Stress During Drying of Two Stone Consolidants Applied in Monumental Conservation
The object of this paper is to evaluate behaviour during drying of two stone consolidants: Wacker OH and Tegovakon V, containing tetraethoxysilane. During drying, the gel network contracts due to capillary pressure generated by solvent evaporation. When the consolidant dries inside the stone porous structure, the shrinkage is constrained in all three dimensions. In these conditions, the dried gel suffers a high stress that could cause it to crack. When there is a free surface, as for a consolidant layer on the surface of a pore, the stress can relax in the direction normal to the surface. In this case, the stress is controlled by network rigidity.
The rigidity of the gel network has been evaluated by mercury porosimetry, while pore size, which controls capillary pressure, has been determined by nitrogen adsorption. The shrinkage of gels under mercury pressure is characterised by high moduli. This fact suggests a high rigidity of the networks. The small pore radii found in the network (<3 nm) indicate that high capillary pressures are generated within the gel network.
Unable to display preview. Download preview PDF.
- 1.G.S. Wheeler, S.A. Fleming and S. Ebersole, in Proc. 7th Int'l Congress on Deterioration and Conservation of Stone, vol. 3., edited by J. Delgado, F. Henriques and F. Jeremias (Lisbon, 1992), p. 601.Google Scholar
- 2.G.W. Scherer and G.E. Wheeler, in Proc. 4th Int'l Symposium on the Conservation of Monuments in the Mediterranean, vol. 3, edited by A. Moropoulou, F. Zezza, E. Kollias, and I. Papachristodoulou (Rhodes, 1997), p. 355.Google Scholar
- 3.M.J. Mosquera, J. Pozo, L. Esquivias, T. Rivas, and B. Silva, J. Non-Crystal Solids, in press.Google Scholar
- 4.G.W. Scherer, D.M Smith, and D. Stein. J. Non-Cryst. Solids 186 316 (1995).Google Scholar
- 5.R. Pirard, S. Blacher, F. Brouers, and J.P. Pirard, J. Mater. Res. 10, 2114 (1995).Google Scholar
- 6.G.W. Scherer, D.M Smith, X. Qiu, and J.M. Anderson, J. Non-Cryst. Solids 186, 316 (1995).Google Scholar
- 7.L. Duffours, T. Woignier, and J. Phalipou, J. Non-Cryst. Solids 186, 321 (1995).Google Scholar
- 8.S.Z. Lewin and G.E. Wheeler, in Proc. 5th International Congress on Deterioration and Conservation of Stone, vol. 2, edited by Presses Polytechniques Romandes (Lausanne, 1985), p. 831.Google Scholar