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Concrete trench drains are floor drains typically shaped like a channel. The formation allows for rapid evacuation of surface water or for the containment of utility lines or chemical spills. As such, many concrete trenches are found in industrial facilities. Over time, the concrete may be damaged by elements such as fire, aggregate expansion, sea water effects, bacterial corrosion, calcium leaching, physical damage and chemical damage (from carbonation, chlorides, sulfates and distilled water), to name a few. This process adversely affects concrete exposed to these damaging stimuli, which may lead to leaking, loss of strength capacity, and the need for repair or replacement.

Concrete damage at a battery distribution plant was extensive and called for structural reinforcement and corrosion prevention. This particular facility was less than 10 years old, and had previously been protected with a novolac coating. This coating had failed, allowing the acid bath from the battery forming process to penetrate the concrete on two tranches. The diluted H2SO4 had a pH of 1-2 and a concentration much less than 98%. Upon evaluation of the trenches, many areas were found to be “mush.” Mush is the result of a chemical reaction between the waterbath and the concrete. The state of the concrete had been corroded to about half of its original thickness, or what was called approximately 35% failed concrete. At the time of repair, there was no exposed rebar and the internal reinforcement had not oxidized. The third party engineer predicted failure within 1 year if repairs weren’t made within 6 months.

corroded trench
Two trenches at this battery manufacturing facility had extensive corrosion due to constant exposure to a diluted acid bath.

Concrete corrosion repair first requires demo and removal of ‘bad’ concrete, and patching of the substrate to bring the surface back to its original, uniform shape. The surface must then be prepared and neutralized. HJ3 removed the loose and mush concrete with an abrasive blast prior to preparing the concrete surface. Following surface preparation and neutralization, HJ3’s CarbonSeal primer was applied, followed by CarbonSeal high modulus paste. HJ3 crew saturated the CarbonSeal carbon fiber reinforcing fabric, which was installed in the trench up to the 2” x 2” shelf. HJ3’s CarbonSeal chemical-resistant top coat was applied to the carbon fiber system, extending 1” across the board and on the 2” x 2” shelf. HJ3’s chemical-resistant coating is designed to withstand 98% concentration of H2SO4, giving the repair the durability required for maximum life extension.

Concrete damage at industrial facilities is a frequently occurring issue nation-wide and worldwide. The global cost of corrosion overall is estimated at over $6 trillion when direct and indirect costs are concerned. Trench replacement at manufacturing facilities can be quite costly when materials, labor and lost production time are concerned. HJ3’s CarbonSeal repair system allowed the facility to be back up and running within a week, saving them 85% compared to trench replacement. The chemical-resistant top coat will withstand the constant acid bath, allowing the trenches to continue operations for years to come. If you have a reinforced concrete trench requiring reinforcement and/or chemical-resistance and would like to learn more about HJ3’s CarbonSeal industrial repair systems, contact our project managers at hj3pm@hj3.com.

concrete trench repair with the CarbonSeal system
The CarbonSeal top coat can resist harsh acids at up to 98% concentration, providing a long-term repair to these concrete trenches.