"Sam Hopkins" wrote in
:

I'd scrub with a scrub brush and throw some clorox on it to get out
any organics. Cement doesn't like to stick to cement so the cleaner
you can get it the better.



I would avoid using chemicals if at all possible they soak into the
concrete and may continue working even after rinsing. The chlorine it
Clorox may degrade the concrete and cause you more problem later on. Not
only that but any chemicals you use may leach out into the pond at a later
date.

Rent a power washer from your local tool rental company and use only plain
clean water. It will do a much better job of cleaning the concrete and will
not leave any chemical residue. Get the highest pressure you can, 3000 psi
has been suggested, it will remove any paint and mechanically etch the
surface providing a good foundation for the sealant. In addition it will
clean in the cracks and crevices where you need to get it really clean in
order to maximize the adhesion of the sealing compound.

Good luck
ANO