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1
Vespia, Maren. "Gypsum Bonnet." The University of Montana, 2010. http://etd.lib.umt.edu/theses/available/etd-06132010-165408/.
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Walworth, James. "Using Gypsum in Southwestern Soils." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/144801.
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Rahmanian, Ima. "Thermal and mechanical properties of gypsum boards and their influences on fire resistance of gypsum board based systems." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/thermal-and-mechanical-properties-of-gypsum-boards-and-their-influences-on-fire-resistance-of-gypsum-board-based-systems(d8eb4bf5-706a-4264-911f-9584ebfbbc83).html.
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Gypsum board assemblies are now widely used in buildings, as fire resistant walls or ceilings, to provide passive fire protection. The fire resistance of such systems is fundamentally due to the desirable thermal properties of gypsum. Yet there is wide variability in reported values of thermal properties of gypsum at high temperatures and a lack of understanding of its integrity in fire. To evaluate the fire protection performance of gypsum board assemblies, it is essential to quantify its thermal properties and obtain information on its mechanical properties at high temperatures. Gypsum boards shrink and crack at high temperatures, and this leads to collapse of parts of the gypsum boards in fire. Fall-off of gypsum in fire affects the fire resistance of the assembly considerably, and cannot be overlooked when evaluating the fire resistance of gypsum board assemblies. The current research proposes a model to define the temperature-dependent thermal properties of gypsum boards at high temperatures. Thermal conductivity of gypsum is considered as the most influential parameter in conduction of heat through gypsum, and a hybrid numerical-experimental method is presented for extracting thermal conductivity of various gypsum board products at elevated temperatures. This method incorporates a validated one-dimensional Finite Difference heat conduction program and high temperature test results on small samples of gypsum boards. Moreover, high temperature mechanical tests have been performed on different gypsum board products; thermal shrinkage, strength and stress-strain relationships of gypsum products at elevated temperatures are extracted for use in numerical mechanical analysis. To simulate the structural performance of gypsum boards in fire, a two-dimensional Finite Element model has been developed in ABAQUS. This model successfully predicts the complete opening of a through-thickness crack in gypsum, and is validated against medium-scale fire tests designed and conducted as part of this research. Gypsum fall-off in fire is a complex phenomenon; however, it is believed that delaying the formation of through-thickness cracking will delay falling off of gypsum in fire, and hence improve the fire resistance of gypsum board assemblies. Finally, a study has been performed on the effects of various detailing parameters in gypsum board wall assemblies, and recommendations are offered for improving the fire resistance of such systems.
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Lo, Nigel. "Crystallization of gypsum in zinc sulphate solution." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ44024.pdf.
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Lo, Nigel. "Crystallization of gypsum in zinc sulphate solution." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20507.
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The purpose of this research is to use a mathematical model to study the removal of calcium in the form of gypsum from zinc sulphate solution by cooling from 80ºC to 30ºC in a batch crystallizer. Factors such as cooling-rates, initial solution composition, and seed amount are analyzed. Using the simulation module developed, it is found that the removal of calcium can be improved by operating at a high temperature, which speeds up both the growth and nucleation kinetics, and produces a higher supersaturation by lowering the equilibrium molality of calcium ion in solution. Also, the addition of seed can reduce the activation energy requirement for nucleation by providing favourable surface for the formation of nuclei and enhance crystallization. Finally, experiments are performed to see if the results qualitatively support the simulation findings.
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Cave, Sion. "Gypsum calcination in a fluidised bed reactor." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/6800.
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Gypsum (calcium sulphate dihydrate) is of great industrial importance with over 95,000 ktonnes being used in the world per annum. The greatest use of gypsum is in the production of plaster (calcium sulphate hemihydrate) for use as an interior finisher. Plaster is produced by the calcination (thermal decomposition) of gypsum. The most popular design is a continuous calciner where gypsum is fed continuously and is directly heated by hot air. There are a number of different phenomena occurring within a calciner, including heat transfer, mass transfer, particle and gas mixing, elutriation and the dehydration reaction itself. All these processes interact with each other. Although a lot of research has been carried out in these areas already, the literature has been found to contain significant discrepancies. This study contains experimental work which has been carried out in order to better understand the physical processes occurring within a gypsum calciner. The rate of dehydration of gypsum (35-67μm in diameter) has been studied in a fluidised bed reactor. Experiments were carried out at bed temperatures of 100 to 170°C. The fluidising gas was air with water vapour pressures of 0.001 to 0.30 atm. The dehydrations were under differential conditions. The results show that the dehydration under these conditions can be successfully modelled using the two dimensional Avrami-Er'ovev expression. A study of the fluidisation and elutriation properties of gypsum in batch vessels (cylindrical and conical) has been carried out. The mechanics of elutriation has been investigated and modelled for various freeboards, superficial gas velocities and air humidities. Tracer tests have also been carried out on a laboratory scale continuous conical kettle. Sodium carbonate was used as the inert tracer material. Runs were carried out at different air and gas flowrates and different bed temperatures. Residence time distributions were elucidated. Finally, the above experimental data and component models have been investigated for their applicability to producing a model of the laboratory scale gypsum calciner.
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Ottman, Mike, Jack Stroehlein, and Tom Christian. "Gypsum Application on Wheat at Coolidge, 1987." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/203768.
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Gypsum is applied to alleviate the problems associated with sodium- affected soils, such as surface crusting and impeded water infiltration. Due to the uncertainties in identifying gypsum-responsive sites, field studies were initiated to further our understanding of conditions responsible for the response of wheat to gypsum applications. Gypsum was applied at rates ranging from 0 to 4 T/A on two commercial farms near Coolidge, AZ. No differences in wheat grain yield, grain protein, stand, grain bushel weight, or plant height were detected at the 5% probability level at either site with the exception of increased plant height at one site. The positive benefits of gypsum have been documented in the past with certain soils; this study is just one of many required to more positively define gypsum-responsive sites in Arizona. The economics of gypsum application involves delivery and application cost of gypsum and the change in yield and value of subsequent crops.
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Rice, Kristi Dawn. "Effects of abiotic factors and cattle grazing on gypsum outcrop plant communities in the Cimarron Gypsum Hills, northwestern Oklahoma /." Read online, 2008. http://library.uco.edu/UCOthesis/RiceK2008.pdf.
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Adams, Jeffrey F. "Gypsum scale formation in continuous hydrometallurgical neutralization reactors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/MQ45576.pdf.
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Verbaan, Cornelis Niels Martijn. "Impurity uptake duting gypsum crystallisation in wastewater treatment." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33350.
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A common wastewater treatment process practised in zinc production plants is the single stage mixing of acidic wastewaters with slaked lime, inducing the reactive precipitation of fine (∼1 mum) gypsum (CaSO 4·2H2O) and other solids with a solids density of less than 10%. These solids report to tailings ponds for containment.The solid-liquid separation step would be more efficient if the size and density of the precipitated solids were increased. Tailings pond life would be increased if the solids density of the precipitated solids was improved. It is the scope of this thesis to report on how high density and clean gypsum may be produced by implementing staging and product recycling. According to this work a staged neutralisation process (each neutralisation reactor operating at different pH) leads to production of large sized gypsum crystals with a high solids density. A continuous lab scale circuit run with synthetic zinc plant effluent produced large (∼100 mum) gypsum crystals with a solids density of 35%.
The effect of various metal impurities (such as Zn, Mn, Mg, Fe(II), Cd, Na) in concentrations ranging from 0.1 g/l to 10 g/l on the morphology of gypsum and their uptake by gypsum is investigated with the view of ultimately controlling gypsum contamination. By implementing staging and product recycling gypsum was produced containing less than 0.025% zinc and minor quantities of other elements hence meeting all industrial specifications for synthetic gypsum.
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Evans, Nicholas Philip. "Isotope systematics of gypsum and its hydration water." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290136.
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Triple oxygen and hydrogen isotope analysis of the structurally-bound water in gypsum can provide a direct measure of past hydrologic variability. This thesis presents the development of the water extraction and isotopic measurement procedures, the calculation of the gypsum-water isotope fractionation factors, and the application of the method to constrain the palaeohydrologic conditions in two temporally and geographically disparate sites. Measurement of the isotopic composition of gypsum hydration water is used to examine the hydrological changes that occurred during the Terminal Classic Drought of the Maya lowlands (~800-1000 CE), coincident with the period when the Classic Maya Civilization of Mesoamerica collapsed. The data provide a complete and direct archive of hydrological conditions that have previously been limited to ice core records. Mean annual rainfall is shown to have decreased by between 41% and 54%, with intervals of up to 70%, compared to present-day conditions. This study has also shown for the first time that relative humidity was 2%-7% lower during the Terminal Classic Drought compared to today. The methodology is also applied to the massive gypsum deposits in the marginal and deep basins of the Mediterranean to interpret the chemical evolution of parent water bodies during the Messinian Salinity Crisis (5.97-5.3 Ma). By combining the measurement of gypsum hydration water with other traditional (e.g. strontium) and novel (e.g. calcium and barium) isotope tracers, the hydrological changes during the deposition of Primary Lower Gypsum units of the Sorbas Basin in southeastern Spain, the Upper Gypsum units of Sicily, and deep basin deposits have been constrained. The results indicate that all deposits experienced a significant freshwater contribution to the mother fluids from which they formed. It is proposed that obliquity-controlled sea level and eccentricity-modulated precession, superimposed on longer-term tectonic restriction of the Mediterranean-Atlantic exchange, together controlled the varying depositional environments during the formation of the Messinian Salt Giant. This thesis demonstrates that the analysis of gypsum hydration water is a powerful tool for palaeoclimate reconstruction. The methodology can be applied to gypsum (and other hydrated minerals) in a wide range of settings across geological space and time, providing a rich source of information about the environmental conditions under which they formed.
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Wong, Ngai Yuen. "Crack coalescence in molded gypsum and Carrara marble." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42927.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
This thesis investigates the fracturing and coalescence behavior in prismatic laboratory molded gypsum and Carrara marble specimens, which consist of either one or two preexisting open flaws, under uniaxial compression. In previous experimental studies, the determination of crack types (shear/tensile) was mainly based on the identification of fractographical features on the crack surfaces. In the present study, a high speed video system was used, which allowed one to precisely observe the cracking mechanisms.Seven crack types, which were characterized by different nature (shear/tensile) and orientations were identified to initiate from the pre-existing flaws in gypsum and marble in the present experimental study. Nine crack coalescence categories with different crack types and trajectories were also identified. The flaw inclination angle (beta), the ligament length (L), i.e. intact rock length between the flaws, and the bridging angle (a), i.e. the inclination of a line linking up the inner flaw tips, between two flaws, have all shown to have different effects on the coalescence patterns. Comparing the fracturing and coalescence behaviors in the two tested materials, tensile fracturing generally occurs more often in marble than in gypsum for the same flaw pair geometries.One of the pronounced differences observed between marble and gypsum during the compression loading test was the development of macroscopic white patches prior to the initiation of macroscopic cracks in marble, but not in gypsum. With the use of the scanning electron microprobe (SEM) and the environmental scanning electron microprobe (ESEM) techniques, the development of white patches and their evolution into macroscopic tensile cracks in marble, and the initiation of hair-line tensile cracks and their evolution into macroscopic cracks in gypsum were studied and compared.
(cont.) The SEM study identified that the white patches in marble were associated withnmicrocracking zones (process zones). The parallel ESEM study on gypsum showed that the extent of process zone development associated with macroscopic tensile cracking wasnless. The different extents of process zone development, related to the inherent material strength and textural properties, are hypothesized to be the key factors in leading to different macroscopic fracturing behavior in gypsum and marble.
by Ngai Yuen Wong.
Ph.D.
13
Thacker, Gary W., Thomas A. Doerge, and Norman P. Oebker. "Effect of Gypsum on Lettuce in Marana, 1988." College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/214261.
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Gypsum was applied preplant on spring lettuce at rates of zero, 2 tons per acre, and 4 tons per acre. There were no significant differences in carton yields or in carton weights. Postharvest soil analyses showed that the application of four tons of gypsum per acre significantly increased the calcium and magnesium levels in the saturated paste solution. There were no significant effects of gypsum application on ESP and SAR values, nor in pH or sodium concentrations.
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Abdul-Jabbar, Heven. "Analysis and purification of synthetic gypsum for industrial use." Thesis, Coventry University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420169.
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Javangula, Harika. "Comparative Studies On Standard and Fire-Rated Gypsum Wallboards." TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1331.
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The long term goal of this research is to improve the fire resistance of gypsum wallboard (GWB). Gypsum wallboard consists mainly of gypsum, i.e. calcium sulfate dihydrate, CaSO4•2H2O. In buildings, the chemical, mechanical and thermal properties of gypsum wallboard play an important role in delaying the spread of fire. To build a fire resistant GWB, it is very important to study the thermal, mechanical, physical and chemical properties of regular GWB and various types of fire-resistant wallboards available commercially in the market. Various fire-resistant GWBs have been compared and contrasted with reference to a standard wallboard in this study. Regardless of the type of wallboard, the main component is gypsum. The fire resistance property is mainly attributed to the absorption of energy related with the loss of hydrate water going from the dihydrate (CaSO4•2H2O) form to the hemihydrate (CaSO4•½H2O) and from the hemihydrate to the anhydrous form (CaSO4) in a second dehydration. The present paper is a comparative study of commercially available standard, fire-rated Type X and firerated Type C gypsum wallboards. Type X wallboards are typically reinforced with noncombustible fibers so as to protect the integrity of the wallboard during thermal shrinkage, while the Type C wallboards are incorporated with more glass fibers and an additive, usually a form of vermiculite. These Type C wallboards have a shrinkage adjusting element that expands when exposed to elevated temperature. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (TMA), scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) were used to characterize and compare the materials. Various properties, such as the heat flow, weight loss, dimensional changes, morphology and crystalline structures of the gypsum wallboards were studied using these techniques.
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Motalane, Mpempe Paulus. "Analytical determination of fluorides in South African chemical gypsum." Thesis, Access to E-Thesis, 2004. http://upetd.up.ac.za/thesis/available/etd-04302005-100153/.
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Doerge, Thomas A., Lowell True, and Mike Kilby. "Effects of Gypsum Applications on Established Thompson Seedless Grapes." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/215734.
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Mancino, C. F., and D. M. Kopec. "Effects of Gypsum on a Wastewater Irrigated Turfgrass Soil." College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/216053.
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Secondarily treated wastewater is used extensively in the southwestern United States for turfgrass irrigation, but deterioration in soil quality can occur from sodium (Na) delivered by this water. Application of gypsum (CaSO₄2H₂O) at 2 240 kg ha⁻¹ yr⁻¹ is often recommended to control the Na. Research to determine if this rate is effective on effluent -irrigated turfgrass sites is lacking. A 2-yr study was carried out on a golf course fairway (typic tomf7uvent soil) with a 10 yr history of effluent irrigation and elevated Na levels (800 mg kg⁻¹). Four rates of gypsum (0, 2 240, 4 480, and 8 960 kg ha⁻¹) were surface applied in November 1986 and 1987. Soil samples were collected every 3 months after treatment (MAT) and analyzed for Ca (total and water - soluble (WSCa)), Mg, K, Na, SO₄⁻²-S (S), pH, and electrical conductivity (EC). Results showed elevated WSCa and S levels 3 and 6 MAT in both years. The two highest rates resulted in elevated S levels 12 MAT. During both years, gypsum at the two higher rates decreased Na levels within 3 MAT. The lowest application rate did not reduce Na levels until 12 MAT in 1987 and its effects were not as great. Following the second annual application, the 2 240 kg ha⁻¹ rate was as effective as the higher rates in reducing Na levels 6 and 12 MAT. Total Ca levels were not affected by gypsum but Mg and K levels did decrease. In both years, a temporary increase in EC and decrease in pH occurred after gypsum treatment. It appears that gypsum at 2 240 kg ha⁻¹yr⁻¹ can be as effective as higher application rates in reducing Na in effluent-irrigated turf soil but only after two applications.
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Walworth, James. "Using Gypsum and Other Calcium Amendments in Southwestern Soils." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2012. http://hdl.handle.net/10150/246053.
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Salih, Mayson. "Disinfection Procedures: Effects on the dimensional accuracy of Gypsum casts." Thesis, University of the Western Cape, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3067_1257931628.
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The aim of the study was to assess the dimensional accuracy of Gypsum models following chemical disinfection of the impressions and to compare it with the accuracy of gypsum models exposed to microwave irradiation disinfection. Results indicated that the dimensional accuracy of the gypsum models disinfected in a microwave oven did not differ significantly from models in the control group. Except for models produced from SS white (SS White group, England) impressions where models irradiated in microwave exhibit significant improvement in the dimensional accuracy when compared with control group...
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Hughes, Paul. "The use of synthetic red gypsum as a construction material." Thesis, University of Newcastle upon Tyne, 2006. http://hdl.handle.net/10443/3619.
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Huntsman Tioxide produce a co-product "red gypsum" (red due to iron content) as a filter cake during the neutralisation of sulphuric acids at the end of the Titanium Oxide production process. Globally, Huntsman produce 925000 tonnes per year of red gypsum. The majority of the material goes to landfill, the rising cost of which has made it essential to find alternative uses. At present cementitious binders are used extensively in the construction industry, principally in concretes but also in applications like ground improvement. In these applications the cost of the binder, typically Portland cement, makes up a considerable percentage of the overall cost of the technique. In addition to the financial cost there is also the environmental cost of quarrying and processing of materials to produce Portland cements. Gypsum based industrial bi-products have been identified as alternative sources of cement (Beretka et al, 1996). Using these materials has two advantages: they have little or no production cost; and the re-use of such material would negate the need for expensive disposal. This thesis describes a programme of laboratory testing and field trials to investigate the potential of using synthetic red gypsum as a construction material. The main applications investigated were deep dry mix soil improvement and the production of paving blocks. Laboratory trials investigated the properties of red gypsum on its own and when mixed with Pulverised Fuel Ash, Ground Granulated Blast Furnace Slag, Lime and steel slag at a range of water contents. An assessment of samples was made on the basis of Unconfined Compressive Strength at 28 days curing. It was found that a red gypsum: Ground Granulated Blast Furnace Slag mix achieved the highest unconfined compressive strengths (up to 39 MPa) and was selected for further investigation as a binder. This binder was then mixed with a range of soils in the laboratory, it was found that red gypsum based binders can perform as well as Portland cement as a soil mixing binder, and that concrete blocks can be produced with strengths approaching that of equivalent Portland cement mixes. A field trial was also conducted in which red gypsum binders to investigate whether the binder would work in situ. It was found that the red gypsum binder performed adequately to pass standard engineering specifications for soil mixing. The thesis concludes that there are several potential applications for the use of red gypsum in the construction industry but that further work is required before it can be used commercially.
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Jafarzadeh, Aliasghar. "Experimental studies of gypsum migration and deposition in soil profiles." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46842.
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Jones, Bevan. "Performance of Gypsum Plasterboard Assemblies Exposed to Real Building Fires." University of Canterbury. Civil Engineering, 2001. http://hdl.handle.net/10092/8277.
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The performance of gypsum plasterboard assemblies is typically evaluated in accordance with standardised test methods such as BS476, AS1530 or ASTM E119.
Standard time-temperature curves give good comparison between tested materials.
However, they are generally less severe than a typical short duration compartment fire, they do not have a decay phase, and may be conservative for long duration fires.
It is not common knowledge that test time-temperature relationships, such as ISO834, have not significantly changed since they were originally formulated in the early
1930's.
Full-scale compartment testing based on typical residential scenarios conducted as part of this study, revealed that temperatures within a compartment can far exceed those of standard time-temperature curves within several minutes of ignition.
Pilot-scale furnace testing to non-standard time-temperature curves has revealed that the performance of light framed gypsum plasterboard assemblies is highly dependent on the severity of the fire exposure. A system that has achieved a fire resistance rating of 60 minutes failed within 30 minutes to a fire exposure that would represent a moderate compartment fire.
Current fire engineering designs often use sophisticated evacuation models to calculate minimum escape times required for safe evacuation of occupants. These evacuation times typically fall in the range from 15 - 60 minutes. The suitability of protecting escape routes using barriers rated against a standard fire test is questioned.
SAPIR, a powerful finite element program, has been employed to predict the thermal behaviour of various gypsum plasterboard assemblies exposed to a range of nonstandard fires. Results from the computer modelling are compared with several full and pilot scale furnace tests. It was found that the model calibrated to results from standard ISO834 furnace testing provided reasonable predictions of temperatures within assemblies exposed to a moderate fire. Temperature predictions of assemblies exposed to severe fires were poor.
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Cera, Rull Andreu. "The ecological significance of nutritional strategies in gypsum plant communities." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673600.
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Gypsophile species are edaphic endemics of gypsum soils, and they are considered specialists of this stressful substrate. Gypsum endemics from different families and regions of the world tend to show a unique leaf elemental composition, similar to the chemical characteristics of gypsum soils. However, the ecological significance of their unique foliar composition remains unknown. The factors underlying the ecological amplitude of gypsophiles remain also poorly studied. The main literature is based on the distribution of gypsophiles linked to gypsum soils in drylands, although some studies suggest a broader physiological amplitude depending on soil type, and a positive influence of disturbance. Therefore, I have assumed that gypsophiles have evolved in disturbed drylands with gypsum soils. In order to adapt to this combination of factors, I hypothesised that gypsophiles have become soil specialists with high capacity of nutrient uptake to be more competitive than other species in gypsum soils. To test this, we conducted a germination trial and a common garden experiment to analyse the ecological restriction of gypsophiles to different substrates, and to analyse the effect of different substrates on the whole-plant elemental composition of plants with contrasting affinity for gypsum soils. In the field, we studied the assemblage of plant communities under different grazing intensities on high gypsum soils, and whether the assembly of plant communities is mediated by any trait related to gypsum specialisation or herbivory resistance. Next, a browsing simulation was conducted to assess individual plant responses in calcic and gypsum pots. In addition, the variation of foliar and rhizospheric soil nutrient contents, and AM fungal colonisation were analysed throughout a year in the field to study the nutrient acquisition strategies of gypsophiles. The results obtained in this PhD thesis show that the fundamental niche of gypsophiles is not only explained by edaphic factors unique to gypsum soils, but seems to be related to alkaline soils with high calcium availability. When analysed under herbivory pressure, species with high gypsum affinity and increased foliar S content (i.e. gypsophiles) were more likely to assemble than other species. These gypsophiles were foliar accumulators of gypsum excess elements, even in calcic pots. They also seem to be adapted to P-scarcity by being less dependent on AMF symbiosis, and adjusting their acquisition strategies to nutrient pulses. Therefore, it seems that gypsophiles are specialists of gypsum soils to be more competitive in disturbed drylands through a unique nutritional strategy.Les plantes gipsòfiles són endemismes edàfics del guixos, i són considerades especialistes d’aquest sòl estressant. Endemismes del guix de diferents famílies i regions del món tendeixen a mostrar una composició elemental foliar única, similar a les característiques químiques dels sòls guixencs. No obstant això, el significat ecològic de la seva composició foliar continua sent desconegut. Els factors que subjuguen l’amplitud ecològica de les gipsòfiles segueixen sent també poc estudiats. La majoria de la literatura es basa en una distribució lligada als sòls guixencs de les zones àrides, encara que alguns estudis suggereixen una amplitud fisiològica més àmplia segons el tipus de sòl, i una influència positiva de les pertorbacions. Per això, he assumit que les gipsòfiles han evolucionat en terres seques pertorbades amb sòls guixencs. Per adaptar-se a aquesta combinació de factors, he plantejat la hipòtesi que s’han convertit en especialistes edàfics amb alta capacitat d’absorció de nutrients per a ser més competitives que altres espècies en sòls de guix. Per comprovar-ho, vam dur a terme un experiment de germinació i un de cultiu per a analitzar la seva restricció ecològica en funció del tipus de sòl, i per analitzar la composició elemental de tota la planta. En el camp, vam estudiar l’assemblatge de les comunitats vegetals en sòls guixencs en diferents intensitats de pasturatge, i si l’assemblatge d’aquestes comunitats està mediat per algun tret relacionat amb l’especialització pels guixos o la resistència cap als herbívors. A continuació, vam realitzar una simulació de brosteig per a avaluar la resposta individual de les plantes en tests amb guix o sòl calcari. A més, vam analitzar durant un any la variació del contingut nutricional de les fulles, arrels i sòl rizosfèric, i la colonització dels fongs micorízics arbusculars, per estudiar les estratègies d’adquisició de les gipsòfiles en el camp. En conjunt, els resultats obtinguts en aquesta tesi doctoral demostren que el nínxol fonamental de les gipsòfiles no sols s’explica per factors singulars dels sòl guixencs, sinó més aviat per sòls alcalins amb alt contingut de calci. I quan afegim la pressió herbívora, les espècies amb alta afinitat pel guix i alt contingut de sofre foliar (és a dir, gipsòfiles) tenen més probabilitat d’assemblar-se que altres espècies. Hem comprovat també que aquestes gipsòfiles són acumuladores foliars dels elements en excés dels guixos, fins i tot quan creixen en tests amb sòl calcari. I que les gipsòfiles semblen estar adaptades a l’escassetat de fòsfor sent menys dependents de la simbiosi amb AMF, i probablement ajustant les estratègies d’adquisició als polsos nutricionals del sòl. Per tant, sembla que les gipsòfiles s’han convertit en especialistes dels sòls guixencs per a ser més competitives en terres seques pertorbades amb sòls guixencs a través d’una estratègia nutricional singular.
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Modi, Deepa. "Potential Utilization of FGD Gypsum for Reclamation of Abandoned Highwalls." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281477085.
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Aghajani, Farzaneh. "Additional Thermal Expansion Of Gypsum-Bonded Investment By Rapid Heating." Thesis, The University of Sydney, 1998. http://hdl.handle.net/2123/4842.
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Wright, Adam. "Impact of Crystallographically preferred orientation on dehydration kinetics of gypsum." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/207204/1/Adam_Wright_Thesis.pdf.
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This thesis contributes to our understanding of temperature driven dehydration of rock forming minerals. It investigates the impact of crystallographic preferred orientation (CPO) on the dehydration of gypsum to bassanite through in-situ heating experiments on natural gypsum rock. The dehydration progress was monitored with synchrotron transmission, small- and wide-angle X-ray scattering (SAXS/WAXS) and tracked by the intensity evolution of three discrete Bragg diffraction peaks. A comparison of the conversion rates for satin spar (strong CPO) with whole-rock alabaster (weak CPO) reveals that a strong CPO decreases the reaction rate of dehydration.
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Breker, Maria Christine. "Influence of Amendments on Chemical and Biological Properties of Sodic Soils." Thesis, North Dakota State University, 2016. https://hdl.handle.net/10365/28268.
Full textAbstract:
Improving productivity of sodic soils has become a concern in North Dakota because of the desire for more land for producing crops. Field and incubation studies were conducted to determine the impacts of different amendments (flue-gas desulfurization gypsum, sugar beet processing by-product lime, and langbeinite) on the chemical and biological properties of two sodic soils. The field study evaluated the amendment effects on the chemical conditions of the soil and the impact on alfalfa yield and quality. Differences were not observed in percent sodium (%Na) in the first 17 months and alfalfa yield was not impacted by the treatments except for the high rate of langbeinite. The incubation study investigated the effects of amendments on both the chemical and biological properties of the soil. Spent lime increased the cumulative respiration but was not impacted by gypsum or langbeinite. Labile carbon (C) was negatively correlated with %Na and electrical conductivity (EC).North Dakota Soybean Council
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Lennaerts, Dennis Stefan Renier. "Effect of sample history on dissolution rates of gypsum {010} surfaces." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1366826120.
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McAloon, Janis Anne. "A Study Of Increased Thermal Expansion Of Gypsum-Bonded Casting Investments." Thesis, Faculty of Dentistry, 1989. http://hdl.handle.net/2123/4202.
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Muryanto, Stefanus. "The role of impurities and additives in the crystallisation of gypsum." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/2038.
Full textAbstract:
Scale formation is one of the persistent problems in mineral processing and related industries. One of the main components of the scale is frequently gypsum or calcium sulphate dihydrate (= CaS04.2H20). Gypsum is formed through the process of crystallisation, and it is well known that crystallisation process is significantly affected by the presence of admixtures. Industrially, scale formation occurs in an environment which is very rarely free from the presence of admixtures. In a typical mineral processing industry, certain types of admixtures are present, which may include metallic ions (e.g. originated from corrosion products) and certain types of the flotation agents used. The effect of admixtures on crystallisation kinetics and cyclical morphology can be very significant, even if they are present in trace amounts. It is important to emphasise that the effects are generally specific, that there is no unified theory that applies to all and every situation. The present study has investigated the effect of certain admixtures on gypsum crystallisation, and was accomplished in three phases of experiments: (1) seeded batch crystallisation; (2) seeded continuous crystallisation, and (3) once through flow system under isothermal condition. The three phases of the work used equimolar solutions of CaC12 and Na2SO4 to produce CaS04 which is the precipitating species. The seeded batch crystallisation experiment explored the effect of two flotation agents commonly used in mineral processing plants: (1) sodium isopropyl xanthate (= SIPX) and, (2) isopropyl thionocarbamate. The experiments were performed at 25, 35, and 45°C, respectively. The initial concentration of the crystallising solution was 2,000 ppm of Ca 21 and it reached the equilibrium concentration values of between 1,000 and 8,00 ppm of Ca 2+ in 90 minutes.The effect of the two selected admixtures on crystallisation was measured by continuous monitoring of the desupersaturation of the crystallising solution with time, which subsequently resulted in the determination of the crystallisation rate constant. The results arc as follows. Firstly, the admixtures selected (either individually or in combination) were able to retard the growth rate of gypsum. In the absence of any admixture, the second order rate constant was between 1,405 x 10-6 and 1,561 x 10-6 ppm-1 min-1. Addition of SIPX at a typical plant dosing level 0.200 g/L) reduced the rate constant to 475 x 10-6 PPM-1 min', while isopropyl thionocarbamate at a typical plant dosing level (= 0.070 g/L) decreased the rate constant to 254 x 10-6 ppm-1 min-'. However, addition of a combination of the two admixtures, each at a typical plant concentration level, reduced the rate constant to 244 x 10-6 ppm-1 min-1, which was only slightly below that in the presence of isopropyl thionocarbamate. Thus, in these batch crystallisation studies, isopropyl thionocarbamate seemed to be dominant over SIPX. Secondly, the batch crystallisation system in the current work did not show any induction time. It was concluded that the seeds added into the batch system could be capable of eliminating the induction time. Thirdly, the reduced growth rate of the gypsum crystals as affected by the admixtures was probably caused by the adsorption of admixtures onto the crystal surface. The second phase of the project involved a seeded continuous (MSMPR) crystalliser. Some parameters used in this experiment (mean residence time, agitation speed and type of one admixture) were taken from the batch experiment carried out in the first phase of the project.Three admixtures were chosen for the seeded continuous crystallisation: (1) SIPX, (2) Fe3+, (3) Zn2-, and they were used either individually on in combination with each other. SIPX was chosen as it is one of the most common flotation agents used in mineral processing. Metallic ions: Fe3+ and Zn2+ were selected, since they were found in substantial amounts in both scale samples and process water in certain minerals processing industries. In general, the admixtures tested were found to be able to inhibit the crystal growth rates, but to enhance the nucleation rates. In addition, the growth rate was found to be dependent on crystal size, and hence, a correlation between these two parameters and the admixture concentration was formulated. For a fixed level of concentration (f 700 ppm of Ca z+ at steady state) and crystal surface area, it was proved that for each crystallisation temperature: 25 and 40°C, the correlation function can be represented as G = k Lα (1 +C)β where: G = linear growth rate, micron/hour; k, α, and β = dimensionless constants; L = (sphere equivalent) crystal size, micron; C = concentration of the admixtures used, ppm. For both the crystallisation temperatures used, the correlation function shows that the growth rate is significantly dependent on crystal size, but a weak function of admixture concentrations. The mechanism of crystal growth inhibition was assumed to be that of adsorption of admixtures onto the active growth sites, thereby decreasing or stopping the growth. Similar to the first phase of the present study, this seeded continuous crystallisation also showed no induction time. The third phase of the project investigated the gypsum scale formation in a oncethrough pipe flow system under isothermal condition and in the presence of admixtures.Four types of pipe materials were tested: PVC, brass, copper and stainless steel. Two admixtures were selected: SIPX and Fe3+. The behaviour of the gypsum scale formation was measured as the mass of the gypsum scale deposited on the substrate per unit area of the pipe surface. Within the range of the experimental conditions applied in this scale formation study, the following results were obtained. Firstly, the mass of the gypsum scale increased with concentration (in the range: 2,000 to 6,000 ppm of Ca t+) and that the correlation between the mass and the concentration can be represented by quadratic functions. Secondly, the mass of the gypsum scale decreased with increasing concentration of the admixtures used. Thirdly, the flow rate of the scaling solutions (in the range: 0.4 to 1.3 cm/sec) did not significantly affect the mass of the gypsum scale. PVC produced the highest mass of gypsum scale, followed by brass, copper, and stainless steel, respectively. Fourthly, the presence of admixtures caused the surface of the scale deposit to become rougher than was the case in a pure system, and longer scaling experimental times resulted in denser scale deposits. In this scale formation project, the induction time was investigated. In contrast with the first and the second phase of the projects, the induction time in the scale gypsum formation experiment was significant. At a concentration of 2,000 ppm of Ca 2+' pure gypsum solutions had induction times of about 105 minutes at 18.3°C and 97 minutes at 20.3°C. In the presence of 10 ppm of SIPX, the scaling solution at 2,000 ppm of Ca2+ and 19.2°C had an induction time of 1,400 minutes. The present study produced three important findings.Firstly, the presence of Fe 3+ or sodium isopropyl xanthate (SIPX) reduced the growth rate of gypsum crystallised either in a vessel (= a continuous crystalliser) or in a pipe flow system. Secondly, the rate of growth of gypsum crystals was found to be consistently higher in the vessel than in the pipe flow system. The rate of growth of the pure gypsum in the crystalliser at 25°C was 0.0389 kg/ m2 hour while those in the pipe flow system were between 0.0289 and 0.0202 kg/m2 hour, depending on the pipe material and the scaling solution flow rate. Thirdly, with respect to gypsum scaling, PVC was the least favourable material, followed by brass and copper, while the most favourable was stainless steel. It is believed that the present study has significantly contributed to the understanding of the effect of admixtures on crystallisation of gypsum, especially in relation to the scale formation.
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Muryanto, Stefanus. "The role of impurities and additives in the crystallisation of gypsum." Curtin University of Technology, Department of Chemical Engineering, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14305.
Full textAbstract:
Scale formation is one of the persistent problems in mineral processing and related industries. One of the main components of the scale is frequently gypsum or calcium sulphate dihydrate (= CaS04.2H20). Gypsum is formed through the process of crystallisation, and it is well known that crystallisation process is significantly affected by the presence of admixtures. Industrially, scale formation occurs in an environment which is very rarely free from the presence of admixtures. In a typical mineral processing industry, certain types of admixtures are present, which may include metallic ions (e.g. originated from corrosion products) and certain types of the flotation agents used. The effect of admixtures on crystallisation kinetics and cyclical morphology can be very significant, even if they are present in trace amounts. It is important to emphasise that the effects are generally specific, that there is no unified theory that applies to all and every situation. The present study has investigated the effect of certain admixtures on gypsum crystallisation, and was accomplished in three phases of experiments: (1) seeded batch crystallisation; (2) seeded continuous crystallisation, and (3) once through flow system under isothermal condition. The three phases of the work used equimolar solutions of CaC12 and Na2SO4 to produce CaS04 which is the precipitating species. The seeded batch crystallisation experiment explored the effect of two flotation agents commonly used in mineral processing plants: (1) sodium isopropyl xanthate (= SIPX) and, (2) isopropyl thionocarbamate. The experiments were performed at 25, 35, and 45°C, respectively. The initial concentration of the crystallising solution was 2,000 ppm of Ca 21 and it reached the equilibrium concentration values of between 1,000 and 8,00 ppm of Ca 2+ in 90 minutes.The effect of the two selected admixtures on crystallisation was measured by continuous monitoring of the desupersaturation of the crystallising solution with time, which subsequently resulted in the determination of the crystallisation rate constant. The results arc as follows. Firstly, the admixtures selected (either individually or in combination) were able to retard the growth rate of gypsum. In the absence of any admixture, the second order rate constant was between 1,405 x 10-6 and 1,561 x 10-6 ppm-1 min-1. Addition of SIPX at a typical plant dosing level 0.200 g/L) reduced the rate constant to 475 x 10-6 PPM-1 min', while isopropyl thionocarbamate at a typical plant dosing level (= 0.070 g/L) decreased the rate constant to 254 x 10-6 ppm-1 min-'. However, addition of a combination of the two admixtures, each at a typical plant concentration level, reduced the rate constant to 244 x 10-6 ppm-1 min-1, which was only slightly below that in the presence of isopropyl thionocarbamate. Thus, in these batch crystallisation studies, isopropyl thionocarbamate seemed to be dominant over SIPX. Secondly, the batch crystallisation system in the current work did not show any induction time. It was concluded that the seeds added into the batch system could be capable of eliminating the induction time. Thirdly, the reduced growth rate of the gypsum crystals as affected by the admixtures was probably caused by the adsorption of admixtures onto the crystal surface. The second phase of the project involved a seeded continuous (MSMPR) crystalliser. Some parameters used in this experiment (mean residence time, agitation speed and type of one admixture) were taken from the batch experiment carried out in the first phase of the project.
Three admixtures were chosen for the seeded continuous crystallisation: (1) SIPX, (2) Fe3+, (3) Zn2-, and they were used either individually on in combination with each other. SIPX was chosen as it is one of the most common flotation agents used in mineral processing. Metallic ions: Fe3+ and Zn2+ were selected, since they were found in substantial amounts in both scale samples and process water in certain minerals processing industries. In general, the admixtures tested were found to be able to inhibit the crystal growth rates, but to enhance the nucleation rates. In addition, the growth rate was found to be dependent on crystal size, and hence, a correlation between these two parameters and the admixture concentration was formulated. For a fixed level of concentration (f 700 ppm of Ca z+ at steady state) and crystal surface area, it was proved that for each crystallisation temperature: 25 and 40°C, the correlation function can be represented as G = k Lα (1 +C)β where: G = linear growth rate, micron/hour; k, α, and β = dimensionless constants; L = (sphere equivalent) crystal size, micron; C = concentration of the admixtures used, ppm. For both the crystallisation temperatures used, the correlation function shows that the growth rate is significantly dependent on crystal size, but a weak function of admixture concentrations. The mechanism of crystal growth inhibition was assumed to be that of adsorption of admixtures onto the active growth sites, thereby decreasing or stopping the growth. Similar to the first phase of the present study, this seeded continuous crystallisation also showed no induction time. The third phase of the project investigated the gypsum scale formation in a oncethrough pipe flow system under isothermal condition and in the presence of admixtures.
Four types of pipe materials were tested: PVC, brass, copper and stainless steel. Two admixtures were selected: SIPX and Fe3+. The behaviour of the gypsum scale formation was measured as the mass of the gypsum scale deposited on the substrate per unit area of the pipe surface. Within the range of the experimental conditions applied in this scale formation study, the following results were obtained. Firstly, the mass of the gypsum scale increased with concentration (in the range: 2,000 to 6,000 ppm of Ca t+) and that the correlation between the mass and the concentration can be represented by quadratic functions. Secondly, the mass of the gypsum scale decreased with increasing concentration of the admixtures used. Thirdly, the flow rate of the scaling solutions (in the range: 0.4 to 1.3 cm/sec) did not significantly affect the mass of the gypsum scale. PVC produced the highest mass of gypsum scale, followed by brass, copper, and stainless steel, respectively. Fourthly, the presence of admixtures caused the surface of the scale deposit to become rougher than was the case in a pure system, and longer scaling experimental times resulted in denser scale deposits. In this scale formation project, the induction time was investigated. In contrast with the first and the second phase of the projects, the induction time in the scale gypsum formation experiment was significant. At a concentration of 2,000 ppm of Ca 2+' pure gypsum solutions had induction times of about 105 minutes at 18.3°C and 97 minutes at 20.3°C. In the presence of 10 ppm of SIPX, the scaling solution at 2,000 ppm of Ca2+ and 19.2°C had an induction time of 1,400 minutes. The present study produced three important findings.
Firstly, the presence of Fe 3+ or sodium isopropyl xanthate (SIPX) reduced the growth rate of gypsum crystallised either in a vessel (= a continuous crystalliser) or in a pipe flow system. Secondly, the rate of growth of gypsum crystals was found to be consistently higher in the vessel than in the pipe flow system. The rate of growth of the pure gypsum in the crystalliser at 25°C was 0.0389 kg/ m2 hour while those in the pipe flow system were between 0.0289 and 0.0202 kg/m2 hour, depending on the pipe material and the scaling solution flow rate. Thirdly, with respect to gypsum scaling, PVC was the least favourable material, followed by brass and copper, while the most favourable was stainless steel. It is believed that the present study has significantly contributed to the understanding of the effect of admixtures on crystallisation of gypsum, especially in relation to the scale formation.
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Aves, Peter Charles. "Mechanics of compaction and dilatancy in triaxilly stressed rocks, under simulated crustal conditions, studied by pore volumometry." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362379.
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Lewry, Andrew John. "The relationship between the microstructure and mechanical properties of setting gypsum plasters." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/7493.
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Chlouveraki, Stefania. "Gypsum in Minoan architecture : exploitation, utilisation and weathering of a prestige stone." Thesis, University College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428531.
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Migabo, Willy Mbasha. "The effect of gypsum phase components on the rheokinetics of cement paste." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2763.
Full textAbstract:
Thesis (Doctor of Engineering in Civil Engineering)--Cape Peninsula University of Technology, 2018.Rheological properties of most ordinary Portland cements are dictated by the hydration reactions that their different phases experience. Cement clinker has four main phases with aluminate being the most reactive. Once in contact with water, the aluminate phase reacts rapidly and generally impedes the early hydration of other cement compounds such as calcium silicates that are responsible for the strength of cement systems. Consequently, the obtained matrix is stiff without much strength. Alternatively, calcium sulphate bearing materials are added within the clinker as set regulators of the aluminate phase hydration. For this purpose, natural gypsum is moslty gound with cement clinker as a source of sufficient sulphate, thereby keeping the cement paste plastic for a certain amount of time, allowing the hydration of silicate phases that are responsible for the early and later strength. However, the heat generated within the mill during the grinding process of clinker and gypsum causes a partial dehydration of natural gypsum into hemihydrate. The final ground cement product is thus comprised of two unexpected types of calcium sulphate bearing materials in an unpredictable proportion. Due to the difference in their solubility, the hydration of the aluminate phase can variably be altered which consequently affects the rheokinetics of the cement paste. Currently, the effect of the available amount of hemihydrate and natural gypsum in the cement sulphate phase, on both the hydration and rheology of ordinary Portland cements (OPC), are not well-understood. An ordinary Portland cement clinker was sampled during the production process of CEM I under stable kiln operations at a local cement plant. This was ground without any form of calcium sulphate bearing material and the final product was considered as relatively pure cement clinker. The degree of natural gypsum degeneration was achieved by partially replacing fractions of hemihydrate with those of natural gypsum. Firstly, the individual effect of these calcium sulphate bearing materials on the hydration kinetics was studied by varying their concentrations from 2-7% within the cement system. Secondly, the effect of their mix proportions at an optimum calcium sulphate concentration on cement paste rheokinetics was investigated. This research confirmed the findings of previous investigations relative to the effect of calcium sulphate on the hydration kinetic , giving new insight on the rheokinetics of cement paste with mix proportions of various calcium bearing materials. Results showed that the reaction rates of cement systems with hemihydrate were faster than those with natural gypsum and generally tended to decrease with the increase in their concentrations. Cements with hemihydrate experiencing shorter dormant durations than those with natural gypsum, likely due to the fact that the consumption rate of calcium sulphate was higher in cement systems with hemihydrate than those with natural gypsum. Consequently, before the exhaustion of sulphate ions, cement systems with hemihydrate had higher degrees of hydration and became almost similar thereafter. More ettringite and portlandite were formed in cement systems with hemihydrate as compared to those with natural gypsum. The amount of ettringite increased with the increase in calcium sulphate concentration up to 4% and thereafter remained constant. Conversely, the amount of portlandite decreased with the increase in calcium sulphate and also remained unchanged after 4%. The strength development of the cement microstructure depended on the concentration of hemihydrate within the suspension. The rigidification of the newly formed network was affected at higher hemihydrate fractions. Rheological parameters were more pronounced when the concentration of hemihydrate exceeded 50%. Below this hemihydrate concentration, cements had almost similar flow properties as those with only natural gypsum. Large changes in yield stress values and variation in plastic viscosity values of approximately 50% were observed. The trend of mixes dynamic yield stress were similar to their corresponding strength rate developments. This rheological behaviour was primarily attributed to the morphology change of ettringite that was triggered by the presence of a higher hemihydrate concentration. It was also noticed that physical performances of cement systems depended on their respective microstructure developments.
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Van, Jaarsveld Francis. "Characterising and mapping of wind transported sediment associated with opencast gypsum mining." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2352.
Full textAbstract:
Thesis (MSc (Earth Sciences))--Stellenbosch University, 2008.This study aims to provide a practical tool for the prediction and management of dust generated by the activities of an opencast mining operation. The study was conducted on opencast gypsum mines in the semi-arid environment of the Bushmanland, 90 km north of Loeriesfontein in the Northern Cape Province from April 2000 to October 2007. The vertical and horizontal components of wind transported sediment were sampled and a dust settling model was designed to predict the settling pattern of dust generated by opencast mining operations. The model was applied to soil samples collected from an area surrounding a mine. The influence sphere of the mining operation was predicted by the application of the model and then mapped. Once the influence sphere is mapped, the dust influence can be managed with the aid of an onsite weather station. By further applying the predictions based on climatic data, the influence sphere can be modelled. The model is not only applicable to the planning phase of an opencast mine to plan the position of dust sensitive areas like the living quarters, office buildings and workshops etc., but also to indicate the historical impact that a mining operation had once a quarry on an active mine is worked out and rehabilitated or a mine is closed. The model application can also aid with the explanation and visual or graphic representation of the predicted impact of planned mining operations on communities or neighbouring activities to them and thus avoid later penalties.
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Mishra, Ratan K. "Simulation of Interfaces in Construction Materials: Tricalcium Silicate, Gypsum, and Organic Modifiers." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333037184.
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Pasini, Rachael A. "An Evaluation of Flue Gas Desulfurization Gypsum for Abandoned Mine Land Reclamation." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250605536.
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Alsharari, Musaed Amish. "Reclamation of fine-textured sodic soil using gypsum, langbeinite, and calcium chloride." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/282872.
Full textAbstract:
The effects of various application rates of gypsum (Aqua-cal = finely ground gypsum), langbeinite (K₂SO₄.2MgSO₄), and CaCl₂ (anhydrous) on exchangeable Na removal and saturated hydraulic conductivity of a sodic soil were investigated under laboratory batch studies and laboratory column leaching studies. The research involved four phases of studies. Characterization of the soil and irrigation water indicated that the soil sample is sodic (ESP=35.3), ECₑ = 3.36 dS/m), and the irrigation water is moderately saline (EC = 2.2 dS/m). The laboratory batch studies showed that CaCl₂ and langbeinite treatments were more efficient in the displacement of Na than gypsum which increased with increasing application rate. In contrast, with gypsum, Na displacement increased to a maximum at an application rate of 7 tons/ha; then, no further increase in displacement was observed above that level. In the column leaching studies, applied amendments at equivalent rates of 7 tons/ha each and leaching with 5 pore volumes of irrigation water resulted in a total Na displacement of 60%, 80%, and 84% for gypsum, langbeinite, and CaCl₂, respectively. Moreover, the SAR of the soil was reduced significantly in the above treatments from 34.5 in the beginning of leaching to 6.80 for gypsum (G7), from 41.8 to 5.60 for langbeinite (L₇), and from 32.6 to 2.5 for CaCl₂(7). When amendments were applied at higher rates (G7 tons/ha gypsum and 13 tons/ha of each of CaCl₂ and langbeinite), the % total Na displaced was 60%, 100%, and 94% for gypsum, langbeinite, and CaCl₂, respectively. The corresponding SAR values at the end of reclamation were 6.80, 4.50, and 5.50 for gypsum, langbeinite, and CaCl₂, respectively. The combination treatments significantly improved the reclamation at 0.05 level as compared to the G7 treatment alone and saved more leaching water and displaced higher exchangeable Na as compared to the gypsum treatment (G7) alone. Saturated hydraulic conductivity (Ks) studies indicated that Ks was increased significantly when the amendments were applied at equivalent weights (7 tons/ha) and at higher application rates as compared to the control. The Ks of the gypsum treated soil (G7) was significantly higher than Ks of langbeinite and CaCl₂ treated soil at both equivalent rates and when applied at higher rates L13 and CaCl₂(13).
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Dias, Hanwellage Yomal Viduranga. "Structural and fire behaviour of gypsum plasterboard and steel sheathed LSF walls." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/134411/1/Hanwellage_Dias_Thesis.pdf.
Full textAbstract:
This study investigated the structural and fire behaviour of steel stud framed walls lined with gypsum plasterboard and steel sheathing. An improved wall stud with greater structural efficiency was developed. Through analytical, numerical and experimental studies, the behaviour of steel sheathed LSF walls built using these improved studs, both under normal service conditions and in fire, was investigated. The findings of this study facilitate the development of structurally and economically superior LSF walls.
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Stojnic, Dragan Lindblad Henrik. "Val av byggproduktionsmetod/ Praktikfall Klammerdamm : Golvgips eller avjämningsmassa." Thesis, Halmstad University, School of Business and Engineering (SET), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-935.
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This report is about how to decide which method is the most suitable as floor covering at project
Klammerdamm in the centre of Halmstad. The covering has to be fire resistant and soundproof in
order to protect the wood structure and stop noise from traveling between apartments. There are
two possibilities either traditional gypsum board or gypsum-based self leveling underlayment.
The roads around the construction site are narrow. A regular twenty-five meter long truck has no
possibility to reach the site. The construction site is small and the storage area is limited. Good
planning is one condition, among many others, that has to be fulfilled to make this project doable.
All relevant parameters has been taken into account and analyzed with a decision model.
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Ahmed, F. B. "The structural stability of reclaimed marsh soils." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382197.
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Cakmak, Hayriye. "Mineralogical And Geochemical Properties Of Messinian Gypsum Occurence In Polatli Sazilar Region, Ankara." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12610237/index.pdf.
Full textAbstract:
The objective of this study is to understand the petrographical, mineralogical and geochemical characteristics of Messinian (Upper Miocene) gypsum occurence in Polatli Sazilar region, Ankara and to determine the impurities associated with gypsum. Moreover, it is aimed to interpret the usability of this raw material with impurities in plaster and plasterboard production based on industrial standards.
Based on petrographical study, the first variety of gypsum which have different physical properties is white massive, micro crystalline, and translucent gypsum. Prismatic, transparent, idiomorphic and cleavage dominated selenite is the second variety. The gypsum rock is also identified that it is composed of sand sized selenite crystals and gypsum grains in a calcite and clay rich matrix. These impurity minerals also observed in thin beds alternating with gypsum.
Scanning electron microscopic (SEM) studies are conducted to determine the relationship between the impurity mineral, gypsum and the selenite. X-ray diffractometry (XRD) studies were used to identify the type of clay minerals. In the samples, Ca-smectite is the essential impurity clay mineral. Rarely, mixed layer of illite-smectite is also identified.
Geochemical studies also shows that as the amount of clay impurity increases, MgO, Al2O3, Fe2O3, Na2O, K2O (wt%) increases with decreasing SO3 (wt%). On the other hand, impurity of calcite controls the CaO (wt%) content in varying amounts. Five different groups of samples indicating different abundance of clay and calcite impurities are interpreted. The clay rich samples are enriched, in general, in vanadium, nickel, copper and chromium.
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Mbogoro, Michael M. "Crystal growth and dissolution of gypsum and analogous materials : a multi-scale approach." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/46892/.
Full textAbstract:
This thesis is concerned with the growth and dissolution of gypsum and analogous crystalline materials, with the aim of understanding the kinetic and mechanistic processes at the mineral-solution interface. The research conducted was a collaborative project sponsored by Saint-Gobain Gypsum. First, an image processing (IP) software package was developed to meet highly specialised IP needs and expedite the extraction of vital surface information from images produced in the growth and dissolution studies carried out in this thesis. A simple but powerful morphological analysis of characteristic etch pit features formed on the basal plane of gypsum was proposed, to aid the determination of intrinsic dissolution kinetics. Limiting the study to short times produced microscopic active features, which exhibited high and quantitative mass transport rates. At early times, the reaction was surface controlled, with the edge planes dominating the process, revealing anisotropic step propagation kinetics. With time, an increased contribution from mass transport was observed, suggesting that at later times, the basal plane dominated reaction kinetics. Common ion effects indicated a greater impact of Ca2+ than SO42- in reducing dissolution rates while inert ions enhanced dissolution in a directionspecific way. With this approach, microscopic phenomena were related to macroscopic measurements thus reconciling experimental length scales. Dissolution of the basal (010) and edge (001) surfaces of gypsum and polycrystalline anhydrite, were probed at the bulk scale by coupling the channel flow cell (CFC) technique which displays high mass transport rates, with off-line spectrometric measurements of dissolved Ca2+. Quantitative modelling of the diffusion-reaction within the CFC yielded a linear rate law for the dissolution process. Rates from the basal plane and anhydrite were found to be consistent with other bulk measurements, while the highly reactive edge plane exhibited high rates indicating a transport-limited process. Sodium trimetaphosphate, a common humid-creep inhibitor was found to significantly retard basal plane dissolution rates. Further CFC studies were carried out on industrially-relevant, chemically modified CaSO4 based materials, using a simple flux approach. It was found that models proposing a dissolution-precipitation pathway as the mode of action of humid-creep inhibitors were less plausible than those proposing a surface binding pathway. Finally, the influence of solution stoichiometry, r = (aCa2+ / aSO42-) on the growth kinetics of microscopic gypsum crystals was determined at a constant supersaturation. Crystal growth was found to be entirely controlled by surface kinetics over the range of r, with the edge planes dominating the process. The highest lateral rates were found at r = 1, diminishing sharply at r ≠ 1, and indicating strong plane-specific dependence on Ca2+ and SO42- availability. Additionally, dramatic changes in the morphology of grown crystals were observed. Propagation of steps on the basal face revealed a complex polynuclear layer-by-layer growth process for this surface. Macroscopic growth rates compared well to previous bulk measurements indicating that the approach used provided a comprehensive multi-scale view of gypsum growth processes.
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Hildyard, Rebecca Christine. "The Textures and Microstructures of the Calcium Sulphate Minerals Anhydrite Gypsum and Bassanite." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526946.
Full textAbstract:
Evaporitic rocks containing minerals such as anhydrite, gypsum and bassanite, are of central importance in a number of geological scenarios. They play an important role in localizing deformation, acting as detachment horizons in many foreland fold and thrust belts, implying that their strength is generally lower than other rocks. Characterizing the microstructure of evaporites is therefore important for interpreting the larger scale deformation history of these rocks. Dehydration reactions of high grade metamorphic rocks, e.g. serpentinite, in subduction zones, are thought to be one mechanism that can trigger seismicity. Similar dehydration reactions of hydrous gypsum to bassanite or anhydrite can be used as analogues for these deeper scenarios. This thesis studies the microstructures of naturally deformed, coarse grained and fine grained anhydrite rocks from the Triassic Evaporites of the northern Apennines, using electron backscatter diffraction (EBSD). The technique was used to measure crystallographic preferred orientation (CPO) and misorientations both within grains and between grains. CPO and grain distortions within the coarse grained anhydrite rocks are found to be consistent with activity on the known (100)[001] easy slip system. It is found that there is little evidence of recovery although some dynamic recrystallization by grain boundary bulging is observed. CPO, grains distortions and misorientation distributions within the fine grained anhydrite rocks indicate activity of the (100)[010] and (001)[100] slip systems. Dynamic recrystallization by grain migration and sub-grain migration is inferred and evidence is found of a possible grain boundary sliding mechanism at the finest grain sizes. A suite of experimentally deformed and dehydrated Volterra gypsum samples are also analysed using EBSD. CPO in post-experiment bassanite is found to mimic the original gypsum c-axis orientation. Bassanite grain size is shown to relate to the degree of reaction overstep. In some samples two distinct morphologies of bassanite grains are found; large (0.5-2 mm), euhedral crystals and small «50 urn), acicular crystals, representing two different bassanite polymorphs.
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Murphy, P. N. C. "The effect of lime, gypsum and phosphorus loss from agricultural soils to water." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411760.
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Fisher, Robin D. "Conversion of gypsum to phosphate materials for novel composites with enhanced macroscopic properties." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/47400/.
Full textAbstract:
This thesis describes the synthesis, characterisation and macroscopic properties of phosphate materials made from gypsum, CaSO4⋅2H2O, using inorganic chemical reactions. The aim was to reduce the degradation of gypsum based materials by water exposure, using strategies that included the complete conversion in hydrothermal conditions to a material having a much lower solubility, e.g. hydroxyapatite, Ca5(PO4)3OH, and coating/binding calcium sulfate crystallites with a more water resistant material. The hydrothermal conversion of gypsum to hydroxyapatite was a poorly understood reaction since all previous measurements on the intermediate and final products had been conducted after the reaction had been quenched, which may have resulted in the crystallisation of species that would not usually form. In–situ X-ray measurements described herein have provided new information about the kinetics and mechanism of this conversion. It has been found however, that this reaction is not viable with respect to stabilising gypsum to water degradation after unsuccessful attempts to increase the reaction kinetics. It was discovered in the in-situ measurements that the conversion proceeds from the outside, towards the centre of monoliths of porous vast gypsum samples and seems to be limited by the rate of ionic diffusion. Increases in reaction temperature caused the crystallisation of other species such as calcium sulfate hemihydrate, CaSO4⋅½H2O and monetite, CaHPO4, decreasing the stability of the product. A novel method of processing gypsum has been found, forming true composites of crystal sulfate anhydrite crystallites, bound by a water resistant phosphate coating. These composites which have the microscopic appearance of a ceramic, have been made for the first time and characterised using an array of analytical techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy and 31P solid-state nuclear magnetic resonance, the latter being extremely informative of binder composition and allowing the identification of an interfacial layer between the anhydrite crystallites and phosphate coating. Physical measurements such as the dissolution kinetics have been made in order to understand the effect of composition on the kinetic stability of the composites to water exposure, related back to the chemical analysis. The phenomenon of thermal diffusion of calcium from anhydrite; thought to be responsible for the composites’ formation, coupled with an apparent lower thermal conductivity, also has exciting implications for other applications of gypsum such as the fireproofing of buildings.
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Ahmed, Khalid Ibrahim. "Effect of gypsum on the hydro-mechanical characteristics of partially saturated sandy soil." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/58191/.
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Gypsum rich soils are of wide occurrence in the Middle East. They cover large areas of Iraq. Gypsum is one of the moderately soluble salts that can have significant effect on the engineering properties of soils. The effect of gypsum content and the stress state on the main hydraulic functions, volume change, shear strength and deformation characteristics of unsaturated silty clayey sand were experimentally examined. Statically compacted specimens of synthetic sand-gypsum mixtures were used. A new stress controllable pressure plate device was developed. The modified device was used to establish simultaneously both the stress-dependent soil-water characteristic curves (SD-SWCCs) and the stress-dependent hydraulic conductivity functions (SD-HCFs) during drying and wetting paths. The test results revealed that the parameters of the drying SWCC such as the water holding capacity, the air-entry suction, the air-entry water content, and the residual suction are clearly increased with increasing gypsum content. Same effect of gypsum was noticed on the wetting SWCC parameters. A clear decrease in saturated water content, desorption rate, absorption rate, and water holding capacity with increasing the applied net normal stress was noticed. Transient outflow methods were used to measure the SD-HCFs. An increase in the SD-HCFs with increasing gypsum content was found. Clear hysteresis effects on k(ψ) and minor hysteresis on k(w) were noticed. It was found that the outflow methods can be applicable between the air-entry suction and residual suction only. Direct shear tests were carried out on saturated and unsaturated specimens. The unsaturated specimens were air-dried and tested under constant water content conditions. Matric suction values were evaluated by incorporating the SD-SWCC test results. The friction angle related to matric suction (b), the effective stress parameter (χ), and the suction stress (s′) were found clearly decrease with increasing gypsum content and with increasing the net normal stress level. However, test results of saturated specimens revealed that the effective shear strength parameters (′, c′) are noticeably increased with increasing gypsum content in the soil mixture.
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Bhamidipati, Raghava A. "Use Of Laboratory Geophysical And Geotechnical Investigation Methods To Characterize Gypsum Rich Soils." UKnowledge, 2016. http://uknowledge.uky.edu/ce_etds/45.
Full textAbstract:
Gypsum rich soils are found in many parts of the world, particularly in arid and semi-arid regions. Most gypsum occurs in the form of evaporites, which are minerals that precipitate out of water due to a high rate of evaporation and a high mineral concentration. Gypsum rich soils make good foundation material under dry conditions but pose major engineering hazards when exposed to water. Gypsum acts as a weak cementing material and has a moderate solubility of about 2.5 g/liter. The dissolution of gypsum causes the soils to undergo unpredictable collapse settlement leading to severe structural damages. The damages incur heavy financial losses every year.
The objective of this research was to use geophysical methods such as free-free resonant column testing and electrical resistivity testing to characterize gypsum rich soils based on the shear wave velocity and electrical resistivity values. The geophysical testing methods could provide quick, non-intrusive and cost-effective methodologies to screen sites known to contain gypsum deposits. Reconstituted specimens of ground gypsum and quartz sand were prepared in the laboratory with varying amounts of gypsum and tested. Additionally geotechnical tests such as direct shear strength tests and consolidation tests were conducted to estimate the shear strength parameters (drained friction angle and cohesion) and the collapse potential of the soils.
The effect of gypsum content on the geophysical and geotechnical parameters of soil was of particular interest. It was found that gypsum content had an influence on the shear wave velocity but had minimal effect on electrical resistivity. The collapsibility and friction angle of the soil increased with increase in gypsum. The information derived from the geophysical and geotechnical tests was used to develop statistical design equations and correlations to estimate gypsum content and soil collapse potential.