Tortuosity in concrete technology - An engineering approach

P. Stroeven

Faculty of Civil Engineering and Geosciences, Delft University of Technology, the Netherlands

Pore tortuosity is one of the relevant parameters in concrete technology underlying porosimetry. The same holds for crack tortuosity in damage analysis. Hence, this paper concentrates on an engineering approach to obtain geometrical-statistical information on this tortuosity. It is stipulated that the model parameters in such analytical methods have old roots. The presented approach as well as comparable data in the international literature point toward an upper limit of tortuosity of 2 for the linear as well as the planar index, so for porosimetry as well as damage analysis on micro-level. Results are depending on magnification in experiments or sensitivity in theoretical approaches. A reduction in magnification finally results in a mono-size, meso-level concept. When pore depercolation is advanced in the cementitious materials, nano-cracking is recognized contributing to porosity and thus to tortuosity. A fractal concept is proposed for modelling this phenomenon yielding enhanced tortuosity in accordance with experimental data in the literature.

Key words: Aggregate, Cauchy, cement paste, concrete, damage analysis, porosimetry, tortuosity