I recently got the following question regarding my blog post “Mix design for cast in place concrete countertop in Cayman“:
Q: What is the size of the rebar? Where was it placed in the slab?
Here is what the rebar looked like:
The rebar size and location were dicated by local practices (and the local structural engineer). While I know from practice (and from being an engineer myself) that the rebar used was grossly oversized, politics were the over-riding influence on the reinforcing schedule.
All the rebar was 1/2″ bar, located in the slab so that there was 2″ of cover measured from the top surface of the countertop. The 2″ cover depth is common where corrosion is an issue. Since this is an outdoor countertop on an island, corrosion is always a concern with concrete exposed to the elements.
Note that too little cover depth can lead to problems other than corrosion. See this article about rebar size in concrete countertops.