By Bob Humer, P.E.
The longitudinal joints are often the weakest link in an otherwise good performing asphalt pavement.
Unless creating a hot-joint by paving in echelon, the typical cold joint will have less density than the center of the paving lane. This occurs for dense-graded mixes, and to a lesser extent for SMA mixes and asphalt-rubber mixes. The deterioration of the joint area is caused by it being permeable. The permeability leads to water and air intrusion, resulting in binder oxidation and a scouring of the mix matrix caused by the combination of traffic and water intrusion. This leads roads to early maintenance/repairs of the joint area, and on airports to earlier-than-anticipated overlays to avoid the risk of Foreign Object Damage (FOD) from dislodged mix. These are the costly results of failing joints and the associated reduction in service life.(more…)