Sustainable Pavement Maintenance Practices (2011)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

INTRODUCTION Increasing societal awareness of the environ- mental effects of constructing, operating, and main- taining the highway infrastructure has led to new demands on transportation agencies to conduct their business in a more environmentally friendly, or sustainable, fashion. One key approach is for agencies to implement a pavement preservation program; restoring pavements that are still in good condition and extending their service life. The FHWA considers pavement preservation as a pro- active approach to maintaining highways. Pavement preservation and maintenance treatments usually provide the least expensive pavement manage- ment strategy available on a life-cycle cost basis (FHWA 2005). This synthesis is directed at benchmarking the cur- rent state of the practice in usage and quantification of pavement preservation and maintenance practices in terms of environmental performance. “Sustainability” in the synthesis refers to promoting environmen- tally friendly practices that also provide technical and economic benefits. The seven sustainability impact factor areas evaluated are virgin material usage, alternative material usage, program for pave- ment in-service monitoring and management, noise, air quality/emissions, water quality, and energy usage and their relationship to typical pavement preserva- tion and maintenance practices. Information in the synthesis examines all pavement types including asphalt, concrete, composite, surface-treated and gravel roads, and pavements. Synthesis Objective The objective of this synthesis is to identify and synthesize current sustainable pavement preservation and maintenance practices. The focus is on determin- ing what the current state of practice is in this area and also to identify needs for future research. The synthe- sis identified those agencies that are demonstrating efforts to quantify environmental performance and stewardship in maintenance and preservation and related areas. To assess the way that environmental sustainabil- ity relates to pavement maintenance, the methodol- ogy of this synthesis was to prepare a literature review, conduct a survey of practitioners and evaluate their responses, and assemble case studies from several exemplary programs. Background Pavement infrastructure is critical to the quality of life and prosperity of society. As the pavement struc- ture deteriorates over time, proper pavement preser- vation and maintenance is necessary to achieve a high-performing, safe, and cost-effective pavement network for the users. In a society where currently resources and funding are limited, it is more impor- tant than ever that transportation agencies seek ways to use these resources to maximize benefits as part of daily operations. At the same time, attention to the notion of environmental sustainability has become more important to society. In general, environmen- tal sustainability has been defined by the Bruntdland Commission as “[meeting] the needs of the present without compromising the ability of future genera- tions to meet their own needs” (Bruntdland Commis- sion 1987). Recently, the FHWA defined sustainable transportation as “providing exceptional mobility and access in a manner that meets development needs without compromising the quality of life of future generations. A sustainable transportation system is safe, healthy, affordable, renewable, operates fairly, and limits emissions and the use of new and non- renewable resources” (Harmon 2010). The basis of environmental sustainability consists of the three elements shown in Figure 1: economy, society, and environment. Sustainable pavement preservation and maintenance are a subset of sustainable trans- portation where the impacts of the treatments on the economy, environment, and social equity are defined and evaluated. It can also be evaluated according to the technical and economic effectiveness and the associated impacts on the natural environment (Jeon and Amekudzi 2005). It can be noted that a study of state departments of transportation (DOTs) indicated 3 Figure 1 Fundamental sustainability model (CH2M Hill 2009).

that although environmental sustainability is not explicitly mentioned in the mission and vision statements of most agencies, many do include the three elements (Amekudzi and Jean 2007; Ramani et al. 2009). The concept of environmental sustainability and how it can be employed in various practice areas is gaining wide support from the general public, gov- ernments, and professionals (Chan and Tighe 2010; Muench 2010). The need of quantifying sustainable practices is also challenging and requires a holistic approach. The initiatives by LEED™ (USGBC 2010), Greenroads (Muench 2010), GreenLITES (NYSDOT 2009), and GreenPave (MTO 2010) certification pro- grams are leading examples of programs that pro- mote and quantify sustainable practices (Chan and Tighe 2010). In addition, there are several other ini- tiatives such as PaLATE (Horvath 2009), EIO-LCA (EIOLCA 2010), and some industry initiatives that will be described later in the report. However, although it is notable that many of the environmen- tal sustainability initiatives consider preservation and maintenance treatments and their contributions to long life pavements, there is limited explicit assessment of those treatments in terms of environ- mental performance. As noted in FHWA’s newsletter, Strategic, Safe and Sustainable: Today’s Vision for Pavements, environmental sustainability is of critical importance (Stephanos 2009). It was noted in that article, in the new decade of environmental awareness, that max- imizing recycled materials in pavement construction and rehabilitation is a priority and this is further advanced through the FHWA participation in Green Highways Partnership, which is an attempt to align various state specifications for using recycled ma- terials. Other initiatives include using warm mix that generates fewer emissions and conducting research on expanding the types and amount of fly ash that can be used in concrete paving. Although these ini- tiatives tend to focus primarily on usage in pavement construction and rehabilitation treatments, they are also an important part of pavement preservation and maintenance treatments. Additionally, recent research in France and New Zealand (Ball et al. 2008) mirrors a U.S. movement from solvent-based binders toward water-based emul- sion binders for use in pavement preservation and maintenance treatments as a result of concern for the environment. Emulsions are “more . . . environmen- tally friendly that . . . cut back asphalts” (James 2006). A New Zealand study confirmed this assertion when it found: “Current indications are that chip sealing emulsions typically would be classified as safe . . . ” (Ball et al. 2008). Thus, adding an environmental sustainability factor to the pavement preservation and maintenance decision-making process is both timely and appropriate. Key Definitions The synthesis will use a number of definitions. It is important for the reader to understand the specific definition of each of the terms to gain a full under- standing of the meaning of this study. The most notable key definitions for this work include pave- ment maintenance versus pavement preservation. For this study, the current FHWA definitions for pave- ment preservation and maintenance terminology have been used. These definitions provide the basis of assessment for this synthesis. Pavement preservation is “a program employing a network level, long-term strategy that enhances pavement performance by using an integrated, cost- effective set of practices that extend pavement life, improve safety, and meet motorist expectations” (FHWA 2005). Pavement preservation is comprised of the following activities: • Preventive maintenance is “a planned strat- egy of cost-effective treatments to an existing roadway system and its appurtenances that preserves the system, retards future deteriora- tion, and maintains or improves the functional condition of the system (without significantly increasing the structural capacity)” (FHWA 2005). • Routine maintenance “consists of work that is planned and performed on a routine basis to maintain and preserve the condition of the highway system or to respond to specific conditions and events that restore the high- way system to an adequate level of service” (FHWA 2005). • Minor pavement rehabilitation consists of “structural enhancements made to the existing sections to eliminate age-related, top-down sur- face cracking that develops in flexible pave- ments due to environmental exposure. Because of the non-structural nature of minor rehabil- itation techniques, these types of rehabilita- tion techniques are placed in the category of pavement preservation” (FHWA 2005). 4

Sustainability Impact Factor Areas Measuring environmental sustainability is an emerging field in the transportation industry, and even more so with respect to the pavement mainte- nance treatment selection process. The literature is rife with newly coined terms to describe a given treatment’s impact on the environment (Takamura et al. 2001; James 2006; Ball et al. 2008; Chaignon and Mueller 2009; Lane 2010; Muench 2010). “The terms ‘Green,’ ‘Sustainable Development,’ ‘Environ- mental Impact,’ ‘Energy Efficiency,’ ‘Global Warm- ing,’ ‘Greenhouse Gases,’ and ‘Eco-efficiency,’ are becoming more widely recognized . . . “ (Chehovitz and Galehouse 2010). Unfortunately, each article or manual focuses its evaluation of environmental impact on a different set of impacts. For example, Takamura et al. (2001) coined the term “eco-efficiency” to describe the com- parative analysis of six parameters: virgin material consumption, energy consumption, land use, emis- sions, toxicity, and risk potential. Pittenger’s research (2010) included virgin material consumption, life- cycle cost, and a factor from the Greenroads certifi- cation program (Muench 2010); whereas Chehovitz and Galehouse (2010) confined their analysis to greenhouse gas emissions and energy consumption. Thus, it is difficult to adopt a single, universally rec- ognized term to identify the process of evaluating competing pavement preservation and maintenance treatment options on the basis of relative environ- mental sustainability. The AASHTO Center for Environmental Excel- lence (CEE) provides a basis for identifying and pro- moting environmental excellence in the efficient delivery of transportation services (Kober 2009). The CEE evaluates sustainability parameters by identify- ing focus areas. Consequently, seven sustainability impact factor areas identified by the CEE will be con- sidered in this synthesis. Each one of the areas and how they relate to pavement preservation and main- tenance treatments is described herein. It should be noted that other life-cycle assessment tools such as the ISO 14040 Standard are available and many of these do cite other environmental sustainability impact factors (ISO 2006). However, for the purpose of this synthesis, the seven aforementioned factors have been examined and are described here. 1. Virgin material usage examines reducing the need to use nonrenewable resources. Pavement materials can be expensive and some resources may be limited; therefore, it is important to make good use of available materials. The primary focus of this area is to consider the reduced need for virgin material usage and demand of virgin materials for treatments. Many maintenance treatments involve in-place recycling, which enables re-use of the materi- als already committed to roadways. Prolonging the time between major rehabilitation and reconstruction through proper pavement treat- ment selection is an effective way to reduce vir- gin material usage. 2. Alternative material usage examines the oppor- tunity to recycle materials and to use other materials in the pavement structure during preservation and maintenance. This could mean incorporating reclaimed asphalt pave- ment, recycled concrete aggregate, recycled asphalt shingles, recycled rubber tire, glass, or any other materials that might be appropriate. Proper processing of these materials can result in equivalent performance to virgin aggregate (Infraguide 2005). Careful blending and crushing of recycled materials is required to achieve consistent gradation and performance of the material (Infraguide 2005). 3. Programs for Pavement In-Service Monitoring and Management assists agencies in finding the right treatment for the right pavement at the right time. Robust information systems help determine existing and forecasted pavement conditions so that decisions can be accurately made and funds programmed for network improvements. Pavement in-service monitor- ing and management would consider the life- cycle and associated serviceability of the treatment. 4. Noise is defined as the unwanted or excessive sound associated with pavement construction and improvements. Studies show that the most pervasive sources of noise in the environment relate to transportation. Therefore, noise is examined as an environmental sustainability factor area whereby pavement preservation and maintenance treatments are evaluated on their noise impacts (CEE 2010a). 5. Air quality/emissions examines six principal air pollutants, namely carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide (CEE 2010b). The intent is to assess each pavement preservation and main- tenance treatment in terms of these pollutants. This would involve both calculations for the 5