Mechauical Properties Research On Asphalt Mortar Under The Condition Of Salt Freezing

In area that is cold in winter, the phenomenon that the road is covered by snow andice is very common. In order to get rid of the snow and ice in time and ensure safety oftraffic, de-icing salt is often used. Many scholars find that the use of de-icing salt wouldcause erosion to asphalt mixture, the surface material of road. However, the specificmechanism of action and function way is still not clear, and the major influencingfactors are not confirmed. Asphalt mortar, as an important part of asphalt concretepavement materials, plays an extremely important role in the viscoelastic property ofasphalt concrete. Setting asphalt mortar as the research object, uniaxial compressioncreep test of asphalt mortar specimens under the stress of300kPa,500kPa and700kPaafter different salt freezing cycles are conducted respectively. Nonlinear fitting is donethrough origin and1stopt software to deal with the time-strain curve. Parameters ofBurgers model are got and then the analysis and comparison of mechanical indexes arecarried. In order to further study the change of microstructure, scanning electronmicroscopy (SEM) is used to observe the surface of asphalt mortar specimens afterfreezing and thawing cycles.In order to further analyze the influence that salt freezing factors have on theperformance of asphalt mortar, the test specimens are regrouped with the method ofgrey entropy analysis. The freezing and thawing cycles are3times,8times,15timesand25times. Stress levels are300kPa,500kPa,700kPa and900kPa. Salt solutionconcentrations are0%,2%,4%and6%. Calculations of asphalt and aggregates are8%,9%,10%and9%in mass. The asphalt types are the SBS modified asphalt, wasterubber powder modified asphalt and asphalt matrix. Then the uniaxial compressioncreep test is conducted under the stress levels of300kPa,500kPa,700kpa and900kPaafter freezing and thawing cycles.To further verify the accuracy of the test data, uniaxial compression creep test isanalyzed by using the finite element analysis software ABAQUS. Similar results areobtained and thus the rationality and preliminary are verified.The experimental results show that:(1) The freezing-thawing cycles times enjoy the largest impact of the performance of asphalt mortar. The more freezing-thawingcycles it experiences, the worse ability of asphalt mortar to resist the axial deformation.It means the compressive strength is decreased with the increase of freezing-thawingcycles. At the same time, the damage between the asphalt and aggregate contactinterface become more serious. Axial pressure within the scope of extreme bearingcapacity enjoys relative less impact on the performance of asphalt mortar thanfreezing-thawing cycles. The effect of de-icing salt concentration is minimal.(2)Salt-freezing cycles have the most destructive effects on the matrix asphalt mortarspecimens, followed by waste rubber powder modified asphalt mortar and SBSmodified asphalt mortar. The greater the asphalt mortar sand ratio, the more obviousthe damage.(3) Through the analysis of the electron microscope scanning images, itcan be concluded that when the salinity and the load are certain, with the increase offreezing-thawing cycles, the cohesiveness between asphalt and aggregate wouldbecomes weaker. The contact surface cracks would become larger and more obvious.The integrity of the aggregate is broken and the aggregate becomes powder. Also thestructure becomes looser.