The paste was a combination of Type I/II cement, fly ash, micro ash, silica fume, a superplasticizer, a non-chloride accelerator, and a liquid color. Early tests indicated that 90-day strength would easily exceed 10,000 psi.
An additional design challenge was how to structurally reinforce the top and especially the legs of the table because of their respective thickness of 2 inches for the top and 3 inches for the legs.
Our sales representative for Forta Fibers, Kenny Juen, suggested we use Forta Ferro structural fibers for reinforcement. It made perfect sense. The four legs for the table contain no traditional reinforcement other than structural fiber, and allowed us to drill holes for bolting the frame into the thin section without fear of cracking.
The pieces that compose the top use only a carbon fiber grid as the primary reinforcement. This type of reinforcement also helped with the imbedded turnbuckle system to join the five pieces together.
Because of the volume necessary to cast all of the pieces at the same time, the concrete had to be mixed in a ready-mix truck. The concrete used a combination of specialty materials, so all of those materials had to be hand-bagged into the truck. Once it was mixed, the concrete was discharged into wheelbarrows and then hand-placed into the forms. A concrete vibrator eliminated air voids.
We removed the forms six days later, flipped over each piece, and placed them on the steel support structure bolted to the legs. We followed this with two weeks of grinding and polishing.Final product
Finally, on Aug. 25, we moved the 3700-pound concrete conference table into the second floor conference room. While forming, placing, grinding, and polishing the table was an operation unto itself, after the table was assembled in the laboratory, we had to disassemble it and move it to the second floor conference room four miles away.
Moving a 450-pound piece of concrete 4 inches is one thing, but moving it four miles is altogether different. In something reminiscent of a military mobilization, 15 members of our team and nine trucks moved the table into place.
Each piece was wrapped and crated for transport. Once all of the pieces were in place, the arduous process of leveling each piece began, resulting in some rather awkward positions.
Once each piece was leveled and secured, we used self-leveling epoxy to fill in the blockouts left for fitting purposes. Returning the next day, the tape was removed, and in-place polishing started.
The finished table is equally as impressive as the effort to get it there. This was one of the most difficult and complicated engineering projects of my career. When people ask if I want to do it again, I politely decline. Unfortunately, my wife has seen it, and we are currently in negotiations to replace her kitchen countertops.
— Richard S. Szecsy is vice president, new product development/risk management, at Lattimore Materials Co., McKinney, Texas. Efirstname.lastname@example.org. Visit the producer atwww.lmctx.com.Products Used in the Project
- Cement: Holcim Type I/II
- Fly ash: Headwaters Class F - Martin lake
- Microash: Boral Materials - Micron 3
- Silica fume: Sika Corp.
- Superplasticizer: Sika Corp. - Viscocrete 2100
- Non-chloride accelerator: Sika Corp. -SikaMix NC
- Color: Solomon Colors - Buckskin
- Coarse Aggregate #1: Lattimore Materials Co. - Stringtown
- Coarse Aggregate #2: Capital Aggregates -Marble Falls
- Fine Aggregate (mansand) #1: Lattimore Materials Co. - Stringtown
- Fine Aggregate (natural sand) #2: Lattimore Materials Co. - Ambrose
- Fiber: Forta Corp. - Forta Ferro
- Sealer: CHENG Concrete Countertop Sealer
- Wax: CHENG Concrete Countertop Wax
- Polishing pads: DeFusco Industrial Supply, 5-inch diamond pads
- Edge forms: Steigmeier