Best Practices for Crack Treatments for Asphalt Pavements (2014)

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2C H A P T E R 1 Purpose of This Report Reportedly the first asphalt pavement was built in about 1828—the National Road between Wheeling, West Virginia, and Zanesville, Ohio (73) {numbers in parentheses are refer- ences in the Bibliography of the report}. Although undocu- mented, it is likely that within a few years of construction of this first asphalt pavement, engineers began to discuss what to do about cracking in the pavements. Cracks are prevalent throughout the approximately 2.5 million miles of paved roads in the United States. The National Cooperative Highway Research Program has published two previous documents on the subject of crack sealing, NCHRP Report 38 by Cook and Lewis in 1967 (29) and NCHRP Synthesis 98 by Peterson in 1982 (60). Crack seal- ing and crack filling are widely used maintenance activities for in-service pavements. The techniques are inexpensive, quick, and well-proven approaches to extend the life of the pavement, predicated on the use of the right materials at the right time using the right protocols. Select the right preventative maintenance treat- ment at the right time for the right road. —Jim Sorenson, quoted by Paul Fournier in Associated Construction Publications (77) In a memo from David Geiger in September 2005 (62), the Federal Highway Administration (FHWA) describes a Pavement Preservation program as consisting of Preventa- tive Maintenance, Pavement Rehabilitation (structural and non-structural), and Routine Maintenance activities. The following definitions were quoted in the Geiger memo and were developed by the FHWA Pavement Preservation Expert Task Group (ETG), the AASHTO Standing Committee on Highways, and the AASHTO Highway Subcommittee on Maintenance. • Pavement Preservation is defined as “a program employing a network level, long-term strategy that enhances pave- ment performance by using an integrated, cost-effective set of practices that extend pavement life, improve safety and meet motorist expectations.” • Preventative Maintenance is defined as “a planned strategy of cost-effective treatments to an existing roadway system and its appurtenances that preserves the system, retards future deterioration, and maintains or improves the functional condition of the system (without significantly increasing the structural capacity).” • Pavement Rehabilitation is defined as structural and non- structural “enhancements that extend the service life of an existing pavement and/or improve its load carrying capacity.” • 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 highway system to an adequate level of service.” FHWA published the guidelines presented in Table 1-1 for the determination of the type of maintenance to be performed (53). These guidelines establish criteria for when to use crack treatments. FHWA categorizes crack sealing as Preventative Mainte- nance and crack filling as Routine Maintenance. Ponniah (34) also describes a crack sealing program as a preventative main- tenance treatment, not a corrective maintenance measure, thereby agreeing with the FHWA definitions. Chong and Phang (35) describe the consequences of not sealing cracks: 1. Increased maintenance costs, because deteriorated cracks are difficult and expensive to repair through corrective maintenance; Introduction

3 2. Increased user costs (vehicle repair and operation); 3. Increased rehabilitation costs, because deteriorated cracks demand special treatment from the designer when pave- ment rehabilitation is scheduled; and 4. Loss of serviceability and, therefore, service life. Crack sealing and crack filling are widely used for preven- tative maintenance of asphalt pavements; however, success- ful crack sealing and crack filling applications continue to be perceived as an art. When not properly applied, these pave- ment preservation treatments can result in early failures and costly corrective maintenance for user agencies. Scope of Work The objective of any crack sealing or crack filling operation is to minimize the intrusion of water into underlying layers of the pavement structure. Such water intrusion weakens the base materials and may lead to structural pavement failures. Much research has been performed in the United States and abroad on the materials and designs for crack sealing and crack filling for flexible pavements; however, little is known about variability in the current state-of-the-practice regard- ing construction techniques and the resulting effectiveness of crack sealing and crack filling. This report summarizes the state-of-the-art and state-of-the-practice of crack sealing and crack filling and concludes with current best practices. This report is limited to crack sealing and crack filling of asphalt pavements, and does not consider joint filling on concrete pavements, reflective cracking retardation techniques, joint construction techniques, or other related issues. The 1967 NCHRP Report 38 on crack sealing stated: “Crack sealing is receiving very little engineering attention. Most cracks are simply filled occasionally with a tar or an asphalt” (29). This statement is still true in some jurisdictions. Nebraska Department of Roads Pavement Maintenance Manual (82): “Crack filling and sealing is our first line of defense in roadway maintenance. Crack sealing should be done within 2 years after an asphalt overlay.” “At a time when highway crew manpower is shrinking, along with the funds to support road maintenance, crack sealing stands out as an economical maintenance technique.” The literature review for this project is summarized in Chapter 2: State-of-the-Art in Crack Treatments. The intent of this project was to develop a Best Practices document. As such, the goal of the literature review is primarily to estab- lish the state-of-the-art, not to be all-inclusive on all research conducted on crack sealing and crack filling. Chapter 3: State-of-the-Practice in Crack Treatments was developed through the use of a survey sent to maintenance engineers and material suppliers. Approximately 150 responses were received from multiple levels of agency personnel (city, county, state, federal), along with a few private-sector practi- tioners. The state-of-the-practice provides insight into current techniques for crack sealing and crack filling. Finally, Chapter 4: Best Practices for Crack Treatments presents the techniques and protocols necessary to achieve good performance from crack sealing and crack filling opera- tions. Variations between the state-of-the-art and the state- of-the-practice exist, as would be expected. The development of best practices emphasizes proper procedures in the hope of improving the state-of-the-practice. Crack Density Average Level of Edge Deterioration (% of crack length) Low (0-25) Moderate (26-50) High (51-100) Low Do Nothing Do Nothing or Crack Treatment Crack Repair Moderate Crack Treatment Crack Treatment Crack Repair High Surface Treatment Surface Treatment Rehabilitation Table 1-1. Guidelines for determining the type of maintenance to be performed (53).