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Pavement Preservation Best Practices Technical Briefs
AdvisorHajj, Elie Y.
Civil and Environmental Engineering
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Preservation treatments are used throughout the United States to mitigate the aging and degradation of pavements. These treatments should be designed to obtain maximum life and for this to occur, the treatments must be designed and constructed properly. This project summarizes current Quality Assurance “best” practices used by selected state transportation agencies to construct chip seal, slurry seal, micro surfacing and thin lift asphalt overlay preservation treatments. These practices, when followed, can result in long-lasting and high-quality treatments, hence the term “best”. There were several identified similarities between the treatments, particularly the micro surfacing and slurry seal treatments. This is not unexpected, as micro surfacing treatments are considered to be a more specialized slurry seal. Some similarities included asphalt binder selection, aggregate gradation, mix design method and verification, equipment and construction inspection and Quality Assurance requirements. Many agencies did not specify seasonal construction limits for construction, even ones that experience drastic changes between seasons. Thus, specific dates should be set to increase treatment performance. All of the selected agencies had Quality Assurance requirements of varying degrees of detail. This is important, as the main goal of this project is to determine Quality Assurance best practices.Interestingly, there is an appreciable difference in specification practices with changes in climate zones. This is also expected, as different climates present different construction challenges. The main practice that showed this difference was in asphalt binder selection—emulsions vs. PG grades. Other differences were observed in the equipment specification requirements, particularly in the calibration requirements. Some agencies have extensive details, and others were broad in detail. Another important difference was observed in the inspection processes followed by each of the agencies for all four treatments. The main differences were in test strip requirements and areas of the construction process that were to be inspected. Some agencies did not require test strips at any time during a project, whereas others required test strips before and even during construction. Finally, All of these similarities and differences help to illustrate that there are several items that must be used when considering what constitutes a “best” practice. Thus, some of these practices were common to the agencies, and others were unique to one agency. By selecting a broad range of practices, both common and unique, one can achieve a well-rounded synthesis that truly can be applied everywhere.