Laying Concrete in Cold Temperatures a 22 Hour Wait

March 30, 2015

When our client requested a large concrete floor in their storage building- we knew we had a challenge on our hands.  The job would involve over 60m3 of concrete with a power float finish in East Yorkshire, during March. Cold weather during the initial stages of Concrete laying can be a disaster, leaving crumbling concrete with below optimum strength. Pryjen Construction rose to the challenge and delivered a fantastic result – a job which involved an overnight pour.

Concrete and the cold

For concrete to set properly and harden, a chemical reaction called “hydration” (also known as the curing process) must take place. The hydration process is when the chemicals in the concrete react with water to bind the mixture together. Curing is one of the most important steps in concrete construction. Fresh concrete frozen during the first 24 hours loses around 50% of its potential 28 day strength. We began our concrete pour at 7:30 am.

Concrete sets much slower in cold weather. In order for hydration to occur. For every 10°C reduction in concrete temperature, the times of setting of the concrete double, thus increasing the amount of time that the concrete is vulnerable to damage due to freezing.

For the concrete reach the specified 28-day strength it must not freeze until cured. Concrete that is protected from freezing until it has attained a compressive strength of at least 3.45 Mpa (500 psi) will not be damaged by exposure to a single freezing cycle. Despite our 7:30 start, we were not satisfied that the concrete has gone off until 5 am the following morning.

Staying with the concrete and preventing it from freezing overnight meant that we could be sure the floor slab was cured and would mature to full strength. Pouring concrete during the British Springtime is possible – it just takes time.

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