Admixtures

It would depend on the type of structure build using the mass concrete. For mass concreting structures like dams, typical admixtures that could be used may include air-entraining admixtures, water reducers, retarding admixtures, surface retarders etc.

The selection of an admixture is also influenced by the things you want to control. If thermal cracking is the primary issue then a low cement factor and the use of a set controlling admixture would be beneficial. If the issue is cold joints during placing then a retarder would be in order. Each set of circumstances has to be evaluated and decisions made based on the end result you are looking for.

When dealing with acid there are at least 3 factors to consider. They are 1) type of acid. 2) strength of solution and 3) the temperature of the acid.

For the most part, silica fume is advantageous because it raises the density of the concrete and helps prevent the penetration of the acid . The primary problem is that the acid attacks the Portland cement causing the concrete to break down.. That having been said probably the best method is to prevent the acid from reaching the cement.

Addition of other supplementary cementitious materials like, Fly ash and Slag in the concrete should help to improve the durability of the concrete against acid attack. The water to cement ratio of the concrete should also be low (use a high range water reducing admixture to achieve this).

If possible in your case, you can also either apply a coating of acid resistance epoxy coating, in case of flooring you can also use a self leveling epoxy flooring or epoxy-aggregate mortar screed as a protective layer on the concrete.

Good luck.