Investigation of the CoreLok for Maximum,Aggregate,and Bulk Specific Gravity Tests

Abstract

The Florida Department of Transportation uses long-established test procedures to determine the maximum specific gravity (G_mm) and bulk specific gravity (G_mb) of asphalt mixtures and the bulk specific gravity (G_sb) of aggregates. The CoreLok, a vacuum-sealing device that can be used to determine these properties, was evaluated by the department for these test procedures. With respect to the G_mm test procedure, for mixtures containing nonabsorptive granites, the CoreLok determined results equivalent to those of the department's test procedure. However, for mixtures containing absorptive limestones, the CoreLok determined higher G_mm values than did the department's test procedure. The apparent reason for the discrepancy is that the CoreLok does not determine a saturated surface dry condition of the sample. With respect to the aggregate specific gravity test procedures, the CoreLok provided test results equivalent to the department's test procedure for the nonabsorptive fine aggregates only. For the absorptive fine aggregates and all of the coarse aggregates, the CoreLok determined G_sb test results significantly different from those of the department's test procedures. The CoreLok may be suitable for determining G_mb for coarse-graded compacted specimens with high porosity and air voids. There are concerns with the accuracy of the CoreLok results because of the bridging effect of the plastic bag over the large surface voids and because of the CoreLok's significant underestimation of the specific gravity of a solid aluminum cylinder.