On Jan 12, 2:52*pm, "bob" wrote:
A few weeks ago a pipe burst in my garage and had a slow leak (drips) which
I didn't detect for weeks. The wall and a raised concrete area were soaked.
I let a fan blew on that area for a few days. The wall (wood and drywall)
seems to be dry.

Later on, little dots of dark mold grew on the paper on the drywall. These
are easily removed with bleach.

But there are also white hairy mold growing out of the concrete! If I shine
an ultraviolet light on them for a few days they disappear. If I remove the
light they grow back. In some area the mold grow so dense it looks like
coral reef in air.

It's very strange because firstly, I thought the concrete has dried.
Secondly, other than water, what's there for the mold to eat?

I turn the uvc light back on. When the white mold disappear, I plan to clean
that concrete area with bleach to see if that would prevent them from
growing back when I remove the light. Is there a better solution?

I don't go examine that area very often to avoid unnecessary exposure to
mold.

Posting a hosted-site picture or two would help, but it might be
efflorescence. Google it and click on the Images tab.

R