TY - JOUR A1 - Binley, A. A1 - Kruschwitz, Sabine A1 - Lesmes, D. A1 - Kettridge, N. T1 - Exploiting the temperature effects on low frequency electrical spectra of sandstone: a comparison of effective diffusion path lengths JF - Geophysics N2 - A number of recent investigations have highlighted the potential value of using relaxation times derived from electrical spectra to infer key physical properties of permeable rocks. To date, most studies have assumed a grain size or pore throat as a measure of the length scale of the ionic diffusive process, although this has been challenged in recent experimental investigations. We compare the electrical spectra of three sandstones, adopting a new approach in which the temperature of the rock samples is perturbed and the relaxation time measured as a function of temperature. Our results suggest that, for the sandstones tested here, the effective diffusion coefficient should be considered as a function of the electrical tortuosity. These findings may help explain the apparent long relaxation times observed in low-permeability rocks in recent experimental studies. We also highlight the need to account for temperature in related studies of electrical spectra. KW - Grain size KW - Porosity KW - Rocks KW - Spectral induced polarization KW - Temperature KW - Sandstone KW - Saturation KW - Diffusion PY - 2010 DO - https://doi.org/10.1190/1.3483815 SN - 0016-8033 VL - 75 IS - 6 SP - A43 EP - A46 PB - Soc. CY - Tulsa, Okla. [u.a.] AN - OPUS4-23860 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - García, O. A1 - Rz-Maribona, I. A1 - Gardei, André A1 - Riedl, Martin A1 - Vanhellemont, Y. A1 - Santarelli, M.L. A1 - Strupi Suput, J. T1 - Comparative study of the variation or the hydric properties and aspect of natural stone and brick after the application of 4 types of anti-graffiti JF - Materiales de construcción N2 - In this article a comparative study of the behaviour of different commercial anti-graffiti on natural stone and brick is presented. 8 different European substrates were selected and 4 commercial anti-graffiti of different chemical nature were applied on these substrates. The variations of their hydric properties and aspect (colour and gloss) with regard to the untreated substrates were later studied in the laboratory. The results obtained permitted to assess the suitability of 4 of the main types of chemical formulations employed to be used as anti-graffiti. This study concludes that the sacrificial anti-graffiti with polymeric paraffins in its composition presents the lowest reductions of the hydric properties of the studied substrates, being also the variations in colour the least perceptible. KW - Graffiti KW - Sandstone KW - Limestone KW - Natural stone KW - Brick KW - Anti-graffiti KW - Porous substrates KW - Surface treatments KW - Anti-graffiti coatings KW - Hydric properties KW - Colour KW - Gloss PY - 2010 DO - https://doi.org/10.3989/mc.2010.45507 SN - 0465-2746 N1 - Sprachen: Spanisch/Englisch - Languages: Spanish/English VL - 60 IS - 297 SP - 1 EP - 14 CY - Madrid AN - OPUS4-21087 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kruschwitz, Sabine A1 - Binley, A. A1 - Lesmes, D. A1 - Elshenawy, A. T1 - Textural controls on low-frequency electrical spectra of porous media JF - Geophysics N2 - The results from several laboratory studies of the relationships between electrical polarization and physical properties of porous media have prompted interest in the potential use of low-frequency electrical spectra to qualitatively or quantitatively map variation in hydrogeologic properties in the field. Compiling several published and unpublished data sets, supported by new measurements, we have examined the low-frequency electrical spectra of a range of natural and artificial porous media to assess the generality of proposed relationships between electrical and physical properties. Our work confirms a significant positive correlation between the magnitude of electrical polarization (quantified as imaginary conductivity at a specific frequency) and the surface-area/pore-volume ratio Spor. Analyzing the parameters of ageneralized Cole-Cole resistivity relaxation model fitted to many electrical spectra, we observe two apparent controls on the electrical relaxation. For samples with abundant relatively large pore throats, we observe a distinct increase in the time constant of the model with modal pore-throat size, in accordance with classical electrical relaxation models. However, for media with pore structures dominated by small pore throats, the diffusion-length scales do not appear to be controlled by modal pore-throat size. We conclude that for such media, the microstructure of the network of small pores leads to some connectivity of diffusion paths; thus, these samples exhibit relatively large time constants. There is potential value in addition to limitations when using electrical spectra to estimate physical properties of porous media, and we see the need for more appropriate generalized theories of electrical polarization in hydrogeologic media. KW - Geophysical techniques KW - Terrestrial electricity KW - Spectral induced polarization KW - Temperature KW - Sandstone KW - Saturation KW - Diffusion PY - 2010 DO - https://doi.org/10.1190/1.3479835 SN - 0016-8033 VL - 75 IS - 4 SP - WA113 EP - WA123 PB - Soc. CY - Tulsa, Okla. [u.a.] AN - OPUS4-23861 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Urs T1 - La composición mineralógica de la arenisca y su influencia en la deposición de dióxido de azufre / The mineralogical composition of sandstone and its effect on sulphur dioxide deposition JF - Materiales de construcción N2 - Los contaminantes atmosféricos son con frecuencia responsables de la aceleración de la degradación de la piedra en los edificios y monumentos históricos de las zonas urbanas. Son muchos los factores que influyen de manera decisiva en el comportamiento de las piedras naturales ante los contaminantes gaseosos. Dos de esos factores son la composición de la atmósfera y el tipo de piedra. Las areniscas en particular son propensas al ataque de los contaminantes atmosféricos debido a su naturaleza porosa, pero muchas de las reacciones de las areniscas no carbonatadas con estos gases no se conocen bien. El estudio presentado tiene por objeto comprender los procesos y factores que controlan el distinto comportamiento de las areniscas respecto al dióxido de azufre. Para el estudio se investigaron siete areniscas distintas procedentes del sur y del este de Alemania. Las areniscas mostraban una diferencia significativa en la composición de su aglomerado. Por lo que respecta a la absorción de SO2, las distintas variedades de arenisca mostraron un comportamiento completamente diferente. Curiosamente, la cantidad de SO2 depositada no estaba relacionada con la superficie específica de las areniscas, este parámetro está relacionado con el contenido en óxidos de hierro. Air pollutants often accelerate stone deterioration in historical buildings and monuments in urban areas. Many factors condition natural stone behaviour with respect to gaseous pollutants. Two of the more prominent of such factors are the composition of the atmosphere and the type of stone. Due to their porosity, sandstones are particularly vulnerable to air pollutant attack. Many of the reactions between noncarbonaceous sandstones and these gases are not well understood, however. The present study aimed to acquire an understanding of the processes and factors governing sandstone behaviour when exposed to sulphur dioxide. Seven different sandstones from southern and eastern Germany were analyzed for the study. The binder composition of the stones varied significantly. They also exhibited completely different behaviour in connection with SO2 deposition. Interestingly, while the amount of SO2 deposited was unrelated to the specific surface area of the sandstones, this parameter was closely correlated to the iron oxide content. KW - Arenisca KW - Contaminantes KW - Deposición KW - Deterioro KW - Catalizador KW - Sandstone KW - Pollutants KW - Deposition KW - Deterioration KW - Catalyst KW - Luftschadstoffe KW - Werksandstein KW - SO2 KW - Verwitterung PY - 2008 SN - 0465-2746 N1 - Sprachen: Spanisch/Englisch - Languages: Spanish/English VL - 58 IS - 289-290 SP - 81 EP - 95 CY - Madrid AN - OPUS4-17506 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reimold, W. U. A1 - Crosta, A. P. A1 - Hasch, M. A1 - Kowitz, Astrid A1 - Hauser, N. A1 - Sanchez, J. P. A1 - Simoes, L. S. A. A1 - de Sanchez, G. J. A1 - Zaag, P. T. T1 - Shock deformation confirms the impact origin for the Cerro do Jarau, Rio Grande do Sul, Brazil, structure JF - Meteoritics & Planetary Science N2 - Cerro do Jarau is a conspicuous, circular morpho‐structural feature in Rio Grande do Sul State (Brazil), with a central elevated core in the otherwise flat “Pampas” terrain typical for the border regions between Brazil and Uruguay. The structure has a diameter of approximately 13.5 km. It is centered at 30o12′S and 56o32′W and was formed on basaltic flows of the Cretaceous Serra Geral Formation, which is part of the Paraná‐Etendeka Large Igneous Province (LIP), and in sandstones of the Botucatu and Guará formations. The structure was first spotted on aerial photographs in the 1960s. Ever since, its origin has been debated, sometimes in terms of an endogenous (igneous) origin, sometimes as the result of an exogenous (meteorite impact) event. In recent years, a number of studies have been conducted in order to investigate its nature and origin. Although the results have indicated a possible impact origin, no conclusive evidence could be produced. The interpretation of an impact origin was mostly based on the morphological characteristics of the structure; geophysical data; as well as the occurrence of different breccia types; extensive deformation/silicification of the rocks within the structure, in particular the sandstones; and also on the widespread occurrence of low‐pressure deformation features, including some planar fractures (PFs). A detailed optical microscopic analysis of samples collected during a number of field campaigns since 2007 resulted in the disclosure of a large number of quartz grains from sandstone and monomict arenite breccia from the central part of the structure with PFs and feather features (FFs), as well as a number of quartz grains exhibiting planar deformation features (PDFs). While most of these latter grains only carry a single set of PDFs, we have observed several with two sets, and one grain with three sets of PDFs. Consequently, we here propose Cerro do Jarau as the seventh confirmed impact structure in Brazil. Cerro do Jarau, together with Vargeão Dome (Santa Catalina state) and Vista Alegre (Paraná State), is one of very few impact structures on Earth formed in basaltic rocks. KW - Serra da cangalha KW - Recovery experiments KW - Piaui state KW - Santa-marta KW - Features KW - Pressure KW - GPA KW - Sandstone KW - Geology PY - 2018 DO - https://doi.org/10.1111/maps.13233 SN - 1086-9379 VL - 54 IS - 10 SP - 2384 EP - 2394 PB - Wiley AN - OPUS4-50029 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -