Effect of nano montmorillonite on the multiple self-healing of microcracks in asphalt mixture

This study investigated the effect of nano montmorillonite at different damage degree on the multiple self-healing properties of asphalt mixture by semicircular bending (SCB) test. Four kinds of asphalt binder were used to prepare the asphalt mixture. The cumulative fatigue life was measured and the multiple healing index (MHI) was proposed as an index to evaluate the multiple healing. The test results of different healing temperatures and damage degrees were fitted to obtain the threshold conditions of multiple self-healing. The fatigue life of asphalt mixture was evaluated by four-point bending beam test. Results showed that montmorillonite (MMT) could improve fatigue resistance and the self-healing ability of asphalt mixture, especially when the damage degree was small. The multiple healing capacity of the mixture decreased with the increased of the degree of damage. After freezing-thawing cycle, the self-healing ability decreased significantly. In addition, the results of multivariate nonlinear fitting showed that when the damage degree of montmorillonite modified asphalt mixture was less than 30% and the ambient temperature reaches 50°C, multiple times of self-healing can be effectively achieved. The fitting results can also be used to calculate the self-healing threshold conditions of other asphalt mixtures.