of wet-dry cycles will promote the further diffusion of water into asphalt concrete,and the water will diffuse both inward and outward during the drying process.The drying speed of asphalt concrete surface moisture is faster than that of constant temperature.