Curing and Demoulding: Initial Curing of Concrete Cubes

Curing and Demoulding: Initial Curing of Concrete Cubes

Immediately after curing, the cubes should be covered with damp matting or other suitable damp material and then with polythene or similar impervious sheeting and stored in a place where the temperature can be kept at 27± 5°C for approximately 16 to 24 hrs.

Demoulding the Test Cubes

Test cubes should be demoulded between 16 and 24 hours after they have been made. If after this period of time the concrete has not achieved sufficient strength to enable demoulding without damaging the cube then the demoulding should be delayed for a further 24 hours. When removing the concrete cube from the mould, take the mould apart completely. Take care not to damage the cube because, if any cracking is caused, the compressive strength may be reduced.

After demoulding, each cube should be marked with a legible identification on the top or bottom using a waterproof crayon or ink. The mould must be thoroughly cleaned after demoulding the cube. Ensure that grease or dirt does not collect between the faces of the flanges, otherwise the two halves will not fit together properly and there will be leakage through the joint and an irregularly shaped cube may result.

Curing Test Cubes

Cubes must be cured before they are tested. Unless required for test at 24 hours, the cube should be placed immediately after demoulding in the curing tank or mist room.

The curing temperature of the water in the curing tank should be maintained at 27-30°C. If curing is in a mist room, the relative humidity should be maintained at no less than 95%. Curing should be continued as long as possible up to the time of testing.

In order to provide adequate circulation of water, adequate space should be provided between the cubes, and between the cubes and the side of the curing tank. If curing is in a mist room, there should be sufficient space between cubes to ensure that all surfaces of the cubes are moist at all times.