A record-breaking heat wave is stretching across most of the United States this week, with about 195 million people under watches and warnings as temperatures peak today and into the weekend.
More than 85% of the lower 48 state's population will see temperatures above 90 degrees Fahrenheit over the next few days, according to CNN meteorologist Dave Hennen, and more than half will see temperatures higher than 95 degrees.
But for those working outdoors, these extreme temperatures are unavoidable—the job still must get done. Besides the risk of experiencing symptoms of heat-related illnesses such as heat cramps, heat rash, heat exhaustion, fainting and heat stroke, concrete contractors also face numerous challenges when temps rise. Placing concrete in extreme weather means managing complications such as accelerated slump loss, plastic shrinkage cracking and faster set times.
To combat these issues, Kryton International offered in a recent blog post the following concrete management tips for working in hot weather:
1. Don’t let tight deadlines tempt you to order or try to place more ready-mixed concrete than you can finish and cover.
2. Make sure you have enough labor and equipment to place concrete quickly. Delays and prolonged agitation lead to higher concrete temperatures and slump loss.
3. Mixers, chutes, pump lines and other equipment in contact with the mix should be shaded, covered with wet burlap or painted white to reduce solar heat.
4. On windy days, install windbreaks.
5. Use refrigerated water, ice or liquid nitrogen to cool the mix during batching.
6. Consider beginning the job in the afternoon to capitalize on lower evening temperatures.
7. Ensure each ready-mix truck carries additional superplasticizer for temperature-related slump loss.
8. To protect against premature water loss, wet down substrates before pouring concrete.
9. Spray aggregate piles to keep them cool and damp.
10. Immediately following final finishing, begin the wet curing process, using specifications produced by the American Concrete Institute (ACI), found in ACI 308R-01 – Guide to Curing Concrete).