Calibration of the CoreLok Method for Determination of Missouri Aggregate Specific Gravities
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Specific gravity and absorption are fundamental aggregate properties needed for hot-mix asphalt (HMA) and Portland cement concrete (PCC) mix design and/or volumetric determinations. MoDOT utilizes the American Association of State Highway and Transportation Officials (AASHTO) standard test methods T 84 (for fine aggregates) and T 85 (for coarse aggregates) to determine these important properties. Criticisms of these procedures are the subjective nature of determining when the aggregates have reached the saturated, surface-dry (SSD) condition (especially T 84) and the substantial amount of time needed to complete the tests. The CoreLok method addresses these criticisms in that it is an objective and faster method for determining aggregate specific gravities. Oven-drying the aggregates to a constant mass is the only sample preparation necessary; there is no need to soak the aggregates for an extended period of time or to obtain the SSD condition in order to complete the test. Apart from sample preparation, the two-part test procedure takes approximately 30 minutes. However, working with dry aggregate poses its own problems and errors are introduced. Therefore to account for these errors, regression analyses were performed to calibrate or “correct” the CoreLok method test results to associated T 84/85 values.