The newly constructed Clarence Brown Conference Center in Cartersville, Ga., is about an hour north of Atlanta. Visitors to the 45,000-square-foot facility are greeted by a polished concrete floor in the main corridor and entrance lobby. Natural gold, black and white surface-seeded aggregate, an intricate saw-cut pattern and a multi-color design throughout the floor create what Middle Georgia Concrete Constructors CEO Scott Truax calls "a contemporary twist on an old, stately terrazzo floor."
Middle Georgia, a full-service concrete construction firm out of Atlanta, Ga., has been offering polished concrete through its decorative concrete division, CSolutions, for four years. About 75 percent of the work through the decorative division is polished concrete. Truax is a CPAA-accredited Craftsman and oversees the work on his team's concrete polishing jobs. "Our focus historically has not been on the big box-type, large floor polishing jobs. There are enough people doing that," Truax says. "Our focus has been these boutique-type jobs — broadcasting aggregate, intricate scoring and dying, public school work, and the kinds of jobs where we can include polishing as part of our entire project package."
The work at the Clarence Brown Conference Center came about after Middle Georgia presented a "lunch and learn" program on surface seeded aggregates and polished concrete for local architects. It was the contractor's third project with this particular architect, and Middle Georgia worked closely with the firm through the design process.
Truax invited the architect to the Middle Georgia headquarters, gave her a 12-inch tray and samples of the company's available aggregates, and allowed her to develop the aggregate blend she wanted. Choosing a dye color wasn't as easy. The floor is made up of different colors, including natural concrete, a reddish-orange and tan. Since none of the standard colors offered the hues the architect was looking for, Truax worked with her to determine the correct blend of colors for the floor.
After samples were cast and accepted, Middle Georgia was awarded the work to place and finished the L-shaped 7,800 square feet of floors that would receive a polish along with the polishing work.
Placing the slab
Middle Georgia placed and finished the concrete slab in four pours over the course of two weeks. In each pour, the crew placed the concrete, floated the slab, broadcast the aggregate, floated the surface a second time and finished the concrete. Quality control is one of the advantages Middle Georgia enjoys when it places its own concrete slab before a polish. Truax explains a few placing and finishing practices the company follows in order to achieve a concrete surface optimized to take a polish.
"When you're broadcasting aggregates, flatness is the key," Truax says. "And once we broadcast the aggregates, we don't go back on the floor and walk on it. The first couple installations we did like this, we walked on the slab with traditional walk-behind trowel machines. You could really see the aggregate pushed down where the men were walking behind the trowel machines."
Truax further explains how this uneven aggregate depth makes it difficult to expose the aggregate evenly throughout the floor on the first pass with the grinders. Now his crews avoid walking on the slab after it broadcasts the rock. In order to do this, the placing crew makes narrow pours so it can access the slab from outside the forms.
An intricate cut
One of the most unique features of this project is the saw cut pattern on the floor. "Before the job we sat down with the structural engineer and came up with a control joint layout plan that also worked with the decorative design," Truax says. "So we looked at it first from a structural perspective and where the joints needed to be to reduce cracking. Then we looked at how to incorporate those joints into the design and where we would add additional cuts to get the design the architect was looking for."