Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
248 1.64.6 Rehabilitation Practices The subject of this Technical Memorandum is considered to provide an alternative for minor rehabilitation. The patching material was placed on two test sites. First, the material was placed over a dense-graded layer of HMA at the Pavement Research Center, located at the University of California Richmond Field Station. This first test site was used to assess workability and ease of application of the material. Additionally, the drainage characteristics of the placed patching material were evaluated. For the first test site, the patching material was placed in a lift of approximately 40 mm over an area of 0.2 m2. In order to simulate a pothole, a wooden frame was used to provide confinement. Frick stated that the patching material was easily mixed and placed and provided adequate drainage materials. The second trial site was a highway where an area of distress was located. The patching material was spread full lane approximately 15 mm thick for several meters. Frick considered this test section to be severe because the thickness was less than desired and there was no confinement of the mix since it was placed full lane width. Results from this second trial site resulted in portions of the patching material raveling within a few months. No mention of whether an attempt was made to bond the patching material to the underlying layer. 1.64.7 Performance Performance of the open-graded patching material was not acceptable as the material began to ravel within just a few months. 1.64.8 Structural Design No specifics on inclusion within structural design were given. 1.64.9Limitations No specific limitations were given. 1.65 Graf, B., Simond, E. âThe Experience with Porous Asphalt in Canton Vaud.â VSS Publication Strasse and Verkehr. Route et Trafic. April 2005. 1.65.1 General The positive experience with porous asphalt within a 15 year period in Canton Vaud of Switzerland is discussed. Porous asphalt was first constructed in Canton Vaud in 1991. Currently, one third or 65km of the surfaces in the Canton are covered with porous asphalt. In addition the use of porous asphalt on bridges was first introduced in 1993. Currently 17 bridges are surfaced with it. The paper discusses noise reduction binder use and winter maintenance. 165.2 Benefits of Permeable Asphalt Mixtures Simond and Graf point out that one square meter of porous asphalt with a thickness of 4cm has a void volume of ca. 9 liter of which 7 liters are interconnecting voids capable of draining 7liters of water.
249 Main benefits: ⢠Reduction of rolling noise of vehicles ⢠Reduction in splash and spray ⢠No aquaplaning ⢠Reduction in reflection from head lights under rainy weather ⢠Reduction in stress level for the driver Disadvantages ⢠Winter maintenance ⢠Reduction in mechanical strength ⢠Reduction in service life 1.65.3 Materials and Design The structure of porous asphalt and dense graded asphalt from Switzerland is presented in Figure 24. Figure 24: Interconnected Voids of Porous Asphalt Seven test sections have been built in Switzerland in 1988/99 with one variable that of binder as follows: ⢠4 sections with commercially available polymer-modified binder ⢠one with B80/100 with SBS polymer modified ⢠one with B55/70 and Trinidad additive ⢠one with special binder with rubber additive A 300m dual layer section was constructed in 2000 with a lower layer of 5cm of porous asphalt with max grain size of 22mm and binder content of 3.9 percent and a upper layer of 2.5 cm with max grain size of 8mm and binder content of 5 percent. As a result of this construction the permeability increased by 25 to 30 percent and noise emission fell by
250 1dB in comparison with the single layer porous asphalt. Binder draindown in the lower layer was noted in the cores and it was concluded that the binder content of the lower layer should be decreased. The dual layer is used in the median for its permeability 1.65.4 Construction Practices Normal construction practices is recommended 1.65.5 Maintenance Practices Winter maintenance practices: ⢠Timing of the application of salt very important as when the snow depth increases it is harder to solve the freezing problem ⢠More salt should be applied in the first application of the season ⢠Application of salt should be repeated regularly ⢠The effect of weather on the porous pavement should be closely watched The winter maintenance of porous asphalt is somewhat more complicated than dense asphalt however not a single Weather related accident has been reported on the porous asphalt in canton Vaud. 1.65.6 Rehabilitation Practices Not addressed in this paper 1.65.7 Performance Reduction in noise through the use of porous asphalt versus dense-graded asphalt at various locations is reported in Table 120. On the average a reduction of 6db is recorded. Table 120: Reduction in Noise Levels at Various Locations Installation date Location Reduction in noise emission after the installation of porous asphalt [dBA] 1991 Pertit 4.1 ... 6.2 1993 Morges 5.4 ... 8.6 1999 Lonay 6.2 ... 8.4 1999 Bex 4.5 ... 6.0 Long-term development of noise reduction was recorded for two sites as shown in Figure 25, indicating that at these sites the noise reduction capability of porous asphalt was maintained even after 9 years.
