Optimization of Production Process Parameters and Anti‐Cracking Mechanism of Plant‐Mixed Hot Recycling Asphalt Mixture Through SCB‐DIC Testing

Abstract

ABSTRACT Plant‐mixed hot recycling technology enables efficient resource utilization of reclaimed asphalt pavement (RAP); However, the resulting mixtures often exhibit inferior anti‐cracking stability compared to virgin mixtures, and the cracking evolution mechanisms remain insufficiently understood. This study investigated the effect of six core production parameters: RAP preheating temperature, new aggregate preheating temperature, asphalt preheating temperature, mixing temperature, mixing regime, and RAP content. A mixed‐level orthogonal experiment was designed to conduct multi‐factor coupling tests. The Semi‐Circular Bending (SCB) test combined with Digital Image Correlation (DIC) technology was employed to precisely capture the entire cracking evolution process, including crack initiation, stable propagation, and unstable failure. Three evaluation metrics—Flexibility Index (FI), Crack Initiation Energy (CIE), and Energy Consumption Rate (ECR)—were adopted to systematically analyze the primary and secondary effects of each process parameter on anti‐cracking performance. Furthermore, meso‐structural uniformity analysis was incorporated to explore the relationship among process parameters, meso‐structural characteristics, and macro‐scale anti‐cracking performance. The results indicated that production process parameters affect the comprehensive performance of recycled mixture in the following descending order: mixing time regime > RAP content > RAP preheating temperature > new aggregate preheating temperature > asphalt preheating temperature > mixing temperature. Notably, mixing regime appeared to be the sole parameter capable of simultaneously controlling both meso‐structural uniformity and macro‐scale anti‐cracking performance, with unequal‐step multi‐stage mixing proving superior to equal‐step mixing. The findings suggested a differentiated control mechanism for crack initiation and propagation: the former was primarily associated with aggregate‐asphalt interfacial bonding, while the latter was linked to mastic integrity and aggregate skeleton stability. The optimal process combination balancing both crack initiation and propagation resistance was established as follows: RAP content 40%, RAP preheating temperature 150°C, new aggregate preheating temperature 200°C, asphalt preheating temperature 180°C, mixing temperature 180°C, and 4‐min unequal‐step staged mixing. These findings offer both theoretical foundations and technical guidance for optimizing production processes and controlling cracking in plant‐mixed hot recycling asphalt mixtures.