Annotated Literature Review for NCHRP Report 640 (2009)

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253 1.66.7 Performance No specific performance measures were given. 1.66.8 Structural Design No specifics on inclusion within structural design were given. 1.66.9 Limitations No specific limitations were given. 1.67 Lane, R. “Cleaning Open-Grade Asphalt To Improve Safety.” International Conference on Surface Friction/ 2005 Papers. www.surfacefriction.org.nz. Christchurch, New Zealand. 2005. 1.67.1 General This paper discusses a trial maintenance program designed at cleaning the void structure of open-graded porous asphalt (OGPA). This work was conducted in New Zealand. 1.67.2 Benefits of Permeable Asphalt Mixtures Lane provided several benefits of the OGPA mixtures used in New Zealand, namely, reduced hydroplaning potential, reduction in splash and spray, improved wet weather friction, improved reflectively of pavement markings and reduced traffic noise. 1.67.3 Materials and Mix Design No specifics on materials and mix design were given. 1.67.4 Construction Practices No specifics on construction practices were given. 1.67.5 Maintenance Practices This paper primarily deals with a trial program to evaluate a method for cleaning debris from OGPA pavements. Though the method and equipment utilized were not discussed in detail, the author indicates the method as “low pressure captive blasting.” The OGPA Cleaning Trial was conducted jointly between the Transit New Zealand and Pavement Treatments, Ltd on a total of 13 sites. In order to evaluate/quantify the level of cleaning that took place, a pavement permeability test was utilized. Another aspect of the test program was to evaluate the point in an OGPA’s life when maintenance is required. Of the 13 pavements cleaned and evaluated, they ranged in age between 1 and 6 years. No raw data was provided to quantify the improvement in permeability of the OGPA layers; however, a figure within the paper did show the improvement in permeability after removing debris for the void structure. Figure 26 is a replication of the figure contained within the paper. Values of Figure 26 were scaled in order to create this figure. Based on Figure 26, Lane indicated that the optimum timing for the first cleaning is between 2 to 3 years in age. Generally, the sections evaluated that had an age less the 3

254 years still maintained an adequate level of permeability. Lane explained the method of measuring permeability of a pavement as a permeability index test. A certain volume of water was allowed to penetrate into the OGPA pavement and the time required for all of the water to penetrate the pavement reported as permeability. All of the sections showed a decrease in time (increase in permeability) after cleaning the pavement. For older pavements, the data also showed that cleaning a pavement a second time would again improve the drainability of an OGPA pavement. 0 20 40 60 80 100 120 140 0 1 2 3 4 5 6 Pavement Age, yrs Pe rm ea bi lit y, s ec After Cleaning Before Cleaning Same Site Cleaned a second time. Note: Raw data not available in original paper. Values scaled from Figure within paper. Figure 26: Effect of Cleaning OGPA 1.67.6 Rehabilitation Practices No specifics on rehabilitation practices were given. 1.67.7 Performance The performance measure utilized by Lane was permeability. Though not fully described within the paper, the test method seems similar to some used in Europe in that the index of permeability has units of time. 1.67.8 Structural Design No specifics on inclusion within structural design were given. 1.67.9 Limitations No specific limitations were given.