Simplifying the hollow cylinder tensile test procedure through volume-based strain

A hollow cylinder tensile tester (HCT) has been developed, which can be used to obtain fundamental properties of asphaltic paving mixtures, such as creep compliance, tensile strength, and dynamic modulus, at low and intermediate temperatures. By applying pressure to the inner cylinder wall of the specimen, a tensile or 'hoop' response is induced. In previous studies, strain gages were used to obtain tensile strain along in the inner circumference. While satisfactory results can be obtained, the application of strain gages is difficult, time-consuming and costly. Fortunately, one of the inherent benefits of the HCT is that, in theory, the cavity volume change can be estimated from the movement of the piston used to pressurize the fluid in the cavity. The volume-based strain measurement system simplifies specimen preparation by eliminating the need for mounted sensors, resulting in a more practical test method. This paper describes the development of such a system, including the sealing system used to retain the cavity pressurizing membrane and the analysis procedure to remove bulk fluid compression and other sources contributing to system compressibility from the computation. Also discussed in this paper is a recent analysis performed to better understand effects of material heterogeneity on the accuracy and repeatability of bench-scale tests, such as HCT.