Using Existing Pavement in Place and Achieving Long Life (2014)

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1This report documents the findings from the second Strategic Highway Research Program (SHRP 2) R23 project, Using Existing Pavement in Place and Achieving Long Life. This project falls within the SHRP 2 Renewal area, which focuses on improving the ability of highway agencies to design and construct long-lasting highway projects with minimal disruption to the traveling public. The project found that construction costs and time can be greatly reduced if the existing pavement can be used in place for part of the rehabilitation solution. The goal of this project was to develop reliable procedures that identify when existing pave- ments can be used in place and what methods are necessary for incorporating the original material into the new pavement structure while achieving long life. SHRP 2 has defined “long- life pavements” as those lasting in service for 50 years or longer without needing major reha- bilitation. This project concentrated on understanding the state of the art of rapid renewal approaches currently used either nationally or internationally to construct long-lived pavement for high-volume roadways. Through literature reviews, industry interviews, international surveys, and extensive inter- actions with numerous state highway agencies (SHAs), this project developed a list of renewal alternatives that use the existing pavement in place. The list of alternatives included not only composite pavement sections but also both flexible and rigid pavements. Project and perfor- mance records from the SHAs and numerous site visits were used to gather valuable information about each renewal alternative. Data on pavement performance captured in the Long-Term Pavement Performance (LTPP) database and detailed analyses of those data using the Mechanistic- Empirical Pavement Design Guide (MEPDG), PerRoad, and other analytical tools were used to evaluate the advantages and disadvantages of each approach under different site conditions and the features critical to achieving long life. From these analyses, criteria on when an existing pave- ment could be used in place were established. The project team also considered situations where modification of the existing pavement structure would be needed before renewal activities to ensure long life. Figure ES.1 shows an unbounded portland cement concrete (PCC) overlay in the state of Washington that is providing excellent performance after 35 years of service. Project Development Guidelines The project team developed a set of decision matrices, organized as tables, to aid highway agen- cies in the identification of renewal strategies. Separate matrices, with associated decision paths, were developed for selecting renewal options for the various, existing pavement types. The deci- sion matrices account for types of deterioration or surface distress in existing pavement, as well as structural response (i.e., deflections), subgrade conditions, and other site-specific constraints. The intent of the decision matrices is to provide a set of feasible long-life alternatives and to include both flexible and rigid pavement renewal options as outputs. Executive Summary

2Additionally, a series of flexible and rigid pavement renewal thickness design tables was established to supplement the decision matrices. These thicknesses provide approximate ranges (or scoping) for long-life pavement designs and are intended as a starting point for project-level design. The design thicknesses were developed based on newer design approaches including the MEPDG, PerRoad, and other analytical tools. Selecting, designing, and constructing an optimal renewal alternative that will achieve long- life performance require attention to detail. While fragments of these details have been addressed in documentation available before the study, a comprehensive set of resources specifically devoted to addressing long-life renewal did not exist. Therefore, this project developed a set of resource documentation that addresses details critical to achieving long life. The documentation addresses long-life concepts at every stage of a project, starting at the assessment stage and continuing through feasible approach selection, design, traffic staging considerations, life-cycle cost analysis, and construction specifications. The following six documents, whose development was part of the study, address each stage of a project. Project Assessment Manual The Project Assessment Manual was prepared to provide a systematic collection of relevant pavement-related data. The manual is meant to complement the design tools developed by the study. The types of data critical for making pavement-related decisions are described along with methods (analysis tools) for organizing the information for decision making. Best Practices for Flexible Pavements and Best Practices for Rigid Pavements The best practices documents for both flexible and rigid pavements provide a collection of best practices for the design and construction of long-life flexible pavement alternatives using existing pavements. Standard practices for added lanes and transitions to adjacent structures are also discussed. Guide Specifications The Guide Specifications document was developed in a format that would allow SHAs to easily make additions or modifications to their existing specifications. The specifications recom- mendations for long life are organized into three sections, which are (1) guide specifications Figure ES.1. Photo of 35-year-old unbonded PCC overlay on I-90.

3for pavement components that are not contained within the American Association of State Highway and Transportation Officials (AASHTO; 2008) Guide Specifications, (2) elements that can be added to or otherwise modify existing AASHTO Guide Specifications, and (3) summaries for relevant SHAs and AASHTO specifications that were used to produce the “elements” in item 2. Life-Cycle Cost Analysis Most public agencies have specific procedures in place for life-cycle cost analyses, and it is expected that those agencies will follow those procedures. For any agency that does not have a specific procedure in place, the team provided a general discussion of life-cycle cost analysis in the Life-Cycle Cost Analysis document. Emerging Technology The document on emerging technology discusses rigid and flexible pavement technologies that are not yet considered to be long life renewal options but that may become so in the future as field performance is accrued. Interactive Software To provide a user-friendly means of navigating the large amount of information, and to auto- mate the use of the decision matrices and thickness design tables, a computer-based application that guides the users through the process was established. A screenshot of the opening screen is shown in Figure ES.2. Product Validations All of the products and tools described above were developed in close consultation with several SHAs. Specifically, extensive interaction took place with seven agencies: Illinois Tollway Author- ity, Michigan Department of Transportation (DOT), Minnesota DOT, Missouri DOT, Texas DOT, Virginia DOT, and Washington DOT. A series of visits were made to each agency over the Figure ES.2. Opening screen from the interactive software.

4course of the project to obtain information and solicit feedback on the products. These visits were typically structured as follows: • Kick-off meetings. The objectives and preliminary findings of the project were discussed. Addi- tionally, field visits were made to multiple renewal projects throughout each agency. Relevant project information was obtained from agency records. • Test case meetings. These meetings focused on soliciting feedback regarding the decision matrices and thickness design tables, as well as the resource documentation. Access to the beta version of the interactive software was provided along with presentations explaining the devel- opment and use of the software. Coordination with each agency took place to identify and obtain information for one project to be used as a test case. This test case was used to compare the agency’s standard design approach for pavement renewal with the recommendations pro- vided by the new guidelines. In many cases, a field visit to the project was made to conduct a visual assessment of the site and capture photographs of the pavement and drainage features. A design report using the guidelines and interactive software was developed for the test case, which included feasible flexible and rigid pavement renewal strategies. The results were com- pared to the agencies’ standard design approach for the project. The Virginia and Washington test cases both included analyses of construction productivity, lane closure alternatives, and traffic impacts using the CA4PRS software. The test-case comparisons generated valuable feedback from the agencies. • Workshops. The team organized and facilitated one pilot workshop in Washington and two regional workshops in Virginia and Missouri. The workshops were attended by representative departments within the agency, as well as local contractors and industry representatives. Adja- cent state agency personnel were invited to attend the regional workshops. Near the end of each workshop, each participant was asked to complete a questionnaire. Overall, the partici- pants viewed the guidelines as valuable and useful. In particular, the resource documentation was viewed by attendees as providing excellent content for pavement designers. All of the comments received were reviewed and addressed in the final guidelines. Through these visits, meetings, workshops, and interactions, the community vetted the prod- ucts developed under this study, and they form a practical set of tools for pavement engineers and designers. Implementation and Recommended Research The guidelines that this project developed provide a single source of current information on a comprehensive list of approaches that an agency can reasonably apply to design and build pave- ments that use existing pavements in place and achieve long life. The products were placed in an interactive program to facilitate use and implementation. The guidelines are unique in that they not only address the design approaches but also provide guide specifications that are congruent with those approaches. To enhance implementation, this product should be housed on the web to ensure accessibility to the pavement community. Recommended future enhancements include modifying the guidelines and resource documents to include design lives of less than 50 years and enhancing the interactive software. Such enhancements would include the addition of a self- directed tutorial and conversion of static documents like the Project Assessment Manual, Guide Specifications, and best practices into a content management system with cross-linked pages to aid in accessibility and to improve search capabilities of the documentation.