Experimental Research On Self-healing Capability Of Asphalt Binder

From the source point of view, the healing phenomenon of asphalt mixtures ishighly dependent on the viscoelastic properties of bituminous binders. Since thebituminous binder is the only part in asphalt mixtures that can heal, knowledge on thehealing characteristics of pure bitumen is important to understand its contribution tothe healing capacity of asphalt mixtures. On the basis of existing research results forreference, this paper focuses on the different test methods towards a betterunderstanding of the pure bitumen’s self-healing capability and mechanism, and theinfluences of the admixtures.(1) The main factors that affect pure bitumen’s healing capability and differenttest methods have been summarized on the basis of a comprehensive previous study.(2) The comparison of different influence factors about pure bitumen healingeffects have been discussed on the evaluation indicator of healing rate which isdefined as the ratio of the tensile length of healed specimen to that of undisturbedspecimen under certain conditions by the Ductility Tensile Healing (DTH).(3) The Dynamic Shear Rheometer (DSR) was used to investigate theself-healing capability of pure bitumen with a special Two-Piece Healing (TPH) setup.During the TPH test, the healing process was achieved by pressing two pieces ofbitumen together under a parallel plate system. Two phases can be distinguished fromthe TPH test being the initial healing phase due to gap closure, and the time dependenthealing phase. The results are summarized as follows:(a) During the initial healingphase there is a three-stage complex modulus increase with the closure of the gapwidth.(b) There is a time dependent healing phase. The time dependent healingresults show a distinctive difference between the results obtained when the gapbetween the parallel plates of the DSR is kept constant and the results obtained whenthe normal force applied is kept constant. It was shown that the compressive normalforce strongly promotes the development of healing.(c) It was also demonstrated thatmany factors can influence the results of test.(4) It is confirmed that the SBS modified asphalt can recovery itself through thetest of DTH, and that healing percentage is highly related with the recovery time andrecovery temperature. The healing percentage of pure bitumen is better than SBSmodified asphalt under the same condition. In filler to asphalt ratio of1.0, withrecovery rate of complex modulus as the only evaluation indicator, the healing effect of asphalt mortar is much worse than pure bitumen through the test of TPH.