Accurate asphalt mixture tensile strength

Tensile strength is an important property that is commonly used to evaluate effects of moisture, and to determine the fracture resistance of asphaltic mixtures. A method was developed to accurately determine tensile strength from indirect tensile test results. The method makes use of the Superpave IDT (indirect tensile test), which accounts for the effects of three-dimensional stress states in indirect tensile specimens. Data reduction and analysis procedures were developed to identify the instant of fracture during strength testing, as well as the stress at the location of fracture (i.e. the true tensile strength). Test data showed that mixture tensile strength determined using conventional (plane stress) analysis methods over-predicts the true tensile strength of asphaltic mixtures. More importantly, the level of over-prediction was found to vary between mixtures, an effect that may result in misleading interpretations of the relative strength between two mixtures.