In venice what component was used to stop water deterioration in the cement for the foundation?

Answer 1

by cement I am assuming that you are refering to concrete since cement is an ingredient in concrete. Water does not deteriorate concrete in fact it makes it stronger during the hydration process in which concrete forms. Concrete is a permiable material that can wick water through its interior but that water does not damage the concrete once it has hydrated. In fact an interesting fact is that concrete can actually be placed wet underwater as long as it is placed and not poured. When a slab is poured on a construction site the best way to get a strong slab is to cover it with wet burlap to increase the rate of hydration. I think that you are getting the corrosion related to steel and wood mixed with concrete. In response to the previous answer, fly ash does not make concrete waterproof it reduced the permiabilty but comes nowhere near waterproof. The romans typically used cow blood in there concrete sturctures that are still around today, the use of fly ash by them is something that I have never heard but I guess it is possible. The water coming through the concrete in the form of moisture is not that big of a deal as long as no corrosive materials are directly on the slab.

Answer 2

The Romans used fly ash in their concrete to make it "waterproof" and it is in better shape today than much modern concrete.