slab on grade reinforcement 1

[deereman]

For an 8" slab on grade reinforced with #3 at 12" o.c. each way, is it better for the reinforcement to continue through control joints or be broken 2" each side of joint. Is a smooth, greased dowel required to allow horizontal movement but no vertical movement.

If no control joints are installed and the concrete is allowed to crack where it wants, will the rebar keep cracks from opening up? joints are 15'-19' o.c. depth of cut 2.66", rebar is centered in slab.

 

[CarlB]

This has been discussed in various forms quite bit, mostly in the structural & concrete forums.

My take is if no control joints are provided, slab will crack randomly, and yes reinforcement will keep them from being excessively large. Customer will probably be dissatisfied. Better to control crack locations and seal them. Spacing <20' for 8" slab sounds OK.

A common(for us anyway) detail is to cut every other rebar at joints. No need for dowels, you still have aggregate interlock, and held together by some reinforcement. Even with no reinforcement I believe dowels only necessary for formed expansion joints. Exception may be for heavily loaded slabs with aircraft wheel loads, and other criteria may kick in.

 

[msquared48]

I agree with CarlB, but would clarify here....

If the slab is so big that it requires a cold joint (cannot be poured in one day), then smooth dowels should be used at the cold joint, with the #3 rebar discontinuous at the joint.

Mike McCann
MMC Engineering

 

[fattdad]

Some of this depends on how the slab will be used. For example whether or not you are anticipating fork lift traffic.

f-d

¡papá gordo ain’t no madre flaca!