Permeability Research with the Romus Air Permeameter: Fid-Bau Portal

Permeability Research with the Romus Air Permeameter

N. Retzer

This report evaluates the ROMUS air permeameter and analyzes the permeabilities of Colorados asphalt pavements. The permeability of an HMA mixture is its ability to resist the passage of air and water through the pavement. Permeability is considered to be a large factor in the deterioration of Colorados pavements because of the number of freeze-thaw cycles the Rocky Mountain Region experiences over the course of a year. Since the 1950s, asphalt pavement permeability has been recognized as a factor that leads to degradation of pavements. Permeability concerns have resurfaced with the emergence of the Superpave design method. Many agencies and research organizations have recently conducted studies and devised various types of apparatus to measure permeability. Previous studies have identified a number of variables that affect permeability such as lift thickness, nominal maximum aggregate size (NMAS), and the coarse or fine gradation characteristic. This study analyzed some of those same variables, as well as the use of pneumatic tire rollers during the compaction process. Other studies found differences between different NMASs and between coarse and fine gradations; this study found little or no difference between those variables. There are, however, similar trends between this study and others regarding permeability versus density trend lines. The use of pneumatic tire rollers was identified in this study as the largest factor impacting permeability. Other variables have been proven to influence permeability, but the largest difference was between projects that used a pneumatic tire roller and projects that did not use this type of roller for compaction. Implementation: This study will be used to encourage CDOT project designers and managers to allow for and use pneumatic tire rollers to compact asphalt mats. Currently, designers and project managers have the option to remove pneumatic tire rollers from their projects for various reasons.