Concreting in Hot Weather

Many of the problems associated with concreting in hot weather are overcome by placing concrete quickly and preventing premature moisture loss by way of adequate curing. In addition, batches of mixed concrete should not be left standing during

periods of hot weather so the timing of mixing and placing is important. Concrete generally, but particularly in hot weather, must be placed in a continuous, smooth operation. If one batch of concrete is left to stand and stiffen before the next batch is placed on or next to it, ‘cold joints’ will form and the concrete will not be one homogenous mass.

Aggregates should be kept cool by spraying with water but allowance must be made when mixing for the increased water content of the aggregate. In addition, or as an alternative, a chemical retarding agent can be added to slow the hydration process.

Ready-mix concrete should be kept agitating in hot weather but care must be taken not to over-mix in case segregation occurs.

Curing should start at the earliest opportunity to avoid premature drying-out of the concrete surface and resultant surface cracking.