Annotated Literature Review for NCHRP Report 640 (2009)

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251 0 1 2 3 4 5 6 7 8 1990 1992 1994 1996 1998 2000 2002 2004 Jahr Lä rm ab na hm e zw is ch en D R A 11 u nd A B [d bA ] Montreux (1991) - 8% de PL Morges (1993) - 10% de PL Figure 25: Change in Noise Levels with Time The seven test sections performed well under an especially heavy snowfall in 1988/99 chains were used. Some raveling was experienced. The section with Trinidad showed the worst performance. 1.65.8 Structural Design Not discussed. 1.65.9 Limitations In accordance with Swiss standards porous asphalt is not used over 600 m elevation. 1.66 Hardiman, C. “The Improvement of Water Drainage Function and Abrasion Loss of Conventional Porous Asphalt.” Proceedings of the Eastern Asia Society for Transportation Studies. Volume 5. pp. 671-678. 2005. 1.66.1 General This paper describes a research effort designed to improve the permeability and durability of porous asphalt mixes. Hardiman evaluated porous asphalt mixes having maximum aggregate sizes of 10, 14 and 20mm. 1.66.2 Benefits of Permeable Asphalt Mixtures Benefits listed in the paper included reduced hydroplaning, improved skid resistance at higher speeds, reduction in noise, reduction in glare at night and good resistance to permanent deformation. 1.66.3 Materials and Mix Design Materials described by Hardiman included crushed aggregates, a combination of hydrated lime and cement as mineral filler and two asphalt binders, a penetration graded 60/70 and

252 a polymer modified. Table 121 presents the design gradations for the 20, 14 and 10mm maximum aggregate size. Table 121: Aggregate Grading Used in This Investigation Sieve Percent Passing by Weight (mm) Gradation 1 Gradation 2 Gradation 3 20 100 100 100 14 77.9 100 100 10 55.8 74.5 100 4.75 25 49 59.3 3.35 10 10.5 11.5 0.425 5.5 6 6.5 0.075 4 4 4 Hardiman evaluated both a single layer porous asphalt and double layer porous asphalt in this laboratory study. An interesting method of creating the laboratory specimens of the double layer porous asphalt was utilized. For the single layer porous asphalt specimens, 50 blows per face were applied to the sample. For the double layer porous asphalt, sufficient mix was placed in the Marshall mold to produce an approximately 50mm of the lower layer with 25 blows of the Marshall hammer. Then, the upper layer was placed on top of the lower layer and compacted with 25 blows in the same direction. Finally, the opposite face was compacted with 50 blows. In all cases, the 20mm maximum aggregate size gradation was used as the lower layer of porous asphalt in the double layer system. The 10 and 14mm maximum aggregate size mixes were used as the upper layer. Testing of the various mixtures included permeability and Cantabro Abrasion testing. Results of the permeability testing showed that permeability increased as the maximum aggregate size of the gradation increased. Mixes with a 20mm maximum aggregate size were more permeable then the 14 or 10 mm maximum aggregate size mixes. Results of testing on the double layer system showed that permeability was controlled more by the top layer than the lower layer. Results of the Cantabro Abrasion testing indicated that the smaller maximum aggregate mixes had lower abrasion loss values. This would indicate the smaller maximum aggregate size mixes are more durable. 1.66.4 Construction Practices No specific construction practices were given. 1.66.5 Maintenance Practices No specific construction practices were given. 1.66.6 Rehabilitation Practices No specific rehabilitation practices were given.