It’s a very good question, often asked by many a builder or contractor at this time of year. Lucky for you, we have the answer.
The short answer is, yes, it does affect pouring concrete. In an ideal scenario, you do not want to pour concrete outdoors in temperatures lower than 3-5 degrees celsius. However, we are going to break down ways you can get around this.
The first thing to take note of is exactly what goes into concrete, which in-turn will give you an idea of why pouring in cold weather is not ideal. Here’s a simple equation to sum it up: stone + sand + cement + water = concrete. This is the traditional (and arguably only) way to mix concrete, with the exception of some mixes for different uses, but for strong concrete these are the ingredients. The main factor we need to pay attention to in the cold is WATER, as it changes form in temperatures nearing, at, or below 0 degrees celsius. The water molecules in the concrete have transformed from regular H2o but if the temperature drops low enough, even slightly above 0 degrees, they can crystallise and/or expand.
Why is this bad for concrete? We really should not need to explain. But, in short, crystals are not strong enough for concrete to act the way it should when it’s setting, and can cause major structural failure if the proper steps are not taken to avoid it. If your concrete is expanding when it should be shrinking slightly as it sets, you have a serious problem and cannot build on it.
Here are some steps to take to avoid disaster in low-temperature concrete pouring:
- DO NOT POUR – The easiest solution is to prevent it altogether, and wait until warmer temperatures
- Lay tarpaulin or a cover on the setting concrete – this will keep the frost off the surface, and significantly decrease the chances of crystallisation/expansion
- A drier mix – the less water in the concrete, the warmer the concrete can stay in lower temperatures. An alternative is using warm water to begin with
- A cement-heavy mix – although it is more expensive, cement helps massively in warming the concrete during the mixing process, which will help make the concrete more susceptible to cold
- Additives – You can purchase a concrete accelerant to speed things along before the temperatures drop later on
At Rhino, we will not pour concrete unless the temperature climbs above 4 degrees. If the temperature is close to this number, we will use more cement and also cover the concrete as soon as it’s poured to insulate it, and we highly recommend you either do the same, or let us worry about it and order direct from us.