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The petrophysical properties and weathering behavior of the sandstones were determined in accordance to the German industrial norms parallel (X-direction) and perpendicular (Z-direction) to the bedding. For further information see Siegesmund and Dürrast (2011). Table 1 gives an overview of the laboratory results.

In general, the sandstones can be divided into 213group one (S1, S3) and group two (S2, S4) of similar petrophysical properties and weathering behavior. Group two is characterized by higher porosities (> 20 vol%) and bulk densities around 2.0 g/cm³. Group two also shows unimodal pore radii distributions with large ratios of capillary pores (> 93 %) and mean pore radii between 0.9 and 5.7 µm. Group one (S1, S3) on the other hand, shows mean pore radii of 0.3–0.5 µm and contains considerable amounts of micropores (< 48 %). Up to nine times higher capillary water absorption (< 9 kg/m2√h) and lower resistance against water vapor diffusion in group two indicate better pore connection than in the sandstones S1 and S3 of group one (Tab. 1). The saturation coefficient S, as an indication of the materials’ frost resistance (Hirschwald 1912), classifies S1, S3 and S4 as frost resistant and S2 as uncertain.

Table 1: Petrophysical properties and weathering behavior of the four analyzed sandstones.

Regarding the moisture expansion, both groups show distinct differences when subjected to water (Tab. 1). While group two (S2, S4) shows barely any expansion (< 0.06 mm/m), the sandstones of group one (S1, S3) expand up to 0.2 mm/m. However, the hydric expansion values of the investigated sandstones can be generally considered low when compared to other sandstones (Siegesmund and Dürrast 2011).

The response to temperature changes is high in all investigated sandstone samples. Under dry conditions the sandstones expand about 0.8 mm/m. This expansion is increased up to 1.1 mm/m (S1, S3) when heating under wet conditions (Tab. 1). The average thermal expansion coefficients α range between 11 and 13 × 10^–6 K^–1 and can be considered very high. These high values, however, are not surprising, since quartz characteristically possesses a high thermal expansion coefficient and the investigated sandstones show high compositional maturity. The residual strains are considerably low under dry conditions and do not exceed 0.2mm/m under wet conditions.

The strength of the rock material is proportional to their dynamic modulus of elasticity (Young’s Modulus), which can be determined via the ultrasonic velocity. The ultrasonic velocity with up to 3.8 km/s as well as the Young’s Modulus with up to 32 GPa are significantly higher in group 1, meaning S1 and S3 possess a higher rock strength. In comparison, group two (S2, S4) shows ultrasonic velocities of 2.5 km/s and Young’s Moduli of up to 13 GPa.

Under laboratory conditions the sandstones show moderate resistance towards salt attack. After 30 cycles of salt bursting test (standard DIN EN 12370), the sandstones show a distinct darkening of their color tone and suffer minor material loss in the form of flaking and scaling (Fig. 7). Only S1 shows a constant loss of material in the form of bursting of edges and smaller components (Fig. 7a).

Figure 7: Discoloration and material loss of sample cubes S1–S4 after 30 cycles of salt bursting test.