基于直剪试验的黏层黏结效果影响因素研究

Study on Influencing Factors of Bonding Effect of Tack Coat Based on Direct Shear Test

为了给沥青路面黏层设计提供依据,揭示黏层黏结效果的影响规律,采用直剪试验方法评价了沥青黏层的黏结效果,针对影响黏层抗剪强度的几个因素,如乳化沥青性质、洒布量、沥青混合料类型、水环境、荷载及老化作用等对黏层黏结效果的影响进行了测试分析。试验结果表明:(1)乳化沥青最佳洒布量在0.4~0.6 kg/m^(2),此时黏层抗剪强度和抗剪强度增长率最大,乳化沥青蒸发残留物60℃动力黏度指标与黏层抗剪强度和抗剪强度增长率具有较强的相关关系,可作为黏层用乳化沥青的筛选指标;(2)下面层沥青混合料为AC-20,上面层沥青混合料为PA-13(PA-13+AC-20)抗剪强度最小,"SMA-13+AC-20"和"AC-13+AC-20"试件的抗剪强度分别提高了22.6%和34.4%,这与沥青混合料上面层与下面层的接触面积相关;(3)动水冲刷相比冻融循环对黏层的损伤作用更为显著,15 000次冲刷后,0.6 kg/m^(2)洒布量下,"AC-13+AC-20"试件的抗剪强度降低45.3%,"PA-13+AC-20"试件的抗剪强度降低62.7%,动水冲刷对上面层为PA-13混合料的黏层的损伤更严重;(4)荷载和老化作用可增大黏层的抗剪强度和抗剪强度增长率,老化对上面层为PA-13沥青混合料的黏层抗剪强度和抗剪强度增长率增大作用更为显著。

In order to provide the basis for asphalt pavement tack coat design and reveal the influence rule of bonding effect of tack coat,the bonding effect of asphalt tack coat is evaluated by direct shear test.Several factors affecting the shear strength of tack coat,such as the properties of emulsified asphalt,spraying amount of emulsified asphalt,type of asphalt mixture,water environment,load and aging,are tested and analyzed.The test result shows that(1) When the optimal spraying amount of emulsified asphalt is 0.4-0.6 kg/m^(2),the shear strength and shear strength growth rate of tack coat are the largest.The dynamic viscosity of emulsified asphalt’s evaporation residue at 60 ℃ has a strong correlation with the shear strength and shear strength growth rate of tack coat,which can be used as the screening indicator of the emulsified asphalt for tack coat.(2) When the asphalt mixture at lower surface layer is AC-20,and the asphalt mixture at upper surface layer is PA-13(PA-13+AC-20),the shear strength is the smallest.The shear strengths of SMA-13+AC-20 and AC-13+AC-20 specimens are increased by 22.6% and 34.4% respectively,which are related to the contact area between upper surface and lower surface layer of asphalt mixture.(3) Compared with the freeze-thaw cycles,the dynamic water scouring has more significant damage effect on the tack coat.After 15 000 times of scouring and at 0.6 kg/m^(2) spraying rate,the shear strengths of AC-13+AC-20 and PA-13+AC-20 specimens are decreased by 45.3% and 62.7% respectively,showing that the dynamic water scouring will cause more serious damage to the tack coat of PA-13 asphalt mixture upper surface layer.(4) Load and aging can increase the shear strength and shear strength growth rate of the tack coat.Aging has more significant effect on the shear strength and shear strength growth rate of the the tack coat of PA-13 asphalt mixture upper surface layer.