Sewage maintenance is one of the most expensive utilities a city operates. They are difficult to access for repair, due to the extra depth to which sewer lines must be installed to protect drinking water supplies.
Repairs are often needed more than other concrete structures, due to the extent of harmful bacteria that passes through the system. I came across an interesting article recently, which discusses the particularly harsh environment that concrete sewers face in the United States particularly.
The unpleasant odor of raw sewage comes from a set of microbes which emits the gas hydrogen sulfide. This gas is then turned into sulfuric acid by another set of microbes, and goes to work eating away the concrete. Concrete cubes immersed in sewage water showed rapid deterioration caused by only about three or four different species of bacteria. Civil Engineer Mark Hernandez discovered that if they created an environment that encourages the growth of good bacteria, which in turn can reduce the amount of the bad.
An interesting concept – but what about treating the concrete to reduce water permeation? Without water as a transporter, the bacteria are limited to the outside surface of the concrete, which can be treated with a specialized sealer or liner. Adding a crystalline waterproofing admixture, such as Krystol Internal Membrane (KIM), is a permanent solution to water permeation through concrete.
When added or applied to concrete, Krystol chemicals create a reaction that causes long, narrow crystals to form, filling the pores, capillaries and hairline cracks of the concrete mass. As long as moisture remains present, crystals continue to grow throughout the concrete, reaching lengths of many inches over time. Once the concrete has cured, the crystalline chemicals sit dormant until another dose of water (such as through a new crack) causes the chemical reaction to begin again. The ability to reactivate in the presence of water gives Krystol-treated concrete the ability to “self-seal”. When cracks form due to curing shrinkage, settling, seismic activity, etc., water entering through them causes new crystals to form and grow, blocking and filling the cracks. The most unique and effective feature is its ability to self-seal cracks, this can help to dramatically reduce the long-term maintenance and repair costs of a concrete structure.
Infrastructure durability is a major concern – especially for cities. Mitigating maintenance needs for the expected life span of a project can save millions of dollars in taxpayer funds – passing the benefits on to the taxpayers themselves.