It has been our practice to repair our concrete tanks periodically. We have.never found coatings satisfactory for our purpose. The tanks hold water containing various chemicals in small concentrations, including ammonium sulfate in concentrations up to about 1.5 percent. Is there any cement we can use in the concrete that will resist the slow but persistent erosion and disruption we experience?
Since you propose not to use a coating for the tanks you should require a concrete strength of more than 4500 psi. The water-cement ratio should be no higher than 0.45. This is the value proposed by the ACI 211.1-74 standard. This water-cement ratio would produce a compressive strength in the range of 5200 to 6500 psi at 28 days for Type I cement and non-air-entrained concrete . Ammonium sulfate is highly aggressive to concrete. All of the mortars tested in the PCA Research Laboratories, including those made with Type V cement and a cement with a zero C3A content, succumbed to attack by an ammonium sulfate solution with a concentration of about 0.66 percent. It is possible that a high alumina cement, which is very resistant to sulfates, would offer a possible solution to the problem. Another solution would be to install a high-alumina cement shotcrete lining. It would be possible to repair the tank again after deterioration takes place, but it is impossible to say whether this would occur after a period of 8 years, 5 years or a much earlier period of time.