drill and dowel

[cvg]

assuming a 3/4" dowel is used to connect new slab to old slab to help prevent differential settlement/movement and is to be epoxied in place. What size drill hole would be required?

 

[MiketheEngineer]

Check with dowel supplier. People like Hilti and Simpson have all the charts and equipment you might need.

 

[cvg]

so far hilti and simpson are of little help

 

[JAE]

cvg - Hilti, for example, does provide bit diameters for their adhesive anchors - see the attached table taken from their catalogue.

 

[cvg]

except I'm not specifiying an adhesive anchor, a drilled and epoxied dowel. My assumption is that contractor will buy plain steel bars, 3/4 x 24" long. Use a 1 inch or 1 1/8 inch or whatever and drill the existing structure. Insert epoxy into hole and insert dowel. Form and pour the second structure.

 

[Ron]

cvg...it makes little difference other than you don't want the dowel to move sloppily in the hole. The dowels won't be taking tension, so the epoxy isn't even necessary other than to keep them in place during construction. With that in mind I would drill for the same size as if you were using an epoxy set for a threaded rod.

As with pavement dowels, grease the exposed side before placing concrete.

 

[civeng80]

I have done exactly what Ron suggests many times over.

No epoxy just drill same hole and hammer in dowels.

Many semis over and never had a problem.

 

[JAE]

cvg - the Hilti RE500 is epoxy.

 

[JennyNakamura]

Ron is right -- it doesn't matter. But if you must have some kind of written justification look up Simpson SET-XP in their catalog or on-line. It list values specifically for rebars -- for a #6 bar as you allude to in your original post, the value for "drill bit diameter" is 7/8". 1/8" larger than dowel size is pretty standard regardless of epoxy manufacturer or application.

 

[catosborne]

Jenny's right. Most manufacturers call for a drill bit sized one eighth larger than the bar size, so in your case a 3/4" or #6 bar would call for a 7/8" drill bit.