Development of a Simple Test to Determine the Low Temperature Creep Compliance of Asphalt Mixtures

This project explores the idea of performing bending test on thin asphalt mixture beams to determine low temperature creep compliance of asphalt mixtures. Work in the first phase has focused on developing a methodology for sample preparation and testing. Thin mixture beams were cut using a simple tile saw. The dimensions for 660 thin beams were recorded to obtain the coefficient of variation for thickness, the most critical dimension. The thickness and width values indicated that beams obtained using the proposed procedure were uniform with very similar sizes. The loading protocol of the existing Bending Beam Rheometer (BBR) device was modified to accommodate the fact that asphalt mixtures are one order of magnitude less compliant compared to asphalt binders at low temperatures. Three methods were investigated: one consisting of a two step loading procedure that did not require any change in the current BBR device, another that used the maximum load of BBR device with software modification that improved resolution of measured deflections and the third involving the use of high and intermediate temperature results and time temperature superposition principle to predict the lowest temperature results. After a comprehensive set of tests performed, it was found that the simplest test method avoided testing at low temperature levels and predicted creep stiffness from data obtained at higher temperature. The loading method that uses the maximum load capacity of the BBR device can be also pursued taking into consideration that the deflection data may be noisy for very stiff mixtures. Although the double step method gives reasonable results, its use is not recommended for routine testing because of its operator sensitivity. Additional testing was performed to identify differences in creep compliance results when testing was performed in two cooling media: ethanol and air. Work in the second phase will focus on testing and data analysis of BBR thin beams. Data on the BBR mixture creep compliance will be obtained and compared with the Indirect Tension Test (IDT) creep compliance data to ascertain equivalence or develop correlations between the creep compliance provided by the two methods. In addition, a method will be developed to allow back calculation of asphalt binder properties from the mixture test using either existing volumetric properties or some simple scanning technique. The outcome of this phase will be a detailed step-by-step method describing how to analyze data from BBR testing of thin asphalt mixture beams.

Language

  • English

Project

  • Status: Completed
  • Contract Numbers:

    Project, 20-30, IDEA

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway & Transportation Officials (AASHTO)

    444 North Capitol Street, NW, Suite 225
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Jawed, Inam

  • Start Date: 20090422
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 22077

Subject/Index Terms

Filing Info

  • Accession Number: 01547252
  • Record Type: Research project
  • Source Agency: National Cooperative Highway Research Program
  • Contract Numbers: Project, 20-30, IDEA
  • Files: TRB, RiP
  • Created Date: Dec 4 2014 1:00AM