A January blizzard may have shut down New York, Washington, and Philadelphia. But the storm missed Massachusetts — and this week, design-build contractor Andrew DiGiammo's crew is pouring foundation slabs. On Tuesday, DiGiammo's crew placed the first of four slabs for a condo building in Fall River.

"It's a beautiful day," DiGiammo told JLC. "It's going to be in the forties. But my guys aren't too happy dragging blankets around in the mud and the slush, getting freezing cold and wet."

A Slab in Winter
Workers remove insulation blankets from a compacted gravel sub-base in preparation for a concrete pour on January 26, 2016. With construction schedules tight, winter cold can't stop concrete work in New England.

In slow times, concrete work stops in winter. And in fact, DiGiammo postponed another job, a custom home with an ocean view, until the weather warms up. But when times are busy, construction can't always stop for the weather. This multifamily project includes three buildings that have to be finished before summer — and that means foundations have to get poured now, cold weather or no. The crew ran underground plumbing for the building earlier in the month; now it's time to get the slabs done. "We'll do a 20-yard pour for one unit at a time, every day," DiGiammo said, "and get the next one ready to pour the next day. You don't want to get too far ahead of yourself in winter — if the weather changes you could get into trouble."

For this job, DiGiammo has a Ground Heater on site, running hot water through plastic tubes on the gravel sub-base for the slabs. The heater keeps the ground warm under the blankets. Once the slabs are poured, the crew will replace the blankets to keep the fresh concrete from freezing while the slabs gain enough strength to be proof against frost damage.

Heating the Ground
An oil-fired Ground Heater (red trailer at rear) provides hot water for hydronic tubing laid on the gravel sub-base overnight to keep the ground thawed and ready for placing a slab in the morning. Active heat and blankets are the traditional solution for wintertime flatwork placement.

That method is time-tested, and consistent with typical practice. But these days, some contractors are pouring slabs without heat or insulation, even in cold weather — and having good success. This month, JLC covers the cutting-edge technology that's making cold-weather concrete work more and more practical — and economical. For an in-depth look, see "Cold Weather Concrete: Experience Drives the Conversation." Connecticut contractor Dennis Purinton explains how monitoring concrete temperatures helps him gauge the "maturity" of his fresh concrete to know when the material is hard enough to withstand freezing, Con-Cure's John Gnaedinger supplies more details about the maturity method, and US Army Corps of Engineers researcher Lynette Barna discusses research into "antifreeze concrete" at the Corps' Cold Regions Research and Engineering Laboratory (CRREL).