This paper describes the development and potential use of the Trapezoidal Fatigue Tester (TFT), currently with Queensland Main Roads Department, Australia. The benefits of using the TFT are that good consistent stress and strain distributions are obtained over the critical areas of the samples and that sample size can be readily varied to account for aggregate size in the mix, and also for use with different materials. Two projects are used to illustrate the use of the TFT. Both involve the evaluation of a specific multigrade bitumen asphaltic concrete produced by Brisbane City Council. The multigrade asphalt was laid as a special trial, block samples were taken from the compacted pavement, and TFT testing carried out in 1992 and 1995. Fatigue testing was carried out at 25 degrees Celsius and 30 degrees Celsius to evaluate the effect of temperature variation. Strain levels were varied from around 150 mu epsilon up to 500 mu epsilon to obtain a good spectrum of fatigue behaviour. The testing indicated that the TFT has good potential as a research tool for studying fatigue predictive relationships, but is of limited use as a routine testing apparatus. Performance of the multigrade asphalt was generally found to be superior to the equivalent C320 Grade asphaltic concrete. (A)
Abstract