Effects of concrete properties and nutrients on fungal colonization and fouling

This study describes the fouling of concrete surfaces by diverse fungal genera under controlled laboratory conditions. A circulating flow-through chamber was designed for testing the effects of different concrete compositions and exogenously added nutrients on fungal colonization and fouling. Fungal strains belonging to the genera Alternaria, Cladosporium, Epicoccum, Fusarium, Mucor, Penicillium, Pestalotiopsis, and Trichoderma were cultured directly from visibly fouled concrete structures and used individually and in a mix to inoculate mortar tiles varying in cement composition, supplementary cementitious material additions, water-to-cement ratio, and surface roughness. A strong positive relationship was observed between tile water-to-cement ratio and the amount of biofouling. In addition, cement containing photocatalytic titanium dioxide and exposed to artificial sunlight strongly inhibited fungal colonization and fouling. Mortar tiles coated with form-release oil and incubated with sterile rainwater were also capable of supporting fungal colonization. Our results indicate that the fouling of concrete surfaces by fungi can be influenced by variations in concrete composition variations and available nutrients.