The Cold War

Lafarge Cement’s Bill Price ponders the weather and its affect on cement and mortars

The season has definitely turned and cold, frosty weather is becoming much more common – so what products are likely to be in demand as winter approaches?

Unfortunately, the amount of concrete and mortar laid in cold weather is usually a lot less than in the warmer months but some intrepid builders will still be working away and they will need the materials most appropriate for winter working.

Setting of concrete (and mortar) is a chemical reaction that slows down significantly in cold weather. In order to prevent newly placed concrete being damaged by frost, it is essential that it is protected from cold until it is strong enough to resist the effects of frost and cold.

A product that sets quickly and gains strength rapidly will always have an advantage in cold weather as it will need protection for a shorter time. So what products would fall into this category?

Good old traditional Portland cement CEM I (the well known and traditional ‘OPC’ of yore) is a useful standby as it gain strength quickly and also generates a bit of heat in the process which helps to keep the concrete warm. Rapid Hardening Portland cement is also available, which gives an additional level of performance. This is not to say that the more sustainable CEM II cements cannot be used in winter, it’s just that they will require a bit more care and attention in order to avoid problems with frost attack.

Products that are packed in plastic come into their own during this season as they can be stored outside, even in snow, without damaging the contents.

There are also a number of specially formulated extra-rapid setting cements on the market that will be particularly useful at this time of year. These should only be used for small areas of concrete, but they are also useful for repairing other concrete damaged by frost. Most post fixing concretes will also work well in very low temperatures and would be a better solution than trying to use conventional concrete to fix fence posts.

Here are a few ideas on what the frostbitten builder may be asking for in the coming weeks, and if you also stock gloves, woolly hats and vacuum flasks, so much the better!

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