SOURCE
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QUESTION
Regarding dowels for construction joints in pathway/ driveway slabs etc, I had an idea I wanted to float… How effective would m12x200mm hex head bolts be at locking a new slab into existing, ie drill 12mm hole into existing and then use impact driver to drive bolt in 100mm deep? Thinking of possible alternative to traditional rebar and chemical anchoring.
REPLIES
Ron
You have two distinctly different applications. Doweling to tie two sections of concrete together requires bonding on both sides. Dowels for pavement application (driveways, roadways) require that only one side be bonded and the other side allowed to slip.
Dowels for tying together two sections of concrete should be deformed bars. You have proposed replacing these with headed bolts. While that will suffice for vertical loads it is not appropriate for lateral loads. The bolts will only penetrate into the concrete on both sides by about 100mm. This is insufficient on the headed side to resist shrinkage stresses as a stress concentration will develop at the bolt head causing a crack. Alternately, the threaded side may have limited friction resistance because of the thread pitch and limited embedment. In either case, you have a failed joint.
I’m not sure why you described hammering rebar into a hole filled with epoxy. That’s an improper procedure. You should have a drilled and cleaned hole that is about 3mm larger than the rebar diameter so that the epoxy can properly distribute and bond around the rebar. Further, the rebar should penetrate into each side of the concrete at least 250mm to provide proper stress distribution in the lateral direction.
If there is a problem in the future with failed joints, you will likely bear the responsibility as such a failure determination is relatively easy (I do failure investigations for a living). Don’t expose you or your company with unnecessary liability when you can do it right without much more effort and a huge savings rather than tearing out a failed concrete structure.
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