Minimum spacing between reinforcement bars

The distance among reinforcement bars must be such to allow the concrete’s gravel to pass be-tween them. In order to have properly anchored reinforcement, it is mandatory for rebars to be surrounded by concrete.

The minimum spacing between two reinforcement bars should be at least equal to the maximum aggregate grain dimension with a margin of 5 mm. For Greece, the maximum aggregate grains dimension for usual concrete, is 32 mm and for self compacting concrete is 16 mm.

Example:

These spacing requirements are easily met in slabs and columns. However in beams extra at-tention must be paid mainly to the support and the joint areas. The problem in beams is related to the concrete’s casting and it can be dealt with three different ways or in certain occasions with a combination of them.

For satisfactory results it is very important not only to use the vibrator in the proper way but also to avoid over-vibrating the concrete of the elements.

Connecting beams in foundation

Concrete casting in foundation connecting beams is not an easy procedure. These beams are not fixed together with a slab as are superstructure beams; consequently concrete has to be purred down the beam’s tight top opening and reach the bottom side.

Because of the fact that connecting beams normally have a large height as well as a large internal lever, it is preferable to place rebars in two or even three layers along their height.