基于SCB试验的沥青混合料宏观断裂愈合性能研究

Research on Macro-fracture Healing Performance of Asphalt Mixture Based on SCB Test

为了研究沥青混合料宏观断裂的自愈合性能,采用半圆弯曲(semi-circular bending,SCB)试验对70#基质沥青混合料和SBS改性沥青混合料进行了断裂-愈合-断裂试验,并将愈合前后加载试验的强度恢复率定义为愈合指数(healing index,HI),分析了愈合时间、愈合温度和压力对混合料自愈合性能的影响.结果表明:发生宏观断裂的沥青混合料在一定环境中愈合后,强度恢复率最高可达45%;温度升高、时间增长和施加压力对沥青混合料宏观可见裂缝的愈合具有一定促进作用,但并非温度越高、时间越长,其自愈合性能越好;最佳愈合温度与沥青软化点和沥青混合料种类有关;当温度不大于60℃时,施加外部压力对沥青混合料裂缝愈合具有显著改善作用,有围压试件获得的HI值最高可达无围压试件HI值的4.5倍;60℃时SBS改性沥青混合料的HI值是70#基质沥青混合料HI值的4倍;超过60℃后,施加压力对沥青混合料自愈合性能无显著改善,且不同沥青混合料愈合性能也无明显差异.

To research the self-healing performance of asphalt mixture macro-fracture,the semi-circular bending（SCB）test conducted using the 70#base asphalt mixture and SBS modified asphalt mixture for fracture-healing-fracture test.The tensile strength ratio before and after healing is defined as healing index（HI）,the effect of healing time,healing temperature and pressure for self-healing performance was investigated.The results indicate that macro-fracture occurs after healing of the asphalt mixture in a certain environment,the strength recovery rate is equal to 45%;raising the temperature,prolonging the time and putting pressure have a certain promoting effect on the macroscopic visible cracks healing of the asphalt mixture,but it＇s not true that the higher the temperature and the longer the time,the better the self-healing performance.The optimum healing temperature is related to the asphalt softening point and the type of asphalt mixture.When the healing temperature is less than or equal to 60℃,putting pressure has a positive effect on the crack healing of the asphalt mixture,the HI value obtained with the confining pressure specimen is up to 4.5 times of that without confining pressure specimen,and the HI value of SBS modified asphalt mixture is 4 times that of 70#base asphalt mixture;when the temperature is more than 60℃,application of pressure does not show significant improvement of the self-healing performance,and the difference in the type of asphalt mixture is also not notable.