BACKGROUND: Variability is inherent in all pavement materials and construction processes; this variability influences pavement quality and performance. Examples of such variability are found in the properties of asphalt pavement materials (e.g., binder content, aggregate gradation, mix volumetrics, and in-place density), the properties of concrete pavement materials (e.g., strength, air content, thickness, and permeability), as well as smoothness of asphalt and concrete pavements.

Observed variability of pavement material properties is influenced by mix design practices, test equipment and methods, material processing and construction practices, use of recycled materials, state departments of transportation specifications, and asphalt and concrete performance tests. Quantifying the magnitude of variability of pavement materials and construction processes is needed to establish its effect on long-term performance. However, there is no widely acceptable procedures or guidelines for quantifying variability in the quality characteristics used for acceptance of asphalt and concrete pavements.

There is a need to identify the procedures currently available for estimating variability in quality characteristics, develop procedures that better address the different applications and related issues, and prepare guidelines for the application of these procedures. These procedures and accompanying guidelines should help construction and materials engineers and paving contractors in enhancing quality assurance programs and construction practices and improve pavement performance.

 OBJECTIVES: The objectives of this research are to (1) recommend procedures for quantifying variability in the quality characteristics used for acceptance of asphalt and concrete pavements and (2) prepare guidelines for their application in quality assurance programs.

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

TASKS

PHASE I: (1) Collect and review information on current practices relevant to the procedures for quantifying variability in the quality characteristics used for acceptance of asphalt and concrete pavements (e.g., material processing, construction practice, and quality measures). This information may be obtained from published and unpublished information and contacts with public and private organizations involved in pavement construction. (2) Evaluate the procedures identified in Task 1, identify potential procedures, and recommend modifications of existing procedures and new procedures that merit evaluation in Phase II. It is anticipated that these procedures will involve statistical analyses and other approaches. (3) Develop a research plan for work to be executed in Phase II to (a) further evaluate the potential, modified, and new procedures identified in Task 2; (b) identify and develop recommended procedures for quantifying variability in the quality characteristics used for acceptance of asphalt and concrete pavements; and (c) prepare guidelines for their application in quality assurance programs. (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 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: (5) Execute the plan approved in Task 4. Develop the procedures for quantifying variability in the quality characteristics used for acceptance of asphalt and concrete pavements and related guidelines. (6) Using the procedures developed in Task 5, prepare examples to illustrate use of the guidelines for different scenarios, and prepare a technical memorandum titled “Implementation of Research Findings and Products” to facilitate implementation of the developed procedures and guidelines. (7) Prepare presentation material in a PowerPoint or other format to facilitate implementation and use of the developed procedures and guidelines. (8) Prepare a final deliverable that documents the entire research effort. Deliverable will include (a) a research report documenting the work performed in the project and used to develop the procedures and guidelines; (b) the guidelines as a standalone document; and (c) a technical memorandum on implementation of research findings and products as a separate document. The procedures developed in Task 5 shall be presented as an appendix to the research report, and the examples presented in Task 6 shall be included as an appendix to the guidelines.

STATUS: Research in progress.