The effect of a tack coat on the bond between asphalt concrete layers was investigated. First, the stresses at the interface caused by aircraft loads were calculated. Second, the effect of using a tack coat was evaluated by examining samples taken from in-service airport pavements. Third, laboratory tests were conducted to investigate how bonding characteristics were influenced by dirt adhering to the existing surfaces. Finally, measures to ensure sufficient bonding were developed.

The following conclusions were obtained. The interval between the construction of the wearing and binder coarses influences the bond strength: the strength decreases as the interval increases because dirt accumulates on the binder course. Adhesion between the courses can be improved by applying a tack coat. The curing time of the tack coat, however, also influences the strength, and the strength after one hour of curing is much less than that after 24 hours of curing. However, satisfactory strength can be obtained by using a newly developed tack coat. In addition, the structural integrity of the surface course can be ensured by introducing a thick lift construction procedure.