This study investigated the influence of several factors on the adhesive bond provided by the tack coat at the interface between pavement layers. These factors included the surface treatment, curing time, residual application rate, and coring location. Three tests were performed for measuring the bond strength between an existing hot mix asphalt (HMA) and a new HMA overlay, namely the Florida DOT Shear Tester, the UTEP Pull Off Test, and the Torque Bond Test. Testing involved a CSS-1 type emulsion as the tack coat.
The results from the three tests were statistically analyzed. Generally, milling provided a significantly better bond at the interface between the existing surface and the new overlay. Curing time had a minimal effect on the bond strength. The results indicated that the absence of tack coat did not significantly affect the bond strength at the interface for the milled sections, whereas it severely decreased the strength for the non-milled sections. The results also showed that increasing the residual rate of tack coat did not significantly change the bond strength at the interface. Lastly, the coring location was found to be an insignificant factor.