Decorative concrete can be an unpredictable animal at times. We find our problem phone calls from contractors increase when the temperatures rise during the heat of the summer and fall in the winter months. The bottom line is, whether you are working with two-component resins, cement-based skim coats or ready-mixed concrete, these materials set much quicker in warmer temperatures and much slower in cooler temperatures.
Recently we poured a 5-yard panel of stamped concrete (which is not a lot for a supposed pro), not taking into account we were using a mix design that we typically use during the winter months or when temperatures are under 80 degrees. This mix has a higher cement content which gives the concrete a needed boost for quicker setting times in the cool season. On our pour we started placing the concrete with no apparent problems other than our sweat burning our eyes on this 97-degree day.
A couple applications of color hardener later and some very fast finishing, we found ourselves removing the last stamping mat from the slab just one hour and fifteen minutes from the time we started placing the concrete. Shame on me for not taking the extreme conditions into account and compensating for the heat! I'm happy to report our test panel came out great thanks to some lightning fast finishing. You can bet some modifications were made to our next mix in addition to step retarding with Fritz-Pak's Mini Delay Set, allowing us much more time in those extreme conditions.
It is scenarios like this where a professional needs to tap into all of his or her past experiences and training in order to overcome jobsite adversities. A contractor can invest in training along with countless hours of practice and just when you think you have mastered certain techniques, wham, something comes up on an actual project that knocks you down, making you feel worn out, dejected and questioning your ability as a craftsman. I can certainly sympathize with you - I've had a number of my own gut wrenching sleepless nights lying in the bed wondering, "What the hell just happened and how could this catastrophe have been prevented?!" The reality of this fickle industry boils down to this - sometimes disaster is unavoidable and your company has to either fix or re-do the work at your expense.
This was the case with Cody Dawkins of Create-A-Crete, an aggressive, young, up-and-coming contractor in the greater Atlanta area who believes in training and doing things the right way. Despite Dawkins' impressive portfolio of successful applications, he had one of these nightmare projects. After a sleepless night, he decided to call me for some advice.
A tale of two pours
Dawkins' project consisted of pouring stamped and colored concrete on an elevated, corrugated metal pan deck, which is kind of scary even in perfect conditions. His first pour went down "flawlessly," as he put it. The concrete was placed around mid-morning with temperatures in the range of 75 to 80 degrees and stamped roughly two and a half hours later with a perfectly consistent imprint. It was the second load of concrete that took the wind out of Dawkins' sails and in the end cost his company labor and additional products. It also left him wondering what had just happened and how the project could have taken so dramatic a turn in only three hours.
With temperatures exceeding 90 degrees by the time the second load was delivered, Dawkins thought it would be a good idea to add a small dose of retarder from the batch plant to extend the setting time of his second load. Because of the size of the area the crew needed to cover, they added additional retarder on the jobsite to prevent the concrete from setting up too quickly. As soon as he and his crew started placing the second batch, someone noted that the concrete seemed "sticky" and "hard to finish."