Читать книгу Monument Future - Siegfried Siegesmund - Страница 351

The in-situ application of the method described above was tested on a quartz sandstone (Hořice quarry) wall after a demonstrative impregnation with a tetraethyl orthosilicate agent. Due to their chemical similarities to sandstones in particular, and their simple application, silicic acid esters 236(SAE) are one of the most commonly and most successfully applied materials in stone conservation, and therefore they were selected for the pilot tests. The average bulk density value of Hořice sandstone is 1,810 kg.m-3, its porosity is 25.84 %, and the diameter of the highest occurring pore is 40.22 mm. The measured US velocities correspond to the references in literature for sandstones of similar bulk density and porosity, e. g. S. Garia et al. or Freund (1992).

Figure 3: Comparison of US velocities measured with double-probe variants on dry and saturated sandstone.

Figure 4: Testing of the influence of the probe distance and the contact effects.

Figure 5: Measured US velocities in stones of different average travel length – 310 mm in stone E; 295 mm in stone I; 375 mm in stone O – compared to velocities for a stone block measured in the laboratory with the scissors device over a travel length of 50 mm and the rail device over a length of 170 mm.

Figure 6: Drilled holes in the treated areas, and the orientations of the transmission waves.

A Hořice quartz sandstone masonry wall was treated, in limited and well-defined areas, with three types of agent: the Remmers KSE 300 – without solvent, with 30 % gel deposition potential; the Remmers KSE 510 – without solvent, with 45 % 237gel deposition potential; the Porosil Z – containing solvent (ethanol), acid catalyst, with 30 % gel deposition potential. The consolidants were applied to the sandstone blocks by brushing. Then a set of holes was drilled.

The impact of the consolidation effect is clearly visible from the obtained data in Figure 7, as are the gradient of its distribution along the depth profile starting from the surface and the attained penetration depth.

Figure 7: US velocities in stones treated with Porosil, KSE 300, and KSE 510 – all applied by brushing – and an untreated stone.