white spots on concrete

(Minnesota)

Q. We have had white spots on our garage floor for about a year. Now they are getting black centers and look like little craters. These are dime to nickle size. We also have a crack that water is coming out of from an unknown source. The water is very rusty and has caused a stain on the concrete along the crack. This is about a foot long and was wet all winter. Any suggestions??

A. The white spots are most likely efflorescence, (minerals that are carried to the surface by the moisture vapor escaping up through the concrete from the subgrade).

These can be removed along with the rust stains with a good power washing and some scrubbing with a stiff bristled brush.

After the concrete is clean and dry (give it 2 days to dry out) you can apply a good concrete sealer. RadonSeal has a good concrete sealer for your situation.

Check the landscaping on the outside of the garage, make sure no water sits or puddles against the foundation. All the water should run off away from the foundation or slab. This should help with the water coming up through the crack.