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The density and air void content of asphalt mixtures affect the durability and performance of asphalt pavements. Pavement longitudinal joints typically have a lower density than the mat because they receive less compaction than the center section of the mat for various reasons. The higher air void percentages resulting from lower densities can lead to high permeability and allow water infiltration; which in turn can cause moisture-induced damage and decrease base and subbase support to the pavement; reducing pavement life. Void-reducing asphalt membrane (VRAM) has been used at the longitudinal joints of asphalt pavements to achieve higher densities and prevent moisture infiltration; thereby reducing deterioration at the longitudinal joints. VRAM is applied before the hot-mix asphalt (HMA) layer is placed and migrates into the HMA to fill 50% to 70% of the air voids. This research evaluated the extent to which J-Band; a VRAM product; increases density and improves performance. Field cores were collected from two sections; one with and one without VRAM. Asphalt mixture performance tests; including disk compact tension and semi-circular bend tests; and push-pull tests were carried out in the laboratory on the field-collected specimens. Volumetric measurements were also taken; and ground penetrating radar was used in the field. It was determined that the pavement sections with VRAM had a lower permeability; higher bond energy; and higher fracture energy than the pavement sections without VRAM.

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.