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. These tests are intended to assess how well the mixture resists common forms of distress. However, BMD lacks consideration of the issues associated with asphalt mixtures produced at production facilities and the effects of placement. Also, there is no widely accepted framework for identifying the combinations of performance tests and procedures for the different applications. There is a need to enhance the BMD process and develop a framework that addresses design, production, and placement of balanced asphalt mixtures. Such a framework should help highway agencies and other organizations evaluate and select balanced asphalt mixtures for use in pavement structure. 

OBJECTIVE

The objective of this research is to develop a framework for design, production, and placement of balanced asphalt mixtures. The framework shall focus on enhancing the BMD design process, address the different applications of asphalt mixtures, and delineate the set of performance tests and procedures required for each application. Also, the framework shall address the different applications of asphalt mixtures and delineate the set of performance tests and procedures required for each application.

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 performance tests addressing failure modes and procedures (e.g., sampling, aging) that can be used for the design, production, and placement of asphalt mixtures in different applications. This information may be obtained from published and unpublished sources, and from public and private organizations.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, evaluate the adequacy of available performance tests and procedures for developing a framework for design, production, and placement of balanced asphalt mixtures. Identify the deficiencies and recommend a process for addressing these deficiencies to support the development of a rational framework for further consideration/investigation in Phase II. 

Task 3. Based on the evaluation performed in Task 2, prepare an updated, detailed work plan to be executed in Phases II and III that includes approaches to (1) developing a framework for design, production, and placement of balanced asphalt mixtures and (2) preparing supplementary material to support adoption and implementation. It is expected that the work plan will include an experimental investigation to obtain the data needed for developing the framework.

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 plan approved in Task 4. Based on the results of this work, prepare and submit a predraft version of the proposed framework for design, production, and placement of balanced asphalt mixtures. Following NCHRP review of the predraft framework, 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 framework is reviewed and the Phase III work is authorized by the NCHRP. 

PHASE III

Task 6. Review and consider the comments on the predraft proposed framework and prepare a draft version of the proposed framework.

Task 7. Illustrate use of the framework developed in Task 6 with examples of different applications and identify means to facilitate its implementation.

Task 8. Prepare material, in a PowerPoint or other format, for use in webinars and presentations to facilitate implementation and use of the framework.

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

Task 10. Prepare and submit (1) a draft final deliverable that documents the entire research effort and includes (a) a research report documenting the work performed in the project and used to develop the framework, (b) the proposed framework, (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.