Building a facility over a coal mine is tricky business, a balance of sorts. The facility must be very durable, since it is to be used 24 hours a day by hundreds of workers. But it will also have a shorter shelf life, which is dependent on the coal excavated from under ground. So the facility will shine bright for a few years and then burn out. It’s an odd balance, but it has been achieved in at least one mine facility in Western Pennsylvania. Arguably, without the use of epoxy on the floors, it wouldn’t have been possible.
Built in 1998 and closed in 2012, this Western Pennsylvania coal mining facility, whose owner chooses to remain unnamed, was designed to last 12 years. Instead, it lasted 14.
The facility included support offices, showers, and locker rooms, yet had no loss in adhesion throughout its use. It also saw 500 workers covered in coal every day. Three times a day, miners assembled, traveled down the 200 feet (60.96 m) to their workplace, and then ascended to clean up and leave. That meant that not only did the floors see 500+ pairs of feet daily, but they also saw a walk-behind floor scrubber at the end of every shift. That floor had a rough life!
So how did this coating crew get the floors to last two years more than planned?
All Systems Go
Made out of concrete, the floors were specified and then coated by Specialty Coatings and Consulting, Inc. out of Pittsburgh, Pa.
“We actually designed the system,” explained owner Phil Scisciani, who’s been in the business for 28 years. As an independent contractor, Scisciani has been able to choose his own products, and for 90 percent of his floors, he’s chosen Coatings For Industry (CFI). This project was no different.
Working 8-hour days, the four-man crew covered the 20,000 square feet (1,858.10 m²) of floors with an epoxy system. The general contractor, who divided the building into three six-to-seven-thousand-square-foot (557.42?650.32 m²) sections, had each craft rotate to a new section every week.
For the coatings crew, they worked Friday to prepare the area, Monday through Wednesday on the three-step process, Thursday they’d finish up and let the area cure, and the following Friday they’d clean up and start over again on the next area. They did that for each of the three areas until the entire project was complete.
To kick it off, they prepped by acid-etching the concrete. Although it’s “kind of unheard of now,” as far as Scisciani is concerned, it worked for them. Once the area was acid-etched, they rinsed and power-washed the floors (using 2,500 psi or 17,236.89 kPa machines) to “rinse and neutralize the acid.” They then let the area dry over the weekend.
On Monday, the crew came in to start applying the coating system. The Specialty Coatings crew duct-taped a horizontal line above the first block of concrete on the wall. This ensured that the floors would come out with a clean line around the edge. With the border set, they moved on to the coatings.
Wearing safety glasses, hard hats, respirators, and knee pads, the crew applied the primer. They poured and rolled out CFI’s Wearcoat CG. Then, they squeegeed the primer to achieve a thickness of 5 to 6 mils (127?152.4 microns) dry film thickness (DFT). They let that coat cure overnight and then came in to apply the slurry coat: CFI’s Wearcoat CG self-leveling epoxy. This step was applied at an average of 60 mils (1,524 microns) DFT using a pin rake. Again, that layer was allowed to cure overnight before they applied the next coat, which was the intermediate coat. This was the first of two layers of CFI’s Wearcoat 100 polyurethane; it was applied at 5 to 6 mils (127?152.4 microns) DFT.
In the intermediate coat, the crew also added aggregate at 40 to 60 mesh, which was also back-rolled. (In particularly slippery areas, such as the showers, an additional layer of aggregate was back-rolled in the final layer to help make it even more non-skid.) Finally, the crew came in the following day to apply the finish coat. This was the second layer of CFI’s Wearcoat 100 polyurethane, applied again at 5 to 6 mils (127?152.4 microns) DFT.
And with that, the system was ready to go.
Applying the epoxy floor here was like applying one on any of Specialty Coatings’ other jobs. However, one distinction — the type of facility — made an aspect of the job particularly interesting.
Working around a 200-foot-deep (60.96 m) elevator meant that the coatings crew needed to build an airtight barrier at the entrance to the shaft. Although the elevator wasn’t running at the time they were setting the floors, there were still a ton of other contracting crews working on site. Therefore, Specialty Coatings needed to take a special precaution for the polyurethane topcoat.
“When we used the poly, we had to make sure it didn’t get sucked down into the shaft,” explained Scisciani. Because the elevator shaft was open, the natural draw of air from the building went underground. And if the polyurethane odors got sucked down below to the face of the mine, it could have presented a problem.
“It’s an unnatural thing underground,” said Scisciani of the polyurethane smells. For people walking into it, it would have been like a “high dose of airplane glue.” Luckily, all of the contractors on site worked to keep that barrier closed. And, once the three-week job was over, all that was left were some shiny new floors and a rough mineral ready to be mined.
Beating a Bad Rap
For Scisciani, though this job was finished over 15 years ago, the amazing part now is that the original coatings lasted for so long in such a highly trafficked area.
Epoxies occasionally have a reputation in the coatings industry for being smelly and short-lived. Unfortunately, that reputation may come mainly from improper use. If you slap down a thin film system on any old concrete, yes, it may come up. But when prepped and applied properly and the right products are chosen, “there’s no reason you can’t get 20+ years out of the system,” said Scisciani. “Preparation and application are 90 percent of the success in any application…and the materials. The reason [the floors have] lasted this long is because they do.”