About the research
Air void content, specifically at longitudinal joints, is well known as a key factor affecting pavement life. 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 over longitudinal joints, leads to poor pavement durability. Poor durability is compounded because water infiltration is increased due to higher air voids, which 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 leads to reduced strength of underlying pavement layers, which accelerates deterioration when the moisture undergoes freeze-thaw cycling in the pavement structure. Multiple studies show for every 1% decrease in air void content an increase of 10% in pavement life can be achieved. The Minnesota Department of Transportation (MnDOT) has required the use of core measured air voids on projects for many years to monitor achieved air void content in the field. To improve upon current asphalt pavement compaction practices in the state of Minnesota, the research team anticipates datamining historical data to quantify the effect of air void content on pavement performance from confined and unconfined joints through the creation of an air void content database. Improvements will come in the form of modification to current construction practices and/or new standard methods.