摘要: |
The presence of water in a pavement is detrimental to its life. Therefore, in the construction of hot mix asphalt (HMA), it is important that there is adequate compaction so the initial permeability is low and there will not be any significant densification under traffic loading. Numerous studies have shown that, for dense-graded mixes, the initial inplace air void content should not be less than approximately 3 percent or greater than 8 percent. Low in-place air voids tend to result in rutting, bleeding, and shoving, while high in-place air voids allow air and water to penetrate into the pavement, leading to an increased potential for oxidation, water damage, raveling, and cracking. For many years it has been believed that high in the in-place air void content of dense graded mixes results in increased permeability of these pavements. During the 1960s, Zube reported that dense-graded pavements became excessively permeable at in-place air voids above 8 percent. This was later confirmed in the 1980s by Brown et al. However, recent experience with coarse-graded Superpave mixes has shown that the size and interconnectivity of air voids greatly influence permeability. |