Handling Weather and Climate Challenges When Placing Concrete
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Weather conditions can drastically affect the results of your concrete project.
Weather conditions can drastically affect the results of your concrete project. This topic will explore both hot weather and cold weather concrete applications. Hot weather should be taken into consideration when planning concrete projects because of the potential effects on fresh and newly placed concrete. High concrete temperature causes increased water demand, which, in turn, will increase the water-cementitious materials ratio and result in lower strength and reduced durability. Higher temperatures tend to accelerate the rate of slump loss and can cause loss of entrained air and has a major effect on setting time of concrete. At higher temperatures, concrete will set quicker and finishing operations will need to occur at a faster rate. Concrete cured at higher temperatures at an early age will not be as strong as at later ages as the same concrete cured at normal temperatures in the range of 70 degrees F. Successful cold weather concreting requires an understanding of the various factors that affect concrete properties. In its fresh state concrete freezes if its temperature falls below 25 degrees F. The potential strength of frozen concrete can be reduced by more than 50% and it will not be durable. Concrete should be protected from freezing with methods demonstrated in this material. Concrete at a low temperature has a slower setting time and rate of strength gain, factors that should be accounted for when scheduling construction operations and form removal. Concrete exposed to freeze/thaw and water contact must have air-entrainment added.
AuthorsKenneth M. Justice, P.E., National Ready Mixed Concrete Association (NRMCA)
Hot Weather Concrete
• Why Is Hot Weather a Problem
• Ways to Protect Concrete in Hot Weather
• Mix Design(s)
• ACI 305 Information
Cold Weather Concrete
• Why Is Cold Weather a Problem
• Ways to Protect Concrete in Cold Weather
• Mix Design(s)
• ACI 306 Information