Contraction Joint for Slab on Grade

[opa123]

i have a slab on grade 150 mm Thickness not heavly loaded(just ground slab for residuntal building) i am now detailing contraction joint, i checked ACI and found i can use Saw cut joint,keyed joint or doweled joint, but i have a question.
can i extend the mesh reinforcement normaly at location of contraction joint when i am using saw cut or keyed joint?
or should i disconnect it?

 

[JAE]

1. Leave the WWF mesh alone
2. Cut it all at the joint
3. Cut every other wire at the joint.

We usually do 1 or 3.

 

[DaveAtkins]

I used to detail the mesh discontinuous at the control joint, until another engineer told me that the mesh will yield when the control joint grows. So I don't worry about mesh running through a control joint.

DaveAtkins

 

[opa123]

well cutting is only for 1/4 or 1/3 the depth of slab of grade
so if i have WWF at the middle then why to cut it?
i think i just cut the SOG to have a weak section where shrinkage is controlled to occur at it. WWF may help in vertical load transfer
that is my opnion

 

[lkjh345]

OPA123:

Generally, I only consider the WWF for tempature and shrinkage crack control, not for load transfer.

Don't know if avialable in your location, but have you considered fibermesh reinforcing. This is becoming quite prevelent in our area (Nebraska, USA). Easier to place than WWF, which tends to get trampled down to the bottom in slab on grades.

 

[SlideRuleEra]

See "How to Specify, Order & Use Welded Wire Reinforcement in Light Construction", a free. pdf download from the Wire Reinforcement Institute. Here is the link

http://www.wirereinforcementinstitute.org/HTDocs/PDFs/TF 202-R-06.pdf

http://www.SlideRuleEra.net

 

[archeng59]

I do not use wire mesh but use #3 bars spaced at 16" or 18" on center each direction in a 4" thick slab. at sawjoints, I detail the slab reinforcing so that every third bar is continuous through the joint. The other bars stop at 3" each side of the joint. I want the slab to crack at the sawjoint. If all of the reinforcing is continuous through the joint, the rebar will restrain the concrete at the joint regardless of the sawed joint and cracks will likely form between the sawed joints. To ensure a weakened section so the crack forms where I want it to form, I cut the bars at the joint. The continuous bars provide some resistance to differential vertical movement on each side of the joint. I have used this configuration successfully for several years.

for slabs with people loads only, using the fibermesh should work well. the sawjoints and construction joints must be placed at about 8 to 10 feet on center in each direction. A concrete mix with a low water/cementitious ratio should be used to help reduce overall shrinkage.