The danger of soil contamination due to leaky walls of sewage tanks in coking plants – description of the concrete destruction process

Currently, several coking plants are in operation in Poland, but many are being closed and post-coke-making areas should be revitalized. The article presents results of laboratory tests of corrosive immersion of hardened cement paste in NH₄Cl water solution. NH₄⁺ and Cl⁻ ions are present in coke sewage, cause concrete corrosion of wastewater tanks, unsealing them. Thus a real risk of the groundwater contamination caused by toxic components is possible, because of leaky tanks. The depth of corroded zone of hardened cement paste in different time of duration the corrosive immersion of hydrated cement paste in NH₄Cl water solution was determined. Results showed the same way of crystalline phases changes in each specimen, but logically the corrosive fronts moved deeper with time. Microstructure undergone transformation. Corrosion products, like gypsum, secondary calcite, thaumasite, secondary ettringite were detected in the outer layers of specimens and compared with the pH of the hardened paste. Thanks to this research, it is possible to create a model of the destruction of reinforced concrete tanks containing a solution with ammonium and chloride ions, which has strong calcium phase dissolving properties.