Device for measuring shear resistance of hot-mix asphalt in gyratory compactor

The development of a gyratory load-cell and plate assembly (GLPA) to measure the shear resistance of hot-mix asphalt mixtures Is described. The GLPA is a simple tool that allows the measurement of the eccentricity of the resultant load applied by the gyratory compactor in real time during compaction. The GLPA is inserted on top of the mixture specimen in the compaction mold, requiring no changes in the compaction procedure. The results from the GLPA give a continuous measure of the resistance of asphalt mixtures to shearing under gyratory loading at a fixed angle. On the basis of a simplified analysis, it is hypothesized that the bulk shear resistance estimated from the GLPA is a good indicator of the compactibility of asphalt mixtures and their potential resistance to rutting under traffic. The shear resistance and volumetric characteristics of a number of trial mixtures fabricated in the laboratory were tested to show the utility of the GLPA. The results show that the shear resistance is highly sensitive to gradation, asphalt content, and temperature. They also indicate that there are interactive effects of these factors that are independent of the volumetric properties. Although the relationship between the results of the GLPA and the field performance of mixtures is yet to be determined, this device has the potential to be a low-cost and effective tool to complement the current volumetric mixture design procedure. It provides a tool to measure an important mechanical property that is a good indicator of bulk shear resistance of asphalt mixtures.