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

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38 C h a p t e r 4 There are obvious benefits to using existing pavements in the construction of long-life pavements. A more rapid construc- tion process can be achieved because it eliminates the need for removal of material from the project and reduces or elim- inates the importation of base aggregates. This type of con- struction can also facilitate traffic staging through the project. This results in reduced construction duration, as well as costs and impact on the traveling public. The guidelines developed in this project provide a range of approaches for the design and construction of long-life pavements using existing pavements. Most agencies used one or more of the approaches identified, but none were found to use all of the approaches identified in this project. A large number of agencies were contacted both nationally and internationally in the development of the guidelines. Some of the agencies that were contacted had tried one or more of the approaches identified and had experienced con- struction problems, which caused them to not consider that approach in future work. In working with the different agen- cies, it became clear that the details related to the success or failure of these processes must be provided in some form of knowledge base. The old adage that “the devil is in the details” applies fully to the use of existing pavements to construct long-life pavements. As such, much of the effort in Phase 2 of this project was devoted to the development of that knowl- edge base. The decision matrices that were developed (and refined through the help of the industry and various agencies’ review) are quite detailed. To facilitate the flow and simplify the use of the matrices, an Adobe Flash–based program was devel- oped. The program also provides the platform on which to place the knowledge base that supports the decision-making process. That knowledge base was separated into six specific documents: • Guide, Chapter 1—Project Assessment Manual; • Guide, Chapter 2—Flexible Pavement Best Practices; • Guide, Chapter 3—Rigid Pavement Best Practices; • Guide, Chapter 4—Guide Specifications; • Guide, Chapter 5—Life-Cycle Cost Analysis; and • Guide, Chapter 6—Emerging Pavement Technology. The Project Assessment Manual contains two unique sec- tions. The Construction Productivity and Traffic Impact sec- tion will be extremely useful because most of the projects considered in these guidelines have a significant traffic-staging component to them. Additionally, the Life-Cycle Assessment section discusses the current approaches to environmental accounting, which is becoming an added consideration in today’s highway program. The guidelines developed under this project provide a single source of current information on all approaches that an agency can reasonably use to design and build long-life pavements utilizing existing pavements. The products from this project offer all of the resources in one location. The guidelines are also unique in that they not only address the design approaches but also provide guide specifications that are congruent with those approaches. The material presented will become dated; thus, the guidelines should be reviewed in about 5 years and updated as needed given advances in the industry. Suggested research The guidelines were produced under a contract that defined “long life” as referring to pavements that provide 50 years of service. Although this is an admirable goal, most agencies that the project team interviewed do not design pavements for 50 years of service. The more typical design life was for about 30 years. In Europe and the United Kingdom, long-life pavement designs are for 30 to 40 years. The one comment that the team heard often was “If we designed for 50 years of service this would be a very good resource,” implying that the guidelines had limited use. All agencies also had funding Conclusions and Suggested Research

39 issues, so the full application of the guidelines was also limited because of the current funding levels. The design process in the guidelines is not restricted to 50 years. The program allows the user to compute traffic load- ing ranging from 30 to 50 years. The decision matrix, however, does not include some approaches that could provide 30 to 40 years of service. The team clearly felt that if the guidelines were shown as providing guidance for long-life pavements (with long-life pavements defined as those that provide 30 to 50 years of service), more agencies would use them. It is recommended that the guidelines be modified to provide design guidance for 30- to 50-year service lives. The bulk of the information contained in the guidelines would not change. The major change would be in the decision matrix to include several applications that were eliminated because they would likely provide only 30 to 40 years of service. These would include bonded portland cement con- crete (PCC) overlays, as well as hot-mix asphalt overlays of continuously reinforced concrete pavement (CRCP). There would also be additional material placed in the best practices documents to describe the design and construction of those approaches. The Guide Specifications would be updated to include guide specifications unique to the construction of those added approaches. There would be little actual change in the guidelines, but it is felt that there would be a percep- tion by many agencies that the guidelines were developed for their use, not just for those few agencies that designed for 50 years. To account for the 30- to 40-year design lives, the following actions are proposed: • Revise decision tables to include bonded PCC overlays and asphalt concrete overlays of CRCP and add design thick- ness estimate tables to match added approaches. • Circulate revised decision tables to agencies and industry for review. • Finalize decision tables based on review comments. • Revise best practices documents and guide specifications to account for added options. • Circulate revised documents to agencies and industry for review comments. • Finalize documents based on review comments. • Revise program based on changes. • Conduct a beta test of the revised program with participat- ing agencies. • Prepare addendum to final report to document revisions. Those agencies that participated in Phase 2 would also be asked to work on the revisions to the guidelines. Those agen- cies would be asked to comment on the revisions and then on the revised program. A workshop or two may be required to help focus the process. Implementation Fully Web-Enable the Guidelines The R23 program application was originally designed for self-contained delivery via CD to minimize the up-front cost and promote rapid development, but ultimately this design has limited its functionality as to the broader use, support, and maintenance of the program: • User inputs and results are not stored, meaning users do not have the ability to “load” or “save” user input and appli- cation outputs to reproduce guidance, compare results between scenarios, or share with colleagues. Once the appli- cation is closed, all inputs and results are lost. • Documentation is not cross-linked, limiting the full effec- tiveness of the information provided. For example, cross- linking would allow the reader to move easily from sections in the best practices to appropriate sections in either the Project Assessment Manual or the Guide Specifications. This will significantly improve access to the information and the utility of the program. • Application and documentation are not indexed or search- able, limiting search engine recognition and ultimately exposure to potential users. • Increased long-term maintenance and support cost would be reduced because the current program has a disconnected distribution environment and dependency on Adobe AIR and Flash framework compilation for any development updates. To promote the implementation of the application and research results, it is recommended that further work be done to improve the functionality of the guidelines. Because of funding and time limitations during this project, the docu- ments that reside on the current program were prepared in MS Word and housed on a host server in PDF format for access by the users. They were developed, however, with the view that the content could be reformatted so that there would be cross connections between the various sections within the documents to increase their utility. Based on feedback from the pilot group of users and the experience of the R23 team, it is recommended that the R23 application be moved into a web-based application with the following elements: • Develop database and security elements to provide users the ability to load, save, and compare various individual application results within their organization. • Convert static documents such as the Project Assessment Manual, guide specifications, and best practices into a con- tent management system with cross-linked pages to aid in accessibility, reduce maintenance costs, and improve search capabilities of the documentation.