Evaluating the CoreLok~(TM) Measurement of Bulk Specific Gravity for Hot Mix Asphalt Samples

摘要

For hot mix asphalt samples with high air voids and high absorption capacity, the saturated surface dry (SSD) method of bulk specific gravity determination yields higher values than predicted. Recently, the CoreLok~(TM) procedure has been found to be a simple, rapid, and nondestructive method for determining bulk specific gravity. This study evaluated CoreLok bulk specific gravity measurements by comparing results for laboratory prepared samples and roadway cores from two types of mixture to those determined by the volumetric and the SSD methods. A linear regression analysis of the results indicated that the SSD and the CoreLok methods had significant differences from the volumetric method for determination of bulk specific gravity. It was found that for most cases, the differences in bulk specific gravity measurements were due to the combined effect of percent air voids and percent absorption. For samples with low air voids, the CoreLok and the SSD methods showed similar but not identical results. For samples with high air voids, the CoreLok method resulted in bulk specific gravity values more representative of the actual values. This study also defined a CoreLok infiltration coefficient (CIC) to evaluate the water infiltration characteristic of dense graded samples. It was shown that fine graded dense mixes had higher CIC values than the coarse graded dense mixes at air void levels around 8%. The study found that water infiltration characteristics of samples with regards to CIC depend on absorption, air void content, and number of air voids.