BACKGROUND: Generally, asphalt mixtures contain asphalt binder, aggregate, and additives such as latex, ground tire rubber, warm mix additives, anti-strip additives, fibers, and mineral fillers. However, because of their environmental and economic benefits, reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) may also be used in asphalt mixtures; state departments of transportation (DOTs) have verified the percentages of RAP and RAS used in asphalt mixtures using different approaches such as stockpile measurements and plant recordation. However, additives are often introduced using equipment and control systems that do not provide good means to verify the added quantities. There is no widely acceptable procedures or guidelines for verifying quantities of materials used in asphalt mixtures at production facilities.
There is a need to identify the procedures currently available for verifying quantities of materials used in asphalt mixtures at production facilities, 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 in enhancing quality assurance programs and ensuring compliance with contractual requirements.
OBJECTIVES: The objectives of this research are to (1) recommend procedures for verifying quantities of materials used in asphalt mixtures at production facilities and (2) prepare guidelines for their application.
RESEARCH PLAN
PHASE I: (1) Collect and review information on current practices relevant to the procedures for verifying quantities of materials used in asphalt mixtures at production facilities, and identify available procedures. This information may be obtained from published and unpublished information and contacts with public and private organizations involved in such operations (e.g., state DOTs, asphalt producers, and manufacturers of production facilities and related technologies). (2) Evaluate the procedures identified in Task 1, identify potential procedures, and recommend modifications of existing procedures and/or new procedures that merit evaluation in Phase II. (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/develop recommended procedures for verifying quantities of materials used in asphalt mixtures at production facilities; and (c) prepare guidelines for their application. (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 verifying quantities of materials used in asphalt mixtures at production facilities and related guidelines. (6) Using the procedures developed in Task 5 prepare examples to illustrate use of the procedures for different scenarios, and identify means to facilitate their implementation. (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. The procedures and guidelines shall be prepared as a stand-alone document suitable for consideration and adoption by AASHTO.
STATUS: Reasearch in progress.
