K. Terheiden¹

1. Chair of building chemistry in Civil Engineering, Bauhaus-University Weimar, Weimar, Germany, kristina.terheiden@bauing.uni-weimar.de

ABSTRACT

For the examination of transport processes of deteriorating salts in building materials there are different driving forces that have to be taken into consideration. One is the salt concentration gradient in the pore solution. This concentration gradient may induce two different transport processes: diffusion and free convection. To separate between these two processes and the characteristic initiating conditions, investigations were conducted into the effect of choosing different types of sandstone, different moisture content of the samples and different concentration of the pore solution. The necessary conditions for the occurrence of free convection in porous building materials were the pore radius, the connectivity of the pore system, and the concentration of the salt solution. In some cases a dependence of the moisture content of the specimen on the occurrence of convection was also detected.

KEYWORDS: Convection, diffusion, salt transport, materials

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