Incorporating Environmental Impact Analysis into Louisiana’s Balanced Asphalt Mixture Design
Ibrahim Elnaml, Heather Dylla, Jun Liu, Louay N. Mohammad, Samuel B. Cooper, Samuel B. Cooper
Abstract
To meet the asphalt pavement industry’s net zero carbon emission goals, increasing reclaimed asphalt pavement (RAP) levels to greater than 25% is considered a critical tactic. However, many state departments of transportation are cautious in adopting high RAP content into their designs because of durability issues resulting from aged RAP binders. This paper assesses the effectiveness of using the Lewis acid catalyst, FeCl 3 , in improving the cracking resistance of high-RAP asphalt mixtures to meet Louisiana’s balanced mixture design (BMD) criteria, and lower embodied carbon of asphalt mixtures. Four asphalt mixtures were designed and tested against permanent deformation, intermediate- and low-temperature cracking, and durability. Mixture 1 is conventional, which contains performance grade (PG) 76-22 polymer-modified asphalt binder with no RAP. Mixture 2 is unmodified PG 67-22 and 30% RAP without catalyst. Mixtures 3 and 4 incorporated an unmodified asphalt binder PG 67-22, a catalyst, and 30% and 50% RAP, respectively. A life cycle assessment (LCA) analysis was conducted on asphalt mixtures that complied with Louisiana’s BMD specifications to quantify global warming potential improvements. Because the performance of both mixtures is expected to be similar, the scope of the LCA analysis was limited to only those life cycle stages that are expected to be different, modules A1–A3 (i.e., cradle-to-gate stages). Results showed that the use of FeCl 3 can improve asphalt mixtures’ cracking resistance containing high RAP contents, whilst it did not have a negative impact on permanent deformation resistance. Further, the addition of FeCl 3 to asphalt mixtures with 30% and 50% RAP levels showed a reduction in greenhouse gas emissions by 28% and 43.4%, respectively.