Tack Coat Application Rate
The goal is to apply just enough and no more. Too much tack coat and it can bleed through and possibly effect the quality of the hot mix asphalt and too little can prevent adequate bonding of the layers. So, the result you are looking for is a thin, uniform coating of tack to cover approximately 90 percent of the surface to be paved. Need a fast answer? Try our tack coat calculator.
Modifications to the Application Rate
Each situation can be different, based on the circumstances. In general, a tight or dense surface requires less tack coat than an open textured or graveled surface. An extreme example would be a milled road surface. A road milled with a drum that has widely-spaced teeth and moving fast will result in very rough texture, increasing the actual asphalt surface up to 40 percent. So the amount of tack applied needs to increase up to 30 percent because of all the ridges and valleys. Even though there is texture created that helps to mechanically bond the layers, there still is a need for tack coat for bonding the two surfaces.
Application Chart for Tack Coat
|
Existing Pavement Condition |
Application Rate in gallons per square yard |
||
|
Residual |
Undiluted |
Diluted 1:1 with Water |
|
|
New HMA |
|
|
|
|
Oxidized HMA |
|
|
|
|
Milled HMA |
|
|
|
|
Milled PCC |
|
|
|
|
PCC |
|
|
|
|
In the chart above, residual asphalt is the amount of asphalt binder remaining on the pavement surface after all water has evaporated from the applied emulsion. Diluted emulsions should be applied at a greater rate than undiluted emulsions to obtain the same residual asphalt coverage. Residual asphalt is the asphalt binder left over after the emulsion has set. As you can see, the application rate is doubled in the chart above so the same final residual results from the application. |
|||
