Joining Different Concrete Layers

[countryjob]

A general question regards joining two different concrete. This refers to an existing slab with a new slab poured on top and making them composite. The pedestal will be subjected to shear and moment as it will be loaded with a surface mounted post.

Any help on the technique of joining different concrete slab pours would be interesting to discuss.

 

[racookpe1978]

In general, you can call for all sorts of concrete surface roughening techniques.

Any or all them work, but the specific best method for your specific situation requires knowing your situation: area of country and type of final loads, snow or ice and salt intrusion, area of the load; thickness of base and cover concrete; roughness of the upper layer now; presence or absence of rebar below, through or above the joint; etc.

Cleanliness now and after prep of the current surface; Spray blast, grinding, paint, oil or tar, grit, gravel, hand ground with abrasives, etc. will affect the method also.