Fatigue performance of hot mix asphalt tested in controlled stress mode using dynamic shear rheometer

Abstract

This study investigates the fatigue performance of hot mix asphalt (HMA) tested using a dynamic shear rheometer (DSR) under controlled stress test mode. Cylindrical DSR samples of 12 mm in diameter and 50 mm in height were prepared from a full HMA using coring technique to be used in fatigue test. Regarding fatigue evaluation, a fatigue index (FI^R) has been developed based on the relationship of stress–pseudo strain hysteresis loop to be used in evaluating fatigue performance. The average values of FI^R, in the relationship of FI^R against normalised shear modulus, were calculated in the range of normalised shear modulus (0.85–0.20) to be used in evaluating the fatigue performance of tested samples. The FI^R outcomes were in agreement in respect to the ranking order with the results from well-known approaches that have also been used for evaluating the fatigue performance, such as the energy ratio and the traditional approaches. In this study, limestone and granite aggregates were used with two binder grades: 40/60 and 160/220 to prepare four mixtures with two different gradations: gap-graded hot rolled asphalt and continuously graded dense bitumen macadam. The study demonstrated that the DSR instrument could be used to perform fatigue testing of full HMA. Also, limestone mixes showed better fatigue performance than granite.

Keywords:

• Hot mix asphalt
• dynamic shear rheometer
• fatigue index
• dissipated pseudo-strain energy and stress test mode

Acknowledgements

The author is grateful to Dr Hussain A. Khalid from Liverpool University for supporting and guiding this work. The author would like to acknowledge the financial support of the Iraqi Government for the award of a research scholarship enabling this work to be conducted as part of a larger research project.