考虑均匀性的沥青混合料最佳沥青用量确定方法

为了确定沥青混合料中的最佳沥青用量, 利用CT技术识别沥青混合料各组分内部结构特征, 并以粗集料、沥青砂浆和空隙各组分的密度和面积为主要特征参数, 提出了沥青混合料的均匀性评价指标, 建立了沥青混合料均匀性评价方法; 分析了沥青混合料马歇尔设计方法中的体积设计参数与内部结构各组分特征的关系, 考虑了沥青混合料内部结构的均匀性, 建立了沥青混合料最佳沥青用量的确定方法, 并选用3种沥青混合料(AC-13、AC-16和AC-20) 对该方法的有效性进行了验证。分析结果表明: 沥青混合料的均匀性评价指标与空隙率具有良好的对应关系, 最小均匀性评价指标对应沥青混合料试件内部结构均匀性最佳时的空隙率; 基于均匀性评价方法所得的空隙率与密度试验测算空隙率的平均差值为0.28%, 并据此计算的间隙率和饱和度与采用马歇尔设计方法得到的间隙率和饱和度的平均值差值分别为0.27%和1.33%, 因此, 利用考虑均匀性的沥青混合料内部结构各组分体积特征参数可以准确地表征沥青混合料马歇尔设计方法中的体积设计参数; 采用最佳沥青用量确定方法与马歇尔设计方法得到的AC-13、AC-16和AC-20三种沥青混合料最佳沥青用量差值分别为0.07%、0.03%和0.05%, 这表明了最佳沥青用量确定方法的有效性。

Determination method of optimum asphalt content in asphalt mixture under considering homogeneity

In order to determine the optimum asphalt content of asphalt mixture, the inner structure characteristics of components of asphalt mixture were identified by using CT technique.The densities and areas of coarse aggregate, asphalt mastics, and air voids were regarded as characteristic parameters, the homogeneity evaluation index of asphalt mixture was proposed, and the homogeneity evaluation method of asphalt mixture was built.The relationship between the characteristics of inner structure components and the volumetric design parameters in Marshall design method for asphalt mixture was analyzed, the homogeneity of inner structure of asphalt mixture was taken into account, a determination method of optimum asphalt content ofasphalt mixture was established, and three types of asphalt mixtures (AC-13, AC-16, and AC-20) were chosen to verify the method.Analysis result shows that there exists a favorable relationship between the homogeneity evaluation index and the volume of air voids for asphalt mixture, and the volume of air voids with respect to the minimum homogeneity evaluation index is corresponding to the optimal homogeneity of inner structure of asphalt mixture specimen.The difference average value between the volumes of air voids obtained by the homogeneity evaluation method and the values measured by the laboratory density test is 0.28%, the average differences between the voids in mineral aggregate and the voids filled with asphalt computed according to the volumes and the values obtained by Marshall design method are 0.27% and 1.33%respectively, therefore, the volumetric characteristic parameters of components of asphalt mixture considering the homogeneity of inner structure can represent the volumetric design parameters in Marshall design method.The differences of optimum asphalt contents of asphalt mixtures (AC-13, AC-16, and AC-20) determined by Marshall design method and the proposed method are 0.07%, 0.03%, and 0.05% respectively, which means that the proposed method is effective to determinate the optimum asphalt content of asphalt mixture.