Volume 32, Issue 5 (September 2004)
Quantifying the Confidence Levels of Deformation Measurements in Asphalt Concrete
An experimental approach for measuring surface strains in asphalt concrete (AC) samples is presented in this paper. It is equivalent to the local attachment of a large number of linear variable displacement transducers (LVDTs) with gage lengths ranging from 5 to 80 mm. The strain distribution properties developed under conditions of uniaxial tension are studied and analyzed for one AC mixture. It is shown that gage lengths of the order of the nominal maximum aggregate size measure a wide range of strain values: from zero strain up to 5 times the average strain. Moreover, as the gage length is increased, the scatter is reduced and the individual measurements yield values that are closer to their average. Subsequently, the confidence levels associated with using a limited number of gages with a given gage length are quantified. The results are then used to assess test protocol recommendations related to AC sample instrumentation. The size scale of the material's Representative Volume Element (RVE) is also addressed.