Methods for Evaluating Longitudinal Joint Quality in Asphalt Pavements

Abstract

Longitudinal joint quality is essential to the successful performance of hot-mix asphalt (HMA) pavements. Longitudinal joints have received a considerable amount of attention recently, because many state agencies are moving toward implementation of longitudinal joint specifications. Most measures of joint quality are based on density determinations. However, distress at the joint is caused by the ability of air and water to enter the pavement structure, an action that is directly related to the permeability of the joint. In other words, density alone may not be sufficient to describe the quality of a longitudinal joint. The objective of this study was to identify the most appropriate test method or methods for describing HMA longitudinal joint quality. Three projects were selected for the study, and four testing stations were identified for each project. At each station, a number of test methods were performed at the longitudinal joint and to either side of the joint to assess the ability of each method to properly discriminate between levels of joint quality. Multiple measures of density, permeability, and gradation were obtained at each station. Overall, the methods providing the most accurate predictions of joint quality and the greatest level of discrimination were the vacuum sealing and saturated surface-dry (SSD) methods for determining the bulk specific gravity of field cores. Although measures of permeability and infiltration showed promise, it was recommended that the vacuum sealing and SSD methods for the determination of field core density be considered in the evaluation of longitudinal joint quality.