Study On Long-term Effects Of De-icing Salt On Asphalt Pavement Performance

Asphalt pavement is widely used as high-grade pavement， which possesses theadvantages of smooth surface，non-seam，comfortable driving，low noise and vibration，short construction period and easy maintenance and repair， etc. In order to reduce trafficaccidents caused by icy skidding， de-icing salt is spread timely for de-icing which is oneof the most commonly used method， in seasonally frozen ground regions of our country.People gradually find that there appear some pavement diseases such as cracks， pits，loose and so on， in newly-built pavement which uses de-icing salt method for long-termground de-icing maintenance. The analysis of de-icing salt’s long-term effect on roadperformance， de-icing salt damage mechanism and its conservation suggestions， whichrelies on laboratory tests， has vital significance to the asphalt pavement in seasonallyfrozen ground regions.First， two frequently-used kinds of pavement structure， SMA-13asphalt mixtureand AC-13asphalt mixture， are determined through mixture designing. Two chloridede-icing salts， sodium chloride de-icing salt and compound de-icing salt， are selected forcomparison. A new design of freeze-thaw cycle method on asphalt mixture specimens isapplied. De-icing salt and asphalt specimen are stored in crisper and the de-icing salt isadded into de-icing salt solution by each freeze-thaw cycle time in order to raise theconcentration of de-icing salt solution with freeze-thaw cycle’s increasing number of times.Second， the attenuation of water stability， low temperature cracking resistance，fatigue properties of asphalt mixture specimen after freezing and thawing cycles in deicingsalt water solution is measured with the freeze-thaw splitting test， cantabro tes and fatiguetest. Comparative analysis of SMA-13asphalt mixture and AC-13asphalt mixtureperformance test results are made; and the impact of sodium chloride de-icing salt andcompound de-icing salt on pavement performance of asphalt mixture are analyzed thoroughcontradistinction. Meanwhile， we also discuss the damage mechanism of de-icing salt onasphalt mixture from two aspects of physics and chemistry.Finally， recommendations are proposed for selection of pavement structural type andde-icing salt type and maintenance measures of road in seasonally frozen area， accordingto the damage forms and degree of the deicing salt on asphalt mixture.The result shows that its water stability， low temperature cracking resistance， fatigue performance of the asphalt mixture of decline and the data of performance indexreduces with increasing times of freeze-thaw cycle, which is equivalent to durable years,significantly after freeze-thaw cycles in de-icing salt solution.The damage extent of sodium chloride de-icing salt to asphalt mixture is more seriousthan compound de-icing salt and compound de-icing salt is preferred for choosing de-icingsalt type. SMA-13asphalt mixture’s ability to resist de-icing salt damage is better than thatof AC-13asphalt mixture and SMA-13asphalt structure type is recommended to selectwhere conditions are right.Asphalt mixture is damaged by de-icing salt with physical and chemical damage.Physical damage mechanism on asphalt mixture is mainly swelling pressure of de-icing saltsolution froze and crystallization crystal; Chemical mechanism is that ions of de-icing saltsolution competes with the asphalt for adsorption on the surface of aggregate， resulting inasphalt peeling-off from aggregates.This study is supported by Research on Rapid maintenance and SecurityIndemnification Technology to Cope with Extreme Weather Conditions for Highway inSeasonally Frozen Region， a project of Western Region Transportation Scientific andTechnological Projects of Ministry of Communications.