Minnesota Department of Transportation
Chris Williamsrwilliam@iastate.edu email >
About the research
Air void content, specifically at longitudinal joints, is a crucial factor affecting pavement life. Compaction affects the Air void content achieved, which directly impacts the performance of pavement, and thus has been identified as one of the most critical factors associated with the performance of flexible pavements. This study examines pavement historical data, constructs an air void performance database, and performs a statistical analysis on factors affecting air void content and then analyzes the effect of air void content on performance. Microsoft Access is used to create a database. JMP, a statistical software program, is used for the analysis of the data from the database created for 43 projects. Air void distribution is determined across and within the projects. An analysis of variance (ANOVA) analysis shows that binder content (%), aggregate size, voids in the mineral aggregate (VMA)%, film thickness, and the amount of reclaimed asphalt pavement (RAP) (%) significantly affect the air void content achieved. The air void contents achieved for most lots of the projects are found to be within the acceptable ranges of 4-8% immediately after construction. The correlation between air void content and the distresses observed for the pavement sections used in this work have R-square values below 0.20, which does not meet the recommended value of being equal to or greater than an R-square value of 0.70. However, from previous literature, National Center for Asphalt Technology (NCAT) researchers suggest that with a 1% decrease in air voids, pavement service life would increase by 10%. Based on these increases in pavement service life, it is estimated that by increasing the density/reducing air voids by 1%, net present value cost savings could be $88,000 out of a $1,000,000 project.