Investigating self healing behaviour of pure bitumen using Dynamic Shear Rheometer

Abstract

Self healing is known as a built-in property of bitumen, which can help bitumen and asphalt concrete to recover its strength after damage. Healing can also extend the service life of asphalt pavements. A two-piece healing (TPH) test was developed to investigate the self healing behaviour of pure bitumen using the Dynamic Shear Rheometer (DSR). During the TPH test, a healing process was directly simulated by pressing the two pieces of bitumen together under a parallel-plate system. Two phases can be distinguished from the TPH healing test, the initial healing phase due to gap closure, and the time dependent healing phase. The results are summarised as following. (1) Initial healing phase: The initial healing phase has a three-stage complex modulus increase with the closure of the gap thickness. A rapid increase of the complex modulus is observed in the second stage of the initial healing curve due to a 0.5mm gap reduction. (2) Time dependent healing phase: The time dependent healing results show a distinctive difference between the gap constant control mode and the normal force constant control mode. The normal force control healing can be decomposed into the time dependent healing during a gap constant mode and additional healing by compression. It was indicated that the compressive normal force strongly promotes healing development. (3) It was also demonstrated that many factors can influence the complex modulus measurement results by using the DSR parallel-plate geometry.