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[en] Aiming to determine the BaSO4, utilized as shielding against ionizing. The type and quantity of aggregate in the concrete are important components for radiation protection properties of concretes. The X-ray spectrum was measured with a cadmium zinc telluride detector (CdZnTe). The samples were irradiated with x-rays with potentials in the radiation qualities ISO N60, N80, N110 and N150. The analyses proved to be effective and led to the identification of the total composition of samples in 95.88%. The results obtained show that the barium content is higher than the sulphate content in the BaSO4 compound regardless of its origin. (author)
[en] Full text: Plaster of Paris is a widely used construction material, which is considered a challenge as far as recycling is concerned. This may be so because not only the sulphates can contaminate water reservoirs. Also, current recycling technologies are not sufficiently effectiveness in terms of cost and engineering properties. This work aims to evaluate the effect of gridding on the hardening properties of calcium sulphate hydrate pastes as a tool to improve gypsum hardening properties. An experimental programme was designed to assess the effect of two levels of gridding time (5 and 20 minutes) on mechanical and microstructure properties. The morphology of gypsum crystals was evaluated by means of scanning electron microscopy. Crystal structural parameters were determined via x-ray diffraction and mechanical properties by means of compressive and flexural strength. The data suggests a strong influence of gridding time with the aspect ratio of the crystals. Also, considerations will be given on the mechanisms of hardening, especially in systems where the calcium dehydrate phase were originated either from bassanite hydration and from gypsum dehydration. (author)
[en] The recycling of civil construction waste gypsum has been the subject of studies due to the nonexistence of economically viable technologies or applications that would allow it to be recycled. However, studies indicate that the material setting time reduces after recycling, generating more waste, but the cause of the phenomenon is not known. In-situ XRPD monitoring of plasters' hydration in their commercial form and after laboratory recycling process is carried out to verify both reactivity and hydration process. The samples are characterized by specific surface area, microporosity, and consistency tests. Sequential and parametric Rietveld refinements are employed to determine the weight fractions of calcium sulfate-based compounds present in the materials as a function of time. The increase in the consistency of the recycled plaster is not only associated with the increase of microporosity and specific surface area but also to the instant formation of gypsum as soon as the material comes into contact with water. These data also confirm the increase in the kinetic activity values calculated from the results of temperature kinetics tests, proving that the formation of hydrated compounds is much faster for the recycled plaster, which is associated with the increase of water contact area. (author)
[en] Zn(O,S) buffer layer electronic configuration is determined by its composition and thickness, tunable through atomic layer deposition. The Zn K and L-edges in the X-ray absorption near edge structure verify ionicity and covalency changes with S content. A high intensity shoulder in the Zn K-edge indicates strong Zn 4s hybridized states and a preferred c-axis orientation. 2–3 nm thick films with low S content show a subdued shoulder showing less contribution from Zn 4s hybridization. Here, a lower energy shift with film thickness suggests a decreasing bandgap. Further, ZnSO4 forms at substrate interfaces, which may be detrimental for device performance.
[en] As you know, the concentration of radon in buildings built with different building materials also varies. Wood and concrete houses can be considered satisfactory in terms of radon concentration. Thus, widespread construction materials such as trees, bricks and concrete produce relatively small radon radiation.In wooden houses, this radiation is minimal (up to 0.5 mZv / year), while brick and reinforced concrete houses are slightly larger (up to 1.5 mZv / year).It should be noted that the increase in radon concentrations inside buildings is not only building materials, but also soil below the building.Therefore, despite the fact that wood is less radiant than other building materials, in some cases wooden homes have more radon levels than brick houses.For example, studies in Norway have shown that concentration of radon in wooden houses is higher than that of brick houses, and it is found that these trees are usually smaller floors and closer to the radon source.During the development of phosphorus sources, calcium-silicate slag is formed as a by-product.This slag, which has long been used as a building material and concrete component in North america (Idaho and Florida) and Canada, has been found to have a sufficiently high radioactivity.Phosphorus mining uses a different technology to produce additional products called phosphogips.
[en] Over the past few years, various materials used in masonry, such as lead, concrete, ceramic blocks and brick, have been studied for use as shielding against ionizing radiation from different energies in radioactive facilities. In the area of diagnostic radiology, lead and barite are the most used materials as shielding, but for bundles of low energy X radiation, as in mammography and dentistry, plaster material can be used, as affirmed by the National Council on Radiological Protection and Measures through its report number 147 (NCRP Report Nº 147). This work developed plaster phantoms as well as gypsum & barite mixing with plate formats with a 10 x 10 centimeter area, aiming to characterize physico-chemically and verify the feasibility of using these materials as shielding against low-energy X-ray radiation, using mammographic X-ray bundles in metrology laboratories. From the irradiation, it was possible to obtain the transmissions curves, to discover the Half Value Layers (HVL) and the Tenth Value Layers (TVL), as well as to acquire the different spectra for each material. The gypsum & barite mixing material had a better shielding response compared to pure gypsum material, however both can be considered as good attenuators against low energy X radiation. (author)
[en] The advanced condition of deterioration of the column’s bases of the courtyard of the Bishop’s Palace of Tarazona (Spain) built in the middle of 16th century required its restoration with Aragonese alabaster. Thus, adapted ageing tests were developed to simulate the environmental conditions in which the stones were and will be exposed. These tests were thermal fatigue by temperature variations, acid rain and water stagnation by immersion tests and a combination of both agents of decay. The results indicated that alabaster did not experimented deformation after thermal fatigue but a progressive dehydration to bassanite. This process entailed an increase of porosity and consequently a loss of structural properties. The dissolution was measured as a lineal weight and volume loss while porosity and capillary uptake remained stable. The conclusions of this study establish the importance of restoration protocols to maintain the alabaster integrity when used and exposed to rainwater and insolation.
[es]Las basas deterioradas de las columnas del patio del Palacio Episcopal de Tarazona (España), construido a mediados del siglo XVI, fueron restauradas con alabastro aragonés. Por lo tanto, se han desarrollado pruebas de envejecimiento adaptadas para simular las condiciones ambientales en las que las piedras estaban y estarán expuestas, fatiga térmica por variaciones de temperatura, lluvia ácida, inmersión en agua y una combinación de agentes de deterioro. Los resultados indican que el alabastro no experimentó deformación después de la fatiga térmica, sino una progresiva deshidratación a bassanita, lo cual implica un aumento de porosidad y una pérdida de propiedades estructurales. La disolución se midió como una pérdida lineal de peso y volumen, mientras que la porosidad y el ascenso capilar se mantuvieron estables. Se desprende la importancia de adoptar protocolos de restauración para mantener la integridad del alabastro cuando se expone al agua de lluvia e insolación.
[en] Full text: Phosphogypsum waste (PG) is a large environmental issue generated by phosphate fertilizer industries. The content of dihydrate (CASO4.2H2O) in PG is generally above 95% and higher than ordinary natural gypsum, presenting attractive recycling potential in the cement production. The objective of this research is to investigate the applicability of unprocessed PG in the composition of eco-efficient cement. The effects on the setting properties and phase contents of PG added in ratios 1, 3, 5, and 10 wt.% to cement were studied. In this way, the best PG content considering the phases and setting time of cement pastes was studied. Physical properties, chemical and mineralogical compositions were analyzed. Thermal analysis and X-ray diffraction were used to understand how the content of PG affects the obtained products and also used to quantify the phase contents. The initial setting was monitored by heat development using isothermal calorimetry and penetration depth in cement pastes, evaluating the evolution of hydration and stiffness of cement pastes. The results showed that an increase in PG content reduced the setting time. Although the presence of PG has an effect on the reactions of hydration, the amounts of phases silicate hydrate gel and ettringite at 28 days did not change significantly. By evaluating properties of cement paste it was concluded that 1-3% PG addition in cement gave satisfactory results. This indicated that the unprocessed PG could sustainably be used as a replacement of natural gypsum in cement manufacturing. (author)
[en] Highlights: • SO3 was introduced in the form of BaSO4 to prepare borosilicate glass-ceramics. • Barite crystals exist in the samples with 5–8 wt% of SO3. • BaSO4 in borosilicate glass melts is more stable than that of Na2SO4. • The sample S6 (6 wt% SO3 addition) can retain 2.17 wt% SO3 after melting at 1200 °C. • The sample S6 has a lower normalized leaching rate of SO42−. - Abstract: In order to increase the solubility of sulfate in glass matrix, barite−borosilicate glass-ceramics were proposed and prepared by melt quenching method. The effects of SO3 addition (in the form of BaSO4, 0–8 wt%, abbreviated as S0S8) on microstructure, phase structure, and aqueous stability of barite–borosilicate glass-ceramics were studied. The sulfate retention of the glass-ceramics was evaluated. The results show that the samples with addition of 0–4 wt% SO3 possess the amorphous structure. Barite phase appears when the addition SO3 content increases to 5 wt%, and the amount of barite crystals increases with further increasing SO3 content. Furthermore, BaSO4 in borosilicate glass melts is more stable than that of Na2SO4. The sample S4 possesses SiO2 and BaSO4 phases in temperature range of 800–1150 °C. The SO3 content in the sample S4 remains almost unchanged when the temperature increases from 800 to 1050 °C, and decreases rapidly with further increasing temperature. About 2.17 wt% of SO3 can be retained in the sample S6 after melting at 1200 °C. Moreover, the normalized leaching rates of Na and B of the samples S4, S6, and S8 after 28 days are one order of magnitude higher than that of the sample S0. The sample S6 has a lower normalized leaching rate of SO42− (∼1.28 × 10−2 g m−2 d−1) after 28 days.
[en] To estimate the interaction of type X ionizing radiation with matter, in order to evaluate the efficiency of materials that can be used as X-ray shielding, Exposure Computational Models (ECMs) are developed. The ECMs are composed, fundamentally, of an anthropomorphic model to simulate radiated geometry (usually referred to as phantom), algorithms to simulate the radioactive source used and a Monte Carlo (MC) Code. The linear attenuation coefficient is the parameter used to measures the X-radiation shielding efficiency. In the exponential model this is related to the half-value layer (HVL) of the absorbing material. The HVL can be obtained by MC methods that have advantages such high speed and low cost. This paper aimed to study and compare X-photon attenuation from gypsum and barite concrete to estimate yours HVL respective. The objective of this study was achieved by means of gypsum and barite concrete phantoms development. These were molded like square plates format, called test bodies, whose dimensions are: 10 cm x 10 cm and thickness ranging from 1 mm to 26 mm. The X-ray apparatus voltage simulated ranging from 50 to 150 kV. This voltage range corresponds to that applied in diagnostic radiology area. In this way, they can be compared with measures and values present in the literature