Study On The Effect Of Water-temperature Coupling On The Performance Of Asphalt Mixture Andthe Prevention And Control Method

Among the highways already been built in China, the early damage of asphalt pavement happens frequently. The main cause of this distress is the water action, especially in cold region. Due to the dynamic water flushing and freeze-thaw action, the accumulativewater in the pavement can aggravate the pavement damage. Although many road workers and researchers have already done a lot of research for many years, the moisture damage and freeze-thaw damage problems in cold region are still not be solved effectively. So the study on moisture and temperature distribution in asphalt pavement, and the study on the process, the mechanism, and the corresponding prevention and control method of moisture damage have important theoretical significance and application value.Considering the moisture transfer in pavement structure and its effect on the thermal physical properties of pavement materials, taking the water content as coupling term, the temperature- moisture coupling model of pavement structure was built. Using Fortran language to write the model subroutine, and implanting it into HVACSIM + simulation environment, the simulation analysis of temperature- moisture coupling model was carried out. Further the reasonableness and accuracy of thetemperature– moisture coupling model in pavement structure were verified based on the indoor actual collected data. Based on this model, the moisture field distribution rule of pavement structure was studied, the distribution feature of moisture field in pavement structure in wet and raining condition was analyzed, and the effects of air voids of pavement materials and the temperature gradient of pavement structure on the moisture field distribution rule in the p avement structure were studied.The self-developed dynamic water flushing tester was used to test the asphalt mixture, and the test parameters were determined. The effects of test temperature, flushing strength, asphalt types and the air voids etc. on the splitting strength and stiffness modulus of asphalt mixture flushed by the dynamic water were analyzed. The effect of dynamic water flushing on the fatigue property of asphalt mixture was studied. The constitutive model of asphalt mixtureconsidering creep continuous damage was built. Based on the high- temperature creep tests of asphalt mixture flushed by the dynamic water, the effects of asphalt types and initial air voids on the high- temperature creep properties of asphalt mixture were studied. The constitutive model of material creep damage was obtained. The damage mechanism of dynamic water flushing on the asphaltmixture was analyzed by the CT scanning technology. The results showed that the asphalt types and initial air voids affected the damage caused by the dynamic water flushing significantly. 8% was the most sensitive air void for the dynamic water flushing tests of asphalt mixture, however, the dynamic water flushing effected the permeable asphalt mixture with 12% air void less. Increasing the viscosity of asphalt binder can enhance the dynamic water flushing resistant of asphalt mixture effectively.Establish a continuous asphalt consider creep damage constitutive model, through high-temperature creep test of asphalt around hydrodynamic flushing of the studied species and initial porosity of asphalt moving water erosion around asphalt high-temperature characteristics The impact has been the constitutive equation of creep damage. By industrial CT scanning technology analyzes the damage mechanism of asphalt mixture flowing water erosion. Studies have shown that asphalt varieties and initial porosity of moving water erosion injury significantly. 8% porosity of asphalt that is moving water erosion most significant impact, while 12 percent of permeable asphalt that is less moving water erosion affected. Increasing the viscosity of bitumen can effectively enhance the ability of asphalt to resist moving water erosion.The freeze- thaw damage characteristic of asphalt mixture was studied by free – thaw cycle test. The effect of freeze- thaw on the strain characteristic of asphalt mixturewas studied by digital speckle correlation method. The influence rule of freeze- thaw cycle on modulus and strength of asphalt mixture was analyzed. The freeze- thaw mechanism of asphaltmixture was analyzed by CT scanning technology. The model considering meso damage parameters of asphalt mixture was built. The change rule of meso structure parameters of asphalt mixture with the freeze- thaw cycles was studied. The proactive prevention technology on the freeze- thaw damage of asphaltmixture was studied. The results showed that the main mechanical indicators of asphaltmixture decrease significantly with the freeze – thaw cycle going on. Due to the frost heaving force, the air voids in asphalt mixture expanded generally. The frost heave action exacerbated the formation and expansion of initial micro cracks in asphaltmixture, resulted in the degradation of macroscopic mechanical performance.The proactive prevention technology on the moisture damage of asphalt pavement was studied. Two kinds of proactive protective materials on the moisture damage were developed, the hydrophobeprotective material and the slow-release salt powder. The formula of hydrophobe protectivematerial was 80% permeable organic silicone resintai- 101 and 20% forming film material. The mass of curing agent tari- 1468 was 5% of tari- 101. The developed hydrophobe protective material had a good permeability, affected little on the pavement skid-resistant, and it can increase the water resistance performance of asphalt pavement significantly. The performance of carrier material of slow- release salt powder was studied. The production technology of slow- salt powder was determined. The performances of slow- release salt produced by different technologies were compared. At last, the actual application effect of freeze- thaw prevention material was verified by experiments.