A Field Test to Determine Tack Coat Adequacy
Tack coat is a light application of emulsion or bituminous binder between existing roadway surface and the new overlay. The main purpose of the tack coat is to bond the two layers to prevent slippage and efficiently transfer traffic loads from overlay to the existing surface layer. In the case of poor quality or improper application of the tack coat, the bond between the layers diminishes and the top layer slips away (figure 1). The end result is the development of various types of distresses in the pavement and the significant reduction of the life of the overlaid pavement system. State roadway agencies have traced failure of overlays to tack coat.
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Figure 1 |
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Figure 2 |