A bit of info that may help you...
As you likely know, fly ash is often used in concrete. Fly ash drastically
reduces the transmission rate.
I believe colored concrete is usually spec-ed where fly ash may not be used.
It might be possible that the non-colored concrete contains fly ash and the
colored concrete does not contain fly ash. Therefore, resulting in large
differences in transmission rates between the colored and non-colored
concretes. Where the colored concrete transmission rate appears to be high
enough to affect the paint.
Similar problems arise on many types of floorings, especially hard wood
floors for gymnasiums.
From: Pat Ebner [mailto:PEbner(--nospam--at)younglove-const.com]
Sent: Wednesday, January 17, 2001 10:38 AM
Subject: Vapor Transmission and Reinforcing Corrosion
I was questioned by a project manager about the possibility of reinforcing
in a slab on grade corroding due to a vapor transmission rate of 10.5. He
said the rate is 10.5 pounds of water per 1000 ft^2 per 24 hours. Part of
the slab is colored concrete and part is not. The owner changed his mind
and decided to paint the floor. Now the paint is peeling in the area where
the colored concrete was used, they measured the vapor transmission rates at
various locations and this question was asked. I can not find anything in
my references on vapor transmission rate and corrosion of reinforcing.
Does anyone have references on this or any experience in this area?
Patrick Ebner, P.E.