Tales from the Dark Side
Horror Stories in Polished Concrete Finishes
By Chris Bennett
Over the years, I have consulted on quite a few projects with exposed concrete (polished concrete) floor finishes. There have been successes and then there have been complete tragedies—slabs so scary that all parties involved lose sleep and sanity for the remainder of their lives!
Perhaps the only comforting part of these tragic journeys for most, is realizing they are not alone. When sitting around the metaphorical construction campfire, you meet other weary travelers who whisper their grim and fearful battles with concrete. Two of those travelers, Keith Robinson of Dialog Design, and Jessica Ledger of CSDA member Royale Concrete, have been brave enough to retell their horror stories here.
Please join us, gentle reader, as we bring you TALES FROM THE DARK SIDE OF CONCRETE! These stories of terror are true.
Keith Robinson had a large government project involving exposed concrete floors. Keith and his team had prepared for everything they had set out to do, included the concrete supplier and finisher as part of their pre-slab meeting, reviewed design intent and had even taken the time to narrow installers down based on visiting previous successful, installations. Just when everyone thought everything was going according to plan the worst thing possible happened.
The General Contractor (GC) decided to take over design intent. Without clearly communicating what was happening, the GC changed the concrete supplier. The supplier, having not attended the pre-pour meeting, was unaware of the expected outcome and thus changed the mix design. Sadder still, was the depressing decision for the GC to self-perform the slab installation! Not having the necessary equipment, the GC rented equipment and hired casual labor. The slab was overworked. The joints were cut two weeks too late and, in an effort to speed-up the curing for the construction schedule, the GC used open-flame propane heaters in some (but not all) of the areas. This caused curing and drying times to be different across the surface of the slab as well as carbonation and other aesthetic problems. After not hitting the specified design intent, the GC did the scariest thing of all—asked for more money to fix its mistake!
This slab was buried in an unmarked grave in the forsaken-facility cemetery, but still tortures the owner to this day.
During my own days in manufacturing, I was consulting on a polishing project in Florida for a wealthy client with very specific design ideas for his commercial office building. The floors were to be bone white with large, jet-black aggregate and then polished to a semi-gloss sheen. Research was conducted for the right amount of aluminum oxide in the mix to create the desired shade of white and a special supplier of dark aggregate was found outside of state lines.
The special aggregate was purchased and then shipped in for the construction of the slab on grade. Everything seemed to be going along well and then the bottom fell out! Too much fly-ash was added to the white mix because the supplier had not read the specification. It turned the concrete a ghoulish grey. The uncertified placement contractor then proceeded to vibrate the special aggregate too deep into the slab. This design intent had indeed died a ghastly, horrible death. Exposed aggregate of any kind was no longer an option and nothing short of cutting out and repouring would ever make this grey slab white. When questioned as to why he had murdered the innocent design intent, the cruel contractor’s only reply was, “I have been doing concrete for 30 years. Nobody is going to tell me how to do my job.”
Sometimes, if you listen at night, you can still hear the spirit of the design intent’s macabre howling, trying to find its way back into the slab.
It was a day just like any other for Jessica Ledger, until the phone rang at Royale Concrete. “Help,” the voice said. “My brand new slab is delaminating and I don’t know why!” Royale Concrete had been contracted to install a polished concrete floor at this very facility and this news did not sit well with Ledger. Rushing over just after midnight, she discovered that the slab was indeed delaminating. It had only been poured within the last six months and she knew this was not suppose to be happening. As if delamination was not bad enough, the slab was also demon-discolored and cracking!
“The customer ran a chain test across the slab and realized there were several hollow spots in the floor and the delamination was confirmed,” said Ledger. “We were brought in as a contractor that could help fix the problem. We were the second contractor to submit a proposal, but the first properly qualified to effectively solve the issue.”
What did Jessica have that the other concrete contractors did not have? Experience and training. But how does Jessica let decision-makers know she has these two important items? Certification. The Concrete Sawing & Drilling Association has a standard and training program for educating professionals on how to measure surface texture grades (STG) for concrete surfaces and it is called CSDA-ST-115. Ledger and her team are not only ST-115 certified, but also have another third-party training and certification from CSDA member Select Concrete Solutions (SCS). This company provides training on slab placement as well as finishing and polishing that specifically address moisture issues.
There can, indeed, be many scary scenarios related to the installation of concrete floor systems. However, proper training and certification combined with the use of defined best practices can help most concrete polishing contractors sleep easy and avoid nightmare projects. I hope you have enjoyed this journey to the dark side of concrete. Sleep well… if you can!