Dissolution of soluble substrates such as gypsum presents a major hazard to dams in many parts of the world. This research simulates hypothesised conditions beneath the Mosul Dam, northwest Iraq, where collapse of a karstic system associated with continuous fresh water supply from its massive reservoir water is a recognised problem. The gypsum substrates at Mosul Dam vary in purity and thickness. Experimental work used gypsum rocks and gypseous soils. Gypsum rocks from northern Iraq and similar rocks from Bantycock gypsum mine, UK, were analysed for short-term mechanical response following immersion (5 to 50 weeks) and long-term loading during immersion (maximum 50 weeks). New experimental devices were developed from a conventional oedometer. Cylinder samples (NX, standard diamond drill core size = 54mm diameter, length/diameter ratio equal to 2.5) provided a proxy for massive gypsum strata, while thin samples (NX = 54mm in diameter, 20mm thickness) represented thin layers and lenses. Rectangular bar samples (240 x 40 x 20 mm and 140 x 40 x 20 mm) were tested for short-and long-term mechanical four-point bending behaviour. Samples were permanently submerged at a variety of water pressures, with the influence of groundwater recharge and flow on dissolution simulated by regular changes of water. Stress on each sample was progressively increased to a maximum of 2688 kPa. Small increases in strain were recorded by the end of each test but no failures occurred within 60 days of tests. However, notable failure due to water pressure and axial stress over long time periods of 166 and 238 days occurred. Visible physical changes were observed, notably a decrease in sample mass and volume. Similar change was recorded in ultrasonic velocities. These indicate that gypsum collapse risk beneath dams requires prolonged exposure to dissolution. Gypseous soils from Iraq and similar artificially-prepared soils were also tested. Gypseous soil samples (diameter = 50mm and length = 20mm) and box model strata results showed that gypseous soils are significantly weakened by dissolution over 15 weeks and 50 weeks respectively. Dams built on gypsum substrates are likely to experience ongoing weakening of their foundations, with a progressively increasing risk of failure. This is expected to be enhanced for dams with a large and deep reservoir that induces high ground water pressure.

Οι περιβαλλοντικές επιπτώσεις από τη λατόμευση και επεξεργασία γύψου στις μονάδες παραγωγής γυψοσανίδων,αφορούν το έδαφος, την ατμόσφαιρα, αλλά και τους επιφανειακούς υδάτινους σχηματισμούς (λιμνοθάλασσα, λίμνες). Στην παρούσα εργασία γίνεται προσπάθεια να ποσοτικοποιηθούν οι παραγώμενοι ρύποι και να περιγραφεί η αλληλεπίδραση των ρύπων με την γεώσφαιρα, υδρόσφαιρα, ατμόσφαιρα και βιόσφαιρα. / The environmental impacts of the gypsum extraction and processing that produces plaster board, inside the gypsum plants, not only affects the soil and the atmosphere,but also the surface water reservoir. With this present task I try to give emphasis to the quantification of the derivative pollutants and a description of the interaction of the pollutants as far as it concerns the geosphere, hydrosphere, atmosphere and biosphere.

<p>This study evaluated SO4 2- removal from circumneutral mine water (CMW) collected from Middleburg coal mine using coal FA collected from Hendrina power station. The following parameters were investigated: the effect of the amount of FA, the effect of the final pH achieved during treatment, the effect of the initial pH of the mine water and the effect of Fe and Al on SO4 2- removal from mine water. The precipitation of ettringite at alkaline pH was evaluated to further reduce the SO4 2- concentration to below the DWAF limit for potable water. Removal of SO4 2- from mine water was found to be dependent on: the final pH achieved during treatment, the amount of FA used to treat the mine water and the presence of Fe and Al in the mine water. Treatment of CMW using different CMW:FA ratios / 5:1, 4:1, 3:1, and 2:1 resulted in 55, 60, 70 and 71 % SO4 2- removal respectively. Treatment of CMW to pH 8.98, 9.88, 10.21, 10.96, 11.77 and 12.35 resulted in 6, 19, 37, 45, 63 and 71 % SO4 2- removal respectively. When the CMW was modified by adding Fe and Al by mixing with Navigation coal mine AMD and treated to pH 10, 93 % SO4 2- removal was observed. Further studies were done to evaluate the effects of Fe and Al separately. Treatment of simulated Fe containing AMD (Fe-AMD) to pH 9.54, 10.2, 11.8, and 12.1 resulted in 47, 52, 65, and 68 % SO4 2- removal respectively. When Al containing AMD was treated to pH 9.46, 10.3, 11.5 and 12 percentage SO4 2- removal of 39, 51, 55 and 67 % was observed respectively.</p>

The ever-increasing quantity of by-products generated from burning coal in the production of electricity has brought about the need for new areas of utilization. This study examined the use of FGD gypsum and fluidized bed combustion ash along with Class F fly ash in the production of low-energy, 100% by-product cement blends. The cement blends used the advantageous properties of the by-product materials to create cementing properties rather than energy intensive clinker used in ordinary portland cement. The FGD gypsum was converted to hemihydrate which rapidly hydrated to provide the cement with early strength gains, whilst the fluidized bed combustion ash reacted with the Class F fly ash to form pozzolanic cementitious phases which provided the longer-term compressive strength and possibly resistance to weathering. The rate of compressive strength gains and minimizing detrimental expansion were two properties of particular interest in the study. Chemical admixtures were used to improve the compressive strengths of the cement mortars and decrease their solubility.

In order to understand, more fully, some of the factors affecting the S requirements of pastures, S³⁵-labelled gypsum fertilizer was applied to several field trials located on soils within the recent, yellow brown earth and high country yellow brown earth soil groups in Canterbury, New Zealand. Among the major processes studied were the incorporation of the S³⁵-labelled gypsum fertilizer into the soil organic matter, its movement in the soil and its uptake by pasture plants. The results obtained showed that on the same soil type, plant uptake of fertilizer S and its incorporation into the organic matter were greater under improved pastures. However, the movement of fertilizer S was relatively unaffected by the pastoral improvement. Rainfall conditions affected all three processes studied, particularly the downward movement of fertilizer S. Over the growing seasons of the first year almost all of the added fertilizer S remained within the upper 15 cm of the soil at a low rainfall trial. On a similar textured soil, receiving almost twice as much rainfall over a similar time period, fertilizer S was distributed evenly to a depth of 60 cm. Where the rainfall was similar, but soils differed in their water holding capacity, large differences in the downward movement of fertilizer S occurred. On a steepland yellow brown earth soil almost 70% of the applied fertilizer S was lost from the 0-45 cm soil depth two months after application. While on a recent soil, with a much higher water holding capacity, greater amounts of fertilizer S remained within the upper 45 cm over the same period.. Large differences in the downward movement of fertilizer S were shown by soils with contrasting retention capacities, but under similar rainfall conditions. On a yellow brown earth soil, with a medium S retention in the subsoil, fertilizer S was found not to have moved beyond 60 cm in the winter following the spring application. In contrast, fertilizer S penetrated beyond the 60 cm on a recent low S retentive soil. Under improved pastoral conditions, applying fertilizer S in late spring rather than early spring, to two different soils gave larger (almost twofold) residual effects the following year. Total recovery of the added fertilizer S in the soil-plant systems studied were generally greater than 80%. The pattern and rate of the downward movement of fertilizer S was little affected by fertilizer rates. Pasture recovery (%) of fertilizer S at the lower rate (22.5 kgS/ha) was slightly higher than that at the higher rate (45 kgS/ha). Fertilizer rates did not produce a consistent effect on the extent of fertilizer S incorporation into soil organic matter. The magnitude of the sulphur cycling pool was determined at each trial location by using the equilibrium specific activity of pasture. This pool was found to vary between trials and showed no relationship to their respective S response patterns. The rate of S cycling appeared to be more important. At some trials a strong correlation was found between the specific activity of the S in pasture and that for phosphate-extractable sulphate in particular soil depths. This relationship was used to assess indirectly, the likely soil zones from which plants extract S to meet their nutritional requirements. A new technique was developed to study, directly, the soil zone from which plants extract S to meet their-nutritional requirements. Carrier-free S³⁵, injected horizontally into various soil depths in a recent and a yellow brown earth soil, showed that both grasses and clovers recovered S³⁵ to a depth of 52 cm, in the spring. However, most of the S³⁵ uptake by plants was found to occur in the upper 30 cm (A horizon) in both soils. In the autumn, S³⁵ uptake experiments on these soils showed uptake to occur at 100 cm on the recent soil, and cease at 52 cm on the yellow brown earth soil. Growth cabinet experiments, using S³⁵-labelled pasture residue, recovered from the field plots, and added to various soils, showed that ryegrass recovery of labelled fertilizer S ranged from 6-16% and it varied according to soil type, degree of pastoral development, type and form of plant residue added. This extent of recovery represents only a small proportion (1%) of the fertilizer S recovered by pasture in the first year. The overall experimental results were considered in relation to both the S response patterns obtained from the present field trials and also those from other similar trials conducted in recent years in the Canterbury area. Some possible reasons for the variable S responses obtained were discussed and methods for improving the efficiency of fertilizer use, at farm level, were proposed.

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 247-250). Also available in electronic format on the Internet.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The good root development directly affects the crop production. The improvement of chemical characteristics of the sub superficial layer brings the benefit of minimizing the effects of water deficit periods to the plants. In this sense the study aimed to evaluate the effect of lime, gypsum and potassium doses on soil chemical attributes, by evaluating crops productivity under no-till. The specific objectives were to analyze: the correction of soil acidity and enhancements of soil chemical attributes in different depths, after 9 and 16 months; the foliar nutrient levels in the soybean plants; the production of soybean and wheat exposed to high doses of gypsum; and which cationic relations influenced productivity. The experiment was conducted in 2012/13, 2013 and 2013/14 in a dystrophic Red Oxisol in the city of Estrela Velha, RS, which presents a humid subtropical climate (Cfa), and average rainfall of 1678 mm year-1. The experiment was arranged in sub plots with three repetitions. The eight treatments were constituted by: two doses of lime + gypsum (0+0 and 5.5+3 Mg ha-1), combined with four doses of potassium chloride (0.0, 0.16, 0.33 and 0.66 Mg ha-1).The soil samples were collected at three times: initial characterization, 9 and 16 months after inputs application. The experimental design was sub plots with three measure repetitions in the sub plots. The data for each dependent variable (soil chemical and crop foliar parameters) were analyzed using all samples by repeated measures using ANOVA mixed linear model, by the method of restricted maximum likelihood (REML). The analyzed soil was stratified in seven depths: from the surface until 0.6 meters depth. Foliar samples were collected to analyze the effect of the treatments in the nutrition of soybean plants, and by manual harvest the productivity was evaluated for each plot. In the first study, the dose of gypsum increased the values of pH, V% and reduced the Al saturation down to 0.10m. Magnesium leaching occurred in all layers, while S was carried done to even deeper layers than the analyzed. Leaching of K was not observed, even in the treatment with the gypsum dose. The elevated doses of potassium reduced soybean productivity in average 12%. While the treatments that had lime+ gypsum presented accumulated production 5% higher. On the second study, a correlation matrix was used to indicate the linear correlations with higher R2, whereas the Ca rate and its saturation presented higher positive correlation with soybean productivity. / O bom desenvolvimento radicular das culturas afeta diretamente a produção. A melhoria química das camadas subsuperficiais traz benefícios, que em períodos de déficit hídrico, podem minimizar os efeitos causado às plantas. Nesse contexto, o trabalho buscou avaliar o efeito de doses de calcário e gesso e potássio sobre os atributos químicos, verificando a produtividade das culturas sob sistema plantio direto. Para tal, os objetivos específicos foram os de avaliar: a correção da acidez e melhoria dos atributos químicos do solo em diferentes profundidades, após 9 e 16 meses; os teores foliares de nutrientes da soja; a produção da soja e trigo expostos a alta dose de gesso; e quais relações catiônicas influenciaram na produtividade. O experimento foi conduzido nos anos agrícolas de 2012/13, 2013 e 2013/14 em um Latossolo Vermelho distrófico típico no município de Estrela Velha, RS, que apresenta clima subtropical úmido (Cfa) e precipitação média de 1678 mm ano-1. Os tratamentos foram dispostos em parcelas subdivididas com três repetições e os 8 tratamentos foram constituídos de: duas doses de calcário + gesso agrícola (0+0 e 5,5+3,0 Mg ha-1) combinadas a quatro doses de cloreto de potássio (0, 0,16, 0,33 3 0,66 Mg ha-1). As coletas de solo ocorreram em três momentos: caracterização inicial, 9 e 16 meses das aplicações dos insumos. O delineamento experimental utilizado foi o de parcelas sub divididas com três medidas repetidas na sub parcela. Os dados para cada variável dependente (parâmetros químicos do solo e foliar da cultura) foram analisados através de todas as coletas usando medidas repetidas por meio da ANOVA de modelos lineares mistos, pelo Método de Máxima Verossimilhança Restrita (REML). O solo analisado foi estratificado em sete profundidades: da superfície até 0,6 metros. Amostras foliares foram coletadas para analisar o efeito dos tratamentos na nutrição das plantas de soja e através da colheita manual avaliou-se a produtividade de cada parcela. No primeiro trabalho, a dose de gesso propiciou a elevação dos valores de pH, V% e redução da saturação por Al até 0,10 m, ocorrendo a lixiviação de Mg em todas as camadas, enquanto o S foi carreado a profundidades maiores das amostradas. Não foi percebido a lixiviação de K, mesmo no tratamento de maior dose de gesso. As elevadas doses de potássio reduziram a produtividade da soja em média de 12%, enquanto os tratamentos que receberam calcário + gesso obtiveram produção acumulada 5% superior. No segundo trabalho foi utilizada a matriz de correlação para gerar as correlações lineares com R2 mais alto, sendo o teor de Ca e sua saturação apresentou maior correlação positiva com a produtividade da soja.

Made available in DSpace on 2014-12-17T14:07:16Z (GMT). No. of bitstreams: 1 JulianaEBC_DISSERT.pdf: 2646496 bytes, checksum: 07a391c02dbd435d514dc67c79541102 (MD5) Previous issue date: 2013-08-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The environmental impacts, caused by the solid residues generation, are an often quoted concern nowadays. Some of these residues, which are originated from different human activities, can be fully reused, reducing the effects of the poor waste management on the environment. During the salt production process, the first formed crystals are discarded as industrial waste. This is mainly made of gypsum that is a calcium sulfate dihydrate (CaSO4.2H2O). The gypsum in question may go through a calcination process due to the plaster (CaSO4.0,5H2O) production and then the application on the cement industry. Considering the necessity of development and application for these industrial wastes, this paper aims to analyze the plaster, called Salgesso, from the gypsum that was generated during the salt production, and its use viability on the civil construction industry in order to create environmental and economical benefits. For characterization, the following experiments were performed: X-ray Fluorescence (XRF), X-ray Diffraction (XRD), thermal analysis (TG/DTG) and Scanning Electron Microscopy (SEM) with EDS. The following tests were also performed to obtain the mechanical characteristics: Thinness Modulus, Unit Mass, Setting Time and Compressive Resistance. Three commercial plasters used on civil construction were taken as references. All of these tests were performed according to the current standards. It was noticed that although there were some conflicting findings between the salt and commercial plasters in all of the studied properties, the Salgesso has its values within the standard limits. However, there is the possibility to improve them by doing a more effective calcination process. Three commercial plasters, used in construction, were used as reference material. All tests were performed according to standards in force. It was observed that although some tests present conflicting findings between the salt and gypsum plasters commercial properties in all of the studied Salgesso have values within the limits imposed by the standard, but can be improved simply by calcination process more effective / Os impactos ambientais, ocasionados pela gera??o de res?duos s?lidos, s?o uma preocupa??o bastante citada na atualidade. Alguns desses res?duos, provenientes das mais variadas atividades humanas, podem ser totalmente reaproveitados, diminuindo o efeito desses impactos, geralmente ocasionado pela m? disposi??o, no meio ambiente. Durante o processo de produ??o do sal, os primeiros cristais formados s?o descartados como res?duo industrial. Este ? constitu?do basicamente por gipsita, um sulfato de c?lcio di-hidratado (CaSO4.2H2O). A gipsita em quest?o pode passar por um processo de calcina??o para a produ??o do gesso (CaSO4.0,5H2O) e subsequente aplica??o na ind?stria cimenteira. Considerando a necessidade de desenvolvimento e aplica??o para estes res?duos industriais, o presente trabalho tem o objetivo de analisar o gesso obtido a partir da gipsita que foi gerada durante o processo de produ??o do sal, denominado Salgesso, e sua viabilidade de utiliza??o na ind?stria da constru??o civil, trazendo benef?cios ambientais e econ?micos. Para caracteriza??o, foram realizados os experimentos de: Fluoresc?ncia de raios X (FRX), Difra??o de raios X (DRX), an?lises t?rmicas (TG/DTG) e Microscopia Eletr?nica de Varredura (MEV) com EDS. Foram realizados tamb?m ensaios para a obten??o de caracter?sticas f?sicas como M?dulo de finura, Massa unit?ria, tempo de pega e resist?ncia ? compress?o. Tr?s gessos comerciais, utilizados na constru??o civil, foram usados como material de refer?ncia. Todos os ensaios foram realizados seguindo a normatiza??o vigente. Foi observado que, apesar de alguns ensaios apresentarem diverg?ncia de resultados entre os gessos salino e comerciais em todas as propriedades estudadas, o Salgesso tem valores dentro dos limites impostos pela norma. Entretanto, h? uma possibilidade de melhora por meio de um processo de calcina??o mais eficaz

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Varieties of masonry units such as burnt clay bricks, stones and concrete products are used for masonry construction. Even though these materials are durable, they are considered as unsustainable options because of the issues concerning energy, environment and conservation of natural resources. The walling materials are consumed in bulk quantities and hence large quantities of natural resources are depleted. There is a need for energy efficient and environment friendly alternative materials for masonry. Fly ash is an industrial by-product from the coal based thermal power plants which can be exploited for manufacturing of masonry units such as fly ash blocks/bricks, which are an alternative for conventional masonry units. Fly ash-Lime-Gypsum (FaL-G) bricks can be manufactured by compaction of a mixture of fly ash-lime-gypsum and water. The behaviour of FaL-G brick masonry is inadequately explored area and hence the thesis is focused on understanding the flexural behaviour of FaL-G brick masonry and bond development phenomenon at FaL-G brick-mortar interface. A brief introduction to the fly ash-based masonry units and literature review with respect to utilizing fly ash in manufacturing masonry units are presented. Characteristics of raw materials used and the procedure followed in casting of masonry units/compacts, mortar and their assemblages including testing methods have been discussed. Characteristics of FaL-G brick, mortars, FaL-G brick masonry are presented. Apart from determining the stress-strain relationships for these materials shear strength parameters of FaL-G compact, mortar and brick-mortar joint were determined. Mohr-Coulomb failure envelopes for FaL-G compact and mortar are presented. The mechanism of bond development in masonry is discussed. FaL-G brick masonry shows considerably higher bond strength when compared with the bond strength of conventional brick masonry. Results of micro-structure analysis (SEM, XRD and TGA) of the FaL-G brick-mortar interfaces confirm the formation of chemical bond in addition to mechanical interlocking of cement hydration products into brick pores. Flexural behaviour of FaL-G brick masonry wallettes in the two orthogonal directions was studied. The flexural strength, displacement profiles and load-displacement curves were determined, and moment-curvature relationships were established. Linear elastic analysis performed closely predicted the cracking flexural stress in FaL-G brick masonry. A brief introduction to the computational modelling of masonry using different approaches has been presented. Literature review with respect to simplified micro-modelling approach has been discussed. The flexural behaviour of FaL-G brick masonry panels under lateral loads was predicted using a non-linear 3D finite element analysis. The finite element model reasonably predicted the flexural behaviour of FaL-G brick masonry panels. The thesis ends with summary of research work with a note on scope for further research.