BACKGROUND

Balanced mix design (BMD) of asphalt mixtures is an approach that addresses different modes of distress through performance tests on conditioned specimens that consider mix aging, traffic, climate, and location within the pavement structure. Results of these performance tests are expected to reflect their sensitivity to the variations in mixture constituents and methods of test (herein called mix and test variables). However, limited information is currently available to demonstrate sensitivity of the results of BMD performance tests to these variations.  Research is needed to acquire the necessary information and determine the sensitivity of test results to the variations in mix and test variables. This information should improve applicability of the BMD process and help highway agencies and other organizations with its implementation.

OBJECTIVE

The objective of the research is to determine the sensitivity of the results of BMD performance tests to the variations in mix and test variables. 

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

TASKS

PHASE I

Task 1. Collect and review domestic and foreign literature, research findings, and information relevant to the effects of mix constituents (e.g., recycled material, binder quantity and quality, aggregate type and gradation) and methods of test (i.e., mix and test variables) on BMD test results for laboratory and plant-produced mixtures. This information may be obtained from published and unpublished sources and from public and private organizations.

Task 2. Based on the review performed in Task 1, identify and evaluate mix and test variables that impact BMD test results. Based on this evaluation, identify the mix and test variables recommended for consideration/investigation in Phase II to support the sensitivity evaluation.

Task 3. Based on the work performed in Task 2, prepare a detailed work plan to be executed in Phases II and III that includes approaches to (1) addressing the recommended mix and test variables and determining the sensitivity of the results of BMD performance tests to their variations and (2) preparing supplementary material to support implementation. The plan shall provide specific information on the different aspects of the proposed work.  

Task 4. Prepare an interim report that documents the research performed in Tasks 1 through 3. Following NCHRP review of the interim report, 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 (1) detrmine the senitivity of the results of BMD performance tests to the variations of mix and test variables, (2) recommend means for using the research findings to facilitate implementation of the BMD process, and (3) prepare and submit a technical memorandum summarizing the findings of the sensitivity evaluation and the recommendations for facilitating implementation. Following NCHRP review of the technical memorandum, 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 memorandum is reviewed and the Phase III work is authorized by the NCHRP.  

PHASE III

Task 6. Review and consider the comments on the technical memorandum and prepare a draft report documenting the research performed in the project.

Task 7. Prepare presentation material, in a PowerPoint or other format, for use in webinars and presentations to facilitate use of the research findings. T

Task 8. Prepare a stand-alone technical memorandum titled “Implementation of Research Findings and Products” to facilitate implementation of the research findings.

Task 9. Submit (1) a draft final deliverable that includes (a) a research report documenting the research performed in the project, (b) the presentation material, and (c) the implementation plan and (2) a final deliverable that addresses the review comments.

STATUS: Contract pending.