ASPHALTIC PLUG (BRIDGING) JOINTS

Asphaltic plug (bridge) joints have gained a significant share of the market in Denmark, at the expense of mechanical expansion joints, since their introduction in 1981. This fact is due to many excellent properties of the asphaltic plug joint. The asphaltic plug joint has, however, a comparatively short service life, as the bituminous component of the mastic ages relatively quickly. The mastic thus becomes hard and inelastic, resulting in adherence failure at the joint and cracks in the surrounding asphalt surfacing. A service life of 5-6 years may be expected for the 1st generation joints examined. A longer life span may be obtained by the improvements in construction, materials and workmanship. The Road Directorate drew up a report in 1986 on the state of these bridge joints, on the frequency of their deterioration and on probable damage factors. The purpose of the present investingation was to: a) implement an updating of the previous report by performing a visual inspection of all the bridge joints of the 1986 survey; b) determine which joints have been repaired and which replaced; c) determine whether either the form or the construction of the joint has changed or improved since the previous survey; d) determine whether the elastic and/or adhesion properties of the mastic have improved since the 1986 survey; e) determine whether the stability of the mastic has improved since the previous survey; f) estimate the total service life of the bridge joints; and g) evaluate the principal parameters which optimize the service life of these joints.