CONCRETE PIPE Exposure Evaluation and Countermeasures The evaluation procedures suggested when aggressively acidic exposures are suspected or indicated are listed in the table below. Exterior Exposure Interior Exposure Accurately determine pH and total acidity. For potential bio-chemical problems in sanitary sewers, determine rate of acid development, if any. Evaluate installation condition from the For acidic effluents, determine pH, standpoint of the potential acid replen- including cyclic variations, as well as ishment. continuous or intermittent flow characteristics. There are a plethora of admixtures and coatings available on the market for concrete products. Due to the variability of site conditions, as well as the limited amount of time existing applications have been in place, it is nearly impossible to validate or predict product performance. Often times, no additional measures are required for the long term protection of concrete, but the uncertainty associated with a given project may force the consulting engineer to make a difficult, and potentially expensive, decision. Please consult with your local Lafarge representative when considering the specification of protective measures. While it may be difficult to provide a definitive solution, we are at the very least able to provide comment based on our experience and outline any applicable limitations. If it is concluded that a problem exists, the following alternative countermeasures are available: Exterior Exposure • Use material with low permeability in pipe zone to inhibit replenishment. • Use calcareous material in pipe zone to neutralize the acid. Exterior and/or Interior Exposure • Use calcareous aggregates in pipe manufacture to provide a higher total alkalinity. • Provide increased concrete cover as sacrificial concrete. • Use protective coatings and linings. In sulfuric acid attack of concrete, there are secondary sulfate reactions. These are usually insignificant, and occur after the concrete has already been damaged. The use of low C3A cement to mitigate these secondary reactions is not helpful, as it does not appreciably increase resistance to acid attack. PAGE 48 LAFARGE PIPE eMANUAL