Many sedimentary stones contain clay that swells when it gets wet. The differential strain between wet and dry regions can result in deformation, stress, and cracking. The photo above shows the condition of the Cathedral of Lausanne, Switzerland, which is thought to be suffering from stress from clay in the sandstone. We are studying the mechanism of swelling and developing methods of treatment to prevent the damage. Our results to date are summarized in several publications.

    We have been exploring the use of a class of surfactants called diaminoalkanes for reducing the swelling of the clays. This method was first suggested by Wendler and Snethlage ["Surfactants and adherent silicon resins - New protective agents for natural stone", pp. 193-200 in Mat. Res. Soc. Symp. Proc. Vol. 185 (Mater. Res. Soc., Pittsburgh, PA, 1991) ]. We are studying the influence of the size of the molecules on their effectiveness. We have found [“Effect of swelling inhibitors on the swelling and stress relaxation of clay-bearing stones”, I. Jiménez González and G.W. Scherer, Environmental Geology 46 (2004) 364–377] that the treatment affects the mechanical properties of the stone (raising the elastic modulus and accelerating viscoelastic relaxation), so we are trying to understand the mechanism by which this occurs.

    This problem was the subject of doctoral thesis research by Inma Jiménéz and Tim Wangler.