Study of Longitudinal-Joint Construction Techniques in Hot-Mix Asphalt Pavements

There is a need to identify suitable longitudinal-joint construction techniques for multilane, hot-mix asphalt pavements that can minimize or eliminate cracking at the joint and raveling adjacent to the joint. It is believed that the longitudinal cracks result primarily from the density gradient that is usually encountered across the joint. This density gradient can be attributed to low density at the unconfined edge when the first lane is paved and relatively high density at the confined edge when the adjacent lane is paved. Seven different longitudinal-joint construction techniques were used on I-25 in Colorado in 1994, including various rolling procedures to compact the joint, provision of a vertical face with a cutting wheel, and use of rubberized asphalt tack coat on the face of the unconfined edge. Two longitudinal-joint construction techniques were used on I-79 in Pennsylvania in 1994: the conventional technique (control) and the New Jersey–type wedge joint. The latter technique uses a 3:1 taper at the unconfined edge of the first lane. The face of the taper is heated with an infrared heater before the adjacent lane is placed. Pavement cores were taken on the joint and 305 mm (1 ft) away from the joint for density measurements in all experimental test sections. Different techniques for joint construction have been ranked on the basis of statistical analysis of all density data. Various joints were also evaluated visually by teams of at least four engineers in June 1995. The performance, or ranking, of the joints in both Colorado and Pennsylvania projects after one winter seems to have been influenced by the overall density at the joint. The joints with high densities indicate better performance than those with relatively low densities. These rankings may change in the future on the basis of the long-term performance as measured by cracking and raveling.