Shopko’s first polished concrete floor is in better shape today than when it was installed three years ago. That’s because Michael Hoeft, who’d placed concrete foundations and floors for Shopko before joining the company as regional construction manager, knew exactly what needed to be done to strengthen as well as preserve the surface.
“Like any finished flooring or floor covering, polished concrete requires maintenance,” Hoeft says. “The big hurdle was that nobody knew what ‘maintenance’ meant.”
Hoeft cleared that hurdle by identifying processes, practices, and products that would maintain surface durability. Then he required his polishing contractor and janitorial supply vendor to give Shopko employees a failsafe guide to maintenance.
Contract language: making maintenance everyone’s job
H.J. Martin and Son Inc., a large interior and specialty contractor based in Green Bay, Wis., had installed carpet and vinyl composition tile (VCT) for Shopko, also headquartered in Green Bay, for years. In 2014, when Hoeft decided to specify polished concrete for a new store in Kasson, Minn., he assembled a team including the designer, chemical company, sealant company, concrete placement company, janitorial supply company, and polishing contractor: H.J. Martin and Son. In addition to ensuring the floor’s success would become a cooperative effort, this opened communication among all involved to quickly get answers to any questions that might arise.
Shopko’s contract required H.J. Martin and Son to provide a year’s worth of cleaning supplies, and a laminated poster illustrating step-by-step maintenance procedures. In part because the process is product-specific, Shopko’s janitorial supply company, Chicago-based Jon-Don Inc., developed and produced the 2-foot-by-3-foot laminated graphic. Posted in the store’s janitorial room, it’s Shopko’s de facto specification for maintaining polished concrete.
“When they left, we had the products, polishing pads, and a spill recovery kit in the maintenance closet,” Hoeft says.
A Jon-Don representative taught the store’s employees how to operate and maintain the autoscrubber. He also reviewed the poster’s instructions and explained how to use the spill recovery kit. “And, of course, at the bottom of the poster was ‘here’s who you call if you have questions,’” Hoeft says.
Chemical basics: don’t mix and match
Hoeft’s research led him to the Consolideck line of lithium silicate-based products, developed by Prosoco Inc. of Lawrence, Kan., for producing and maintaining polished concrete floors. After consulting the company, he specified Consolideck LS lithium silicate hardener/densifier for polishing and Consolideck LSKlean, a blend of degreasers, detergents, and lithium silicate for floors that have been treated with Consolideck LS, for maintenance. In doing so, he followed a cardinal maintenance rule: Don’t mix chemistries. Manufacturers have different products for polishing, daily cleaning, and deep cleaning. Many contain lithium silicate to harden any “soft” calcium left over from the original hardening/densifying treatment or exposed by traffic or abrasion. But because each manufacturer also has its own formulation, using products from the same company ensures chemical compatibility.
Concrete, which is naturally alkaline, has a pH of around 10.2. VCT cleaners are closer to neutral, with a pH of 7 to 8. Therefore, applying VCT cleaners to polished concrete damages it.
“You’re essentially putting an acid on it,” says Mark Schuler, vice president of sales for Las Vegas-based Mr. Clean Maintenance Systems and MRC Concrete Polishing. The company cleans 14 million square feet of flooring every night, and a growing portion of that is polished concrete.
Like most solutions developed specifically to clean polished concrete, LSKlean, with a pH of 11.0, is less acidic than cleaners used on other hard surfaces.
It’s also important the cleaner matches what you’re trying to clean. Petroleum-infused grit and grime responds best to an emulsifier; animal fat, to a saponifier. In both cases, avoid scratching the surface by using cleaning pads that aren’t too aggressive.
“When you use high-quality products, you’re constantly building the resistance, the hardening of the floor,” Hoeft says. “And the aesthetics continue to improve.”
Timing is everything
“Maintenance begins when the finisher steps off the slab for the last time,” Hoeft says. “It’s not like when it was just a slab that at some point would be covered with finish flooring. Now, the framer, drywaller, painter, fire protection, and other trades are doing their work on top of your finished product, so you have to protect it. I always tell my guys when we’re done, ‘Nothing on this floor but water: no food, no coffee, no pop, no energy drinks, no cigarettes.’ It’s hard, but it’s important.”
Once polished concrete is placed in service, the next defense is matting. According to ISSA (formerly the International Sanity Supply Association), a 12-foot-long entrance mat removes 80% of the dirt from peoples’ shoes.
“We use industrial-grade carpet tile that extends 40 feet from the exterior auto entrance into the store,” Hoeft says. “This is maintained using a commercial extractor and has proven to be very serviceable.”
Regular sweeping is the next step. Frequency depends on foot traffic volume, but without regular sweeping dust and grime quickly accumulate. Supermarkets, for example, sweep a broom or dust mop every one to three hours. “They do this to get sandy material off the floor,” Schuler says. “When sand and salt are left for an extended period, people walking will start to scratch the finish and damage surface clarity.”
Daily cleaning with an automatic scrubber is a best practice, although low-traffic areas may only require scrubbing every two or three days. “Use the recommended chemical methods and nothing heavier than a scrubber pad,” Schuler says. “Maybe a red buff pad or, if your floor doesn’t get very dirty, a white polishing pad.”
Beyond the weekly schedule
Even with conscientious maintenance, polished concrete inevitably wears. Especially in high-traffic areas, the floor’s shiny appearance will begin to get dull or hazy. Fortunately, a little loving care brings back it back up to par. Schuler recommends running diamond-impregnated pads, or something similar, to restore clarity every four to six weeks.
Floors where spills have degraded or stained the concrete may require restoration. Although not as involved as the original polishing, the process usually requires deep grinding, densifying, burnishing, sealing, and buffing.
Minding the gap
For crack control, Hoeft specifies early entry sawcutting when slabs are being placed. That results in 6,000 feet of joints that require filler, a maintenance item for which new owners of polished concrete often fail to plan.
Unlike sealants that are formulated to expand and contract with the floor, joint fillers transfer sidewall load from slab to slab and are stiffer than sealants. This can lead to separation from the sides of the joint as the concrete shrinks.
Hoeft says about 300 feet, or 5%, of joints require replacement. Most shrinkage that adversely affects fillers occurs within the first year or two of placement, so his team keeps an eye on joint condition for the first 12 to 24 months of service.
The underlying high value of maintenance
Shopko tried polished concrete because of its lower installation cost compared to other flooring options, but the greater benefits are proving to be longevity and substantially lower maintenance requirements than carpet and VCT. Hoeft says that in every case where the floor has received “reasonable maintenance, we’ve not yet gotten to the threshold where we felt like we had to go back and do restorative maintenance.”
One new store unintentionally tested the floor’s durability: Automatic scrubbing was neglected for a time. “We just started to scrub routinely using a restorative pad—kind of putting the process into overdrive for a time—and recovered the finish,” Hoeft says. “If polished concrete floors are taken care of the way they should be, they just keep getting better.”