Annotated Literature Review for NCHRP Report 640 (2009)

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178 information or data was provided]. In summary to the 2002 survey, the following statement was made “… even the advocates among the road operators seem inclined to move away from conventional porous asphalt even though its benefits with regard to noise control are generally appreciated.” 1.42.6 Rehabilitation Practices No information is provided on construction practices of friction course. 1.42.7 Performance No information is provided on the field performance of friction course. 1.42.8 Structural Design No information is provided on structural design of friction course; however, the paper does state that porous asphalt pavement layers are placed at 40 mm (1½ in). 1.42.9 Limitations No information is provided on limitations of use. 1.43 Padmos, C. “Over Ten Years Experience with Porous Road Surfaces.” Ninth International Conference on Asphalt Pavements. International Society of Asphalt Pavements. Copenhagen, Denmark. 2002. 1.43.1 General This paper presents a ten year summary on the use of porous asphalt in the Netherlands. Padmos states that the use of porous asphalt is attractive because of the noise reducing capabilities of this mix type compared to dense-graded mixes. He states that approximately 57 percent of the motorway network within the Netherlands is surfaced with porous asphalt. Any time a layer must be replaced, the current policy is for porous asphalt to be used as the wearing surface. Up until the writing of this paper, only single layer porous asphalts were being used. However, there was a push to use double layer porous asphalt wearing surfaces because of the noise reduction capabilities. 1.43.2 Benefits of Permeable Asphalt Mixtures Benefits mentioned by the author include noise reduction and reduced splash and spray during wet weather. Padmos indicates that porous asphalt reduces noise levels by 3 dB(A). 1.43.3 Materials and Mix Design Typical gradations used in the Netherlands have a maximum aggregate size of 16 mm. 1.43.4 Construction Practices No specifics on construction practices were given. 1.43.5 Maintenance Practices Padmos states that during winter events, all lanes on porous asphalt are closed except for the design lane. The reasoning being that the traffic will help prevent snow and ice