bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of the petrophysical properties of two types of Alsatian sandstone subjected to simulated freeze-thaw conditions
Authors: Thomachot C. , Jeannette D. 
Published: September 2007

Abstract
Stone monuments in Alsace (eastern France) are built with two types of Buntsandstein sandstone (Lower Triassic). Their different pore structures cause them to have mixed petrophysical properties and occasion a different response to frost. To understand these differences, frost simulation experiments have been carried out on samples of both stones. Four series of 30 freeze-thaw cycles were reproduced on samples maintained at constant saturation, either total or partial, without drying or rewetting. Macroscopic and microscopic change due to frost was observed by scanning electronic microscope, by mercury porosimetry and P-wave velocity measurements. Change of tensile strength and capillary kinetics was also assessed before and after each series. Results demonstrate that frost action increases heterogeneity of the porous network particularly in the initially more heterogeneous sandstone. When saturation is partial, no macroscopic cracking occurs and capillary absorption decreases. When saturation is total, macroscopic cracking prevails over microscopic heterogeneity and capillary absorption increases. Control tests have also been carried out to evaluate the effects induced by absorption-drying cycles without frost, and dilation experiments have been added to assess freeze-thaw action on dilation of sandstones. The results of all these experiments demonstrate that frost plays a less decisive part in the weathering mechanisms of stones than wetting-drying.
Salt weathering: a selective review
Authors: Doehne Eric 
Published: September 2007

Abstract
The past decade has seen a growing scientific interest in the still poorly understood subject of salt weathering, a phenomenon with significant cultural and economic consequences. This interest has led to an increase in research results and growing clarification of the roles salts play in weathering and decay. The development of improved mitigation methods to reduce the decay of building materials by salts has been a slow process, often arising from the analysis of unique field situations and otherwise dependent on simplified laboratory experiments and computer modelling. Collecting, reviewing, synthesizing and disseminating the existing data on salt weathering is a difficult task. The size and scope of the topic are mirrored in the diverse disciplines that have historically contributed to understanding the action of salts in porous materials and mitigation methods. Nevertheless, an appreciation of existing, even contradictory, data is an important tool for increasing understanding. There are now over 1800 research articles on the topic of salt weathering originating from several disciplines, as well as over 6000 references on the general problems of building material decay. In order to navigate such a vast collection of data and knowledge, this article describes the multidisciplinary nature of the study of salt damage to porous building materials, provides a framework for considering the complexity of salt damage, and serves as a selective literature survey largely focused on recent work and those articles with relevance for conservation.
Thermal tresses and microcracking in calcite and dolomite marbles via finite element modelling
Authors: Weiss Thomas , Siegesmund Siegfried , Fuller Edwin R. 
Published: September 2007

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.
Depositional environment and diagenesis as controlling factors for petro-physical properties and weathering resistance of siliciclastic dimension stones: integrative case study on the ‘Wesersandstein’ (northern Germany, Middle Buntsandstein)
Authors: Weber Jutta , Lepper Jochen 
Published: September 2007

Abstract
A case study on the ‘Wesersandstein’ (Middle Buntsandstein) indicates that weathering resistance and quality of dimension stones are functions of depositional environment, and of diagenetic alterations (eogenetic as well as mesogenetic) during geological history.
Two types of dimension stones, one deposited in a braided and the other in a meandering river system, were compared with respect to the fluvial architecture, the diagenetic modifications, the raw block prospectivity, and the petro-physical properties. The integrative synthesis of all these approaches indicates that depositional environment (type of fluvial architecture) and diagenesis (quartz cement and clay matrix contents) are the key processes which generally control the petro-physical properties and the weathering resistance of siliciclastic dimension stones. The highly quartz cemented ‘Grauer Wesersandstein’ with low clay matrix content, deposited as channel fill (braided river system), is characterized in general as a high quality dimension stone with very good petro-physical properties (e.g. high compressive strength, tensional strength, abrasion resistance, and freeze-thaw resistance) and high weathering resistance. In contrast to this, the ‘Roter Wesersandstein’, deposited as point bar and floodplain deposits of meandering rivers with low quartz cement and high clay matrix contents shows minor quality petro-physical properties (e.g. minor compressive strength, tensional strength, abrasion resistance, and freeze-thaw resistance) and weathering resistance.
This new integrative approach combines hitherto isolated studies on dimension stone quality. It shows the complex interrelations between the geological background on the one hand and specific dimension stone properties on the other hand.
The anisotropy of itacolumite flexibility
Authors: Siegesmund Siegfried , Vollbrecht Axel , Hulka Carola 
Published: September 2007

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.
Physico-mechanical and microstructural characteristics of historic and restoration mortars based on gypsum: current knowledge and perspective
Authors: Middendorf Bernhard 
Published: September 2007

Abstract

The use of gypsum based mortar can be traced back over 4500 years. In Germany, in the vicinity of natural gypsum outcrops, in addition to lime mortars, calcium sulphate based mortars were widely used for joints in exterior walls of sacred buildings. There are several medieval buildings with well-preserved calcium sulphate-based mortars. The high water solubility of gypsum (CaSO
4
•2H
2
O) is a disadvantage that makes it difficult in general to handle calcium sulphate based building materials in areas exposed to weathering. Physico-mechanical as well as mineralogical investigations of historic calcium sulphate based mortars have shown that long-term weathered mortars have a much denser microstructure, larger average grain sizes, and a higher compressive strength than laboratory prepared mortars. Porosity models of these mortars will be presented which are helpful to prepare calcium sulphate based mortars with a higher water resistance for restoration purposes. The reason for the change of crystal size and morphology as well as of porosity and strength can be explained by crystallization and recrystallization processes of these calcium sulphate based mortars, as a consequence of long-term weathering. Since it is obvious that crystal size and its distribution have an enormous effect on the weathering resistance, the development of mortars with comparable structural properties is of present interest. In current use are chemical additives which modify the morphology and size of gypsum crystals of set mortars. Another possibility to influence the weathering resistance is the addition of hydraulic and/or latent hydraulic admixtures.
Thermal behaviour of weathered and consolidated marbles
Authors: Ruedrich J. , Weiss T. , Siegesmund S. 
Published: September 2007

Abstract

To optimize stone consolidation it is necessary to understand the mechanisms of weathering in marbles, and its control by the mineralogical composition and the rock fabric. A knowledge of how the stone consolidants affect the weathering mechanisms and if they are compatible with the stone is also an important consideration. The weathering of marble can begin with thermal stress whereby cracks are generated. To verify whether consolidation influences the thermal behaviour of marbles, we compared the behaviour of weathered and consolidated marbles. For the investigations four marbles were selected with various fabrics (e.g. texture, grain size, grain boundary geometry, etc.) and different weathering conditions. Three consolidation approaches were adopted: a solved polymethyl-methacrylate (PMMA
sol
) dissolved in xylenes, a polysilicic acid ester (PSAE) and a total impregnation with a monomer methyl-methacrylate (PMMA
poly
). Measurements of the porosity and effective pore size distribution evidenced a strong modification of the pore space by consolidation. Both PMMA approaches show a re-establishment of cohesion which can be determined by ultrasonic velocity measurements. By reaching the respective glass transition temperatures of PMMA
sol
and PMMA
poly
, a strong modification of thermal behaviour occurs. The PSAE consolidated marbles show only minor changes of dilatation, but due to its low bonding effect no significant cohesion between the crystals occurs.
The influence of petrographic, architectural and environmental factors in decay patterns and durability of granite stones in Braga monuments (NW Portugal)
Authors: Matias J. M. S. , Alves C. A. S. 
Published: September 2007

Abstract
In order to discuss decay patterns and susceptibility of granite types used in architectural works, the decay features of 39 monuments built with granite stones and presenting diverse architectural characteristics, date of construction and environmental characteristics (including exposition conditions, traffic intensity, etc.) are compared. Decay patterns of biotite-rich medium- to fine-grained (frequently porphyritic) granite stones are related to weathering inherited from the quarry (expressed by yellowing), to the presence of heterogeneous elements (enclaves and phenocrysts) and to grain size variations. Fine-grained leucogranitic stone decay is mainly controlled by tectonic foliation. The characteristics of stone application, including how and where stone was used, influence decay patterns by favouring salt pollution concentration, biological colonization and fixation of atmospheric pollutants. Erosive decay features (linked mainly to salt pollution) and stone coatings (linked to biological action and atmospheric and organic pollution) are wide-spread decay forms that affect granite stones in Braga monuments.
Bowing of marble panels: on-site damage analysis from the Oeconomicum Building at Göttingen (Germany)
Authors: Koch A. , Siegesmund S. 
Published: September 2007

Abstract
The use of natural stone panels or cladding material for building facades has led to some durability problems, especially with marble slabs. To examine the effects of intrinsic and extrinsic parameters on bowing, a very detailed study was performed on the Oeconomicum Building at the University of Goettingen. In total 1556 panels from the whole building were measured with respect to bowing using a bow-meter. The variation of bowing ranges from concave (up to 23 mm/m) to convex (up to −11 mm/m). The variation is not controlled by the position with respect to the geographical coordinates, height above ground, shadows, temperature etc. On the north facade the different rock structures visible on the panel surfaces are a result of the marble slabs being cut in different directions. The different degrees of bowing are associated with the structure of the marble since all other influencing factors are relatively constant (position, temperature, moisture content, building physics). Experimental data on the expansion behaviour under dry and/or wet conditions reveal different degrees of bowing with respect to the rock fabric and may help to explain the observed differences in bowing. The effect of the rock fabric, especially of the lattice preferred orientation in this case, clearly controls the deterioration of the marble and the degree of bowing. The bowing is also characterized by an increase in the porosity, decreasing values of ultrasonic wave velocities and flexural strength. The loss of cohesion in the strongly deteriorated panels is clearly visible in the microstructure by the open grain boundaries which are interconnected to intergranular microcracks.
Principal decay patterns on Venetian monuments
Authors: Fassina Vasco , Favaro Monica , Naccari Andrea 
Published: September 2007

Abstract
In most Venetian monuments studied, the stone decay was ascribed to the transformation of calcium carbonate into calcium sulphate. This phenomenon is commonly observed elsewhere and has been pointed out by many authors. In order to explain why different forms of decay are present on a building facade, samples were taken from different areas of many monuments. Analytical results were related to different forms of decay, defined respectively as white washing, dirt accumulation and dirt wetting. A simplified model of stone decay is presented and its validity tested on several Venetian monuments. Results showed that the features visible on stone surfaces corresponded to different degrees of deterioration. Sulphate formation is greatest in the black dendrite-shaped crusts, which are generally formed at the interface between the white washing areas and the sheltered ones, which were defined as dirt wetting area.
The decay forms of the most common lithotypes used in Venetian monuments were also studied. Results obtained showed that in compact limestone, gypsum formation affects the stone only on the surface. In contrast, on marble a different mechanism of decay takes place: the decohesion of calcite crystals, due to thermal changes, favours the penetration of sulphuric acid solution into intergranular spaces, thus causing the transformation of calcium carbonate into calcium sulphate, not only on the surface, but also inside the marble.
Implications of future climate change for stone deterioration
Authors: Viles Heather A. 
Published: September 2007

Abstract
Climate change over the next 100 years is likely to have a range of direct and indirect impacts on many natural and physical environments, including the built environment. Important influences on the built environment will include alterations in temperature, precipitation, extreme climatic events, soil conditions, groundwater and sea level. Some processes of building stone decay will be accelerated or worsened by climate change, whilst others will be retarded. The impacts on individual processes can be conceptualized, but it is difficult to assess or quantify the overall risk posed by climate change given currently available data. Linking global-scale changes to the response of individual walls or buildings remains a challenge. Overall changes in decay rates could also be related to climatic change. As an example downscaled climate predictions, knowledge of stock at risk and long-term decay rates can be used to assess the future of building stone decay in the UK. Using the UK Climatic Impacts Programme’s (UKCIP98) regional climate change projections an increasing NW-SE climatic gradient is predicted, which should enhance chemical weathering of silicate building materials in the NW and increase crystallization damage of limestones in the SE.
A rapid method for the determination of cation exchange capacities of sandstones: preliminary data
Authors: Schäfer Mathias , Steiger Michael 
Published: September 2007

Abstract

A rapid and efficient single-extraction procedure for measuring cation exchange capacities in sandstones has been developed and tested. The method is based on the use of a SrCl
2
(0.25 mol l
−1
) solution to displace the exchangeable cations. The cation exchange capacities (CEC) of three types of natural building stones were analysed, both in freshly quarried material and in weathered samples. Large differences in the sorptive properties of these materials were observed. The measurement of profiles of CEC in weathered sandstones revealed a significant decrease of CEC in the weathered zone close to the exposed surface, most likely reflecting the partial dissolution of clay minerals due to acid attack. CEC measurements appear to be a very sensitive indicator of chemical weathering profiles.
The role of magma in the development of the Afro-Arabian Rift System
Authors: Buck W. R. 
Published: September 2007

Abstract
The initiation of the Afro-Arabian Rift System on three nearly straight segments occurred shortly after massive amounts of basalt poured out of the triple junction of those segments in Afar. The synchroneity of magmatism and rifting may reflect the fact that normal continental lithosphere is too strong to rift without magmatic dyke intrusions and the straightness of rifts reflects a localized source for the magma feeding those dykes. Simple relations are derived for the minimum extensional force needed for lithosphere cutting dyke intrusions as functions of the density structure and thickness of the lithosphere. As long as the density contrast between continental crust and magma is small compared to the density contrast between the mantle and magma, then the force needed to rift scales with the square of the thickness of the mantle lithosphere. Thus, continental regions with normal-thickness lithosphere may rift when reasonable levels of extensional force and sufficient magma are available. Very thick mantle lithosphere may not rift at levels of force that are likely to arise on Earth. Two main sections of the Afro-Arabian Rift System, the Red Sea and the Ethiopian Rift, appear to have developed as magma-assisted rifts in normal continental lithosphere. The northern and southern ends of the system are bounded by regions of very thick mantle lithosphere where dykes could not open. In the south, the Tanzanian Craton, with normal-thickness crust and a very deep lithospheric root, was also not split by the rift. In the north, the rift opened along a nearly straight line from the centre of the flood basalt province 2000 km to the edge of the Mediterranean Sea. The old oceanic lithosphere of this margin may be no thicker than the adjacent continental lithosphere of Egypt, but the thinner oceanic crust means that Mediterranean lithosphere may be too thick and dense to rift magmatically. The role of magma in the third branch, the Gulf of Aden, is not so clear given the lack of syn-rift dykes.
Basaltic magmatism and the geodynamics of the East African Rift System
Authors: Rogers N.W. 
Published: September 2007

Abstract
The major and trace element and radiogenic isotope compositions of basalts from throughout the East African rift system are reviewed in the context of constraints from previous geophysical studies. The data indicate the presence of two mantle plumes, the East African and Afar plumes, which dynamically support the East African and Ethiopian plateaus. Rifting across the plateaus is accompanied by the generation of large volumes of basaltic magma and associated evolved derivatives. Relatively few mafic magmas have an unambiguous Afar mantle plume signature, notably the MgO-rich picrites and ankaramites from the 29–31 Ma Ethiopian traps, and the most recent basalts (<5 Ma) from Afar. The Eocene Amaro basalts from southern Ethiopia also have a plume source but their lower source temperatures and isotopic characteristics are distinct from those of Afar. The remaining basalts from the Ethiopian rift, and throughout the Kenya and Western rifts, have a lithospheric source region as reflected in both radiogenic isotope and trace element characteristics. The Amaro basalts are suggested as the first manifestations of magmatism from the East African plume; subsequent magmatic activity being represented by progressively younger episodes further south through Turkana, Kenya and into Northern. Tanzania, as the African plate migrated north. Despite their clear lithospheric characteristics, U-series data on geologically recent basalts from the axis of the Kenya rift show that they were generated in a dynamic melting regime. Melting is effected when lithospheric mantle heats up and becomes incorporated into the convecting mantle, hence leading to greater degrees of lithospheric thinning than are indicated by extension across individual rift basins.