Abstract
ABSTRACT Self-healing of asphalt is assumed to be a flow process where bitumen flows into cracks to close them. Hence, the rheological behaviour of bitumen is one of the main factors affecting self-healing together with damage history, healing duration and pressure (external compressive forces or internal thermal expansion). Bitumen-filler interaction influences the flow and it is hypothesised that the material flowing into cracks during self-healing is a mixture of bitumen, filler and eventually fine aggregates. In the paper, the self-healing ratio was determined by mechanical testing and the self-healing was accelerated by an increase of temperature to 100°C. Material draining from asphalt mortar beams into a horizontal gap, representing a crack, was found to be a mixture of bitumen and aggregates with increasing self-healing observed with increasing bitumen and filler content. For the mortar mixture used in this study, a bitumen content of 5.4 wt% was identified to be the limit for self-healing.
Highlights
A continuous increase in traffic volume and the natural degradation of asphalt during ageing impose a burden on asphalt road structures
3.1.Macro-crack self-healing The surface temperatures of the asphalt mortar beams increased due to inducing healing in an oven at 100°C
The equilibrium surface temperature was independent of filler and bitumen content, as it only depended on the oven temperature
Summary
A continuous increase in traffic volume and the natural degradation of asphalt during ageing impose a burden on asphalt road structures. The contribution of bitumen flow, or occasionally referred to as creep, towards the self-healing was identified at different material scale lengths. The self-healing rate, velocity of observed functional recovery, for bitumen and mortar at the meso-scale is related to the viscosity of the bitumen used The Newtonian transition temperature is identified for bitumen through measuring the changes in the viscoelastic behaviour of bitumen with temperature and makes the transition to a near Newtonian flow behaviour. This transition temperature was observed to coincide with the start of self-healing in asphalt mixtures The filler type has an influence on the healing activation energy calculated from fatigue tests on mastic. The optimum filler to bitumen ratio is between 0.33 and 0.35 (Zhang et al, 2019)
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