摘要: |
Mineral filler plays an important role in the construction and performance of hot mix asphalt (HMA) pavements. Very little attention was given to the study of mineral filler (often referred to as the minus 200 fraction) during the Strategic Highway Research Program, although the Superpave mix design method includes a recommendation on the dust-to-binder ratio. Some field experience suggests that this ratio may be too restrictive. In certain cases, constructibility and performance can be enhanced with the use of additional filler as long as the filler is properly specified. The nature and quantity of mineral filler are especially important in specialty mixes like stone matrix asphalt (SMA) mixes where the mineral filler, which forms a mastic with the asphalt binder, contributes significantly to compactibility impermeability, and in-service pavement performance. There is also some evidence that certain mineral fillers are incompatible with anti-strip agents and modified binders. Moreover, the composition and reactivity of mineral filler are normally not determined but could have a significant impact on aging and other HMA performance characteristics. Specification of mineral filler for HMA is given less emphasis in the United States than in Europe. A number of different test methods and more defined criteria are often part of European HMA specifications. Given the importance of mineral filler to the overall performance of HMA as well as the diversity and abundance of mineral fillers available to industry, a significant national study on the testing and specification of mineral filler is clearly warranted. The objectives of this study were to (1) identify or develop test methods for mineral filler that characterize its mechanical and chemical effects on the performance of mastics (combinations of asphalt binder and mineral filler) and hot mix asphalt (HMA) and (2) recommend specification criteria for mineral filler that optimize HMA performance. |