Most peoples’ eyes will likely glaze over when you mention concrete tanks unless you also mention “swimming pool.” But as you know, concrete tanks have an important place across many industries as a means of storage and containment. Some media, however, can be too aggressive even for concrete. Take sulfuric acid and cyanide, for instance.
Sulfuric acid is used as an industrial cleaning agent as well as being a reagent in the production of fertilizer. Cyanide, on the other hand, is used in mining as a way to separate gold and silver from other ores using a technique called the cyanide process. In both situations, the safe storage of these chemicals is of top concern and concrete tanks need an additional protective coating to avoid corroding. In this article, we will discuss the role of concrete tanks, the process of relining concrete tanks, and how a concrete protective liner is a good alternative to other concrete protection methods.
The need for concrete tanks
Steel tanks often carry the benefit of being relatively cheaper than other options while also being easier to install. However, steel (and most metal tanks) suffer from a lack of longevity and do not work well as a long-term structure. Steel tanks are also not well suited for underground storage. Concrete structures, on the other hand, function well underground thanks to concrete’s excellent load-bearing capabilities. Concrete tanks are also longer lasting, capable of being designed with a service life ranging between 60 and 100 years. Proper maintenance and care of the concrete tank will ensure it can remain in service for decades without problems.
Depending on the application, a concrete mixture can be modified with a number of additives to help make it more resistant to certain types of chemical attack. Metakaolin (MK) and limestone filler (LF) can be added to increase concrete’s resistance against sulfuric acid attack (1). However, increases to resistance through additives often comes at the cost of structural strength. For sewage systems that are exposed to relatively low concentrations of sulfuric acid, a moderate combination of MK and LF can be sufficient. The same cannot be said for dedicated concrete tanks with year-around exposure to higher concentrations of those compounds. In these situations, the surface of the concrete has to be augmented with a protective coating or liner.
Relining concrete tanks
Spray-on coatings are one of the more popular ways of protecting concrete tanks. The coating is generally made of a hydrophobic compound that has also demonstrated high resistance to the chemical in question. The coating serves as a skin that prevents chemicals from coming in contact with the concrete. The hydrophobic properties of the coating also help reduce the amount of water transmitting through the concrete’s micropores, which could cause its own set of damage to the structure depending on local conditions and construction method. While spray-on coatings are sufficient for many situations, they have little to no backpressure resistance. Without resistance to backpressure, the coating can be lifted up and peeled from the concrete’s surface over time—greatly reducing the service life of the product. For concrete tanks utilized in applications that will expose the tank to periods of backpressure or tanks that will experience prolonged exposure, an alternate concrete protection method is recommended. An alternative, more permanent solution for concrete protection is using a concrete protective liner that is anchored in the concrete.
- Joorabchian, Seyed M., “Durability of concrete exposed to sulfuric acid attack” (2010). Theses and dissertations. Paper 1486.