In vitro microbiologically-induced concrete corrosion behavior of Ag + loaded zeolite-polyurethane coating for concrete sewer applications

Microbiologically-induced concrete corrosion (MICC) refers to chemical reactions between biologically produced sulphuric acid and with hydration products in the hardened concrete paste, resulting in an early reduction of strength, deterioration, and very severe circumstances, structural failure. This paper explores the bactericidal characteristics of cementitious materials with surface coated with modified zeolite-polyurethane. The zeolite-polyurethane coating incorporated with silver was studied in environments inoculated with A. thiooxidans bacteria for 8 consecutive weeks. The antibacterial characteristics were evaluated in terms of pH, optical density (OD), sulphate production and bacteria count to determine the effectiveness of the zeolite-polyurethane coatings in environments inoculated with A. thiooxidans bacteria producing the sulphuric acid. The results revealed that the samples incorporated with silver modified zeolites generally showed antibacterial performance (regardless of the zeolite type) compared with unmodified polyurethane coating. This was evaluated by the lack of bacteria attachment and the deformed microcolonies on the sample surface, lag in pH reduction, increase in OD, and sulphate production. The silver zeolites gained their antibacterial performance from the release of silver ions (Ag + ) when the sample comes into contact with aqueous solutions. This results in the inhibition of cell functions of the bacteria and subsequently causes cell damage.