Asphalt pavement is a crucial element of our infrastructure, and maintaining it helps keep our society moving. But what do you do when faced with pavement cracks and distresses that are too wide or too numerous for conventional crack sealing?

For about 20 years, intrepid pavement professionals have been perfecting the use of hot-applied mastic to repair wide cracks and distresses. Where past users might have pumped excess sealant into a wide crack or pooled sealant over entire cracked areas, mastic allows a more targeted approach with more appropriate material characteristics. Because crack sealant is formulated to stay pliable in specific temperature ranges, it isn’t designed to be load-bearing. Excessive use of sealant can also create slick spots.

Mastic is designed specifically for those situations. It contains many of the same raw ingredients as hot-applied crack sealant but is thicker and includes aggregate to lend load-bearing and skid-resistance properties. Mastic is flexible enough to absorb the thermal expansion and contraction of the surrounding pavement, but still firm enough to stand up to traffic. And just as with crack sealing, mastic repairs enhance the effectiveness of surface treatments like chip sealing. Mastic repairs generally provide years of maintenance-free protection, depending on the specific application, pavement condition and other factors.

When should you use mastic instead of crack sealant? Mastic is typically used for cracks wider than 1.5” and for distresses that are too large for crack sealing but too small for repaving. One of the main uses for mastic is repairing deteriorated longitudinal joints, where it creates a smooth transition between courses and halts degradation.

Wide cracks are just the beginning. Over the years, innovative practitioners have developed ways to use mastic for a variety of problems, like sealing alligator cracking, filling wheel ruts, leveling around manholes, smoothing bridge deck approaches, sealing fiber optic trenches and more. Mastic has been adopted by state Departments of Transportation, local streets agencies, utilities and contractors of all sizes. In recent years, the use of mastic in public projects has been standardized by ASTM D 8260, providing testing methods and usage guidelines that ensure reliability.

Compared with a typical “mill and fill” repair, mastic requires a smaller crew, less preparation and less time to apply thanks to its simplicity. Mastic can be used on a wider variety of distresses than HMA, and it’s ready for traffic as soon as it cools – usually within an hour.

While mastic application shares some similarities with crack sealing, there is one major difference concerning equipment. The inclusion of aggregate would damage the pump in a crack sealing melter, so mastic melters don’t have pumps. Instead, the material is gravity-fed with assistance from the agitator paddles.
Besides melters, the use of mastic has spawned a class of specialized tools that make the job quick and intuitive. Rectangular metal frames called drag boxes are towed behind the melter and fed continuously from a material chute, applying mastic smoothly over a long run. There are a variety of drag boxes available, from 4” wide all the way up to 48”.

The hand-operated version of a drag box is called a shoe box, which allows for greater maneuverability on meandering cracks and around obstacles. Ironing wands are heated in a side chamber on the melter and used to smooth out imperfections as needed. An applicator cart with a propane burner, hand agitator and built-in shoe can be used to apply several gallons of material in areas inaccessible to a full-size melter.

For long, linear cracks like a failed longitudinal joint, the best approach is towing a narrow drag box along the crack. Some melters allow configuring the drag box outside the machine’s wheel path, which allows for closing only one lane of traffic and minimizes the crew’s exposure to vehicles.

For wide distresses like wheel path fatigue and rutting, a large drag box is towed behind the melter, leaving an even coat of mastic that fills in depressions and levels the surface.

An applicator cart is often the most efficient tool for meandering cracks because it combines maneuverability and volume. Alternatively, a shoe box and bucket can be used on small jobs. Experiment with each approach to find the one that works best for you.

Adding new equipment to your setup is an investment, but there is an easy on-ramp for those who want to try before they buy. Renting a mastic melter and the associated tools pays for itself by saving you time and money compared with other repair methods. Once you’ve experimented with mastic application, you can evaluate whether the added capability is worth your investment.

Like any innovative tool, hot-applied mastic is a versatile option that simply makes the job easier. Explore the world of mastic repairs and see how it can help you deal with problem areas once and for all.

If you would like more information on mastic repairs, Crafco is happy to help answer any questions. You can reach out to Crafco at info@crafco.com.