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Given a choice, Pepper Construction would prefer to pour concrete when temperatures are consistently above 40° Fahrenheit. Curing concrete slabs in sub-freezing temperatures come with a unique set of challenges. “The only time we pour concrete in the winter is when we have to do it,” says Brett Johnson, Sr. superintendent for Pepper Construction. “We are concerned about the concrete cooling too quickly and the water freezing, both of which can ruin a new slab.”

This past winter, a tenant of a new strip mall development just outside of Kenosha, Wis., where Pepper was working moved up its grand opening. Johnson ran into one of those situations where Pepper had to pour in sub-freezing temperatures. “We started the project in January and the only alternative was a winter concrete pour,” mentions Johnson.

With temperatures fluctuating between 5° and 35° F, Pepper needed specialized heating equipment to complete the job. “Labs will not let us pour concrete on frozen ground, and most villages in Wisconsin want 40° and rising temps to pour concrete,” Johnson adds.

Pepper consulted with Lincoln Contractor’s Supply, Inc. (LCS), the Milwaukee-based Wacker Neuson dealer, for options. After speaking with Johnson, LCS representatives knew that the application required a dual-purpose machine: first to thaw the ground; and second to cure the concrete. “After learning the pour size would be approximately 1,100 ft², I knew the E1100 was the right machine for the job,” recalls Jeff Deinhammer, territory manager for LCS.

With 1,100 ft of hose, the small-but-powerful Ground Heaters E1100 hydronic surface heater from Wacker Neuson delivers standard thawing and curing capacities of up to 2,200 ft². The unit provides 110,000 BTU-per-hour heat output with 87% heater efficiency, the highest in the industry. With its 72 gallon fuel tank, the E1100 offers up to a 115 hour run time between refueling.

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Dual Purpose E1100
LCS delivered the E1100 heater to the strip mall, and it immediately got the attention of Pepper’s crews. “I expected them to bring out a huge heater, but I was pleasantly surprised by the compact size of the E1100,” recalls Johnson.

The hydronic heater first went to work thawing the frozen ground. “We kept hose spacing at 1 ft and covered the hose with one layer of poly and two layers of blankets,” explains Deinhammer. Within a mere four days, the E1100 had thawed the entire 1,100 ft² section to a depth of 3.5 ft Pepper’s crews then removed the soil that could not be compacted, replaced it with gravel and prepped the area for the pour.

Being a shopping center, concrete aesthetics was of great importance to the department store, and Pepper did not want to risk leaving marks in the concrete by placing the heater’s hoses at the surface. For the cure, LCS recommended replacing the heater’s standard flexible rubber hose with a 5/8 in Pex tubing, which could be permanently placed in the concrete.

Within an hour, the Pex line was placed at 18 in centers and zip-tied to the rebar. After nearly 20 yd³ of concrete was poured and finished, the outgoing temperature on the E1100 was set at 80° F, so that returning temperatures were in the 55° to 60° F range. Crews then covered the concrete with blankets and let the machine run overnight. On day two, they came back to saw the expansion joints and check that the concrete temperature remained at 60° F. The E1100 was allowed to run another six days to allow the concrete to fully cure.

Helping to reduce labor and fuel costs, the E1100 was hooked up to standard 120-volt power. The on-board generator was used only to heat the boiler. “It’s an awesome little unit,” exclaimed Johnson. “We used about 1 gallon per hour to thaw the ground and less than 0.5 gallon per hour when during the concrete cure.” Peter Soccorso with Pepper adds, “It was nice to be able to fill the tank on Friday and know that we were good until Tuesday.”

At the end of day seven of the concrete cure, Pepper’s crews removed the blankets to reveal a flawless, properly cured concrete slab. The Pex tubing was then cut, the glycol removed from the lines and the ends were capped.

Having the heater made Johnson rest a little easier with this sub-freezing concrete pour. “I wouldn’t want the responsibility of concrete poured in the winter without heat,” confides Johnson. “If we consistently poured a lot of concrete in below freezing temperatures, the E1100 is one piece of equipment that I’d want around.”

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