On the floor of my unfinished basement there are cracks and they seem to be growing something white and fuzzy, that I think is mold. Anyone know for sure what this is, and how to get rid of it?

I tried dousing it with bleach, but its coming back after about a week.

KeepItSimpleStupid

Efflorescence is caused by the salts in the block leaching to the surface this usually happens in areas of high humidity. It can be removed by washing with either a strong detergent or muriatic acid such as sure klean or similar product. But if you don't find the source of the moisture can and most often will reoccur.

Cleaning masonry surfaces and muriatic acid from the Natural Handyman home repair and do it yourself website

Muriatic acid is dilute hydrochloric acid. Think battery acid. Get a few drips on your clothes and when you wash them, your clothes come out as swiss cheese.

Dry Loc makes a powder thats mixed with water that's a little safer.

Idontknowhow

Thanks, I have got muriatic acid, couldn't find the pre-mixed stuff, so now I'm just wondering about a safe disposal method after I finish with what I need?

KeepItSimpleStupid

Here is a link to the MSDS (Material Safety Data Sheet) for muratic acid.

Sanitary sewer neutralized with sodium bicarbonate (baking soda) or at a hazardous waste drop-off location. Reminder - to never add water to acid, but add acid to water.

This was the other stuff I talked about. UNITED GILSONITE LABS 01908 "DRYLOCK ETCH" CLEANER 12OZ
which is a powder and requires mixing with water.

ballengerb1

Muriatic acid is already premixed, prior to mixing it was hydrocloric acid. Keep it simple gave you the perfect answer. Now keep in mind that this stuff is not hazardous just unsightly. You could leave it or just scrape and sweep when it bugs you.