by Bill and Mary Weaver

When potholes in parking lots or heavily traveled roads become a problem, workers who fill the damaged pavement with UNIQUE Paving Materials (UPM® mix) cold mix asphalt, find that the potholes are permanently fixed. In over 90 percent of cases, these potholes never need patching again. In fact, “The patch is guaranteed,” stated Tony Guizzotti, Account Executive for UNIQUE Paving Materials Corp (UPM). “If the municipality is not satisfied, they don’t have to pay! In many cases, the patch will outlast the surrounding pavement.”

This is quite a contrast to the typical patch and re-patch cycle common with most cold mixes. UNIQUE Paving Materials Corp., located in Cleveland, Ohio, specializes in top of the line pavement repair products. They have sales across the country and around the world. Their success is due to the assistance of the excellent quality control in the UNIQUE lab.

We first heard about this remarkable product from Bill Zetty, Superior Asphalt’s yard manager and Stacie Newman, paving foreman and Superior’s PR director. Zetty keeps a large pile of UPM cold mix on his winter HMA lot, ready for use. Zetty, with 20 years’ experience in the asphalt business, said, “UPM cold mix is THE best mix in the industry. I would not use any other cold mix.”

UPM cold mix is also easy to use. It is guaranteed to stay loose and pliable in a stockpile for up to a year, even uncovered straight through the fall and winter weather. For application, no heavy equipment is required. The only items needed are a shovel and a tamping tool or vehicle to rollover and compact. UPM cold mix can even be applied under water. It will retain the same characteristics, and the fix will be permanent.

Widely used

UNIQUE’s cold mix has been used to permanently repair more potholes than any other cold asphalt mix or cold patch in the industry. It is available across the U.S. in various container sizes and forms. UNIQUE has contractual agreements for the use of its cold mix with companies overseas as well.

In the Federal Strategic Highway Research Program (SHRP) Report, UPM mix was the standard by which other cold mixes were judged. The mix has been used by the Ontario Ministry of Transportation on highways in Ontario, Canada. There, it stands up to 90,000 cars per day.

How it works

Don Koehler, UNIQUE’s sales manager, explained why UNIQUE’s UPM cold mix can actually be guaranteed as a permanent fix. “Our company founder began experimenting 58 years ago using a coffee can and a welding rod with the intent of becoming the best in the business. Since then, we have focused on (product) survivability: how long the mix stays in the hole.”

“Each and every batch of our ‘secret recipe’ is individually lab tested. Our lab knows how to adjust the chemistry of the recipe for different conditions and types of aggregate. Our mix does not harden until it is compacted in a pothole, and below the compacted surface layer, it always retains some flexibility. We add modifiers and additives to our binder so it is not rigid and hard, even in cold weather. Because of the quality of the asphalt film on the aggregate, UPM cold mix glues itself into the pothole wall, in addition to profiling the hole, as HMA and other cold mixes.”

If there is water in the pothole, UPM cold mix will push it aside. “UPM chemistry doesn’t like water,” noted Koehler. (If there is ice in the pothole, it needs to be removed because the ice takes up volume in the hole.)

Preparing the pothole

To prep the hole, all you need to do is get the loose debris out (although square cutting is ideal, Koehler noted.) “With our STIFFWITCH® broom, you can get very aggressive at removing all the bits and pieces of loose aggregate. For optimal survivability, your repair needs to be bordered by sound material.”

Once UPM cold mix is compacted in a pothole, vehicles can drive over it right away. It will form a 1½-inch crust that will support the weight of traffic. Months later, if you probe below the surface with a screwdriver, you’ll find that below the crust, the mix is still soft and flexible due to the viscosity modifier in the binder. This formulation is designed to stay in the binder and doesn’t evaporate easily, even when stockpiled for lengthy periods.

The continued flexibility of the mix below the surface compacted layer holds the aggregate in place so the mix stays strong but flexible. It expands and contracts as needed. “That’s why our pothole repairs can, and often do, outlast the surrounding asphalt road surface.” It is the column of aggregate that supports the traffic load. The UPM mix holds the aggregate in place.

“The characteristics of the aggregate are key to a successful cold mix,” explained Tim Flanagan, the UNIQUE rep. who, along with his wife Sonya, mixes UPM cold mix on site for the stockpile at Superior Asphalt. The Flanagans use a portable pug mill plant and tanker truck. “Because rock is so expensive to ship, we try to use locally available rock. In this area, aggregate from crushed limestone from much of the Niagara escarpment, which extends along the Great Lakes from Michigan to Wisconsin, typically works well. We put the rock through a series of tests for hardness, absorbance and gradation of sizes.”

Mix design and quality control

Flanagan said that over time, on a national basis, they have found that about 50 percent of the samples sent to them are rejected. The rock is too dirty, too soft, too absorbent, or the sample may not contain a proper mix of aggregate sizes. Also, it may not be properly crushed to provide the angularity need for interlocking.

Koehler explained that the size gradations are important. “To support the weight of traffic, the various aggregate sizes plus the fines must form a rock on rock column. The rock itself must be crushed to create lots of angular surfaces. Additionally, it must be hard enough to withstand the freeze-thaw cycle in northern areas.”

The space between the rocks in this “rock column” is filled with smaller rocks, fines, air, and asphalt mix made with UNIQUE‘s ‘secret recipe.’ “The performance of virgin aggregate in cold mix is the absolute best, but our lab can alter the chemistry of the recipe so if a contractor wants to use, say, 10 to 20 percent RAP by weight, or incorporate some slag, we can work with that. We can change the chemistry of the special recipe to deal with individual situations and still get the desired performance,” noted Koehler.

UNIQUE tests its mixes continually around the country. “We conducted a study in Lexington, KY for 12 years. During that time, we reduced the number of potholes in the city by 60 percent. We fixed potholes permanently and stopped the endless re-repair cycle that is so common in many municipalities. However,” Koehler added, “if there is water running under the road, it is very difficult to solve a pothole problem. A strong base must support the surface driving course. The water may wash away the small particles and dirt, creating a sinkhole, and the entire road could eventually collapse.” Pavement base failures are the cause of many surface failures. “It’s important to maintain the road base as well as the road surface.”

Purchasing cold mix based on the price of the mix, although common, ignores some vital facts. The mix itself is a small part of the cost of pothole repair — less than 10 percent. The majority of cost is labor and equipment. A lot of time is spent driving from pothole to pothole. Frequently traffic controllers must also be hired while the repair is being made.

UNIQUE’s UPM cold mix does cost more. “Testing is not free, and maintaining the best in class is never the cheapest. UNIQUE made the decision to be the best.”

With UPM cold mix, each pothole is fixed once and done. “Because of the quality of UNIQUE’s cold mix, which is guaranteed, you only need to pay the labor and equipment cost to fix each pothole once. Buying the best (highest survivability) cold mix, in the end, is the best strategy and provides the lowest overall cost.” For more information visit www.uniquepavingmaterials.com .