About the research
Hot mix asphalt (HMA) pavements historically constructed in Minnesota typically have air voids around 7% in the mat and often approach or exceed 10% directly over longitudinal joints. Mix density is very important in terms of the effect on durability performance in constructed pavements. Higher air voids in the mat, especially at longitudinal joints leads to poor pavement durability. Poor durability is compounded because water infiltration is increased due to higher air voids that leads to more required maintenance at longitudinal joint locations and can lead to the need for earlier reconstruction of the pavement. Infiltration of moisture in higher air void joints also lead to reduced strength of underlying pavement layers, which accelerates deterioration when the moisture undergoes freeze-thaw cycling in the pavement structure. Previous research on longitudinal joints has shown that lower air voids mixtures (3% to 5%) are stronger and more durable than 7% to 10% air void mixtures. To achieve higher density/lower air voids in the mat directly at longitudinal joints, the Maryland joint construction method has been implemented in conjunction with an improved longitudinal joint density specification in Minnesota. However, density cores are not taken within 6 in. of the longitudinal joint in Minnesota, and is where deterioration of the pavement starts. Pavements are Minnesota’s Department of Transportation (MnDOT)’s largest asset, valued at $29.5 billion. J-Band is a hot applied asphalt membrane used to extend the life of longitudinal HMA joints by migrating into 50% to 75% of the HMA void structure after rolling, thus reducing permeability at the joint. The reduction in permeability minimizes water and air intrusion into the joint resulting in reduced cracking and stripping and improved pavement performance. Extending the pavement life by one year saves MnDOT 5% per year in life extension costs. The research team anticipates using field produced cores with and without J-Band to evaluate how J-Band improves the performance of asphalt pavement mat at longitudinal joints against deterioration due to water and air infiltration through extensive lab testing of field cores.