connect new concrete floor section to existing slab 1

[towneng]

I am designing new drainage to replace a strip drain in a highway department garage floor. I want to know the best way to connect the new concrete section to the existing slab. The slab is 5" thick. The new section will be 5' wide and 88' long. Should I use dowels epoxied into the old concrete or some other method?

 

[dbuzz]

Recommend you use 600mm long by 20mm diameter dowells at 400mm centres. Contact surface should be water jet blasted to expose a clean rough surface with coarse aggegate exposed (but firmly fixed in the concrete matrix), together with a suitable joint seal (prepared and primed surafce, backing rod and sealant).

 

[towneng]

Thanks dbuzz. That helps me.

 

[JAE]

dbuzz - no worries about water jet blasting damaging the underlying subbase?

 

[dbuzz]

JAE, that's certainly something to consider. Perhaps scabble the contact surface with a kanga hammer or similar instead.

 

[jheidt2543]

Since it is a slab on grade, why not construct it just like a doweled construction joint. Forget roughening the existing side of the joint and install the dowels IF you need them. Will you actually have traffic across the joint between the new and old sections? If yes, use the dowels to transfer the load, if no then forget the dowels.

Use a non-tracking, two part, semi-ridged joint sealant to keep water and debris out of the joint.

 

[dbuzz]

Since the joint is in a strip drain, I'd be inclined to roughen the contact surface to acheive some contunuity in the concrete matrix and prevent water ingress to the subgrade, rather than rely on the joint sealant which may (will?) deteriorate over time.

 

[Ron]

Don't forget about the transverse joints. Significant shrinkage will occur longitudinally, restrained by the dowels and the bonding along the joints. Cut transverse joints at closely spaced intervals (not exceeding about 6 feet for a 5-foot wide slab).

Agree with the dowelling and other comments.