基于细观尺度下布敦岩沥青混凝土低温开裂特性研究

Research on Low-temperature Cracking Characteristics of Buton Rock Asphalt Concrete Based on Microscopic Scale

为了更详细地描述布敦岩沥青的低温特性及裂缝发展规律。采用数字散斑成像技术(DIC),对布敦岩沥青混凝土试件在低温弯曲破坏试验中的裂缝扩展过程进行细观尺度下的观测和分析,通过DIC技术捕捉试件在加载过程中裂缝的形成、扩展,以及裂缝尖端的位移和应变变化。结果表明,①从DIC位移云图来看,裂纹从小梁试件底部开始萌生,随着加载进行,试件散斑点向两侧水平方向位移增大,跨中区域散斑面积变窄,出现散斑区域尖端,裂缝向上部开始延伸,散斑位移变化率减小,直至裂纹扩展至破坏;②从应变云图来看,试件在水平及竖直方向均存在拉应变与压应变,初期试件底部出现多个小范围受拉区域,衍生出若干细小裂纹,受拉区域汇聚、增大,随着加载增大,两侧对称的拉应变向跨中移动,底部压应变范围迅速增大,裂缝不断扩展直至破坏;③同条件下最终裂缝长度排序为SBS改性沥青>布敦岩沥青>基质沥青,裂纹破坏所需加载时间排序为SBS改性沥青>布敦岩沥青>基质沥青,表明布敦岩沥青的低温抑制宏观裂缝性能优于基质沥青。

In order to describe the low-temperature characteristics and crack development law of Buton rock asphalt in more detail,the crack extension process of Buton rock asphalt concrete specimens in low-temperature bending damage tests was observed and analyzed at a fine scale by using the digital image correlation(DIC)technique.The formation and extension of cracks,as well as the changes in displacement and strain at the tip of the cracks in the specimens,were captured during the loading process.The results show that:(1)from the DIC displacement nephogram,cracks start to sprout from the bottom of the beam specimen,and as loading proceeds,the displacement of the specimen's scattering spots increases in the horizontal direction on both sides,the scattering area narrows in the mid-span region,and the tip of the scattering area appears,and the cracks begin to extend upwards,and the rate of change of the scattering spot displacements decreases until cracks are extended to damage;(2)from the strain nephogram,it can be seen that there are tensile and compressive strains in both horizontal and vertical directions,in the initial stage,multiple small tensile regions appeared at the bottom of the specimen,giving rise to several small cracks,and the tensile region converges and increases,with the increase in loading,the symmetrical tensile strain on both sides moves towards the middle of the span,the range of bottom compressive strain increases rapidly,and cracks continue to expand until the damage;(3)the final crack length under the same conditions in descending order is:SBS modified asphalt,Buton rock asphalt,and matrix asphalt,and the crack damage loading time in descending order is:SBS modified asphalt,Buton rock asphalt,and matrix asphalt,indicating that the low-temperature inhibition macro-cracking performance of Buton rock asphalt is better than that of matrix asphalt.