BACKGROUND

Balanced mix design (BMD) of asphalt mixtures is an approach that addresses different modes of distress through mechanical tests on conditioned specimens that consider mix aging, traffic, climate, and location within the pavement structure. However, mix-aging protocols incorporated in BMD are not practical for use in quality assurance where quick results for plant-produced mixtures are required. There is a need to address the challenges of incorporating aging methods and their effects in quality assurance and develop guidelines for incorporating these effects on BMD for quality assurance. Such guidelines should help highway agencies and other organizations with developing quality-assurance programs that incorporate aging effects on BMD.

OBJECTIVE

The objective of this research is to develop guidelines for incorporating aging effects on BMD for quality assurance.

Accomplishment of the project objective will require at least the following tasks.

TASKS

PHASE I

Task 1. Collect and review relevant domestic and foreign literature, research findings, and information relevant to the effects of aging on BMD test results and their consideration in quality assurance. This information may be obtained from published and unpublished information and contacts with public and private organizations.

Task 2. Based on the review performed in Task 1 identify and evaluate (1) asphalt-mixture factors that influence aging and (2) the aging methods currently used for BMD and their applicability for use in quality assurance. Identify and evaluate the challenges associated with the use of aging methods on BMD tests for quality-assurance applications (e.g., using aging-correction factors) and identify the challenges recommended for consideration in Phase II to produce viable information on the effects of aging on performance to support the development of rational guidelines for incorporating aging effects on BMD for quality assurance.

Task 3. Based on the work performed in Task 2, prepare a detailed work plan to be executed in Phase II and Phase III to (1) address the challenges recommended for further consideration and prepare draft language for consideration by AASHTO to incorporate the research results into a future edition of the AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing, and AASHTO Provisional Standards (herein called Proposed Guidelines) and (2) prepare supplementary material to support adoption and implementation. The plan shall provide specific information on the different aspects of the proposed work. It is expected that the work plan will include an experimental investigation.

Task 4. Prepare an interim report that documents the research performed in Tasks 1 through 3. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the NCHRP 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. The decision on proceeding with Phase II will be based on the contractor’s documented justification of the updated work plan.

PHASE II

Task 5.  Execute the Phase II work plan approved in Task 4. Based on the results of this work, prepare and submit a predraft version of the Proposed Guidelines. Following review of the predraft Proposed Guidelines by the NCHRP, the research team will be required to make a presentation to the NCHRP project panel. Work on Phase III of the project will not begin until the predraft Proposed Guidelines are reviewed and the Phase III work is authorized by the NCHRP.

PHASE III

Task 6. Review and consider the comments on the predraft Proposed Guidelines and prepare a draft version of the Proposed Guidelines.

Task 7. Illustrate applicability of the Proposed Guidelines by examples using data from state departments of transportation or industry.

Task 8. Prepare presentation material, in a PowerPoint or other format, for use in webinars and presentations to facilitate the use and adoption of the Proposed Guidelines.

Task 9: Prepare a stand-alone technical memorandum titled “Implementation of Research Findings and Products” to facilitate implementation of the Proposed Guidelines.

Task 10. Submit (1) a draft final deliverable that includes (a) a research report documenting the work performed in the project and used to develop the Proposed Guidelines, (b) Proposed Guidelines, (c) the examples, (d) the presentation material, and (e) the implementation plan and (2) a final deliverable that addresses the review comments.

STATUS: Contract pending.