Abstract Germany has an enormous number of different carbonate rock units, which vary widely in their geological age and sedimentary depositional environment. Limestones quarried from these exposures have a wide range of usages and applications, such as dimension and ornamental stones, floor tiles and panelling, and for use as paving stones and massive stones. Since antiquity, limestones were used as building materials in areas where they were naturally available and abundant. Limestones exhibit a relatively good weathering resistance, which is mainly controlled by the mineralogical composition and the rock structure. The susceptibility of limestones to weathering and alteration is only secondarily related to the stone's contact with rainwater and its exposure to frost. In this situation the pore space is the main controlling factor. Industrialization and the subsequent increase in air pollutants, which started at the end of the nineteenth century, led to the formation of dark and unsightly crust deposits on the limestones surfaces. These crusts, being the result of man-made activities, are the main weathering problem for carbonate dimension stones.

Abstract The Austroalpine basement underwent a multistage Precambrian to Tertiary evolution. Meta-magmatic rocks occur in pre-Early Ordovician and post-Early Ordovician units. Protolith zircon ages and whole-rock trace element data define two magmatic evolution lines. An older trend with Th/Yb typical of subduction-related metamorphism, started by 590 Ma N-MORB-type and 550–530 Ma volcanic arc basalt-type basic suites which mainly involved depleted mantle sources, and was continued by mainly crustal-source 470–450 Ma acid magmatic suites. A presumably younger evolution by tholeiitic MORB-type and 430 Ma alkaline within-plate basalt-type suites is characterized by an intraplate mantle metasomatism and multicomponent sources. These magmatic trends can be related to a Neoproterozoic to Ordovician active margin and a subsequent Palaeo-Tethys passive margin along the north-Gondwanan periphery. During Variscan collision, the Austroalpine basement underwent multiphase deformation and metamorphism. Early deformation involved non-coaxial shearing with formation of sheath folds and calcsilicategneiss bodies in some regions. Syndeformational clockwise P–T paths in lower basement parts passed high-pressure and high-temperature amphibolite-facies stages and are interpreted by a Devonian to Carboniferous crustal stacking. A post-collisional Permian thermal event is documented by pegmatite intrusions, LP-HT assemblages and monazite ages. Ductile overprinting under greenschist-facies conditions during the Cretaceous is indicated by foliated pegmatites and monazite ages in samples with retrogressed garnet. The emplacement of the Oligocene Rieserferner pluton was controlled by sinistral shear zone deformation along the Defereggen–Antholz–Vals line. Shear zone activity ceased at 15 Ma and was superseded by brittle strike-slip movements along NW and SE trending faults.

Abstract The weathering of historical buildings, as well as that of any monument or sculpture using natural stone (or man-made porous inorganic materials) is a problem identified since antiquity. Although much of the observed world-wide destruction of these monuments can be ascribed to war and vandalism, many other factors can contribute significantly to their deterioration. These threaten the preservation of the current inventory of historically, artistically or culturally valuable buildings and monuments. Furthermore, a drastic increase in deterioration has been observed on these structures during the past century. This prompted Winkler (1973) to make a pessimistic prediction, that at the end of the last millennium these structures would largely be destroyed because of predominantly anthropogenic environmental influences. Fortunately, this has proven not to be the case. There is a general belief that natural building stones are durable, and not for nothing does the Bible refer to the Rock of Ages. However, all rocks will weather and eventually turn to dust. If rocks are cut and used in buildings, the chance of deterioration increases because other factors come into play. To understand the complex interaction that the stone in a building suffers with its near environment, (i.e., the building, and the macro environment, the local climate and atmospheric conditions), requires an interdisciplinary approach with the work of geologists, mineralogists, material scientists, physicists, chemists, biologists, architects and art historians. Although most historical buildings use natural stone as the main construction material, other materials, such as mortars for masonry or rendering and ceramic

Abstract The deterioration of three marbles (Palissandro, Sterzing and Carrara) differing in composition and rock fabric has been studied using measurements of the thermal dilatation in the temperature range from −40°C up to 60°C. A long-term freeze–thaw experiment was performed to characterize the frost weathering via Young’s modulus. The results show that the combined effect of heating and cooling under dry and water-saturated conditions significantly influences the material properties. The thermal dilatation and its anisotropy can be explained by the crystallographic preferred orientation of calcite and dolomite as well as with the thermal expansion behaviour of these minerals. The residual strain, i.e. the permanent length change, after thermal treatment is different for the investigated samples and less pronounced for the dolomitic marble from Palissandro. The hygric expansion is of only minor importance and weak in the phlogopite-bearing Palissandro sample within the direction parallel to the foliation. Fresh and artificially weathered marbles were exposed to 204 freeze–thaw cycles. The Young’s modulus for the Carrara marble decreases from 55 GPa to 28 GPa while the porosity increases from 0.25% to 0.62%. The effect on the Palissandro and the calcitic Sterzing marbles is less pronounced while the artificially weathered ones clearly exhibit a drastic reduction in Young’s modulus. The progressive loss in strength is caused by progressive microfracturing or the loss of cohesion along grain boundaries due to the crystallization pressure of ice growth. The experimental data along with existing theoretical models lead to the conclusion that the physical weathering of marble is influenced by cooling and heating under mid-European climatic conditions.

Abstract Marbles as ornamental stones as well as in their natural environments show complex weathering phenomena. The physical weathering of marbles due to thermal treatment is often discussed as the initial stage of deterioration. Eighteen different well-known marble types were selected to quantify experimentally the effect of heating and cooling within the temperature range of 20°C to 85°C while three different ramps at 40°C, 60°C and 85°C were performed. The marbles differ in composition from calcitic to dolomitic as well as in their fabrics. The average grain size varies from 50 μm up to 3 mm, while the grain boundary geometry differs from a granoblastic foam structure to those with weakly inequigranular-amoeboid structure. The lattice preferred orientations are also highly different in c-axis and a-axis distributions. With respect to the heating and cooling cycles three distinct groups of marbles can be distinguished: Type I is characterized by an isotropic thermal expansion (α) and large isotropic residual strain (permanent length changes); Type II exhibits an anisotopic α and no or small isotropic residual strains; while Type III shows an anisotropic α and anisotropic residual strain. Most samples show deteriorations due to thermal treatment, which cannot be uniformly explained without taking into account the rock fabrics. The magnitude and directional dependence of the thermal expansion is mainly controlled by the lattice and shape preferred orientation. The composition, grain size, grain boundary geometry and pre-existing microcracks modify in a more complex way the progressive loss of cohesion due to dilatancy caused by the anisotropic thermal expansion.

Abstract Microstructure-based finite element simulations were used to study the thermomechanical behaviour of calcite and dolomite marbles. For a given mineral microstructure, thermal stresses and elastic strain energy varied with the single-crystal elastic constants and coefficients of thermal expansion. Moreover, they were a strong function of crystallographic texture. Given the same morphological microstructure and crystallographic texture, calcite had larger thermal stresses and elastic strain energy than dolomite. Hence, calcite has an earlier onset of microcracking upon either heating or cooling, and has a greater extent of microcracking at a given temperature differential. However, the variation in thermal stresses and microcracking propensity for either mineral with different randomly assigned textures was greater than the variations between the two minerals. The measured bulk thermal expansion anisotropy suggested that the random representations had some degree of texture. Simulations using the actual texture of the real microstructure, as determined by electron-backscattered diffraction, showed the largest degree of bulk thermal expansion anisotropy, the smallest strain energy, and hence the smallest amount of thermal microcracking. Microstructure-based finite element simulations are considered an excellent tool for elucidating myriad influences of microstructure and physical properties on the thermal degradation of marbles and other rocks.

Abstract Technical properties of building stones are of critical importance in applied geosciences such as engineering geology, and also with respect to construction or building physics. Among the many factors which control the technical properties, special importance is given to the rock fabrics influencing the anisotropy of these technical properties. To demonstrate this relationship a sequence of mylonitic rocks, i.e. metagranitoid progressively deformed to mylonite and ultramylonite, was selected. The mineralogical and chemical composition of the protolith and mylonite is nearly identical. All investigated parameters (tensile strength, compressive strength, abrasive strength, magnetic susceptibility and ultrasound wave velocities) are anisotropic and finally controlled by the mineralogical composition and the different fabric elements like microstructural features, the crystallographic and shape preferred orientations and the state of microcracking. The development of the rock fabric with mylonitization, in particular the preferred orientation of mica, seems to be most important for the directional dependence of rock physical properties, at least in mica-rich rocks. However, various sets of microcracks, the degree of grain size reduction, the intensity of the foliation and the compositional layering can significantly modify the results. The interaction of superimposing parameters for different technical properties does not allow any simple cross-correlation.

Abstract Itacolumites are very special rocks due to their high flexibility. The investigated Brazilian itacolumites and associated non-flexible quartzites are of comparable composition but differ in their rock fabrics. The shape and size of quartz is mainly controlled by the mica fabric. Quartz textures and grain boundary migration features are indications for deformation at temperatures of about 500°C. The flexibility is mainly related to a penetrative network of open grain boundaries which enable a limited body rotation of individual quartz grains. Continuous layers of white mica display deformation features indicative of shear along the layer-parallel cleavage planes. As demonstrated by simple bending experiments, the flexibility is a highly anisotropic phenomenon which can be related to a directional dependence of grain shape fabrics and corresponding grain boundary pore spacing. According to quantitative estimates, the amount and anisotropy of bending can be explained by the rotation of separated quartz grains between layers of mica which act as flexural slip planes and are also responsible for the observed elastic rebound. Solution along grain boundaries, volumetric strain by thermal contraction of quartz and bulk extension are processes discussed for the origin of the extreme values of secondary grain boundary porosity.