Fungal Growth On Concrete Surfaces Of Floors And Walls

Generally, a high pH-value (above 12) in building structures is considered to be an inhibitory factor against fungal growth. However, fungal growth can in some cases be detected on concrete surfaces in new buildings shortly after commissioning and in existing walls retrofitted with internal insulation installed using cement based adhesive mortars. This paper deals with two building envelope structures: newly casted concrete floors fitted with vapor membranes and existing walls fitted with internal insulation. In both fungal growth has been detected and linked to the decreasing pH-value and lingering moisture. For floors, several new buildings were investigated and the cleaning method, moisture content, concrete age after casting and fungal species were registered. Furthermore, the development in pH-value was measured on newly casted concrete to determine the decrease in pH-value. For walls, laboratory and field experiments were conducted both under realistic and worst-case condition. After 1-4½ years, samples of the internal insulation were taken to investigate fungal growth, fungal species, moisture content and pH-value behind the insulation. Moreover, the development in pHvalue of fresh cement-based adhesive mortars was investigated. The results showed that the fungal species, Aspergillus versicolor, was common in both floors and walls and indicate that the A. versicolor spores can survive the high pH-value (above 12), and then later germinate and grow when pH-value decreases and moisture content increases. Furthermore, the results showed that the pH-value decreased faster, when the surface/interface has access to air and that only a totally clean surface would prevent later fungal growth in the interface, if the pH and moisture conditions change in favour of fungal growth.