Abstract
Microbiologically Induced Corrosion (MIC) is a complex problem facing global concrete sewer structures. Despite the substantial efforts made, MIC of concrete sewers remains a significant challenge. Concrete is susceptible to corrosion induced by microbial species which convert the main binding agent Ca(OH)2 to CaSO4, leading to the disintegration of concrete, loss of strength and structure failure short of its predicted life. Concrete specimens were prepared with corrosion inhibitors and immersed in sodium sulfide and sulfuric acid solutions for more than 400 days. The concrete samples without inhibitor or admixtures showed more than 33% loss of compressive strength, roughly 6.2 mm layer of sulfate attack and concrete disintegration. The concrete samples treated with admixture and surface applied corrosion inhibitors demonstrated no loss of compressive strength and less than 0.12 mm layer of the sulfate-- attack after 400 days immersion in the aggressive solutions. A combination of admixture and highly hydrophobic surface applied corrosion inhibitor is recommended for aggressive waste water systems such as manholes, channels and pipes to assure a satisfactory performance for these concrete structures.
