Effect Of Calcium Chloride Solution On Pavement Performance Of Asphalt Mixture Under Freeze-thaw Cycle

In winter,the road surface in north China is often frozen,which poses a great hidden danger to traffic safety.Usually,the road surface is quickly cleared by spreading de-icing salt,but the use of de-icing salt will make the road stay in the environment of salt-freezing cycle for a long time,and then the asphalt pavement will be cracked,pooled and loose.Combining with the gansu area’s climate condition,adopt the method of combining theoretical analysis and laboratory test,with a low grade road with AC-13 type matrix asphalt mixture,was studied in different freezing and thawing cycles under the action of the calcium chloride solution of different concentrations and common impact on road performance of asphalt mixture,and the salt frost damage mechanism analysis.Through laboratory tests,it was found that the melting concentration of calcium chloride solution was 0.11g/ml,and its deicing capacity first increased and then decreased with the increase of concentration.When the concentration was about 21%,the deicing effect was the best.The high and low temperature performance test of asphalt under salt-freezing cycle shows that with the increase of freeze-thaw times and the increase of calcium chloride solution concentration,the low temperature crack resistance of asphalt decreases and the high temperature performance increases.When the solution concentration is greater than 14%,the asphalt ductility value cannot meet the requirements of the specification.The effects of freeze-thaw cycle of calcium chloride solution on the void fraction,adhesion between asphalt and aggregate,high temperature stability,low temperature crack resistance and water stability of asphalt mixture were studied by laboratory experiments.The results show that with freezing and thawing times increase,concentration of calcium chloride solution,specimens larger air voids,asphalt and aggregate adhesive variation,low temperature crack resistance significantly reduced,high temperature performance,reduce the water stability,high and low temperature performance of asphalt indicators with asphalt mixture with high and low temperature road performance index has good linear correlation.In general,the effect of freeze-thaw cycle is greater than the concentration of calcium chloride solution.Considering the influence of calcium chloride solution on the long-term freeze-thaw cycle of asphalt pavement,it is suggested that the solution concentration should not be more than 13%.By analyzing the salt freeze-thaw cycle of asphalt mixture,it is concluded that the salt freeze damage of asphalt mixture is caused by the expansion pressure caused by internal water freezing,salt solution erosion and salt crystallization expansion.The freezing expansion rate of calcium chloride solution was studied.The results showed that the volume of the solution first contracted and then expanded with the increase of freezing time,and the growth rate of the volume expansion rate decreased significantly with the increase of the concentration of calcium chloride solution.Taking into account the effect of calcium chloride solution on asphalt performance and pavement performance of asphalt mixture under the action of freezing cycle and the deicing effect at different concentrations,this paper suggests that the use concentration should not exceed 14%in the deicing project.In addition,attention should be paid to uniform spreading.