Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments (2021)

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4 Overview Most state departments of transportation (DOTs) use pavement preservation practices as part of their process of managing pavements. In recent years, federal requirements for state agencies to develop transportation asset management plans (TAMPs) further promoted the importance of pavement preservation and led to its increased use and application. For example, the Illinois DOT TAMP states that it intends “to increase the use of pavement preservation treatments . . . to help control costs and extend the useful lives of existing transportation assets” (Illinois DOT 2019), while the Nevada DOT TAMP proposes “a proactive preservation strategy that increases the amount of preservation activities” and describes its function as “maintenance and preserva- tion strategies to extend a pavement’s service life to defer the need for rehabilitation” (Nevada DOT 2019). At the network level, the impacts of pavement preservation are broadly acknowledged to include benefits such as extending pavement life, enhancing system performance, reducing operation and maintenance costs, and improving safety. However, no two programs are iden- tical, and the following are some of the conditions that lead to differences among preservation practices: • Overall condition of the pavement network. • Environmental conditions. • Traffic loading. • Available materials. • Contractor capabilities. • Local preferences. • Available funding. At the project level, in addition to depending on good project and treatment selection, the success of a pavement preservation application hinges on factors specific to that project, such as inclement weather during or immediately after construction, the skill of the construction crew putting down the treatment, and the compatibility and quality of materials used on the job. One project-level factor is common to the long-term success of almost every preservation project: the extent to which necessary maintenance and surface preparation actions are effec- tively completed prior to application of the treatment. For example, before an asphalt pavement edge-to-edge treatment (such as a chip seal, microsurface, or thin bonded wearing course), crack sealing, partial- and full-depth patching, and surface profile corrections may be required. Similarly, for concrete pavements, diamond grinding may be preceded by partial- or full-depth repairs (followed by joint resealing). If needed pre-preservation maintenance activities are not performed, the expected benefits from applying a preservation treatment are unlikely to be fully realized. C H A P T E R   1 Introduction

Introduction 5   Many references cite the performance of specific pavement preservation treatments, focusing on treatment life or extension to pavement life, but very little information is available on combining preservation treatments with maintenance activities performed in advance of the treatment to ensure its success. Although such pre-treatments are not always necessary, where they are advised, they become an integral part of a successful pavement preservation project. The absence of available information on the combination approach represents a primary reason for the development of this synthesis report. Synthesis Objectives This synthesis documents the types of maintenance and surface preparation activities that DOTs conduct before pavement preservation treatments are applied. Its purpose is conveying how agencies address maintenance and surface preparation needs prior to pavement preserva- tion by exploring the following topics: • Types of maintenance and surface preparation prior to preservation on flexible- and rigid- surfaced pavements. • Methods to identify the need for maintenance and surface preparation. • Techniques to complete the maintenance and surface preparation. • Agency practices to track maintenance and surface preparation. The following three approaches were used to collect the information presented in this synthesis: • A literature review. • An electronic survey of DOT practices, distributed to the voting members of the AASHTO Committee on Maintenance. • Follow-up telephone interviews with selected agencies. Terminology “Maintenance,” “surface preparation,” and “preservation” are key terms used throughout this document, and they have different meanings for different agencies. As part of the instructions to survey recipients (Appendix A), the following definitions were provided, not to supplant existing definitions or to create new definitions but rather to strive for a consistent understanding (and they are repeated here with the same goal): • Pavement maintenance: actions taken to slow the rate of pavement deterioration by correcting specific pavement defects; examples include crack sealing and patching. In the context of pavement preservation and this project, the focus is on maintenance activities undertaken to improve the performance of a preservation treatment and not those applied as a band-aid or stopgap treatment. • Surface preparation: actions taken on an existing pavement surface to improve smoothness, geometrics, cross-slope, or bond, prior to the application of subsequent edge-to-edge treat- ment. Examples of surface preparation include milling or micromilling, diamond grinding, and rut filling. They do not include actions that are part of the treatment construction process, such as sweeping or applying a tack coat. • Pavement preservation treatment (also referred to as preventive maintenance treatment): a product applied to an existing pavement to prevent, delay, or slow the progression of pavement distresses, and to correct or restore surface characteristics such as smoothness and friction, without adding structural capacity. Examples of pavement preservation treat- ments for flexible pavements include chip seals, micro surfacings, and thin (usually less than

6 Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments 1.5 inches thick) overlays, while examples for rigid pavements include diamond grinding and load-transfer restoration. Surface preparation prior to thicker overlays, including structural overlays, is not considered as part of this synthesis. An available NCHRP synthesis report covers that topic (Tenison and Hanson 2009). Report Organization In addition to this introductory chapter, this synthesis report is organized into the following chapters and content. Chapter 2 – Literature Review A literature review identified maintenance and preservation practices and associated pre- treatment activities documented in various studies and reports. The literature search used the following key terms: • Maintenance and pavement preservation treatments. • Maintenance before pavement preservation treatments. • Surface preparation and maintenance before pavement preservation treatments. • Combination pavement preservation treatments. • Maintenance operations and pavement preservation. • Timing of pavement preservation applications. • Sequence of pavement preservation treatments and application. • Timing of pavement maintenance. • Pre-treatment and pavement preservation. No specific time limit was placed on the search, but most of the references were from 2005 or thereafter. Chapter 3 – State of the Practice A survey of practice was carried out by distributing an electronic questionnaire to the AASHTO Committee on Maintenance voting members from each of the 50 state DOTs. Appendix A rep- licates the questionnaire. The responses to the questionnaire are presented in Chapter 3. Ulti- mately, 45 of the 50 agencies returned the survey; a summary of the responses is included in Appendix B. The discussion of results is organized into the following topic areas: • Typical practices for flexible pavements. • Typical practices for rigid pavements. • Identification of the need for maintenance or surface preparation prior to preservation. • Performance of maintenance or surface preparation before preservation. • Quantification of the effects of maintenance or surface preparation prior to preservation. • Policies and programs connecting maintenance or surface preparation to preservation. Within each topic area, questionnaire results are analyzed. Chapter 4 – Agency Case Examples Based on questionnaire results, state DOTs were identified that could share more information about the practices associated with maintenance and surface preparation prior to preservation. Information collected during interviews with those organizations provides greater detail on the

Introduction 7   processes and practices for identifying, completing, and tracking maintenance and surface prep- aration prior to pavement preservation. Each case example includes sections addressing the following topics: • Agency’s pavement preservation background. • Determination of the need for maintenance or surface preparation. • Practices in completing or contracting for maintenance or surface preparation. • Tracking of maintenance and surface preparation actions. This chapter includes the reasons for selecting the state DOTs that were interviewed. Chapter 5 – Conclusions The final chapter summarizes the overall findings from each of the sources of information presented in Chapters 2, 3, and 4 and offers recommendations for future research. Appendices The following appendices are included: • Appendix A: Questionnaire. • Appendix B: Summary of Received Questionnaire Responses.