Sustainable Pavement Maintenance Practices (2011)

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air quality/emissions for the equipment and materials. Also considered would be the asso- ciated impact the treatments have on the trav- elling public in terms of emissions associated with traffic delays resulting from the treat- ment placement. Part of the calculation of this factor would be the preventive maintenance treatment’s service life. 6. Water quality evaluates the effects of transportation-related impacts associated with alternative maintenance strategies and materials. Regulatory requirements relate to the operation and maintenance of municipal storm sewer systems, storm water discharge associated with construction activities, and effluent standards related to the total maxi- mum daily effluent discharge standards. Treatments and programs should be evalu- ated for their individual and collective effect on these resources (CEE 2010c). 7. Energy usage relates to the quantification of cumulative energy usage of the pave- ment preservation and maintenance treat- ment throughout the life cycle. Energy usage is important in its correlation to emis- sions of greenhouse gases and their relation- ship to climate change. Study Approach The approach used to complete the synthesis essentially relied on three independent sources of information. The first was a comprehensive review of the literature. An effort was made to obtain not only the most current information but also historical information, so that any changes over time could also be properly described and documented. The second source of information included the survey responses of U.S. and Canadian maintenance engi- neers employed by the state or provincial highway agencies. Finally, case studies based on both the sur- veys and literature were included. Collectively, this information was used to identify current gaps in the state of the practice and identify how these gaps can be addressed in future research. Protocol to Develop Conclusions and Recommendations for Future Research The major factor in developing a conclusion was the intersection of trends found in the literature, sur- vey, and case study documentation. All three tools were used to develop the conclusions and sugges- tions presented in this synthesis. Organization of the Report The information collected in this study is pre- sented as follows: • Summary of Literature Review and Survey and Results • Quantifying Environmental Sustainability in Pavement Preservation and Maintenance • Case Studies • Conclusions and Future Research Needs. SUMMARY OF LITERATURE REVIEW AND SURVEY AND RESULTS Introduction This report employed the following major study instruments: • A comprehensive literature review. • A survey of U.S. state DOTs and Canadian provincial transportation agencies. • Case study analyses of selected U.S., Cana- dian, and one New Zealand sustainable pave- ment preservation and maintenance programs. • The structure and content of each of the instru- ments were integrated to identify trends in the data. The literature found in sustainable transportation is largely about design, construction, and material selection. Very little information was found that was specific to sustainable pavement preservation and maintenance quantification. Most of the studies involved the comparison of specific pavement preser- vation and maintenance treatments, such as chip seal- ing or microsurfacing, to hot mix or portland cement concrete overlays or rehabilitation. Although this information is valuable, there is no single source of environmental sustainability data on the suite of commonly used pavement preservation and mainte- nance treatments. The Recycled Materials Resource Center’s (RMRC) website (http://www.rmrc.unh. edu/) appears to have the most current and complete collection of highway environmental sustainability research. A search of that archive revealed that the majority of the research has been in the area of mate- rial science and hazard analysis. RMRC Project No. 23 notes that: “We have not found publications on the environmental effects of the different maintenance 6

activities” (Horvath 2004). This demonstrates that environmental sustainability research that is related specifically to post-construction operations is an emerging field. Thus, the first conclusion reached in this synthesis is that there is an immediate need for maintenance-specific research to provide agency pavement maintenance engineers with the fundamen- tal data on the relative environmental sustainability of common treatments and preservation programs. A survey was issued to the state and provincial maintenance engineers in the United States and Canada (see web-only Appendixes A and B for details). A general survey on sustainable pavement preservation and maintenance practices provided 49 responses from 42 U.S. state DOTs and 7 Canadian provincial ministries of transportation shown in Fig- ure 2. This corresponds to an individual response rate of 84% for the United States and 70% for Canada. The survey also received responses from three U.S. counties; however, the number of responses from nonstate-level agencies was small and they are not included in the analysis. This analysis separated the U.S. and Canadian responses to account for the dif- ference in the construction contracting regulatory environment that exists in both countries. Addition- ally, information from the international agencies is added as appropriate throughout the synthesis. The case studies were identified after a review of the available literature and responses to the survey, along with input and recommendations of candidates familiar to the synthesis panel. Although there is limited available data and the field is relatively new, case studies were found that highlight each of the environmental factors Opportunities to Implement Sustainability in Maintenance The literature is rich with information on sustain- able practices that can and have been applied to highway design and construction, although not to maintenance. Each study represents an opportunity for maintenance engineers to potentially adopt aspects of the sustainable practices in maintenance and preser- vation. In other cases, the identified sustainable prac- tices will likely need to be adapted or altered before their use in pavement preservation and maintenance applications. Table 1 consolidates the information found in the literature and extends each study’s result to possible pavement preservation and maintenance applications. In most cases, the possible application was mentioned in the cited report or paper, and the mention took the form of a recommendation for addi- tional research to validate the concept. The report by Denevillers (2010) detailed actual field testing of 7 Figure 2 Survey responses.

8Table 1 Alternative, recycled, and renewable highway design and construction literature review results Material/ Literature Possible Preservation Possible Maintenance Technique Cited Uses Uses Remarks HMA = hot-mix asphalts; PCC = portland concrete cement. Bio-fluxing Agent Bio-binder Recycled Con- crete Aggre- gate (RCA) Recycled Glass Gravel Fly Ash Bottom Ash Flue Gas Desulpheriza- tion Gypsum Kiln Dust Baghouse Fines Crushed Slag Ultra-High Pressure Water Cutter Shotblasting Recycled Motor Oil Recycled Tire Rubber Denevillers (2010) Denevillers (2010) Gardner and Greenwood (2008) Melton and Morgan (1996) MnDOT (2005) Carpenter and Gardner (2007) Benson and Edil (2009) MnDOT (2005) ISSA (2010) Chappat and Bilal (2003) Pidwerbesky and Waters (2007) Transport Canada (2003) Waters (2009) Beatty et al. (2002) • Prime coat • Chip seals • Microsurfacing • Chip seals • Microsurfacing • Whitetopping • Untried • Microsurfacing mineral filler • Slurry seal mineral filler • Microsurfacing mineral filler • Microsurfacing mineral filler • Slurry seal mineral filler • Prime coat • Microsurfacing • Microsurfacing mineral filler • Slurry seal mineral filler • Chip seal aggregate • Restore macro- texture on chip seals • Restore micro- texture on polished HMA and PCC pavements • Dust palliative • Otta seals • Chip seals • Thin overlays • Overlay tack coat • Cold mix • Warm mix • Cold in-place recycling • Chip seals • Road marking • Full-depth patching • Partial-depth patching • Unbound base courses • Concrete maintenance mixes • Microsurfacing • Subase under gravel surface • Concrete maintenance mixes • Prime coat • Microsurfacing • Untried • Special binder road mix • Retexture chip sealed roads prior to resealing • Restore skid resistance on resealed PCC bridge decks • Otta seal as surface course • Chip seals • Thin overlays Trade name is Vegeflux® Trade name is Vegecol® RCA acts to sequester CO2 in addition to recycling Potential use on gravel roads Widely used in a variety of products Uses no virgin material and the sludge can be recycled as precoating for chip seal aggregates Uses no virgin material and the steel shot is recycled for reuse in the process Motor oil is refined before use Also found to reduce road noise

vegetable-based carbon emulsions. One of the prin- ciples of environmental sustainability is to minimize the use of nonrenewable resources. For example, the use of a renewable bio-fluxing agent as a prime coat was successfully demonstrated in Morocco, and also tested and used in chip seals on Route 960 in Saumur, France. The same is true for the bio-binder, which has been successfully applied in Canada and seven European countries. Although it is not in the table, it can be noted that it has successfully been used in road marking paints in France and England. It can be noted that many of these treatments can be evaluated in the broader environmental sustainability context as details in the literature were limited. Table 1 illustrates that whereas fundamental research has been done on enhancing highway envi- ronmental sustainability through the use of recycled materials, alternate materials, and green construction technologies, the information necessary to extend these promising opportunities to pavement preserva- tion and maintenance must still be developed through future research and field testing. Additionally, the eco- nomic analyses contained in those reports are very rudimentary. A recent study found that the standard FHWA-approved life-cycle cost analysis method for new construction is not easily applied to pavement preservation projects (Pittenger 2010). As a result, rig- orous research would be needed to apply a life-cycle cost analysis algorithm that goes beyond merely look- ing at treatment construction costs and provides a rig- orous methodology to assign a value to such things as carbon sequestration and resource renewability. Sustainability Within Agency Maintenance Programs In recent years, transportation agencies have been placing increasing importance on maintenance efforts; as funding becomes scarcer, it becomes critical to take care of the infrastructure they already have. Therefore, influencing the environmental sustainability of pave- ment maintenance efforts within DOTs will have a meaningful impact. Table 2 summarizes the survey responses regarding the relative magnitude of pave- ment preservation and maintenance programs in the United States and Canada. In those agencies on the low end of the funding spectrum, the need for an aggressive pavement preservation program is criti- cal to getting as much value out of each maintenance dollar as possible (Galehouse et al. 2003; NHI 2007). Pavement preservation promotes environmental sus- tainability because it seeks to minimize the amount of natural resources consumed over a pavement’s life cycle (FHWA 2005). Focusing on pavement preser- vation rather than reactive maintenance and repair furnishes a broad foundation on which to build an agency’s pavement maintenance environmental sus- tainability program. The survey contained a number of questions designed to draw a relationship between agency pave- ment preservation and maintenance programs and environmental sustainability (Table 3). The conclu- sion from these data is clear. Most agencies do not consciously consider either environmental perfor- mance or environmental sustainability when planning and conducting pavement preservation and mainte- nance activities. A comment on the Louisiana DOT’s response accurately describes current state of the practice: “We are concerned about environmental sustainability but have no active program in pave- ment maintenance.” The agencies that did indicate that some kind of pavement environmental sustainability program existed in their organizations were Ontario, Florida, Missouri, New York, and Texas. New York and Ontario are detailed in the case studies in addition to providing some information from a few other agen- cies. Note that some of these were not directly related 9 Table 2 Summary of annual maintenance budgets from survey respondents Approximate Annual Maintenance Budget Range Low Average High Canada $2.8 million $99.0 million $276.4 million $US per lane-mile $1,127 $26,064 $51,054 % of 2009 Program 1.9% 15.9% 26.7% U.S. $15.0 million $278.5 million $1.7 billion $US per lane-mile $1,650 $15,669 $79,589 % of 2009 Program 1.4% 14.9% 33.4%