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[en] Cement samples commonly used in building constructions in Egypt and Yemen were analyzed for natural radioactivity using a Hyper-pure Germanium detector (HPGe). The radioactivity content of 238U, 232Th and 40K isotopes in the cement samples was studied. In the Egyptian cement samples, the specific activities for mentioned isotopes were found as follows: for 238U, ranged 18 - 35 Bq/kg, with an average value of 27.9±6.9 Bq/kg; for 232Th, ranged 7.2 - 16.1 Bq/kg, with an average value of 13.1±4.1 Bq/kg; for 40K, ranged 24.8 -107.1 Bq/kg, with an average value of 73.3 ± 35.2 Bq/kg. In the Yemenian cement samples, specific activities for mentioned isotopes were found as follows: for 238U, in the range 19.6 – 193 Bq/kg, with an average of 68.8± 71.9; for 232Th, in the range 17.3 – 256 Bq/kg, with an average of 79.1±102.2 Bq/kg; for 40K, in the range 272.7-858.6 Bq/kg, with an average of 421.6±252.3 Bq/kg. In both country cases, the specific activities were compared with the reported data in other countries and world average limits (global values reported in UNSCEAR publications). The determined specific activity of 238U, 232Th and 40K was found to be less than the world average values (50 Bq/kg, 50 Bq/kg and 500 Bq/kg, respectively, for the considered nuclides) except for Block waver cement samples. It was shown that the averages of radiation hazard parameters and the annual effective dose for cement samples are lower than the accepted level of 370 Bq/kg for Radium equivalent (Raeq) and lower than unit for internal hazard index, the external hazard index and the annual effective dose, except for Block waver cement samples. Excluding the Block waver cement samples, the rest of cement samples do not pose radiological hazards when are used as materials for buildings construction. (author).
[en] Demolition ceramic wastes (DCWs) were investigated in order to determine their potential use as supplementary cementitious materials in Portland Blended Cements (PBCs). For this purpose, three ceramic wastes were investigated. After characterization of the materials used, the effect of ceramic waste replacement (8, 24 and 40% by mass) was analyzed. Pozzolanic activity, hydration progress, workability and compressive strength were determined at 2, 7 and 28 days. The results showed that the ground wastes behave as filler at an early age, but as hydration progresses, the pozzolanic activity of ceramic waste contributes to the strength requirement.
[es]Se estudiaron residuos cerámicos de demolición (DCWs) a fin de determinar su potencial uso como materiales cementicios suplementarios en cementos mezcla (PBC). Para este propósito, se investigaron tres residuos cerámicos. Luego de la caracterización de los materiales a utilizar, se analizó el efecto del reemplazo por residuos cerámico (8, 24 y 40% en peso). Se estudió la actividad puzolánica, el progreso de la hidratación, la trabajabilidad y la resistencia a compresión a 2, 7 y 28 días. Los resultados mostraron que los residuos molidos se comportaron como fillers a edades tempranas, pero con el progreso de la hidratación, la actividad puzolánica de los residuos cerámicos contribuye a los requerimientos de resistencia.
[en] Besides bricks, granites and sands cement is one of the main components of building materials Cement is made from a combination of rocks and soils which is known to contain natural radioactivity. The objectives of this study were to determine the level of natural radioactivity and associated radiological hazard caused by natural radioactivity in Malaysia's Portland cements. Portland cements samples were obtained from the manufacturers or bought directly from local hardware stores. Natural radionuclide concentrations of 226Ra (238U series), 232Th and 40K were determined using gamma-ray spectrometry. Activity concentrations of 226Ra (238U series), 232Th and 40K were found in the range of 7.76 - 82.91 Bq kg-1, 9.79 - 49.37 Bq kg-1 dan 81.89 - 377.10 Bq kg-1 respectively. Radium equivalent were found in the range of 35.36 ± 0.60 to 135.94 ± 15.27 Bq kg-1 while the average annual equivalent dose and internal hazard index were found in the range of 80 ± 2 to 300 ± 30 μSv year-1 and 0.12 ± 0.00 to 0.56 ± 0.07 respectively. (author)
[en] The main purpose of the research is to study the lightweight cement slurry based on vermiculite and its parameters in accordance with GOST 1581-96 requirements as well as improvement of its formulation by polymer additives. Analysis of vermiculite-containing mixture providing the lowest density while maintaining other required parameters was conducted. As a cement base, cement PTscT-I-G-CC-1, cement PTscT – 100 and vermiculite M200 and M150 were used. Vermiculite content varied from 10 to 15 %; and water-to-cement-ratio ranged from 0.65 to 0.8. To sum up, despite the fact that lightweight cement slurry based on vermiculite satisfies GOST 1581-96 requirements under laboratory conditions, field studies are necessary in order to make a conclusion about applicability of this slurry for well cementing
[en] In many radioactive waste repository designs, cement-based materials are expected to dominate the repository and models of cement evolution predict that leaching of the cementitious material in the repository by groundwater will produce an initial stage of hyperalkaline (pH - 13.3) leachates, dominated by alkali hydroxides, followed by a longer period of portlandite and C-S-H (CaO-SiO2-H2) buffered (PH - 12.5) leachates. It has also been predicted that, as the hyperalkaline porewater leaches out of the near-field, significant interaction with the repository host rock and bentonite buffer and backfill may occur. This could possibly leak to deterioration of those features for which the host rock formation and bentonite were originally chosen (e.g. low groundwater flux, high radionuclide retardation capacity etc). The precise implication of cement leachate/repository host rock interaction has been studied in the laboratory and in underground research laboratories (URLs) and this work has been supported by study of natural cements in Jordan. These natural cements have been produced by the combustion of organic-rich clay biomicrites and are very close analogues of industrial cement. Following interaction with groundwaters, natural hyperalkaline leachates are produced and these move out of the cement into the surrounding host rock, subsequently interacting with and altering it. (author)
[en] In the Area de Gestión Ezeiza (AGE), at present day, 25 m3 of liquid radioactive wastes (LRW) are stored. Such wastes were generated mainly in radioisotopes and nuclear fuel production and in R&D activities, carried out in the Ezeiza Atomic Center (CAE). The chemical and radiochemical composition of the LRW, differs according to the source process. The average rate of generation of this kind of wastes is approximately 1,000 liters/year. The mentioned LRW, are stored in metallic containers in which they were collected, some of them for more than 15 years. In order to minimize the possibility of dispersion of radioactive material, by possible deterioration of the containers, formulations for immobilization by cementation were developed for these LRW. For such purpose, simulated non active waste of similar composition to the waste of higher annual production rate was prepared and cemented. The formulations were adjusted to reach optimal mix workability and setting times higher than 4 hours. The mechanical properties at lab scale were evaluated according IRAM 1622 standard, and fall test (5 meter) at 20 liters scale was performed. Also simulated non active LRW were cemented at full scale (200 liters drum) and now there are in progress leaching tests according to ANSI/ANS 16.1 standard. Summarizing, formulations for scale: 2, 20 and 200 liters were evaluated, with cemented non active simulated LRW, that allow to immobilize by cementation radioactive wastes generated in the Mo-99 production (high alkaline liquid, containing aluminate or sulphates in solution), in the recovery of targets of Mo-99 ( acid liquid, containing aluminum in solution) and in laboratories (organic liquid). According to the tests results, it is possible to immobilize by cementation the LRW stored up to date in the AGE, obtaining homogenous products with a compressive strength > 10 MPa, and capable to incorporate between 50 and 120 liters of liquid radioactive waste per 200 liters drum, using ready commercially available materials and suitable equipment owned by the Radioactive Waste Management Programme (PNGRR). (author)
[es]En el Área de Gestión Ezeiza (AGE), actualmente se encuentran almacenados 25 m3 de residuos radiactivos líquidos (RRL), generados principalmente en la producción de radioisótopos y elementos combustibles y en actividades de investigación realizadas en el Centro Atómico Ezeiza (CAE). La composición química y radioquímica de los RRL, difiere acorde al proceso de origen. La tasa de generación promedio de estos residuos es de aproximadamente 1.000 litros/año. Los RRL mencionados, se encuentran en los contenedores metálicos en los que fueron colectados, algunos de ellos hace más de 15 años. Para minimizar la posibilidad de dispersión de material radiactivo, por posible deterioro de los contenedores, se desarrollaron formulaciones para la inmovilización por cementado de dichos RRL. Para ello, se prepararon residuos simulados no activos de similar composición a los RRL de mayor tasa de generación anual y se cementaron. Las formulaciones se ajustaron hasta alcanzar óptima trabajabilidad y tiempos de fraguado mayores a 4 horas. Se evaluó la resistencia mecánica a escala laboratorio (IRAM 1622) y escala 20 litros (ensayo de caída desde 5 metros). También se cementaron RRL simulados no activos a escala real (tambor de 200 litros) y están en proceso ensayos de lixiviación (ANS 16.1). Se cuenta entonces con formulaciones, evaluadas a escalas: 2, 20 y 200 litros, con residuos simulados no activos, que permiten inmovilizar por cementado residuos generados en la producción de Mo-99 (líquidos alcalinos, con compuestos de aluminio ó sulfatos en solución), en la recuperación de blancos de Mo-99 (líquidos ácidos, con compuestos de aluminio en solución) y en laboratorios (líquidos orgánicos). De acuerdo a los resultados obtenidos, es posible inmovilizar por cementado los RRL actualmente almacenados en el AGE, obteniendo productos homogéneos y con resistencia a la compresión > 10 MPa, incorporar entre 50 y 120 litros de residuos radiactivos líquidos por tambor de 200 litros y utilizando materiales de amplia disponibilidad comercial y equipamiento disponible en el Programa Nacional de Gestión de Residuos Radiactivos (PNGRR). (author)
[en] The authors deal with the problem of electron paramagnetic resonance application for the examination of cement minerals. The theoretical foundations of the method and experimental technique are presented and the advantages of this new method are emphasized. Also the possibility for application of this method, in future, in rapid examination of cement raw materials reactivity for the sake of new cement plant design as well as for industrial practice, is mentioned. (author)
[en] This study is part of a broader investigation on the processing and re-solidification of cemented radioactive wastes (CRW) for the production of stabilized waste materials suitable for disposal. One of the objectives of the study is to develop and assess various cementing matrices for the solidified material. The leaching resistance of those potential matrices has to be assessed. A series of tests on the leaching of cesium was performed and the results are presented in this paper. Surrogate Cemented Waste (SCW), representative of the CRW, was reduced to a particle size suitable for mixing with cementing material (cement and other cementitious materials) and water to produce mortars. The mixture optimization program included several parameters such as the composition of the SCW, the cement-to-SCW (C/SCW) and the water-to-cementitious materials (W/C) ratios of the mortars, and the use of different types and proportions of supplementary cementing materials (SCMs). In this part of the study, the cesium leaching resistance was determined on a number of mortars of different compositions at various ages using the ANSI leach test. As an indicator of the durability, the calcium leaching resistance was also determined on selected specimens. Reducing the water-to-cementitious materials ratio (W/CM) of the mixtures resulted in the improvement of the leaching resistance of the mortars, however, the effect of the use of SCMs was not clear. In general, the use of zeolites resulted in a relatively good performance in the leaching. The amount of calcium leached from the mortar exposed to water, an indication of the long-term durability, was determined during the extended cesium leaching test. The calcium leaching appeared significant, however, the extended-test leachability index values for cesium indicate that the integrity of the cement matrix was not much affected by the longer exposure to water, at least not enough to affect significantly the cesium leaching resistance of the mortars. (author)
[en] Immobilisation of spent ion exchange resins (spent resins) using Portland cement blending with organic material for example bio char was investigated. The performance of cement-bio char matrix for immobilisation of spent ion exchange resins was evaluated based on their compression strength and leachability under different experimental conditions. The results showed that the amount of bio char and spent resins loading effect the compressive strength of the waste form. Several factors affecting the leaching behaviour of immobilised spent resins in cement-bio char matrix. (author)
[en] Ion exchange resins (IERs) are widely used by nuclear industry to decontaminate radioactive effluents. Spent resins have to be conditioned and the cementation process is adequate, relatively simple and inexpensive. However, several specificities of IERs have to be taken into account to design a cement formula: -) their ability to exchange ions with the cementitious medium, which may influence the cement hydration process, -) their low mechanical strength, which strongly weakens the compressive strength of the solidified waste forms, -) their strong dimensional variations which can, under severe conditions, induce swelling and cracking of the cement-based matrix. These dimensional variations can result from various processes: osmotic pressure and ion exchange in saturated medium, relative humidity variations in de saturated medium. Free deformations of IERs are measured as a function of different parameters: nature of the ions fixed on the functional groups, ionic strength of the aqueous solution in which the resins are immersed, water saturation degree of the resins. Particular attention is also paid to the quantification of swelling pressures induced by resins in a confined environment, as it may be the case in the cement-based matrix. Cements containing high amounts of blast-furnace slag are more appropriate than Portland cement (OPC) to solidify cationic IERs saturated with sodium or potassium. The rapid expansion observed during the first days of hydration with OPC can indeed be strongly reduced with the blended binders