Dowel Bar Oil / Epoxy / Plastic Sleeves 4

[Riversidean]

So I am designing a concrete pad via ACI360. For a unreinforced concrete pad it recommends dowel rods at joints with oil used as a bond breaker from the concrete. I have searched online for a standard on what type of oil / epoxy / sleeves to use, but nothing is coming up.

Can anyone point me in a direction? Or is per the dowel rod manufacturer's recommendation? Dowel rods are constructed at a steel shop correct? So would they even know?

-Riversidean

 

[JedClampett]

You might want to consider what these lubricated dowel bars accomplish. They're intended to limit the diferential deflection between adjacent slabs. Their effectiveness is not assured. If there is grease or oil in there, it wears out. If the slab really wants to settle, they'll break out. Contractors hate them, not that that's a reason to not do them, but it means they'll be an afterthought. Unless settlement is a big issue, I'd eliminate them.

 

[GeoPaveTraffic]

I've always just used form release oil. This, in theory, provides a bond break allowing the slabs to move horizontally with respect to one another. Also only one side of the dowel needs to be oiled.

Mike Lambert

 

[Ron]

The purpose of oiling or greasing a dowel rod is to prevent its bond to the surrounding concrete. That can be accomplished by a variety of means including....form oil (as GPT noted), wheel bearing/axle grease (my preference), petroleum jelly, waxed paper, etc. I also require a 1/2" piece of foam placed on the end of the dowel to create expansion space.

A steel shop would not know the purpose or the specifics of dowel use...just how to fabricate them. They should be smooth, round rod made of hardened steel. They should be sized in accordance with AASHTO requirements and spaced accordingly.

 

[TXStructural]

You do want dowels to keep from faulting across joints. Dowels are a standard feature of certain kinds of pavement and will work well. Dowels should be smooth and in the range of 1-1/4 to 1-1/2" diameter. Standard metallurgy as found in rebar complying with ASTM A615 or A706 is typical and adequate.
There are also many kinds of dowel assemblies, including plate dowels. These assemblies will work as long as they are used within their limits.

Be sure all dowels are parallel and do not put dowels near corners - the result of violating that will be restraint which will cause cracking and failure of the slabs. Keep dowels at mid-height or slightly lower (so any cracking will appear at the bottom, not the top of the slabs.)

The subgrade under unreinforced slabs needs to be adequate and stable.
If the slab is exposed, be sure the joints are sealed.
When placing the concrete, attend to curing to avoid curling as the top surface dries. Failure to do so increases the appearance of cracks and reduces durability.

 

[KootK]

[link Ron]They should be sized in accordance with AASHTO requirements and spaced accordingly.[/url]

Can you point me to a section Ron? I'd like to check this out. I've got AASHTO but I'm not well versed in it and it's a rather large document.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Ron]

KootK....Check Table 2.6 for load transfer coefficient the figure the size and spacing from there.

 

[Ingenuity]

These are commonly used in Australia - simple to use and a time-saver: Speed Sleeve Link

 

[Riversidean]

Thanks for all the info guys!

 

[Riversidean]

For form release / oils or bearing axle greases are there any recommended brands? I realize I may not have the same exact brand available in my area, but I could use to the material for a comparison for what is around me locally.

In good humor I curse ACI / ASTM for not having a standard on dowel bar oil / release. Although that might make for great material for another circular they could sell....

 

[Ron]

Castrol, Valvoline, Pennzoil, Chevron...etc. All make wheel bearing grease. No big deal about specs on it...just a separating lubricant that prevents concrete from contacting the dowel and bonding.

You can use petroleum jelly as well.

If life gets really tough, go to the local grocery store, buy some Crisco and use that. You can also soak a piece of your kraft paper grocery bag in vegetable oil and wrap it on the dowel. Will work as well as any other. If your grocery store only uses plastic bags, wrap one of those on the dowel.....

My point is that this is not rocket surgery...break the bond...that's all.

 

[Ingenuity]

You could also use DENSO petrolatum tapes if corrosion is an issue too.

It comes in various tape widths, of which I have used 2" wide on numerous UNbonded PT repair projects.

Denso Petrolatum Tapes link

 

[Riversidean]

Understood! Ron. Thank you.

 

[bb29510]

i love the plastic sleeve, you can screw them to a 2x10 and they stay in place, strip the form, there your hole for the dowels. great