Identification of the optimal implementation of the microwave self-healing technology for pavements based on sustainability assessment and technical parameters

Self-healing is a preventive maintenance technique developed to extend the service life of road pavements, accordingly, increasing their sustainability: energy consumption savings, lower emissions, and a decrease in the use of non-renewable resources. Microwave (MW) self-healing technology consists of heating the binder so it can flow and fill the cracks in the pavement. To promote and enhance this asphalt self-healing capacity, electrically conductive susceptible particles like steel slag can be added as aggregates in the asphalt mixture, and a combination of heat and re-compaction energy (thermomechanical treatment) can be applied to improve healing rates. However, one of the key issues is determining how to take full advantage of asphalt mixtures self-healing capacity to maximize the extended life span of asphalt pavements in order to avoid the use of a great number of non-renewable resources and energy in the rehabilitation of deteriorated pavements. Although some different factors that affect self-healing effectiveness are being studied, the optimal implementation conditions and moment to apply the MW treatment have yet to be determined. Hence, this paper aims to identify variables and establish an optimal implementation of the MW self-healing technology including steel slags and a thermomechanical treatment (MW heating and re-compaction). For this purpose, the influence of the implementation conditions, the moment of application, and the mixture design have been assessed by Life-Cycle Greenhouse Gas emissions, Cumulative Energy Demand, and cost evaluation. Results have shown that the optimal moment to apply the MW treatment would be around the half-life span of the asphalt pavement, being the most beneficial solution when applied over asphalt mixtures using steel slag as this allows reducing energy requirement during the MW application process and minimise costs.