The spacing between the reinforcement bars must be adequate in order for the concrete to be casted and compacted successfully and develop sufficient coherence.
The minimum spacing sØ,min
between two parallel bars, horizontally or vertically aligned, should be:
sØ,min=max{k1×max(Ø1, Ø2),
(dg+k2), 20mm}, where dg
is the maximum dimension of the grain of aggregate.
For k1=1.0 and k2
=5mm and as a rule:
the maximum grain dimension of ordinary concrete is dg=32mm,
while the maximum grain dimension of self-compacting concrete is
dg=16mm. Hence:
Ordinary concrete:
sØ,min
=max{max(Ø1, Ø2), 37mm}
self-compacting concrete:
sØ,min=max{max(Ø1, Ø2), 21mm}
In slabs, generally, there is a large margin since the reinforcement bars are fixed with relatively large spacing
between each other.
In earthquake resistant columns, the columns’
dimensions are generally large and the reinforcement bars can be easily fixed in the column’s perimeter.
However, in beams there
are usually space constrains that require a careful selection of the beam’s width and, what is more, an accurate placement of reinforcement bars in the node areas.