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 October 2007
Tech News

Road and Paving Materials Committee Developing Fatigue Testing for Asphalt Concrete

Interested parties are invited to participate in the ongoing development of a proposed new standard, WK15543, Test Method for Determining Fatigue Failure of Compacted Asphalt Concrete Subjected to Repeated Flexural Bending. The proposed standard is being developed by Subcommittee D04.26 on Fundamental/Mechanistic Tests, which is part of Committee D04 on Road and Paving Materials.

Richard W. May, past chair of Committee D04 and performance testing laboratory manager, SemMaterials, L.P., says that because it is time consuming, fatigue testing will never be a routine part of pavement design. However, there is a need to use the best and most appropriate material model available because it is important for estimating the longitudinal fatigue cracking performance of an asphalt concrete mixture in a pavement cross-section.

The proposed test method will be run at different strain levels to establish a performance curve that describes the relative strain sensitivity of a mixture type and the impact of specific characteristics, such as binder grade, binder content and aggregate gradation. “Layered or finite element pavement analyses can be used to estimate the tensile strains that will occur on the highway under different traffic loads,” explains May. “Then, these calculated strains can be used with the fatigue curve, produced using the proposed standard, to project the future performance of the roadway.”

May notes that the proposed standard will provide information with which to judge the variation of their results and a better method for determining the failure point to those advanced testing laboratories and universities who are already doing this kind of fatigue testing.

The subcommittee encourages participation in the ongoing development of WK15543. “I believe that a major source of variability in this proposed test method is specimen preparation,” says May. “Members of D04.26 and other members of D04, particularly those who are oriented toward developing better equipment, could help improve WK15543 by helping to address this issue. There is a need for an improved compaction process to consistently create uniform specimens, which are representative of the field rolling process.”

May also notes that the subcommittee will eventually be organizing and conducting a round robin test to develop an estimate of multilaboratory precision. “For that effort, we will be looking for many laboratories to voluntarily participate by doing some fatigue testing of replicate specimens,” says May. //

CONTACT

Technical Information: Richard W. May, SemMaterials, L.P., Tulsa, Okla.
Phone: 918/524-7114

ASTM Staff: Daniel Smith
Phone: 610/832-9727

Upcoming Meeting:
Dec. 4-6
December Committee Week
Tampa, Fla.