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271 1.73.4 Construction Practices As mentioned previously, this paper did not specifically deal with porous friction courses. However, the paper does describe two pieces of equipment that can be used to construct a safety edge. The safety edge is essentially constructed as a tapered edge approximately 6 to 8 inches in length. One piece of equipment was developed by the Georgia Department of Transportation (GDOT) and the second equipment was designed and built by TransTech Systems, Inc. Both pieces of equipment are generally a wedge that mounts onto a paver. The GDOT device mounts only the end gate of the paver screed. Mixture passes underneath the device and results in a taper from the layer thickness to the desired height of the vertical pavement edge. The authors indicate that the GDOT safety wedge demonstrated the ability to create a safety edge from a dropoff of 0 to 6 inches. The TransTech Systems, Inc. Safety Edge Maker (SEM) mounts onto a variety of different type pavers. The system has a self adjusting spring that allows the device to follow the roadside surface. A self adjusting screw allows for setting the initial height and the taper to create the safety edge. The authors concluded that both pieces of equipment successfully constructed safety edges. This was demonstrated with a very fine 9.5 mm nominal maximum aggregate size mixture and a coarser 12.5 mm nominal maximum aggregate size mixture. 1.73.5 Maintenance Practices No specific maintenance practices were given. 1.73.6 Rehabilitation Practices No specific rehabilitation practices were given. 1.73.7 Performance No performance measures were given. 1.73.8 Structural Design No specifics on inclusion within structural design were given. 1.73.9 Limitations No limitations on the use were given. 1.74 Martinez, F. C. and R. A. Poecker. âEvaluation of Deicer Applications on Open-Graded Pavements.â FHWA-OR-RD-06-12. Oregon Department of Transportation. Salem, Oregon. April 2006. 1.74.1 General This report documents a research study to evaluate the effects of deicing/ant-icing liquids (magnesium chloride and calcium magnesium acetate) on the friction characteristics of open-graded pavements to determine if their use is associated with any changes in the road surface traction that would result in slick conditions. The intent was not to evaluate the effectiveness of the deicing/anti-icing liquids in preventing snow and ice from
272 bonding with the pavement or melting the snow and ice, rather there were concerns that the liquids may affect the frictional properties of the pavement surface immediately after application and prior to snow and ice forming. 1.74.2 Benefits of Permeable Asphalt Mixtures No specific benefits are given. 1.74.3 Materials and Mix Design No specifics on materials or mix design were given. 1.74.4 Construction Practices No specifics on construction practices were given. 1.74.5 Maintenance Practices The authors devised a research approach that would allow for the testing of both dense- graded and open-graded pavement surfaces at the following points in time: 1. First baseline skid tests. These tests were to be conducted at the end of summer to provide a baseline of performance. 2. Second baseline side tests. These tests were to be conducted immediately after the first rainfall of 6mm or greater. 3. Early winter skid tests. These tests were to be conducted between 30 minutes and two hours after the deicing/anti-icing liquids were applied to the pavement surface at the beginning of the winter season. 4. Late winter skid tests. These tests were also to be conducted between 30 minutes and 2 hours after treatment, but were to be conducted late in the winter season. All friction testing was conducted with a K. J. Law locked-wheel pavement friction tester. Unfortunately, coordination issues did not allow the researchers to obtain either the first baseline skid tests or the early winter skid tests. Only half of the sections were tested to obtain the late winter skid tests. Based upon the data collected, the authors concluded that the application of the deicing/anti-icing liquids had little effect on either the dense-graded or open-graded pavement friction. The authors did, however, indicate that the data set was relatively small and further research was needed. 1.74.6 Rehabilitation Practices No specifics on rehabilitation practices were given. 1.74.7 Performance Pavement friction was utilized as a performance indicator.
