The overlay process itself was a challenge in timeliness. Concrete Visions crew members had only 15 minutes of working time to seed the overlay after the material started to pump. “We needed to have plenty of people on site and they had to know their jobs,” Bowman explains. “I also had someone on site to step in and take over if something got held up. And before the pour started we walked through the job on a dry run.”
The crew used a 38-in. gauge rake to ensure the overlay was placed to the proper depth; about 18 inch of this would be ground off during the polishing process. Crew members then ran over the material with a spiked roller, also known as a “porcupine roller,” which is a tool on a long handle that looks like a 2-foot-wide paint roller covered with tiny spikes. The tool’s spikes draw out air bubbles from the overlay. Then crew members seeded the 18-inch and smaller mirrored glass chips on top of the overlay using hand-held grass seeding equipment. Then they smoothed the top of the overlay very gently with a trowel equipped with a flexible rubber blade.
Once poured and seeded, Concrete Visions let the overlay sit an extra day before beginning the grinding and polishing process.
As Concrete Visions set out on an eight-day polishing sequence, the crew struggled with working around other contractors. Finally they found a compromise everyone could agree to. “We wouldn’t let other trades on the floor during wet polishing steps,” Bowman says. “But during the dry polish we told them they could use the floor as long as their feet were clean.”
Bowman says the key to this overlay project was wet grinding. “The main reason we water ground was the glass,” he explains. “If we heated up the floor too much the glass could have fractured. The best way to keep the diamonds and glass cool was to water grind.” He adds that the wet polishing process also helped remove many of the polymers in the overlay itself; the issues with the polymers in a dry grind is that the polishing process can polish the polymers instead of the concrete, a situation that should be avoided.
Concrete Visions started the polishing process with 120-grit metal bond abrasives. “If we started with 70-grit metal abrasives we could have ground through our small glass pieces too quickly,” Bowman explains. “We ran multiple passes with the 120-grit metal abrasives in order to reach full refinement with that grit.”
From there, crews moved up to 220-grit metal bond abrasives, then dropped back to 200-grit resin bonded abrasives. The 200-grit resin bonded abrasives were the last wet step in the polishing sequence. It was also after this step that the crew densified the floor.
From there, the Concrete Visions team used a 400-, 800- and 1,500-grit resin bonded abrasives sequence. The crew followed with a 3,000-grit Vortex pad on a burnisher, cleaned the floor and applied a stain guard as specified.
Concrete Visions team members performed edge work with the main polishing sequence. Crews also auto scrubbed between each grit sequence and utilized a slurry compressor on the job, which recycles the polishing water and forms slurry into semi-dry cakes that can be thrown in the trash.
Bowman emphasizes that a polishing job isn’t finished until a contractor leaves the owner a maintenance plan. The plan Concrete Visions presented was tailored to the products used on the project. Bowman adds it is important to consider the products used in writing a maintenance plan and emphasize to an owner how good maintenance can help a floor retain high traction levels.
Despite the many challenges on this project, the Concrete Visions crew members overcame them through organization and forethought. “Overlays are challenging, but they are manageable with proper planning,” Bowman says. And most importantly, the end result produced the effect the owner and architect were looking for.
Company: Concrete Visions, Inc.
Services Offered: Polished and densified floors, overlays, surface prep, floor coatings, and concrete countertops.
CPAA Certification: 2 Master Craftsman and 5 Craftsman
Key Products and Equipment: CTS Cement Rapid Set TRU self-leveling overlay; SASE 780 grinders and Edge-Pro 180; DeWalt variable speed hand grinders; LM Construction Chemicals LiON Hard densifier; GranQuartz polishing abrasives; Substrate Technology, Inc. slurry compressor; Midwest Rakes CAM Gauge Rake, Magic Trowel smoother and Spiked Roller; W.R. Meadows Bellatrix guard product.