Best Practices for Tack Use on Preservation and Other Projects

Last week, we looked at three methods for maintaining a customer’s parking lot(s) and residential streets. If the project calls for milling and overlaying, you’ll add a tack coat to the process to ensure success. Let’s make this week’s tip how to tackle the tack coat.

Your distributor truck driver or tack wagon operator can give your project an added layer of success. If the truck is kept in proper, pristine condition and if the operator sprays the optimally diluted ratio of tack at the perfect rate, your paving crew gets the perfect glue.

Depending on the type of tack required for the job at hand, he’ll defer to the manufacturer’s guidelines for dilution. (Keep in mind, every state department of transportation (DOT) has specs for the type of tack, dilution allowed and application rate when it’s used on a federally funded project.) For our commercial and residential project discussion where you don’t have as strict rules and regs, you might look for less costly guidelines.

Here are the recommendations from the National Cooperative Highway Research Program Project 9-40. These may or may not be less rigorous than your state DOT, but they offer best practices to consider for top quality bonding between layers.

• When the surface type is a new asphalt mix, the tack application rate should be 0.035 gallons per square yard.
• When the surface type is an existing/old asphalt pavement, the tack application rate should be 0.055 gallons per square yard.
• When the surface type is a milled asphalt pavement, the tack application rate should be 0.055 gallons per square yard.
• When the surface type is PCC, the tack application rate should be 0.045 gallons per square yard.