Investigating the blending of reclaimed asphalt with virgin materials using rheology, electron microscopy and computer tomography
Investigating the blending of reclaimed asphalt with virgin materials using rheology, electron microscopy and computer tomography
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DOI：
10.1016/j.compositesb.2014.07.025
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发表时间：
2014-12
影响因子：
13.1
通讯作者：
E. Rinaldini;P. Schuetz;M. Partl;G. Tebaldi;L. Poulikakos
中科院分区：
文献类型：
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作者：
E. Rinaldini;P. Schuetz;M. Partl;G. Tebaldi;L. Poulikakos
利用动态剪切流变仪(DSR)、电子显微镜和计算机层析成像(CT)等多尺度方法研究了再生沥青路面(RAP)与原始材料的混合性质。为了简化原始材料和再生材料混合的可视化，生产了五种特殊设计的热沥青混合料，其中包括大量矿物质(8/11 mm)的原始集料和RAP与原始沥青混合的小部分(2/4 mm)。从共混物中回收的粘结剂的复数模数和相角介于RAP和原始粘结剂之间。压实圆柱体试件(直径150 mm×高120 mm)的CT切片可以考虑压实对混合的影响。它们显示具有原始大集合体的块状区域以及RAP集合体的块状区域。利用显微CT研究了不同粘结剂在微观尺度上的空间分布。可以区分毫米大小的不同的原始粘结剂簇和说唱粘结剂簇。在大的原始集料旁边存在RAP粘结剂，这表明旧的RAP粘结剂从RAP集合体迁移到原始集合体。从这些CT图像中，无法证实原始粘结剂和旧粘结剂之间是否发生了混合。利用电子显微镜，在旧粘结剂和新粘结剂之间的区域发现了微裂纹形成，表明存在可能导致较大裂纹形成和扩展的薄弱环节。然而，使用能量色散X射线光谱可以看到二氧化钛示踪剂在混合物中的原始粘结剂中的良好的定性分布，表明在所调查的位置进行了良好的混合。因此，结果表明，在整个样品中，混合并不是均匀的。有些位置表现出良好的混合，而另一些位置则表现为未混合，在粘结剂边界上形成了微裂纹。
The nature of blending of virgin materials with reclaimed asphalt pavement (RAP) has been investigated using a multi scale approach using the dynamic shear rheometer (DSR), electron microscopy and computer tomography (CT). In order to simplify the visualization of the blending of the virgin and reclaimed materials five specially engineered hot asphalt mixtures were produced incorporating large mineral fraction (8/11 mm) of virgin aggregates and small fraction (2/4 mm) from RAP mixed with virgin bitumen. The complex modulus and phase angle of reclaimed binder from the blended mixtures were found to be between that of RAP and virgin binder. The CT slices of compacted cylindrical samples (150 mm diameter × 120 mm height) could incorporate the effect of compaction on the blending. They show lumped regions with virgin large aggregates as well as lumped regions of RAP aggregates. Using micro CT the spatial distribution of the different binders was investigated at the micro-scale. Millimeter size distinct clusters of virgin binder and clusters of RAP binder could be distinguished. The existence of RAP binder next to large virgin aggregates indicated the migration of the old RAP binder from the RAP aggregates to the virgin aggregates. From these CT images, it was not possible to verify if blending between the virgin and old binders occurred. Using electron microscopy micro-crack formations in the zone between old and new binder were identified suggesting weak spots that could lead to larger crack formation and propagation. However, using energy-dispersive X-ray spectroscopy good qualitative distribution of titanium dioxide tracer in the virgin binder in the mixture could be seen, indicating good blending at the investigated location. Hence, the results show that blending is not homogeneous throughout the sample. Some locations show good blending whereas other locations appear non-blended with micro-cracks forming at the binder boundaries.