Support for the Implementation of a Longitudinal Joint Density Specification for Hot-Mix Asphalt Concrete (5-1757-01-1)

Research project 0-1757 assessed the density of the longitudinal construction joint of many pavements in Texas and identified that a significant joint density problem existed, which justified the implementation of a joint density specification. This specification is now included as part of the Standard Specifications for Item 341 (Dense-Graded Hot-Mix Asphalt). To facilitate the implementation of the research and specification, the following objectives were included in this implementation project: - identify the most promising construction techniques aimed at achieving longitudinal joint density; - develop and conduct training seminars for the districts on construction of longitudinal joints and on the new TxDOT testing and specification requirements; - acquire non-nuclear density gauges; and - evaluate current longitudinal joint density criteria and the ability of contractors to meet the criteria. Project 0-1757, which provided the background supporting the need for a longitudinal joint density specification, reported densities near the unconfined edge averaging 6 to 7 lb per cubic foot below the densities taken at the center of the mat. Since the implementation of a joint density specification, a significant improvement in the longitudinal joint density has been observed. Data from some of the projects presented herein indicate a joint density of only 1.0 pcf (or less) below the density of the mat interior.