Annotated Literature Review for NCHRP Report 640 (2009)

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199 1.48.2 Benefits of Permeable Asphalt Mixtures Poulikakos et al state that porous asphalt has the benefits of noise reduction and improved safety under wet conditions. 1.48.3 Materials and Design Poulikakos et al state porous asphalt is used on top layers and has an air void content of 20% or greater. 1.48.4 Construction Practices Poulikakos et al did not discuss construction practices. 1.48.5 Maintenance Practices Poulikakos et al did not discuss maintenance practices. 1.48.6 Rehabilitation Practices Poulikakos et al did not discuss rehabilitation practices. 1.48.7 Performance Poulikakos et al did not discuss performance of porous asphalt. 1.48.8 Structural Design Poulikakos et al did not discuss structural design of porous asphalt. 1.48.9 Limitations Open structure of porous asphalt exposes surface to the effect of air and water, thus leading to rapid aging of the binder which can lead to particle loss and adhesive failure. As pavement life proceeds, porous asphalt has voids that become clogged which leads to loss of permeability. 1.49 Tan, S.A., T.F. Fwa and C.T. Han. “Clogging Evaluation of Permeable Base.” Journal of Transportation Engineering. American Society of Civil Engineers. Reston, VA. Volume 129. Issue 3. May 2003. pp. 309-315. 1.49.1 General This paper addresses clogging of a permeable asphalt base layer from an experimental and theoretical approach. Tan et al explain that clogging occurs when particles (sand, sediment, construction material, etc.) collect in porous asphalt layers. They further elaborate that this phenomena is common on public roads and highways due to the increased frequency and type of vehicles. The experimental portion of the Tan et al research involved laboratory testing of four common base mixes: Modified Base 1, Modified Base 2, US Army Corps of Engineers

200 Open Graded Base, and FHWA permeable base [No specific gradation or mix design information was presented in this paper]. Each mix was subjected to a permeability test using the NUS falling head permeameter, a clogging evaluation where 63.5g of clogging material (sand) was placed onto the mix and then water was gently showered so that the clogging material could flow, and a clogging material collection procedure where the clogging material was collected after it traveled through the specimen and quantified. The amount of clogging material collected was then subtracted from the initial amount to yield the amount that actually remained in the specimen. This experimental process was repeated until low to no permeability existed in the specimen. Tan et al validated their experimental procedure by utilizing Wu and Huang’s theoretical model, which was derived from the Kozeny-Carmen equation. Results showed that the theoretical results and experimental results showed close agreement up to the addition of the fifth increment of sand. Tan et al experiments showed that particle retention increases with gradation openness. Also they found that narrow gradations will yield larger voids and thus allow the mix to retain more particles before losing permeability. 1.49.2 Benefits of Permeable Asphalt Mixtures Tan et al did not discuss any benefits of permeable asphalt mixtures. 1.49.3 Materials and Design Tan et al did not discuss materials and design. 1.49.4 Construction Practices Tan et al did not discuss construction practices. 1.49.5 Maintenance Practices Tan et al did not discuss maintenance practices. 1.49.6 Rehabilitation Practices Tan et al did not discuss rehabilitation practices. 1.49.7 Performance Tan et al did not discuss performance of permeable asphalt mixes. 1.498 Structural Design Tan et al did not discuss structural design. 1.49.9 Limitations A clogged permeable layer will have reduced drainage and water storage capacity.