This winter is one of the snowiest (47 inches to date) and one of the coldest (40 below wind chills) in recent history. While most of us are inside trying to avoid the snow and cold, construction crews on the sites of Eckstein Hall and Zilber Hall are out working in the arctic air. Pouring concrete and erecting steel in the cold weather present many challenges, but if the proper building construction techniques are followed, construction can progress on schedule.
Concrete can be successfully poured in cold weather. According to the American Concrete Institute, cold weather conditions exist when the average daily temperature drops below 40°F (5°C) for more than 3 successive days. When cold weather conditions exist, there are special precautions that can be taken in the placing, finishing, curing, and protecting of concrete. In order for concrete to cure properly, temperature minimums and moisture levels must be managed during the curing cycle to ensure the proper strength characteristics are attained.
Some of the special precautions include;
On the construction site of Eckstein Hall, the foundation walls of the first parking level and deck of the second parking level were poured before the cold weather began, allowing the lower level to be enclosed and heated. The heating of the first level creates radiant heat for work that is being done on the second level. The snow has been more of a delay than the cold temperatures as the snow and ice has to be completely removed before work can proceed. The second level deck is a large area with a lot of recesses for piping, so that can take a good portion of the day!
The Zilber Hall foundation is complete except for the section that allows access to the lower level of the building. The structural steel framing is nearly complete. Structural steel erection in cold weather is difficult due to winds and exposure. The technical aspects of steel erecting are not different for cold weather conditions, but on certain buildings, the expansion and contraction of the steel due to temperature changes can affect quality.
There are steel erection operations that are affected by weather, such as welding, laying of metal deck, and high-strength bolting, that could prevent steel installation. Welds must be preheated in very cold weather to prevent the premature cooling of the deposited metal. Shear studs will not weld properly when there is ice on the steel. Metal deck becomes very slippery with only a little precipitation on it. High-strength bolts sometimes do not perform properly when used in extreme conditions, and must be kept dry, clean and warm. Steel beams must have the snow and ice removed from the top of them before they are covered with deck.
Working in cold weather conditions is a balance of safety and production. The construction crews on both jobs prepare for the snow and cold by dressing in layers and taking warming breaks. Breaks are staggered so the warm job trailers are available to everyone on site. Even in Wisconsin's cold weather people expect their buildings to be build. With the right crew and proper building techniques, construction can progress on schedule.