Consideration for Hot Weather Concreting

The main things to consider during hot weather concreting are:

a) minimising the early loss of water from concrete;

b) preventing early setting through too-rapid drying.

If these problems are not anticipated, there may be:

• Strength reduction

• Shrinkage cracks

• Crazing or cracking

• Finishing difficulties.

In very hot conditions the following steps should be undertaken:

• Thoroughly moisten the sub-grade, reinforcing steel and wooden forms before placing the concrete.

• Avoid delay in placing the concrete. Have sufficient labour and equipment on hand to perform the placing

quickly.

• During placement in very hot weather, try to shade the concrete from direct sunlight.

• Use wet coverings until final finishing can be completed.

• If a float finish is required, uncover only a small section immediately ahead of the finishers.

Cover again at once after final finish.

• Keep covers wet.

• Start curing as soon as possible, using a method that will keep temperature of the covered concrete at or

about a constant 21ºC.

• Discharge concrete from waiting trucks as soon as possible. Heat builds up in mixer drums if this is not done.

• In very hot weather shade concrete from sunlight or use wet coverings until finishing can be completed.