Micromechanical analysis of damage evolution in splitting test of asphalt mixtures

A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was used to simulate the damage evolution of asphalt mixture through splitting test. Aggregates were modeled to be linearly elastic, and the mastics were modeled to be plastically damaged. The splitting test simulation results show that the material heterogeneity, the properties of aggregates and air voids have significant effects on the damage evolution approach. The damage behavior of asphalt mixture considering material heterogeneity is quite different from that of the conventional hypothesis of homogeneous material. The results indicate that the proposed method can be extended to the numerical analysis for the other micromechanical behaviors of asphalt concrete.     

New method to quantitatively evaluate the homogeneity of asphalt mixtures

To evaluate the homogeneity of asphalt mixtures,the images of sections obtained by cutting the asphalt mixtures specimen horizontally or vertically were analyzed with digital image processing techniques,and the particle area ratio was achieved by applying sector scan for horizontal specimen and vertical scan for vertical one.The research result indicates that the influence of random distribution of aggregates in cutting the specimen can be eliminated by using colored aggregates to distinguish coarse and fine aggregates and using color threshold to segment the images.Choosing three typical gradations,proving particle area ratio obeying normal distribution and using the variability of particle area ratio as an index,it is feasible to quantitatively evaluate the homogeneity of asphalt mixtures.     

应用弯沉盆反算土基回弹模量

为准确反算土基回弹模量,利用层状弹性体系理论和冲击荷载沿路面结构下传扩散的特点,建立了路表变形响应与模量反算模型.通过层状弹性体系计算程序计算路表弯沉值,构建结构层参数与路表弯沉值之间一一对应的数据库,并基于此数据库建立了由路表弯沉盆反算土基回弹模量的回归模型.理论弯沉盆和实测弯沉盆反算的算例分析表明:计算结果与国内外一些著名的反算程序差异不大.距离荷载中心较远位置处的路表变形响应只受到土基的影响.     

基于DMA方法的沥青胶浆微观结构

采用动态力学分析(DMA)方法对沥青胶浆的微观结构进行了研究,通过对沥青胶浆的动态黏弹性能的变化规律以及Han曲线的温度依赖性进行分析。比较了沥青胶浆和改性沥青胶浆的相态结构的区别,并且根据沥青及沥青矿粉胶浆的损耗因子tanδ计算出参数A,用来评价沥青与胶浆的界面粘结程度。研究结果表明了用DMA方法可以很好地研究沥青胶浆的微观结构,从而为更好地改善沥青胶浆的路用性能提供了理论依据。     

沥青低温粘弹性能的预测

鉴于弯曲梁流变仪和动态剪切流变仪在研究沥青低温粘弹性能时存在一定局限性,通过动态剪切流变仪测定常温下沥青的动态粘弹性能,利用时温转换原则和沥青动静态粘弹函数的转换关系,转换为沥青的低温粘弹性能,与弯曲梁流变仪在低温下直接测定的低温蠕变性能相比较,分析了两者试验结果的相关性。结果表明,通过常温下沥青的动态粘弹性能可以很好地预测沥青的低温粘弹性能,并且可以得到更宽广的时间范围内沥青的低温粘弹性能。     

道路交通安全与沥青路面技术的进步

随着道路交通量增加和交通速度提高,对道路交通安全的要求日益增强,如何利用路面工程建设技术保证交通安全已经成为道路设计系统的一个重要课题。本文主要介绍国内外道路交通安全与路面工程技术的现状,以促进国内外高新技术在我国的推广应用,全面提高我国的道路交通安全水平。     

多层粘弹性半空间轴对称问题的理论解

利用积分变换和传递矩阵的方法推导了多层粘弹半空间轴对称问题的理论争。引入Ｆ．Ｄｕｒｂｉｎ的方法实现Ｌａｐｌａｃｅ逆变换,通过实例计算路表弯沉表明初始时段所得结果与弹性解基本一致。随着时间的推移,多层粘弹体系表面弯沉增大,这种现象说明随时间的推移,材料的粘性起到更大的作用,与实际情况相附。本文的方法可以很容易推广到多层粘弹体系的动力学问题之中。     

新型嵌段共聚物改性沥青的研究

高等级路面的交通特点对路面材料提出了更高的要求。近年来关于改性沥青的研究和应用已越来越深入和广泛。本文采用高速剪切工艺制备了两种新型嵌段共聚物改性沥青-SEBS改性沥青和P聚合和物改性沥青,并将其与SBS改性沥青的显微结构和性能做了对比,实验结果表明,SEBS改性沥青在制备贮存稳定性及力学性能上均不及SBS改性沥青;而P聚合物改性沥青在感温性、高温性及低温性能上有较大改善,且P聚合物改性沥青混合料的疲劳性能较原沥青有较大改善,适合在高等级道路上推广使用。     

Research on segregation evaluation methods of asphalt pavement based on air voids distribution

Eye observation was used to evaluate the segregation degree of asphalt pavement, which was not much creditable. To the asphalt pavement, road surface texture measuring method which has appeared recently can identify gradational segregation; but it can’t reflect the influence of the temperature segregation. However, using infrared temperature detector to evaluate the segregation must be taken during paving, which brings much inconvenience. In this paper, measuring the air voids distribution using non-nuclear density gauge to evaluate asphalt pavement segregation was introduced. Result shows that this method can directly reflect the comprehensive results of the two types of segregation in a high efficient and accurate way. Moreover, using the sketch map of segregation area can help to analyze the segregation reason visually.