Investigation of the CoreLok for Maximum, Aggregate, and Bulk Specific Gravity Tests (05-1518)**
Gregory Allen Sholar, Florida Department of Transportation
Gale C. Page, Florida Department of Transportation
James A. Musselman, Florida Department of Transportation
Patrick B Upshaw, Florida Department of Transportation
Howard L. Moseley, Florida Department of Transportation

The Florida Department of Transportation uses long established test procedures to determine the maximum specific gravity (Gmm) and bulk specific gravity (Gmb) of asphalt mixtures and bulk specific gravity (Gsb) of aggregates. The CoreLok, a vacuum-sealing device that can be used to determine these properties, was evaluated by the Department for these four test procedures. With respect to the Gmm test procedure, for mixtures containing non-absorptive granites, the CoreLok determined equivalent results compared to the Department’s test procedure. However, for mixtures containing absorptive limestones, the CoreLok determined higher Gmm values compared to the Department’s test procedure. The apparent reason for the discrepancy is because 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 equivalent test results to the Department’s test procedure for the non-absorptive fine aggregates only. For the absorptive fine aggregates and all of the coarse aggregates, the CoreLok determined significantly different Gsb test results compared to the Department’s test procedures. The CoreLok may be suitable for determining Gmb for coarse graded compacted specimens with high porosity and air voids. There are concerns with the accuracy of the CoreLok results due to the bridging effect of the plastic bag over the large surface voids and due to the CoreLok’s significant underestimation of the specific gravity of a solid aluminum cylinder.