Concrete Tank with No Contraction Joints.
Concrete Tank with No Contraction Joints.
(OP)
I have a project where the contractor did not put contraction joints in the walls of a Wastewater treatment tank. The wall is 75 feet long and 14" thick. The horiz. wall reinf is #5 at 12 along each face. The design plans specifically called out for contraction joints to be spaced at 25' oc. max. It is no surprise that shrinkage cracks have developed in the walls. (they are about 6 to 8 feet on center, full height of the wall).
There are construction joints 12.5 feet from the ends of the walls, so there is about 50' of wall with no joints. (i.e. the contractor should have put one contraction joint in this area).
My question is, does anyone have any ideas on how to fix other than removal and replacement of the conrete? I have thought about epoxy injecting the cracks, but I think that new cracks will eventually form after some freeze thaw cycles.
My thought is to repair the cracks with epoxy, but in the center of the 50' section have the contractor cut out about a 6' or 8' wide section and dowel rebar into the wall install a proper contraction joint with a waterstop. Along the cut surfaces of the wall to remain, we would have them install an Rx type waterstop. Anyone got any better ideas?
There are construction joints 12.5 feet from the ends of the walls, so there is about 50' of wall with no joints. (i.e. the contractor should have put one contraction joint in this area).
My question is, does anyone have any ideas on how to fix other than removal and replacement of the conrete? I have thought about epoxy injecting the cracks, but I think that new cracks will eventually form after some freeze thaw cycles.
My thought is to repair the cracks with epoxy, but in the center of the 50' section have the contractor cut out about a 6' or 8' wide section and dowel rebar into the wall install a proper contraction joint with a waterstop. Along the cut surfaces of the wall to remain, we would have them install an Rx type waterstop. Anyone got any better ideas?






RE: Concrete Tank with No Contraction Joints.
RE: Concrete Tank with No Contraction Joints.
RE: Concrete Tank with No Contraction Joints.
Let mother nature put in her contraction joints and seal them with epoxy. And #5 @ 12" horizontal is not enough steel. With no expansion joints, you should provide rho of .0052.
To really scare the contractor make him extend his warranty. If its one year, make him extend it to five years. It's meaningless, but it will really piss him off.
RE: Concrete Tank with No Contraction Joints.
Brad
RE: Concrete Tank with No Contraction Joints.
Our typical construction joint and contraction joint details only allow 50% of the horizontal steel to pass across the joint, creating a weak point. (The only difference in the joints is the type of waterstop used) We are not designing the wall to span horizontally.
RE: Concrete Tank with No Contraction Joints.
Steel=Cheap
Cracks=Expensive
RE: Concrete Tank with No Contraction Joints.
RE: Concrete Tank with No Contraction Joints.
RE: Concrete Tank with No Contraction Joints.
Checked with the Repair Contractor, and it turns out that we didn't repair our cracked tanks with epoxy injection. We used a "Krystol Crack Repair System" by Kryton.
RE: Concrete Tank with No Contraction Joints.
RE: Concrete Tank with No Contraction Joints.
Contraction joints in a straight wall for an environmental structure? Use of contraction joints relies on too many unknowns.
Use construction joints ("cold joints") at 30' to 50', and high horiz bar reinf ratio (at least 0.004bh) both between joints and across joints (i.e. continuous).
The 50% horiz steel continuous thru the contraction joint works about 50% of the time. Okay for concrete paving, not for retaining fluid.