Monument Future. Siegfried Siegesmund

The high values of sulfate may be due to the use of cement mortar, implemeted during restoration works on the roof. Moreover, rain water caused immense infiltration, which is noticable by the crust formation on the outer masonry shell (Fig. 1b). The basalt ashlar of the masonry (BW) shows a clear water absorbtion by Karsten tube, probably due to its remarkable porosity of 23.5 %. Its surface hardness with around 300 HLD is comparably low. The basalt ashlar of the foundation does not show any water uptake by Karsten tube tests. With around 700 HLD under dry conditions and 624 HLD under wet conditions a more than twice as high surface hardness than the ashlar of the walls could be measured for the BF variety. Cracks were only found in the lower part of the façade, probably due to seismic activities in the past (Fig. 3c).

      In contrast to the basaltic ashlar (BF and BW), the natural rock material shows low values of surface hardness ranging between 275 and 300 HLD under dry and 261 HLD under wet conditions. A small 260reduction of 5 % at the lowest point. The clastic material (RC) also shows various values ranging from 130 to 450 HLD under dry conditions also depending on the rock clasts. The clasts show values between 250 and 450 HLD. The matrix reaches an average value of around 250 HLD under dry and 227 HLD under wet conditions, which is a reduction of 9 %. Sanding and back-weathering of the matrix is the main weathering form observed on the rock cut architecture (Figure 3d).

      Figure 3: a) The floor plan of the monastery. Areas of investigation indicated. b) Architectonic drawing of the investigated church façade. c) Damage mapping. d) Crack formation or scaling of the rock material. d) Typical back-weathering of a porous basalt ashlar.

      In some parts of the upper wall active water infiltration takes place. Electrical conductivity and capacity reaches critical values at various parts of the inner walls of the rock cut structure. The exposed rock also shows crust formation and cracks (Figure 3d). These cracks are partly closed by a restoration mortar to prevent water infiltration.

      Water uptake by Karsten test pipes show high values for the rock. This also corresponds to the high porosity of the rock material investigated in the laboratory (Table 1).

       Laboratory investigations

      The porosity of the basaltic building stones range between 17.4–23.5 % (Tab. 1). The rock material shows a very high porosity of 30 % (RC) to even 38.2 % for the RF variety (Tab. 1). The fine variety (RF) contains a microporosity (0.001–0.1 µm) of 10.2 %, whereas the RC variety contains 23.2 % microporosity (Fig. 2 below).

      The saturation degree S of all investigated samples is high. The S-value of the RF variety is 0.94 and for the RC variety 0.97. The two basalt varieties show similar values: 0.97 for the basalt sample of the foundation and 0.95 for the sample from the wall.

      Directional water uptake of the rock material, however, shows different values. Z means perpendicular to the bedding, X parallel to the bedding and Y parallel to the bedding and parallel to the lamination of the stone material. Water uptake for the clastic rock (RC) sample attains a value of around 11.8 kg/m²/√h in all directions. Much lower values 261were determined for the fine-grained variety (RF), which show values of 4.6 and 4.5 kg/m²/√h for the XY direction and 5.2 kg/m²/√h for the Z direction, thus attaining an anisotropy (A) of 13 %. This tendency could also be shown by the measurements of ultrasonic velocity, expecially in the case of the fine-grained rock variety (RF), (Tab. 2).

Table 1: Porosity and density of the investigated stone samples.

Sample	Porosity (%)	Density (g/cm3)	Matrix-density (g/cm3)
Basalt (BF)	17.4	2.3	2.78
Basalt (BW)	23.5	2.3	7.8
Rock (RF)	38.2	1.5	2.42
Rock (RC)	30	1.73	2.48

      The rock material shows a different hydric dilatation. Both varieties show remarkable swelling, while the clastic material (RC) with up to 1.04 mm/m reaches high and critical values (Fig. 4). The fine-grained rock material (RF) only shows half of that dilatation, but a higher anisotropy of more than 50 % (Fig. 4).

      Ultrasound velocity decreases in both rock varieties under water-saturated condition (Tab. 2). This particularly affects the RC variety with an average of 38 % and an average of only 7.5 % for the RF variety (Tab. 2).

Table 2: Ultrasonic velocity of the rock samples.

Sample	X (m/sec)	Y (m/sec)	Z (m/sec)	A (%)
RF dry	1,905	2,340	1,464	37.4
RF wet	1,791	2,110	1,366	35.2
RF KSE	2,200	2,377	1,692	23
RF sol	2,210	2,355	1,802	21.6
RC dry	1,570	1,544	1,250	20.3
RC wet	909	783	930	13.8
RC KSE	1,585	1,553	1,780	12.7
RC sol	1,593	1,610	1,795	11.3

       Conclusions