Results 1 - 10 of 236
Results 1 - 10 of 236. Search took: 0.021 seconds
|Sort by: date | relevance|
[en] In spite of the fact that gypsum is one of the most environmentally friendly binders, utilization of gypsum products is relatively narrow. The main problem of gypsum materials is their low resistance to the wet environment and radical decrease of mechanical properties with increasing moisture. The solution of the problem could be in use of composed gypsum-based binders, usually ternary, comprising gypsum, pozzolan and alkali activator of pozzolan reaction. These materials have a better moisture resistance and often also better mechanical properties. Paper provides literature survey of the possible compositions, properties and ways of utilization of the composed gypsum-based binders with latent hydraulic and pozzolan materials together with some results of present research performed by authors. (paper)
[en] In this paper, properties of composite materials containing ternary binders are determined. Except gypsum, ternary binders containing also pozzolans and alkaline component, which serve as an activator of pozzolanic reaction. The main aim of this research was to investigate changes in physical and chemical properties and pore structural characteristics due to additions of ternary binders. Experimental results showed that changes in the properties of the composite depend not only on the amount of the addition, but also on the kind of pozzolan. (paper)
[en] The present study describes the lithostratigraphic characteristics of the Canelles Gypsum Formation (lower Keuper) and the Lécera Gypsum Formation (Lower Jurassic) in the area of Camarasa, in the Catalan South Pyrenean front. The Lécera Formation forms a cyclic alternation of gypsum and carbonate layers of about 300 m thick. Gypsum displays gray laminated, white laminated, and white massive lithofacies. Carbonate forms minor layers of dolobreccia and thin bedded dolomicrite lithofacies. On the contrary, the Canelles Formation forms a 100 m thick massive sequence mainly composed of white and brown laminated gypsum, with carbonate layers restricted to the base of the formation and to its middle part. On the base, the carbonate layers consist of laminated dolomicrite lithofacies, while in the middle part they display laminated dolomarl, thin bedded dolomicrite and oolitic lithofacies, which are arranged in four carbonatic cycles of few meters thick. Both formations originated in similar evaporitic environments of very stable sulfate lagoons fed by sea water and away from the influence of detrital inputs. In such lagoons sedimentation mainly consisted of laminated gypsum with minor carbonate beds, representing sediments of relatively high and low concentration of the lagoon water respectively, but without precipitation of more soluble salts (halite).
[es]En el presente estudio se describen las características litoestratigráficas de las formaciones yesíferas de Canelles (Keuper inferior) y de Lécera (Jurásico Inferior) aflorantes en la zona de Camarasa, en el frente Surpirenaico Catalán. La serie de la Fm. Lécera constituye una alternancia cíclica de capas de yesos y carbonatos de cerca de 300 m de espesor. El yeso es de litofacies laminada gris, laminada blanca y masiva blanca. Los carbonatos son brechas dolomíticas y dolomicritas finamente estratificadas. Por el contrario, la Fm. Canelles forma una serie yesífera masiva de 100 m de espesor, con capas menores de carbonato restringidas a la base de la formación y a su parte media. En la base el carbonato es de litofacies dolomicrita laminada, mientras que en la parte media es de litofacies margodolomía laminada, dolomicrita laminada y oolítica, formando cuatro ciclos de pocos metros de espesor. Ambas formaciones se originaron en sistemas evaporíticos de tipo lagoon sulfatado, muy estables, alimentados por aguas marinas y alejados de la influencia de aportes detríticos. En estos lagoons la sedimentación fue principalmente yesífera, en facies laminada, y con niveles subordinados de carbonatados, representando respectivamente estadios de mayor y menor concentración relativa del agua, y sin registro de sales más solubles (halita).
[en] The paper introduces a new type of green building which suits for the construction of rural dwellings in Xinjiang, China. Results of the shaking table test on building model show that the single-layer gypsum-adobe structure has better seismic performance. And it also analyzes the construction features and engineering practice, which means that it is significant to extend this type of building to the drier regions in China.
[en] Present article is devoted to study of physicochemical and biological properties of malb-zincate. In order to decrease the negative properties and increase the effectiveness the malb-zincate has been synthesized. Physicochemical and biological properties of malb-zincate have been defined.
[en] The results of studies of solubility in invariant points of Na2SO4-Na2HCO3-H2O system at 0 deg C have been considered. The diagram of Na2SO4-Na2HCO3-H2O system at 0 deg C has been constructed.
[en] Highlights: • An alternatives X-ray shielding material produced using local abundant minerals. • Monoclinic BAS phase is found to enhance the shielding ability against X- rays. • Barium aluminosilicate (BAS) is the major shielding phases for the ceramics. • The optimum X- rays shielding ability of ceramics is discern at 70 kV. • The effectiveness of shielding are shown by LE thickness and dose reduction. - Abstract: Mullite-barite ceramic (MBC) is an emergent material for effective shielding of redundant ionizing radiation exposure. The composition dependent mechanical, thermal, and microstructure properties of MBC that makes MBC a high performing novel radiation shielding candidate remained unexplored. This paper examines the possibility of exploiting Malaysian kaolin (AKIM-35) and barite (BaSO4) derived ceramic (MBC) system for X-ray shielding operation. Using conventional pressing and sintering method six ceramic samples are prepared by mixing AKIM-35 with barite at varying contents (0, 10, 20, 30, 40 and 50 wt%). Synthesized pressed mixtures are calcined at 400 °C for 30 min and then sintered to 1300 °C for 120 min at a heating rate of 10 °C/min. Sintered samples are characterized via X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), lead equivalent (LE), uniformity and dose reduction analyses. XRD pattern of prepared ceramics revealed the presence of monoclinic barium alumino-silicate (BAS) and orthorhombic mullite as major shielding phases together with other minor phase of barite and hexagonal quartz (SiO2) structures. Furthermore, FESEM images of ceramics (between 0 and 30 wt%) displayed the existence of compacted monoclinic plate of BAS and acicular mullite morphology (ceramics at 40 and 50 wt%). Radiation tests displayed the capacity of ceramics (at 0 and 10 wt%) to shield the X-ray radiation emanated at tube potential range of 50–120 kV. The highest radiation attenuation is ascertained at 70 kV where the dose is reduced remarkably between 99.11% and 97.42%. Ceramics at 0 and 10 wt% demonstrated the highest lead (Pb) equivalent thickness (LE) of 0.44 mm and 0.34 mm, respectively. It is established that such MBC may contribute towards the development of shielding material against ionizing radiation in diagnostic radiology (X-ray) dose range.
[en] This paper extends the previous work of the authors and deals with the study of fracture of sandwich panels of plasterboard and rock wool under in-plane bending and tensile loading. It presents the results of the experimental campaign focused on the size effect of the tested specimens. To this end, mixed-mode (Iand II) fracture tests have been carried out with specimens of three different sizes. The experimental results are compared with the values obtained from the numerical simulation of the test by using a model based on the embedded cohesive crack developed by the authors in previous published works. Comparison of the results shows how the model is able to reproduce the size effect of the specimens in this material from the parameters that characterize fracture behaviour. The aim is to use the cohesive model proposed by the authors to move from laboratory tests to a built panel.
[es]Este artículo extiende el trabajo de los autores y aborda el estudio de la fractura en flexión en su plano de paneles de sándwich de yeso laminado y lana de roca. Se presentan los resultados experimentales del estudio del efecto tamaño de fractura en modo mixto (modos I y II) de probetas de tres tamaños. Los resultados experimentales se comparan con los obtenidos de la simulación numérica empleando un modelo de fisura cohesiva embebida presentado por los autores en trabajos previos. El resultado muestra que el modelo reproduce adecuadamente el efecto de tamaño en fractura de los paneles ensayados a partir de los parámetros de caracterización del material. El modelo usado facilita el paso de los resultados de laboratorio al panel construido.
[en] Water treatment at active or closed uranium mining sites is required whenever the effluent from a mine, a waste depository or any other entity reveals higher concentrations than permitted under the respective Water Act or with respect to dose calculations according to the radiation protection regulations. Decision criteria for the selection of the optimal treatment approach are site-specific and include (a) type and concentrations of the contaminants to be removed, (b) possibility or requirement to recover certain components, (c) flow rate and contaminant loads to be removed, (d) time frame at which water treatment is needed, (e) fluctuations of water composition, contaminant load and/or flow rate, (f) type and amount of residues produced. The list of ‘best available technologies economically achievable’ (BATEA) has been collected most recently for the Canadian mining industry (Hatch 2014). The most commonly used active treatment process worldwide is lime treatment. This technology produces contaminant-laden iron and/or gypsum-rich sludge which has to be properly managed and disposed. Most lime operations internationally are HDS (high density sludge) plants. Yet there are several locations with other treatment technologies, such as ion exchange or reverse osmosis, but their application is restricted to localized cases. Besides the minimization of emissions, preferred mine water treatment concepts are intended to recover the mineralization loads not as waste but rather as valuables, such as uranium, metals, fertilizers or sulphur. Passive treatment is often the choice for low flow or low pollution waters and for remote abandoned mine sites, however, those options are not applicable for all types of mine water, and treatment efficiency can be limited due to seasonal changes in the systems parameters.
[en] To determine the mean decrease in MASI score after topical 10% zinc sulfate solution in treatment of melasma. Back ground: Melasma is a common, acquired, benign skin disorder, characterized by symmetrical hyperpigmented patches on exposed areas, predominantly the face. This study was designed to assess the efficacy of topical zinc sulphate solution (10%) in the treatment of melasma. Methods: This quasi experimental study was done at department of dermatology Sir Ganga Ram Hospital/Fatima Jinnah Medical University, Lahore, from November, 2016 to May, 2017. Seventy patients, who had epidermal type of melasma on face (assessed by woods lamp examination), of any severity and duration, were selected. All patients underwent treatment with 10% topical zinc sulfate solution twice daily for 8 weeks. The patients were advised to use sunscreen during day . The severity of melasma was assessed by MASI score at baseline and one day after completion of 8 weeks therapy. The findings were recorded on a predesigned proforma for each patient. MASI score next day after the completion of treatment was subtracted from the baseline MASI score for each patient and then mean decrease in MASI score was calculated. Results: All 70 patients completed the study. 14.3% (n=10) were male and 85.7% (n=60) were females, with mean age of 33.23+6.75 year. We recorded mean decrease in MASI score before and after treatment as 4.76+1.72 (47.36%). Conclusion: Study showed that topical 10% zinc sulfate solution is a cheap, safe and effective agent for the treatment of melasma in our population. (author)