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Six Portuguese magmatic ornamental stones were submitted to Soxhlet experiments during 10,000 hours (approximately 416 days) in order to evaluate how the rain water affects the rock behavior as a dimension stone. Macroscopic alterations were observed in the rock fragments and chemical analysis of leaching water solutions revealed how major elements were mobilized from rock-forming minerals allowing to compare weathering susceptibilities between different natural stones.

The study of building materials constituting cultural heritage is fundamental to understand their characteristics and predict their behavior. When considering materials from archaeological sites, their characterization can provide not only relevant information for a broader understanding of the site and its importance and significance but can also increase knowledge about ancient materials and their performance. The Palace of Knossos is a very important archaeological site in the European history context, and its preservation benefits from the characterization of the constituent materials. Samples of mortars from this monument were collected under the scope of the H2020 HERACLES project, where a multi-analytical approach was chosen using established protocols for the different sample typologies. Instrumental techniques such as optical microscopy (OM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and simultaneous thermogravimetry and differential thermal analysis (TG-DTA) were used for the chemical, mineralogical, and morphological characterization of these mortar samples. The results indicate that the majority are lime mortars, both aerial and hydraulic, but gypsum-based mortars were also identified. Differences in the chemical composition of the samples in distinct areas of the monument allowed us to reflect on the variety of materials used in the construction of the Palace of Knossos. info:eu-repo/semantics/publishedVersion

Calcarenite stone samples from a historic building (Bizerte, Tunisia) were collected and treated under different environmental conditions with several consolidating products: alkoxysilane (ethyl silicate), a surfactant-templated novel sol–gel, Ca(OH)2, and SiO2 nanoparticles. These were subjected to marine aerosol accelerated aging cycles and studied by several non-destructive tests and techniques to assess the stability of the products. Results show that weathering caused by salt crystallization is not inhibited but it is slowed down due to the enhancement of superficial mechanical properties (surface cohesion and micro-hardness) achieved after one month of treatments application. A high or low relative humidity of the consolidation environment significantly affects the final mechanical and aesthetical physical properties and therefore conditions the durability of the treated substrates, even producing higher damage than observed in the blank specimens, depending on the product.

The authors would like to thank MSc Vitor Silva for all the help during the experimental campaign and to project DB-Heritage - Database of building materials with historical and heritage interest (PTDC/EPH-PAT/4684/2014).

The salt mist present in the coastal shoreline constitutes an important weathering agent of the building materials applied in these regions. Portugal has an extensive coastline, which has a high population density. It holds a long tradition in the use of stone as a building material, due to the abundance of this natural resource, but also because of its durability and beauty. Considering the main ornamental stones mined in Portugal, limestones are the most susceptible to the action of saline atmospheric aerosol, because, in most cases, they present open porosities higher than those of other stone types. This feature facilitates the penetration of saline aerosol in their structures. Six widely applied Portuguese limestones, with different technological properties, were selected for this study. After accessing their petrographic and main technological features, the limestones were submitted to salt mist test. The test method, established in the respective European standard, was complemented with further determinations (variation on water absorption and flexural strength after salt mist cycling). The results allowed evaluating the limestones’ suitability for the main types of applications and for specific usage conditions, within each one. Thus, it was possible to set the recommended uses for each limestone, in order to maximize its durability. Salt mist testing made possible to determine the limestones’ resistance to the climatic conditions of coastal areas. The detailed analysis of the salt mist results strengthens the knowledge that the open porosity plays a decisive role in the limestones’ behaviour to this test.

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This paper aims at studying the influence of different clay/coffee waste mixtures in structural ceramics by incorporating different amounts of spent coffee grounds as an additive. Clay paste with 5, 10, 15 and 20 wt-% of coffee waste was used to mould clay bodies, which were then fired at the temperatures of 900, 1000 and 1100°C. Morphological aspects were evaluated through SEM images, while several laboratory tests provide the physical and mechanical properties. Incorporation of coffee waste increases the water absorption and apparent porosity, and increasing the firing temperature causes an overall decrease in pore size. Samples with up to 10% coffee waste are in the highest grade of mechanical strength standards. The addition of 20% decreases by 70% the thermal conductivity value. The coffee waste residues could be used as a secondary clay raw material to form proper bricks with excellent thermal insulation proprieties.

Seven silicate rocks used as ornamental stones and having different surface finishing were submitted to salt fog atmospheres in order to compare different susceptibilities to alteration. Polished, honed, hammered and flamed finishing types were tested. Rocks come from Portugal, Brazil and Angola and are widely commercialized. Samples covered quartz rich rocks, silica saturated and undersaturated rocks, mono and plurimineralic rocks, coarse and fine grained rocks. Mineral composition, texture and open porosity showed to be important parameters which determine mass loss among samples, but the finishing type was very effective within samples. Mass loss and porosity increase are higher on hammered samples, contrasted with the lowest loss values on polished samples. The effect of surface hydrophobicity and roughness on the samples having polished finishing was also analysed by atomic force microscopy (AFM) and water contact angle (WCA), indicating that texture and mineral diversity influence the hydrophobic character of the rock surfaces.

Mediterranean calcarenite stones are exposed to several weathering processes related to the climate and environment, producing alteration features conducing to loss of cohesion in their structures. Samples of these building materials were collected from the Spanish Fort of Bizerte (Tunisia) to carry out laboratory tests in order to assess the consolidation effect of the nowadays most frequently used products and most innovative consolidation materials based in nanoparticles. Stone specimens were consolidated with the most employed alkoxysilane product (ethyl silicate), with a surfactant-templated novel sol-gel product (that avoids the tendency to crack) and with inorganic products based on calcium hydroxide nanoparticles (Ca(OH)) and silica nanoparticles (SiO) under very humid and dry environmental conditions. Samples were characterized by scanning electron microscopy, peeling test, superficial hardness, drilling resistance, water absorption by capillarity and under vacuum, water desorption and spectrophotometry, before and after one month of the application of the products to evaluate their consolidation effect under different environmental conditions. The results show great differences in the consolidation effect and in the changes produced in the physical properties of the substrate after using alkoxysilane products (even nanostructured) or products based in nanoparticles. In the case of alkoxysilane and nanostructured products, especially exposed to high RH conditions, the mechanical properties of the substrate, internal and surface, increase. In both cases a layer on the substrate which occludes the pores is generated maintaining a hydrophobic behavior after one month causing drastic changes in the hydric behavior with visually detectable aesthetic changes. In the case of inorganic nanoparticles, changes in the porosity of the substrate caused by the creation of micropores occur in both cases. In the case of SiO nanoparticles, moderate physical changes occur in dry conditions resulting in less shrinkage and color changes. Finally, Ca(OH) nanoparticles are the products with the lowest surface and internal consolidation effectiveness which barely change the physical properties of the stone., This work has been carried out at Instituto de Geociencias (CSIC,UCM) and supported by Rafael Fort and GEOMATERIALES (S2009/MAT-1629) Program. The work was also supported by a JAE-PreDoc fellowship program (2010–2014) of the Spanish National Research Council (CSIC) and the Adaptability and Employment Program of the European Social Fund (ESF 2007–2013).

Limestones and silicate rocks used as dimension stone were submitted to cycles of salt fog, totalizing 140 days in a salt spray chamber. Rock samples comprised three types of limestone, three different marbles, six types of granites, two syenites, one gabbro and one basalt. Mineral changes and variation on surface luster, weight loss and salt crystallization on rock surfaces were some of the features observed along the exposure. While losses of weight and surface luster were the most striking features observed on carbonate rocks, mineral degradation was the main modification on silicate rocks, in which biotite showed to represent a key mineral in the alteration process due to its cleavage and possibly to its composition.

An educated estimate of changes of mechanical properties of polymeric mortars under environmental actions requires further knowledge since data are insufficient and the understanding of alterations incomplete. An experimental program to generate information on those aspects for artificially aged coupons of polyester and epoxy mortars is described. At pre-established temporal stages, flexural tensile bending and compression strength of coupons was determined and compared. Environmental conditioning consisted of cycles of (i) temperature; (ii) humidity and (iii) salt fogging, emphasis being, herein, placed on the effects of the temperature and humidity cycles. Thin lamellae of the tested coupons were cut along the ageing process and observed under petrographic microscope. Changes on the aspect of air voids and textures are reported. A systematic SEM study of the mineralogical and textural aspects is also presented that qualitatively contributes to the interpretation of the results. Higher degradation was detected in the samples submitted to the temperature and salt fogging cycles selected in the study and seen to intensify past 3000 h of accelerated environmental action.

The effects of particulate matter (PM) from diesel and leaded gasoline motor vehicles exhaust emissions on sulfation of granites, syenite and gabbro stones have been experimentally studied. Abundant gypsum crystals and corrosion features developed on stones covered with diesel PM (DPM) following 72 h exposure to 100 ppm SO2 at a relative humidity of 100%. In contrast, very small amounts of gypsum were observed on stones covered with gasoline PM (GPM), while no effect was observed on naked control stones. Abundant elemental C and Fe-rich particles in DPM play a critical role in the catalytic oxidation of SO2 and the formation of H2SO4, which is responsible for silicate stone sulfation. Conversely, organic C and Pb-rich particles that are main components of GPM, do not play a significant role in sulfation. The response of each stone type towards sulfation is related to the stability of their constituent silicate minerals towards acid attack. Thus, the stones most susceptible to sulfation are those including nepheline (syenite), olivine, and pyroxene (gabbro), while granites in general, are most resistant to sulfation-related chemical weathering. These results help to explain how black (gypsum) crusts develop on silicate stones, and support limitations for (diesel) vehicular traffic and emission loads in urban centers.

Os materiais estudados foram denominados de Verde Netuno, Verde Santa Cruz e Verde Choró, respectivamente para os granulitos das regiões de Itapipoca, Granja e Chorozinho. Foram pesquisados quanto aos aspectos tecnológicos e alteração/alterabilidade quando em uso. O objetivo principal deste trabalho foi estudar as alterabilidades das rochas selecionadas e observar os seus comportamentos uma vez expostas à ação dos agentes de alteração em laboratório, em condições correlacionáveis às do ambiente em que poderão ser aplicadas. Os estudos de alterabilidade realizados em rochas granulíticas demonstraram que, mesmo rochas aparentemente pouco susceptíveis a alteração, podem apresentar problemas de degradação quando submetidas a ambientes poluídos quimicamente agressivos. Sobre estes aspectos, observou-se que as características petrográficas e os índices físicos (porosidade e absorção) são ferramentas muito importantes para a avaliação da durabilidade das rochas como materiais de revestimento. No contexto geral estas rochas mostraram-se bastante resistentes para uso como materiais de revestimentos.

A performance relativa entre “granitos negros” foi estudada através de ensaios de lixiviação acelerada sobre corpos de prova submetidos a imersão total numa solução de 300 ml de H2SO4 (pH = 3), ao longo de 8 ciclos de 15 dias. Nos intervalos de cada ciclo foram medidos os brilhos a seco de faces polidas, antes da imersão seguinte dos corpos de prova (5 x 5 x 2 cm) em solução ácida renovada. Os valores de pH foram determinados nas soluções residuais filtradas (< 0,45 µm) de cada ciclo. O comportamento destas variáveis foi interpretado em termos da dinâmica do processo reativo hidrolítico agindo sobre as composições mineralógicas das rochas testadas, inferindo-se a progressão do estado estético dos corpos de prova por suas perdas relativas de brilho, comparadas aos brilhos iniciais em suas faces polidas. Os resultados em escala de bancada sugerem a viabilidade da previsão comparativa da performance entre esses produtos, considerando-se os seus aspectos estéticos observados em revestimentos externos, sob condições intempéricas e tempos de aplicação similares. authorsversion published

A indústria das rochas ornamentais leva à produção de elevadas quantidades de resíduos, que promovem a ocorrência de impactos ambientais e paisagísticos negativos bem como o facto de constituírem um grande constrangimento com elevados custos para as empresas. Estes resíduos, resultantes da extração de rochas ornamentais e industriais, são essencialmente poeiras, lamas e massa mineral rejeitada. As lamas provêm fundamentalmente das operações de desmonte com recurso a fio diamantado e das operações de beneficiação dos blocos devido à utilização de serras, impregnando água. Estas lamas, provenientes dos vários processos de transformação, como corte, serragem e polimento, são enviadas para um decantador no qual é realizada a remoção das partículas sólidas por sedimentação com recurso a floculantes. Após decantação, a água é reintroduzida no sistema e as lamas formadas são enviadas para um filtro prensa onde são concentradas e onde o seu volume é reduzido, sendo posteriormente enviadas para escombreiras ou para o aterro. Esta investigação tem como objetivo estudar a viabilidade da incorporação de resíduos produzidos no sector das rochas ornamentais, particularmente, de lamas carbonatadas, resultantes dos processos de extração e transformação de calcários utilizados como rochas ornamentais, na cerâmica. Deste modo, é possível reduzir os impactos ambientais na indústria de rochas ornamentais assim como a quantidade de resíduos produzidos, que têm como destino final a deposição em aterro. Para este efeito, elaboraram-se provetes de argila cinzenta com misturas de resíduo nas percentagens de 0%, 5%, 10%, 15% e 20%. Estes provetes foram submetidos a três temperaturas distintas, nomeadamente a 900°C, 1000°C e 1100°C. Após a sua cozedura às diferentes temperaturas, cada um dos provetes foi sujeito a ensaios tecnológicos de modo a averiguar a influência da incorporação de diferentes quantidades de lamas carbonatadas na cerâmica, permitindo assim tirar conclusões relativamente à viabilidade da sua incorporação. Os resultados indicaram que a incorporação de lamas carbonatadas melhora propriedades como a trabalhabilidade, retração linear térmica, perda de massa após cozedura, bem como o grau de brancura dos cerâmicos. Relativamente às propriedades físicas da argila, verificou-se um aumento da absorção de água e porosidade aberta e diminuição da massa volúmica aparente, o que poderá vir a ser benéfico na produção de produtos cerâmicos com bom isolamento térmico e acústico. Em relação às propriedades mecânicas, o ensaio de resistência à flexão indicou uma diminuição desta propriedade com a adição de resíduo, quando comparado aos valores de referência (0%), sendo que a percentagem com resultados mais satisfatórios foi a de 15% à temperatura de 1100°C. Verificou-se ainda que não houve uma perda de massa significativa dos provetes cerâmicos após serem submetidos ao ensaio de nevoeiro salino, para além de não se ter evidenciado alterações morfológicas dos mesmos, pelo que se considera possível a aplicação de cerâmicos com incorporação deste resíduo, em zonas litorais. info:eu-repo/semantics/publishedVersion