BACKGROUND: The properties of asphaltic binders used in preservation surface treatments are very important to the performance of the treatment in which they are used. However, asphaltic binders used in such treatments are often selected based on availability and other factors that are not necessarily related to the performance of the final product. Often distress, such as stripping and raveling of these treatments, can be traced directly to improper binder selection and use. Clearly, proper binder selection is necessary for attaining desired performance. Performance-related specifications (PRS) that specify quality in terms related to long-term performance will help in the selection of the proper binder for a specific application. Although such PRS have been developed for the constituents of hot-mix asphalt mixtures used in pavements, PRS are not readily available for binders used in preservation surface treatments. Therefore, research is needed to (1) evaluate existing binder tests and, if necessary, identify new tests that relate to performance and (2) develop PRS for preservation surface treatments that provide a direct relationship between key quality characteristics of asphaltic binders and performance. These specifications will help highway agencies specify binder characteristics that will provide the desired performance of preservation treatments.
OBJECTIVE: The objective of this research is to develop recommended performance-related specifications (PRS) for asphaltic binders used in preservation surface treatments. For the purpose of this research, preservation surface treatments are treatments that are applied to a large surface area of an existing roadway to slow future deterioration and maintain or improve its functional condition (without increasing structural capacity) such as chip seals, microsurfacing, and slurry seals.
TASKS: Accomplishment of this objective will require at least the following tasks.
Phase I: (1) Collect, review, and summarize information relevant to asphaltic binders used in preservation surface treatments (see Special Note A). This information may be obtained from published and unpublished reports, contacts with public- and private-sector agencies, industry organizations, and other domestic and foreign sources. (2) Identify the performance parameters of surface treatments (e.g., stripping, raveling, etc.) that are influenced by binder properties. (3) Identify and evaluate short-term and long-term inder properties that influence constructibility and performance of surface treatments, and recommend binder properties for use in developing PRS. Also, identify existing test methods that can be used for determining these properties or recommend new test methods for development in Phase II if appropriate. (4) Prepare an updated, detailed work plan for developing PRS using the binder properties and test methods recommended in Task 3. The plan shall include short-term validation using data from in-service projects. (5) Prepare an interim report that documents the research performed in Tasks 1 through 4. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the project panel. Work on Phase II of the project will not begin until the interim report is approved and the Phase II work plan is authorized by the NCHRP.
Phase II: (6) Execute the work plan proposed in Task 4 and approved in Task 5. Based on the results of this work, prepare the recommended PRS for asphaltic binders used in preservation surface treatments. (7) Prepare a plan for long-term validation of the recommended PRS using in-service projects .(8) Submit a final report that documents the entire research effort. The recommended PRS shall be prepared as a stand-alone document suitable for consideration and adoption by AASHTO; the plan for the long-term validation of the recommended PRS shall be presented as an appendix.
STATUS: Work is progressing at a substantially slower rate than expected; completion is expected by the end of July 2015.