Abstract: In order to describe the voids distribution characteristics of the asphalt mixture accurately, medical CT was used to scan four types of asphalt mixtures (e.g., AC-13, AC-16, ATB and AM) to obtain the internal section image. Then, digital image technology was used to extract the voids characteristics of CT scanning images of asphalt mixture specimens. Finally, the multifractal spectral characteristic parameters of voids distribution were calculated out with the help of MATLAB software. The relationship between the splitting strength of the mixture and the characteristic parameters of the multifractal spectrum was analyzed. The results demonstrate that: the void distribution has multifractal characteristics and the multifractal spectral parameters can reflect the voids distribution from different angles. The peak value of multifractal spectrum fmax has a good logarithmic regression relationship with the surface voidage, and the fractal dimension D0 of the void increases with the increase of fmax, which means the porosity is larger. The spectrum width Δα reflects the whole range of the regional void distribution, while the height difference between both ends of the fractal spectrum Δf reflects the degree of void relative aggregation and dispersion. The splitting strength is significantly correlated with the porosity and the uniformity of distribution. The multifractal characteristics of voids distribution of asphalt mixture can provide a new method and idea for analyzing its pavement performance.

Key words: highway engineering, asphalt mixture, multifractal, voids distribution, digital image technology

摘要： 为了精细化描述沥青混合料内部空隙的分布特征，采用医用CT对AC-13、AC-16、ATB、AM等4种类型的沥青混合料进行扫描以获取其内部截面图像，运用数 字图像技术提取沥青混合料试件CT扫描图像空隙特征，借助MATLAB软件工具计算得到空隙分布的多重分形谱特征参数，分析了混合料劈裂强度与多重分形谱特征 参数的关系。结果表明：空隙分布具有多重分形特性，多重分形谱参数能从不同角度反映空隙分布情况；多重分形谱峰值fmax与面空隙率有良好的对数回归关系 ，fmax越大，空隙部分的分形维数D0增大，空隙率也会增大；谱宽Δα反映了区域空隙分布情况的整体范围，分形谱两端高差Δf则反映了空隙的相对聚散程度； 劈裂强度与空隙率大小、分布均匀性具有明显相关性。沥青混合料空隙分布的多重分形特性能为分析其路用性能提供一种新的方法与思路。

关键词: 道路工程, 沥青混合料, 多重分形, 空隙分布, 数字图像技术