Читать книгу Monument Future - Siegfried Siegesmund - Страница 136

In general the measured ultrasonic velocities were rather slow compared to the other values of granitoids given in literature (Hoffmann 2006: 80; Vasconcelos et al. 2008: 27), which indicate an advanced degree of deterioration (Svahn 2006: 21–23). This assumption was supported by the WA measured with the contact-sponge and Karsten tube method. Although it was not very high (compare Vandevoorde et al. 2009), it proves a moderate weathering of the respective material.

The lack of signals in the upper third of the main stele (in right angle to the layering) confirmed the visually determined heavy decay. It showed that delamination is advanced and cracks and cavities run through the entire material. Also the smaller stele seems to suffer from advanced delamination as the pulse was only partly transmitted from bottom to top (in right angle to the layering). As the steles absorbed little to no water it can be assumed that they are hardly affected by disintegration or fissures.

Figure 4: Water absorption measured with Karsten tube (4 ml, contact time up to 60 min) at the two steles (no. 1 and 10) and the sculptures (no. 2, 4, 7, 9, 11).

The failed or partial transmission of the pulse at all of the animal- and human shaped sculptures 105indicated that the material suffered from advanced disintegration. This assumption was confirmed by the water absorption behaviour of the stones. Interestingly, this finding contradicted the macroscopic examination, which indicated a rather good condition (hardly cracks and no sanding). Particularly the sculptures no. 9 and 11 with the highest water absorption (contact-sponge and Karsten tube) showed a rather slow or no signal during ultrasonic measurements. In general, sculptures with a comparatively higher water uptake also had a slower or no transmission of the pulse.

The combined use of the three non-destructive fields test and the comparative analyses of results helped to gain a better understanding on the degree of decay among the individual sculptures. Results mutually support and confirm each other. Thus a clearer picture of the state of condition could be gained.