By Bill Palmer, for Concrete Construction Magazine
Participants on a Whole Foods polished floor project offer advice on how to make a polished concrete slab job come together smoothly.
One way to get a polished concrete slab or floor is to have the low-bid concrete contractor place a floor and then take bids from concrete polishing contractors and again take the low bid and hope for the best.
Another way is to assemble a team of the general contractors, concrete contractor, and polishing contractor that has experience and works together well, and pay them fairly for quality work.
Clearly, the latter approach will lead to a better polished concrete floor although far too many floors have been placed with the first approach.
When Whole Foods decided to build a new store in Birmingham, Mich., they knew they wanted a floor as nearly perfect as possible and hired contractors accordingly. “We had the right team members, it was a well-put-together project,” says Brad Baker, vice president, construction operations for C.E. Gleeson Constructors, the general contractor on the job. “The best thing about this project was the communication and coordination among the concrete contractor, the polishing contractor, and the other trades.”
Whole Foods representative Jim Szymczak was impressed by the way Albanelli Cement Contractors and Applied Flooring approached the project.
“It was the way they worked from the start. They knew what they needed to do the job right and they stood their ground with the GC and told them if you do this we can’t give you the quality you are expecting. They worked well with the plumbers and electricians. There was no arguing.”
Preplacement meeting
The key, all parties agreed, is getting everyone together early and working out the details in a way that put the ultimate goal first: a successful and beautiful polished concrete floor. “Having an owner who knows what he wants is important,” says Paul Albanelli. “The owner came to the preconstruction meeting with a list of items to consider and we talked through them.”
“The differences from a normal project started with the mix design and went through to the placement,” says Wayne Albanelli. “We had the polishing contractor work with us on the bid and he was at the pre-bid meeting and the scope review meeting. The owner’s rep turned up with a list of things he wanted and everyone knew what to expect?there were no surprises.”
Baker agrees. “We had a big meeting the first week of the project and the Whole Foods representative, the polishing contractor, and the concrete contractor simply put everything on the table. This was the same team that did a Whole Foods polished floor in East Lansing a couple of years ago. There were some small issues in East Lansing that were paid attention to in Birmingham and resolved.”
“The pre-pour meeting is essential on a project like this, even though I don’t like going to them since 75% has nothing to do with me,” says Steve Parker with Applied Flooring that did the polishing. “But it was critical, especially with the heavy grind and exposed large aggregate that Whole Foods wanted. Overall, we just talked it out with a goal of trying to achieve the floor everyone wanted. It’s easy to play the blame game but that didn’t happen here.”
“The specification from the architect and the actual floor we provided were much different,” says Wayne Albanelli “The architect used a spec for a hard troweled floor but the owner’s representative knew what he wanted. We as the slab contractor and the polishing contractor and the owner collaborated on this to get the best result. We even included the plumber since there were floor sinks, refrigeration conduits, and trench drains he had to work with us.”
Placing and finishing
The polished floor at the Birmingham Whole Foods is 30,000 square feet with a deep exposed aggregate grind and polish. The back of the store was placed first and polished as a mock-up that Szymczak approved.
The concrete has 395 pounds of cement, 169 pounds of ground granulated blast furnace slag, and three different aggregates. The slag contributes some color. No integral color was needed. “This was a mix Whole Foods had used at a store in Chicago and they liked the look,” says Paul Albanelli. “The aggregate here is a little different but it still gave them what they wanted.”
In a grocery store, there are a lot of penetrations for drains, cleanouts, electrical stubs, and refrigeration lines: more than 200 penetrations at the Birmingham store. “The biggest difficulty was with the concrete placement,” says Paul Albanelli.
“If you are tailgating the concrete and using a laser screed, that size isn’t a problem but with all the penetrations we couldn’t use the laser screed and had to place it by hand. It took a 10-hour pour, although we were ready for it and got it done. Whole Foods insisted that the important central sales area was placed in a single placement with no construction joints, only saw-cut contraction joints.”
One issue at the previous Whole Foods store in East Lansing had been around the drains. “In East Lansing, we assumed that the drains would be hidden under coolers or equipment, but there are several places where they are visible,” says Parker.
“But the concrete next to the drains was not finished in a way that we could do a good polish and get the coarse aggregate exposed. With a coarse deep grind, we can remove a lot of problems but we can’t insert large aggregate when it isn’t there. We discussed that if they could leave us something better in those locations we could get the right finish.”
Albanelli’s solution was simple but clever. They first cut 1/8-inch thick squares or circles of Thermo-Ply structural sheathing to match the size of the drains and cleanouts. These were adhered to the tops of the penetrations and that became the finished elevation of the floor. Then when the grinders took off the top layer of concrete, the floor grade came down to be flush with the tops of the drains and cleanouts.
“We were careful to consolidate very well around the drains,” says Wayne Albanelli. Workers would finish by hand around these penetrations, then the power trowels could go right over the top.
“We were also careful not to leave footprints in the concrete, although with this floor there was a fairly deep exposure so it wasn’t so critical.” Parker even suggested that they seed in aggregate wherever they walked into the wet concrete. “That was an interesting idea,” says Paul, “but we didn’t have time to do that since we placed the entire customer area of the store in one placement.”
With the deep grind, a hard troweled finish would have been a detriment. “We told Albanelli the level of finish we needed?no burn,” says Parker. “We did need it to be flat and the drain and cleanout elevations needed to be right.”
“Some guys who are polishing want an FF50 but with the deep exposure that’s not necessary there’s really no need to talk about FF and FL,” says Paul Albanelli. “They need it flat and well-consolidated but not burnished or hard-troweled.
In the past, we gave the polishing contractor a hard troweled floor and that surface made it difficult for them to cut through. In this case, we gave them a lightly finished rough floor which worked much better.”
Polishing the floor
“We started cutting the floor a week to 10 days after placement,” says Parker. “We used?RetroPlates Kickstarter to do the initial grinding wet. We used to do this kind of deep grind dry but that resulted in lots of popouts that had to be grouted. Once we moved to a wet grind with the cutting fluid that didn’t happen. The result was greater clarity in the floor.
“We started with 16 to 25 diamond grit to expose the aggregate and then 150 grit metals. We then backed down to an 80 grit resin grind. There were a total of five steps ending with a 1500 grit finish.”
On a floor this big, five polishing steps take some time and other construction work needed to proceed. Parker says that they did the polishing work on a quarter of the floor at a time so other trades could be working on the remainder. “Once we finished a quarter, Gleeson put down RamBoard so that protected the polishing.”
Applied Flooring did not use any sort of guard on the floor, just finishing with a treatment of RetroPel penetrating sealer. “We don’t use a guard, says Parker, “it tends to wear off with foot traffic. In East Lansing after more than a year, the slab still shows no signs of wear, although that’s partly a result of the great job they do maintain it.”
Polished Concrete Slab… Finished
“Everything went seamlessly,” says Baker. “We had a realistic schedule that everyone bought into and we stayed right on schedule to the end didn’t miss any dates.”
“We did a previous store with Albanelli eight years ago and we saw that they knew what they were doing,” says Szymczak.
“I’ve worked with other guys who didn’t but Albanelli did. They aren’t the cheapest but we were very comfortable with them and very happy with their performance. I would recommend them to anyone.”