Impact of Various Mix Design Factors on Cracking Resistance of Epoxy-Modified Recycled Asphalt Mixtures: A Sensitivity Analysis

Low-temperature cracking resistance remains a critical design consideration for epoxy-modified recycled asphalt mixtures (ERAM) that incorporate high content of reclaimed asphalt pavement (RAP). In this study, ERAM with varying design parameters (epoxy content, gradation, asphalt content, aged asphalt ratio, RAP heating temperature, and number of RAP fractions) were subjected to three-point beam bending tests. The effects of these design variables were then analyzed using analysis of variance (ANOVA) and principal component analysis (PCA). The optimal mix formulation was finally selected through a comparison of performance, cost, and carbon emissions. The results indicate that epoxy content has the greatest impact on cracking resistance, followed by the aged asphalt ratio, asphalt content, gradation, and RAP heating temperature. The superior strength of epoxy asphalt mitigates the impact of RAP variability and permits the coarser RAP screening of two fractions. An excessively high aged asphalt ratio (greater than 50%) leads to a sharp reduction in cracking resistance. Instead of using a high epoxy content of 40%, it is more cost-effective for ERAM to adopt finer gradation and a moderate epoxy content (20% or 30%). These findings offer valuable insights into ERAM mix design and construction practices, improving its feasibility in pavement engineering.