On May 17, 8:00*pm, (Doug Miller) wrote:

How are they going to get bigger while they're encased in concrete?

It really surprises me that you have such problems understanding
this. Your personal observation of those funky brown stains on
concrete structures everywhere should indicate that something is
rusting. If you can't see what's rusting, and are keen enough to
realize that rust doesn't just magically appear on concrete, you'll
probably latch on that the rust is coming from inside the concrete.

In a nutshell. Concrete is not waterproof. It wicks up moisture.
The steel doesn't care that it is encased in concrete and will rust in
the presence of the H2O. Concrete sucks in tension - something on the
order of 1/10 its strength in compression. Constant tension on
concrete leads to cracking. Cracking allows in more moisture, and the
cycle continues until the structure falls apart.

Please, DAG. There's a hole in your education.

R