Efflorescence on exterior & interior basement walls
Posted by Robert from Cottleville, MO, US on March 20, 2007
Hi, my name is Robert Sims
I have a villa that is 6 months old. Foundation poured in July or August 2006. We now have efflorrescence on both the exterior and interior walls. The builder brought in a Technical Service Engineer to take a look at it and give me a report on it.
He checked the compressive strength in numerous places with a Swiss Impact Hammer. The results were 4710psi. He gave the build instructions on cleaning it up and sealing the walls.
A couple of questions that weren’t answered are;
Can this cause damage to the rods or metal ties in the foundation that would cause weakening in years to come?
Can this cause corrosion in the concrete itself which would be a problem later.
My electrical box is attached to the wall in question, should this be removed and cleaned and sealed behind. Can this eat into the metal and wiring?
Can this re-occur?
Do you know of a company in my area to use for a second opinion?
Thank you for any assistance you can give me in this matter.
God Bless
Bob
If the wall is made of concrete blocks, then there shouldn’t be any issue of corrosion, but if they are made of reinforced concrete, efflorescence can cause corrosion.
Efflorescence occurs when free calcium hydroxide from the concrete is transported by water through the capillaries to the surface of the concrete. On the surface calcium hydroxide reacts with carbon dioxide in the air to form an insoluble material calcium carbonate (white deposit).
The migration of calcium hydroxide to the surface creates channels through which harmful materials like chlorides; contaminated water can enter the concrete and react with the steel to cause corrosion.
During corrosion the steel rusts and expands, which may lead the concrete to spall.
Efflorescence if present should be cleaned and the concrete surface should be sealed with a penetrating sealer (coating). There are products available for this in the market. Do a google search for “Stopping efflorescence” for more information.
