Minimum size of principal rebar in concrete 2

[umgrego2]

One of the more experienced engineers at our firm has made the comment that you shouldn't use 10M bar as the principal reinforcement in concrete. He maintains that 10M should only be used as ties and stirrups. The problem is, that it doesn't say this in the concrete code.

Has anyone heard this rule of thumb before? If so, do you know what the reasoning is for not using bars smaller than 15M as the prinicpal reinforcemtent?

 

[Bbird]

I can't recall any rule on the minimum diameter of tensile reinforcement and have seen both 10mm and 8mm used in very thin slab (insitu layer pour over precast concrete slabs).

Frequently used mesh reinforcement are around 10mm to 8mm.

Many codes do specify minimum diameter for compression reinforcement though.

 

[kayah]

Typically we would use 15M as the minimum diameter because 10M bars have a tendency to be disturbed (bent) during construction - particularly when they are stood on.
Using 15M bars often makes placement easier too as fewer bars can be used.

The code probably wouldn't specify a minimum as it would depend on the situation - more a matter of good practice for the location.