About Concrete

 

Frequently asked questions

How quickly does concrete set?
Concrete remains workable for a little over an hour, although the exact time depends on the type of concrete mix and the ambient temperature; concrete sets faster in hot weather.
If you are not used to handling concrete it can seem as though one minute you have a workable ‘slush’ and the next there is a hard surface. When concrete starts to set there is little time for remedial action. In special circumstances a retarder can be used and we will be pleased to discuss any particular requirements.

Concrete footings may be ready for the first layer of bricks on the day after pouring but most mixes require two days. It is best to keep off drives or roadways for at least 48 hours and avoid running heavy loads - including cars - over them for seven days (ideally 10 in winter). Concrete reaches most of its full strength by around 28 days.

What does it mean to ‘cure’ concrete?
Curing concrete is the term used for stopping new concrete from drying out too quickly. This is done because, if left to dry out of it's own accord, concrete will not develop the full bond between all of its ingredients. It will be weaker and more prone to crack.

The simplest way to cure concrete is to place a polythene sheet over the slab for seven days in summer and 10 in winter. If there is any risk of freezing leave an air gap by placing the sheet on timber battens.

When do I need to add steel reinforcement?
Any requirement for steel mesh reinforcement will be decided during the planning stage by the architect, engineer or local authority. There may be alternatives, including the use of fibre concrete but this will depend of the specific project and on local ground conditions.

If steel is used it is important to notify the concrete supplier before placing the order as this may influence the selection of certain ingredients in the mix.

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