摘要: |
The Kansas Department of Transportation (KDOT) pavement preservation program actions for asphalt-surfaced pavements include route and crack seal, chip seal, 1- to 4-inch overlay, 1- to 4-inch inlay, heater scarification, cold in-place recycle (4-inch), ultra-thin bonded bituminous surface (Nova chip), modified slurry seal, and cold milling. The ultra-thin bonded bituminous surface (UBBS or Nova chip) is a thin gap-graded hot mix which is bonded to the existing surface with a modified emulsion membrane. This surface has been found to reduce noise, minimize back spray and increase visibility. Since its introduction in the United States in 1998, more than 50 million sq. yds. have been constructed. KDOT has been using UBBS since 2001. From 2002 to 2006, more than 150 miles of UBBS have been placed on the Kansas state highway system, and its use is increasing. Most of the mileage is on full design bituminous pavements, pavements with higher truck traffic as shown. Thus far, the performance of this thin surface treatment strategy has been good. KDOT is currently extending its use from the treatment of existing surface to in conjunction with some sort of surface preparation such as, surface recycling. As some of the UBBS sections approaching rehabilitation, the question now is how to rehabilitate the sections with UBBS. Since the layer is gap or open graded, conventional overlay might result in moisture trapping in the layer causing stripping of the underlying layers. Despite the claim of the marketer of this technology that the UBBS layer will be clogged by the time of rehabilitation, there are no data to support this. They also heavily promote rehabilitation of the UBBS pavements with another UBBS layer. However, this may not be possible when strengthening is required or investigation needs to be done whether structural strengthening is possible with double UBBS layer just like double seal coat. |