Water Journal : Water Journal April 2013
167 Water Business In the wastewater industry, Hydrogen Sulphide gas (H2S) is produced, leading to the formation of sulphuric acid (H2SO4). The acidic water can lead to severe degradation of the structure, potentially resulting in the exposure of the supporting steel re-bar, prone to corrosion in the absence of concrete cover. This problem is most commonly experienced in enclosed environments such as anaerobic digestion tanks, sewer linings and manholes. It is hard to believe that similar deterioration is seen in the clean water industry -- not because of corrosive H2S, but due to soft water, which is very pure. It is known to eat away at the cement within the concrete because it tries to strip away the minerals that are absent from the water. Over time, without protection, all concrete structures deteriorate to the point where the structures and the owner are faced with the loss of a valuable asset or contamination of the surrounding area. The cost and time implications of unplanned remediation are severe, and often in the water and wastewater industry this is not possible as some areas cannot be shut down for extended periods of time. A more effective solution is to embed a maintenance ritual into the plant's existing schedule to include any necessary remediation of the structure prior to treating the asset with a highly waterproof, protective coating. The use of protective coatings not only reinstates the water-retaining characteristics, but also increases the longevity of the concrete structure, thus increasing the return on the initial investment. International Paint has introduced the Intercrete product range, a compact group of products used for concrete repair. They are Portland cement-based and show excellent compatibility by chemically reacting with the concrete substrate to become 'one'. These repair mortars and protective coatings can be used in a maintenance context to signi cantly extend the service life of an existing asset, or at the construction phase to provide long-lasting concrete protection, minimising future maintenance. The use of Intercrete 4840 signi cantly enhances the durability of the concrete in an acidic environment. It is a technologically advanced epoxy and polymer modi ed cementitious coating, with enhanced chemical resistance as well as impact and abrasion resistance. Test reports demonstrate that Intercrete 4840 shows good chemical resistance to H2SO4 even at 20% concentration. The key bene ts of the product are that it is easy to install, no substrate primer is required and it can be applied on damp concrete, making it an economic and practical solution to speed up the remediation process. For cases where steel reinforcement bars are exposed, 2 x 1mm coats of Intercrete 4871 may be brushed over to rapidly reinstate the passivating layer, providing long-term corrosion protection. A repair mortar such as Intercrete 4801 may be applied to ll large defects before using Intercrete 4840 to provide lasting protection. Chemical attack on concrete.
Water Journal February 2013
Water Journal May 2013