| A Hollow-Cylinder Tensile Tester (HCT) was developed to obtain fundamental tensile properties of asphalt paving mixtures at low and intermediate temperatures. The HCT device was developed as a surrogate test device for the Superpave Indirect Tensile Test (IDT), which is capable of obtaining fundamental mixture properties including creep compliance, tensile strength, and resilient modulus. Because the HCT is a simple, portable, and rugged test device, it is a very useful and powerful tool for mixture design, control and forensic evaluation. The device is particularly suited for the design of mixture to resist thermal cracking, and the resulting data is directly compatible with Superpave thermal cracking software for performance prediction.; Unlike creep compliance, which is a fundamental property, tensile strength of cementitious materials, such as asphalt concrete, is both sample size and test mode dependent. In this study a variety of bituminous mixtures were used to compare creep compliance and tensile strength values as measured in the HCT and Superpave IDT. First-failure strength and ultimate tensile strength were considered. Techniques for detecting crack initiation and propagation through HCT specimens were developed, involving wire-type gages. The first-failure strength was computed based upon the point of crack initiation, as determined using these techniques. On the other hand, ultimate tensile strength was determined using the peak pressure required to break the specimen.; The HCT device was found to be both accurate and repeatable. The coefficient of variation was measured for the HCT and IDT tensile strength results. In general, the coefficient of variation of the HCT strengths was found to be lower than that of the IDT strengths, particularly for ultimate tensile strengths. The HCT and IDT were found to compare favorably in the determination of creep compliance at higher loading times, and first-failure strength. Thus a fundamental, test-independent strength property can be obtained with either device. On the other hand, ultimate tensile strength was found to be test mode and mixture-dependent. In general, ultimate tensile strengths were considerably higher in the HCT than the IDT, particularly for polymer-modified mixtures. The HCT ultimate strength was found to be strongly correlated to modification level, as opposed to the IDT ultimate strength, which was very weakly correlated to modification level. |
