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Decreased bio-inhibition of building materials due to transport of biocides

S.J.F. Erich1, 2, S.M. Mendoza1, W. Floor1, S.P.M. Hermanns1, W.J. Homan1, O.C.G. Adan1, 2
1 TNO Built environment and Geosciences, Delft, the Netherlands
2 Eindhoven University of Technology, Eindhoven, the Netherlands

Bio-inhibition of buildings and structures is an important issue. In many cases building materials have biocides added to prevent growth of micro-organisms. Growth of micro-organisms on building materials has several negative effects; (1) Aesthetic damage, e.g. fungi, algae grow on the material, resulting in early replacement and high cleaning costs, (2) Material damage, and (3) Health problems. However, current legislation forces manufacturers to reduce the biocide load, which requires manufacturers to look for alternatives or other improvements. One way is to increase the efficacy of biocides. There are several factors which rule the efficacy of a biocide in a building material. In this paper we will give a short overview of the mechanisms that lead to a decrease in efficacy of biocides. One of the mechanisms, leaching into and from the materials is researched by using leaching experiments. This because leaching of biocides into and from building materials has not been researched to a great extent. In our experiments the leaching of Propiconazole (Wocosen 50TK) has been tested in gypsum layers applied on aerated concrete. The sample was then placed into an artificial rain setup which releases the biocides. The analyses of the samples show that the biocide leaches out of the gypsum layer and simultaneously into the aerated concrete. From the results it may be concluded that a biocide will leach from a plaster into an aerated concrete wall, which opens opportunities to improve the biocide efficacy by preventing this process from occurring.

Key words: Fungal growth, bio-inhibition, biocides, transport, moisture, building materials