Q.: The late winter and early spring concreting seasons are coming up. Are there any special precautions we should take?

A.: We asked Art King of Materials Service Corp., Chicago, to help us answer your question. He recommends that you work with your supplier to get the most from your investment in admixtures and energy costs. When required, use heaters to warm up the forms or subgrade. Consider energy, labor, and materials costs to determine the most cost-effective approach. Although relatively expensive, nonchloride accelerators are available for work where chloride-based accelerators are prohibited. This may require an additional submittal to the architect/engineer.

As a general guide, if you're not comfortable laying on the subgrade, it may be too cold for the concrete. Consult "Cold Weather Concreting," ACI 306R-88, for recommended curing temperatures and durations. Art mentioned that many ready mix suppliers stop heating materials and rely on heated water as the weather improves. Check with your producer and review your materials and procedures if you are placing concrete during a cold snap.