Annotated Literature Review for NCHRP Report 640 (2009)

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185 1.45 Rogge, D. “Development of Maintenance Practices for Oregon F-Mix.” Oregon Department of Transportation. FHWA-OR-RD-02-09. Corvallis, Oregon. 2002. 1.45.1 General This report documents a research study conducted to evaluate maintenance practices for use on OGFC layers. In Oregon, OGFC mixes are referred to as F-mixes and have been used as wearing layer since the 1970’s. Experience has shown that standard pavement maintenance practices for dense-graded mixes tend to reduce the drainage capacity of OGFC mixes and change the noise and ride characteristics of the road. The specific questions to be answered during this research study included: 1. Are fog seals the best preventative maintenance strategy for OGFCs? If so, what is the optimum frequency and procedure? 2. Are better techniques available than those that have historically be used for dense- graded layers? 3. Can OGFCs be obtained in small enough quantities such that they can be used for small repair and patching activities? 4. What maintenance activities should be conducted during snow, ice and freezing fog? The organization of the report includes an initial survey of Oregon Department of Transportation (ODOT) maintenance personnel to determine the most common distresses encountered with F-mix, then documentation of common repairs for these distresses, and then a conclusions and recommendations. 1.45.2 Benefits of Permeable Asphalt Mixtures Benefits cited by Rogge include reduced hydroplaning, splash and spray, rutting and tire/pavement noise. 1.45.3 Materials and Mix Design No specifics on materials and mix design were given. 1.45.4 Construction Practices No specifics on construction practices were given. 1.45.5 Maintenance Practices One section of the report dealt specifically with the use of fog seals during maintenance. Of the 78 respondents, 56 percent of the respondents indicated that they did not utilize fog seals while 41 percent indicated that fog seals were used (3 percent did not respond) (Figure 19). Of the maintenance supervisors that did use fog seals; over half indicated that fog seals had been placed on less than 30 percent of their pavements containing F- mix (Figure 20). Of the 78 respondents to the survey, Figure 20 also shows that roughly one-quarter of the maintenance supervisors have utilized fog seals on up to 30 percent of the pavements using F-mix as a wearing course. This led the author to the following statement, “… the survey confirmed that ODOT continues to lack convincing evidence

186 about the effectiveness of fog sealing as a preventative maintenance technique for F- mix.” Respondents That Utilize Fog Seals on F-mix 56.4% 41.0% 2.6% Don't Use Use No Answer Figure 19: Response to Whether ODOT Maintenance supervisors Utilize Fog Seals

187 Use of Fog Seals on Projects 0 1 2 3 4 5 6 7 8 9 10 <10% 11-20% 21-30% 31-40% 41-50% 51-60% 61-70% 71-80% 81-90% >90% Percent of F-Mix Layers That Have Been Fog Sealed N um be r o f R es po nd en ts T ha t H av e U til iz ed Fo g Se al 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent of A ll R espondents Number of Respondents That Have Used Fog Seal Percent of All Respondents Figure 20: Use of Fog Seals as Preventative Maintenance Another portion of the survey requested the responding maintenance supervisors to rank the effectiveness of 16 different maintenance treatments. Figure 21 presents the results of this survey. The scale utilized for this portion of the survey was from 1 to 4. A rating of 1 indicates a maintenance technique that is “not at all successful” and a rating of 4 indicated a technique that was “completely successful.” Based upon Figure 21, the top six techniques had an average score ranking between somewhat successful and completely successful. These techniques included C-mix (a dense-graded HMA) machine patch, F- mix inlay, B-mix (dense-graded HMA) machine patch, C-mix inlay, C-mix screed patch, and C-mix blade-in. The remaining ten maintenance techniques were rated somewhere between “not very successful” and “somewhat successful.” One concern of the results shown in Figure 21 was that it might not be feasible or economically advantageous for the use of F-mix in order to correct minor surface defects during maintenance. Therefore, the author surveyed the ability of ODOT to obtain 60 tons of F-mix for maintenance applications. Results of this survey indicated that 46 of the 78 maintenance supervisors said that they could not get such a small quantity of F-mix. Nine of the 78 indicated that they could order 60 tons while 23 did not know.

188 1.00 1.50 2.00 2.50 3.00 3.50 4.00 C-mix machine patch F-mix inlay B-mix machine patch C-mix inlay C-mix screed patch C-mix blade Emulsion chip seal Crack sealing D-mix screed patch D-mix blade patch Profile with grinder Pothole with rock/percol F-mix machine patch Hot asphalt chip seal Pothole with premix Tack/rock/spray/compact Not at all successful Not very successful Somewhat successful Completely Successful Figure 21: Rankings of Maintenance Techniques for F-Mix Another portion of the survey dealt with common winter maintenance techniques. Table 97 presents the most common techniques for winter maintenance. Sanding and de-icing agents, either alone or in combination, were the most common method of winter maintenance techniques reported. It was noted, however, that there is a need for more frequent and longer application for the porous F-mix as compared to dense-graded surfaces. Some specific comments related to sanding operations included: “You have to stay on top of it,” “It tends to plug it up,” Sanding is a last resort,” “Sanding is less successful than deicer,” and “Cinders are best – they go down into pores more easily.” Specific comments relating the use of deicers in general included: “You have to do it within 60 minutes before a storm. We don’t do pre-treating because it’s not effective. The material go down into the asphalt,” and “They are all effective, but magnesium chloride is more temperature sensitive than CMA.” Specific comments related to the use of magnesium chloride included: “It is more effective than CF7 or CMA,” “Pre-treating with magnesium chloride works best as a deicer,” “Need to apply it twice as heavy,” and “We’ve been really effective with it.”

189 Specific comments relating to the use of CMA included: “Use CMA for frosting,” “CMA is temperature and moisture sensitive,” and “Thirty percent solution CMA has proven somewhat successful.” Table 97: Typical Winter Maintenance Techniques for F-Mix Treatment Number Sanding 20 Liquid de-icer or anti-ice agent 15 Magnesium Chloride 15 CMA 7 Larger quantity of de-icer 7 Run shoes on plows 5 Reduce plow speeds 2 Rubber bits 1 CMA & CF7 1 Magnesium Chloride & CF7 1 1.45.6 Rehabilitation Practices No specific rehabilitation practices were given. 1.45.7 Performance The initial part of the study was a survey designed to determine the most common types of distresses encountered in F-mixes. Responses to the survey were returned from 78 of 83 maintenance supervisors, for a 94 percent response rate. Results from the 2001 survey are presented in Figure 22. Within this figure, the various maintenance engineers were requested to rank the various distresses by their frequency using a ranking system of 1 to 4. The higher the ranking, the more frequent the distress was encountered. A ranking of 1 indicates that the distress is never seen and a ranking of 4 indicates that the distress is pervasive. Based upon the survey, the top seven distresses were considered closer to scattered than to rare. These seven distresses included tire stud rutting, icing problems, raveling, gouging/scarring, deformation rutting, clogging and potholes. The other seven distresses included in Figure 22 were considered closer to rare than scattered.