I was about to spray some bleach/water on my concrete floor, then scrub it with a nylon brush. Then I saw this article.
Is this person correct that bleach won't actually penetrate far enough to kill the mold roots?
I couldn't find anywhere else that backs this up, but you never know.
Thanks!
It is incorrect I believe. Chlorine molecules are smaller than water molecules (175pm vs 275pm respectively), so I don't see how water would be able to get into places that chlorine could not.
I can't say I've had problems with bleach; it has worked well every time. I would start with a 1 cup bleach to 1 gallon water mix.
If for some reason that fails, you could use a fungicide to kill it; any home improvement store would have several products most likely.
I live in Florida, where conditions for mold to grow and thrive are abundant.
While bleach, and bleach and water combinations are routinely used to clean mold off outdoor surfaces, it is known and even expected that the results will not last.
The story suggests that while the bleach may clean the surface, it will not or cannot get to the root of the living organism. Therefore the mold will come back. Life experiences in Florida have proven that to be true.
My condo association has experimented with a somewhat new method of cleaning mold using an outdoor cleaner that does not contain bleach.
As with most things there is a give and take. While bleach will clean immediately, it does not have the chemical properties to last long. (It depletes quickly in the sun, which we have much of.) The outdoor cleaner does not clean quickly. It actually leaves the surface looking like nothing has been done. However it does kill the organisms and the rain and wind clean the surface over time. The cleaner also has a residual property and will continue to create an environment that is counter to the growth of mold, mildew and other living organisms. ( The chemistry of the 2 products was explained to me by a member of the board who was a DR. and also had a PHD in chemistry.
I cannot remember enough to repeat it.)
I can attest to these properties. It takes about 3 months for a clay tile roof to appear clean and free from the black mold that stained it. It will continue to be free from growing mold again for a period of about 26 months. ( Again, I know because I was part of the community trying and documenting the results of the cleaner.) There were similar results when concrete driveways and walkways were cleaned.
The bottom line was there had to be a decision made to have instant gratification of clean roofs with bleach, or long term results with a wait to witness clean roofs.
So the story has credence. At least in an environment of high humidity, that is positive to the growth of mold, cleaning with bleach is a short term solution.
Your link is bunk. If true, then nobody would worry about the effect of deicing salt on reinforced concrete.
How old is the concrete? As concrete ages, carbonation reduces concrete pH moving from the outside inward. Typically the transition point moves at about 1/16" per 2 years. Due to the high pH inside the concrete, the mold couldn't be deep in there unless the concrete is older. Try to avoid or at least minimize the use of corrosive chemicals with reinforced concrete, though. For a slab supported by soil, I wouldn't worry about a bit of corrosion. For any sort of elevated concrete, however, I would be far more cautious.
