RAP variability intelligent control framework for hot in-plant recycling of asphalt pavement

• An RAP classification and storage method based on DBSCAN clustering is proposed. • A maximum RAP content calculation method based on variability is developed. • An intelligent mobile application is developed for RAP variability control. • The proposed RAP control framework is validated in a highway maintenance project. • Lifecycle carbon emissions are reduced by 8.59% at 32% RAP content. The hot in-plant recycling technology for asphalt pavement, as a solid waste recycling method, can significantly reduce environmental pollution and lower construction costs. However, the variability of Reclaimed Asphalt Pavement (RAP) materials greatly affects the quality of hot in-plant recycled pavement. Effectively controlling the variability of RAP materials has become key to ensuring the long-term durability of recycled pavements. To address this issue, this study proposes an intelligent framework for controlling RAP variability, introducing a method for RAP classification and storage based on the original performance of the pavement, as well as a method for calculating the maximum RAP incorporation rate based on RAP variability. First, road sections are classified and milled according to their original performance to control RAP variability. Then, the maximum RAP content in the hot in-plant recycled asphalt mixture is controlled according to the RAP variability. This proposed framework has been applied to highway maintenance projects in Jiangsu Province, China. After the implementation of the classification and storage method, the coefficient of variation in the passing rate of each sieve in the recycled asphalt mixtures was reduced, and the coefficient of variation in the oil-stone ratio decreased by 1.6%, demonstrating a significant reduction in variability. Additionally, the carbon emissions of recycled asphalt pavement containing 32% RAP were evaluated, showing an 8.59% reduction in carbon emissions compared to the actual pavement constructed with 20% RAP content.