Project Superintendant Jim Fleissner of MCL Construction, Omaha, Neb., admitted he was concerned.
Hardened gray concrete smeared and spattered the cream-colored precast walls of three of the entryways of the new Methodist Women’s Hospital in Omaha, the construction of which he was overseeing.
The spatters and smears landed on the walls of the entryways during installation of the concrete sub-floor. They reached about 4 feet up the walls, and had hardened and cured for two months.
Somehow, the messy splatters escaped notice until after installers laid brown and blue carpet in the entryways.
Removing jobsite staining and soiling, including excess mortar from newly constructed buildings is a routine part of construction – when it’s on the exterior. Cleaning exteriors involves hundreds, sometimes thousands of gallons of water to pre-wet the surface and then to rinse off the spent cleaner.
It’s fairly simple when you’re outside. It’s fairly simple when you remove the excess mortar before it’s had time to fully develop its hardness – 14 to 28 days.
But when the concrete is on the inside, and it has hardened like rock, and the only solution that will dissolve it may also dissolve what it’s on, and will also eat the carpet and nearby drywall, you are right to be concerned.
You can also add the customer to that list of concerns.
“Methodist Health System is one of our best clients,” Fleissner said. “But they’re very particular. It’s like they’re buying a new car. They don’t want a scratch on it.”
Fortunately, the A-team was already working on site.
“I’ve worked with Craig Christensen (SparkleWash Construction Services, Omaha) many times,” Fleissner said. “He’s knowledgeable about the surfaces that need to be cleaned and what it takes to clean them.”
Methodist Women’s Hospital was not the first hospital MCL Construction called on Christensen’s crew to clean.
They’d previously worked together on Lakeside Hospital, Bergan Mercy Medical Center and Immanuel Medical Center, all in Omaha.
“So I was comfortable I had the best guy for the job,” Fleissner said.
While cleaning Methodist Women’s Hospital’s eight stories of precast concrete and inset clay masonry; its sidewalks; and even its exterior metal surfaces was routine, Christensen put his own “best guy,” Foreman Hector Hernandez, on the entryways. Hernandez has been cleaning masonry and concrete with SparkleWash Construction Services since 2001.
“The project super gave his word to the owner that this would be perfect,” Christensen said. “And I gave my word to him.”
Hernandez and his crew started by developing tactics – prime considerations being the protection of the carpet and nearby drywall from water, rinse-water and the cleaner, and protection of the precast concrete walls, while still achieving 100 percent removal of the concrete splatters.
They covered the carpet with sheet rubber. Over that went a layer of polyethylene sheeting. They taped off the drywall with blue painter’s tape.
The team brought in shop vacs to suck up pre-wetting and rinse water as soon as it came off the walls. They tested to find the highest dilution rate of the mildest cleaner that would dissolve the offending concrete, without etching or discoloring the pre-cast walls.
Confident their plans and precautions were enough to back up their pledge of perfection, Hernandez and crew went to work. First step – mechanically removing as much of the built-up concrete as they could with metal hand tools.
Even here they had to balance the force needed to detach the hardened concrete with the care needed to leave the precast unscathed, Christensen said.
Next came a thorough soaking of the walls with clean water. By filling up the microscopic pores in the precast, the “pre-wetting” keeps the cleaner on the surface where it does its job of dissolving the concrete residues left from the scraping.
Hernandez and crew hit the gray concrete residues with Sure Klean® VanaTrol®. The specialty cleaner was developed for cleaning mortar smears off light-colored clay brick that get their color from metallic vanadium salts in the clay.
If not used with total care and attention to detail, even traditional proprietary masonry cleaners can react with the vanadium in the bricks to mobilize ugly green and brown stains.
VanaTrol® – its unique name a contraction of “vanadium” and “control” – allows for safe and quick cleaning of these sensitive masonries.
Since its introduction in 1960, contractors have found VanaTrol® to be effective for safely removing excess mortar from other surfaces requiring utmost care, such as the new limestone masonry installed at the Pentagon following 9-11.
Hernandez and crew diluted the VanaTrol® one part cleaner to three parts water, and applied it with hand pumps. They scrubbed gently, and cleaned the entire wall surface, Christensen said, for a uniform appearance.
They let the VanaTrol® dwell three to eight minutes before rinsing, Christiansen said, depending on the stubbornness of the concrete smears.
“We got about 80 percent of the residue off with the VanaTrol®,” he said.
For the rest, Christensen said, Hernandez personally spot cleaned with Sure Klean® Custom Masonry Cleaner, which is a little stronger than VanaTrol®, but made specifically for cleaning excess mortar off architectural concrete.
“Cleaning those entryways was nerve-wracking,” Christensen confessed. “We worried every minute that somehow the water was finding its way to the carpet. Thankfully, it never did.”
The exterior presented its own challenges. Along with general grit and grime from new construction darkening the precast walls, contaminants included glue and rust.
Glue smears got on the walls where inset thin bricks had fallen out and had to be glued back in place. Rain water dripping off metal exteriors put small rust stains into concrete sidewalks.
“They weren’t huge problems,” Christensen said. “But we’d promised a perfect job.”
The SparkleWash Construction Services crew restored the intended appearance of the precast exterior with Sure Klean® Light Duty Concrete Cleaner.
Light Duty Concrete Cleaner got the nod, Christensen said, because it’s safe for use around the architectural metals prominently featured in hospital’s design.
The glue came off with spot application of Sure Klean® Fast Acting Paint Stripper.
“The building looked nice before, but after Craig and his team got done, it was really something special,” Fleissner said. “It was the difference between seeing a car in a parking lot, and seeing that same car, brand new in the showroom.”
Methodist Women’s Hospital has since been named a co-winner (with St. Joseph Regional Medical Center, Mishwaka, Ind.) for Best Healthcare Facility, 2011, by PCI (Precast/Prestressed Concrete Institute).
“Our client was extremely pleased,” Fleissner said. “I was too.”
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