[Coral-List] Cement blocks harmful?

[Philippe Sanchez]

Hi all,

My company needs to put up a few signposts that will hold information on
local species. Some of them will be inside the mangrove and in the water,
and I was wondering if this would be harmful or if the damage done is
negligible.

I know I read about coral reef balls using a specific cement mix that had
neutral pH, but that is aimed at having corals grow on it. Would this be
necessary in a mangrove creek?

If needed, where can I find the composition for this cement mixture?

Thanks in advance!