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1
Williams, Ross Peter. "Optimising Geopolymer Formation." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/2359.
Full textAbstract:
Geopolymers are versatile materials, often made with ash from coal Power Stations. Applications include low green-house-gas emission cement, fireproof barriers and many more. This thesis furthered the understanding of geopolymer formulation by: • Demonstrating novel methods for mixture design and determining the degree of reaction during and after curing. • Analysing the role of formulation on cost and green-house-gas emission. • Developing a new material that can be used for structural neutron shielding.
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Bai, Chengying. "Highly porous geopolymer components." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3427257.
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The geopolymers, semi-crystalline three-dimensional silico-aluminate inorganic polymers, have attracted increasing attention from a wide range of scientific interests. The topic of this study deals with the synthesis, the characterization and the potential applications of porous geopolymers (PGs) or geopolymer foams (GFs, total porosity > 70 vol%), realized through different processing routes. Firstly, the processes are divided into five categories: (i) direct foaming, (ii) replica method, (iii) sacrificial template, (iv) the 3D printing, and (v) others. The microstructure, porosity, and properties of porous geopolymers also compared and discussed. Secondly, K-based porous geopolymers were produced by direct foaming using hydrogen peroxide as chemical pore-forming agent (PFA) combined with three types of stabilizing agent (SA, egg white, Tween 80, vegetable oils), and by direct foaming plus reactive emulsion templating. Furthermore, open-celled phosphate-based porous geopolymers were obtained by a simple direct foaming method (using Triton X-100 as physical pore-forming agent). The porosity, pore morphology, high temperature performance, adsorption, mechanical, and insulating properties of PGs were investigated. High strength PGs with tailored porosity and controlled macro-porous structure were fabricated by different processes. The results suggest that the porous geopolymers are promising low-cost highly porous candidates for potential applications such as catalyst or membrane supports (high open porosity and high strength), adsorption (high removal efficiency and adsorption capacity with high open porosity) and insulating (low thermal conductivity, high porosity, and acceptable strength) materials.I geopolimeri, polimeri inorganici silicoalluminati tridimensionali semi-cristallini, hanno attirato crescente attenzione da una vasta gamma di interessi scientifici. L'argomento di questo studio riguarda la sintesi, la caratterizzazione e le potenziali applicazioni di geopolimeri porosi (PG) o schiume di geopolimeri (GF, porosità totale> 70% vol), realizzati attraverso diversi percorsi di lavorazione. In primo luogo, i processi sono suddivisi in cinque categorie: (i) schiumatura diretta, (ii) metodo di replica, (iii) modello sacrificale, (iv) stampa 3D e (v) altri. Anche la microstruttura, la porosità e le proprietà dei geopolimeri porosi sono state confrontate e discusse. In secondo luogo, i geopolimeri porosi basati su K sono stati prodotti mediante schiumatura diretta utilizzando perossido di idrogeno come agente chimico di formazione dei pori (PFA) combinato con tre tipi di agente stabilizzante (SA, bianco d'uovo, Tween 80, oli vegetali) e mediante schiumatura diretta più reattivo emulsione che modella. Inoltre, geopolimeri porosi a base di fosfato a cellule aperte sono stati ottenuti con un semplice metodo di schiumatura diretta (usando Triton X-100 come agente fisico di formazione dei pori). Sono state studiate la porosità, la morfologia dei pori, le prestazioni ad alte temperature, l'adsorbimento, le proprietà meccaniche e isolanti delle PG. I PG ad alta resistenza con porosità adattata e struttura macroporosa controllata sono stati fabbricati con diversi processi. I risultati suggeriscono che i geopolimeri porosi promettono candidati altamente porosi a basso costo per potenziali applicazioni come catalizzatori o supporti a membrana (elevata porosità aperta e alta resistenza), adsorbimento (alta efficienza di rimozione e capacità di adsorbimento con elevata porosità aperta) e isolanti (basso materiali di conducibilità termica, elevata porosità e resistenza accettabile).
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Sundqvist, Martin. "GEOPOLYMERS WITH GREEN LIQUOR DREGS : An investigation of the possibility tomanufacture a geopolymer based on residual streams." Thesis, Umeå universitet, Kemiska institutionen, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-185528.
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The pulp and paper industry make up a large part of the Swedish industry and is alsogrowing worldwide. With its growth, the amounts of residuals that are produced alsoincrease. The estimated annual global amount of residuals generated from pulp millsexceeds 1 million tons. The residuals include fly ash (FA) and green liquor dregs(GLD), which can cause harm to the environment as well as to the human health ifnot taken care of properly. Therefore, new, sustainable uses for these residual streamsare in strong need to be found. The construction sector is one of the most energy-intensive and CO2-emitting sectorssince ordinary Portland cement (OPC) is one of the most manufactured materials inthe world and causes large amounts of CO2 emissions when produced. Research hasfocused on reducing the CO2 generated by OPC. One approach is to include FA andGLD in a so-called geopolymer, which is a cementitious material formed when aninorganic material rich in aluminium (Al) and silicon (Si) reacts with an alkalineactivator such as sodium hydroxide (NaOH). A strong geopolymer including FA andGLD would not only create a use for these residuals, but it would also be a lessenergy craving alternative to concrete. Using FA and GLD from the Metsä Board pulp mill in Husum in various proportions,this study aimed for creating a geopolymer that is suitable as a construction material.The composition of the geopolymer blends differed depending on the proportions ofGLD and FA added, as well as regarding the water contents of the blends, and thequantity of alkaline activator solution added. The compositions also varied regardingthe addition of kaolin, an additional aluminosilicate source. Lignosulfonate, a ligninbasedproduct from the sulfite pulping industry was also evaluated as an additive dueto its water-reducing properties when used in concrete. The geopolymers wereevaluated in terms of blend workability and by uniaxial compressive strength (UCS)tests after 7 and 28 days of curing. The strongest geopolymer, in which GLD constituted 20 wt.% of the dry components(sand and alkaline chemicals excluded), endured a pressure of 2.3 MPa after 28 daysof curing. Increasing the water content made the geopolymer blend more workable,but also resulted in a UCS decrease of the geopolymer. Addition of cement to themixture and an increased quantity of alkaline activator solution both resulted in alower UCS as well. Compared to cement mortar (20 MPa at the 7th curing day) andliterature values of other geopolymers, the strengths of the manufacturedgeopolymers were low overall (0.4–1.4 MPa at the 7th curing day). One reason for thelow UCS could be the use of kaolin instead of a more reactive aluminosilicate source.Moreover, the FA showed to have low Si and Al contents, which can affect thegeopolymer strength. Further investigations are needed to develop a strongergeopolymer.
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Suwan, Teewara. "Development of self-cured geopolymer cement." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/12975.
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To support the concept of environmentally friendly materials and sustainable development, the low-carbon cementitious materials have been extensively studied to reduce amount of CO2 emission to the atmosphere. One of the efforts is to promote alternative cementitious binders by utilizing abundant alumina-silicate wastes from the industrial sectors (e.g. fly ash or furnace slag), among which “Geopolymer (GP) cement” has received most attention as it can perform a wide variety of behaviours, in addition to cost reduction and less environmental impacts. The most common geopolymer production, fly ash-based, gained some strength with very slow rate at ambient temperature, while the strength is evidently improved when cured in high (above room) temperature, e.g. over 40°C. The major challenge is to step over the limitation of heat curing process and inconvenience in practice. In this study, the testing schemes of (i) GP manufacturing in various processes, (ii) inclusion of ordinary Portland cement (OPC) in GP mixture, called GeoPC and (iii) GeoPC manufactured with dry-mixing method, have been intensively investigated through mechanical testing (Setting time, Compressive strength and Internal heat measurement) and mechanism analysis (XRD, FTIR, SEM and EDXA) in order to develop the geopolymers, achieving reasonable strength without external sources of heat curing. It is found that the proposed (dry) mixing process could have generated intensive heat liberation which was observed as a comparable factor to heat curing from any other external sources, enhancing the curing regime of the mixture. The additional calcium content in the developed GeoPC system not only resulted in an improvement of an early strength by the extra precipitation of calcium compounds (C,N-A-S-H), but also provided a latent heat from the reaction of its high potential energy compounds (e.g. OPC or alkaline activators). The developments from these approaches could lead to geopolymer production to achieve reasonable strength in ambient curing temperature known as “Self-cured geopolymer cement”, without external heat, and hence provide construction industry viable technologies of applying geopolymers in on-site and off-site construction.
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Adesanya, E. (Elijah). "Fiber-reinforced mineral wool geopolymer composites." Master's thesis, University of Oulu, 2015. http://urn.fi/URN:NBN:fi:oulu-201506271885.
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This thesis investigates the utilization of mineral wool (glasswool and rockwool) as precursor with metakaolin in geopolymerization. In 2015, mineral wool waste in Europe is estimated to be 2.4 metric tonnes, and it is currently landfilled. The utilization of this waste in geopolymer composites is one of the motivation towards this study. Indeed, addition of these mineral wools to metakaolin-based geopolymers matrices showed significant improvement in the mechanical properties.
The literature section of this thesis describes the previous knowledge on geopolymerization, the materials used in geopolymer and the factors affecting the mechanical strength. In the experimental part, the first goal was to achieve mix composition with highest mechanical strength and also a workable paste of geopolymers. This was done with the following factors held constant: SiO₂/Al₂O₃ = 3.8 and Na₂O/Al₂O₃ = 1, and varying the following: H₂O/Na₂O from 10 to 13, SiO₂/Na₂O from 3.21 to 4.02, mineral wool/metakaolin mass ratio from 0–1, and water/binder (w/b) mass ratio from 0.42 to 0.55.
The different mix compositions was calculated at varying substitution (10%, 20%, 30%, 40% and 50%) of metakaolin with mineral wool using both glasswool and rockwool in different matrices to determine the effect of mineral wool substitution on the properties of the geopolymer. Mechanical strength tests were done to determine the effects of mineral wool addition in the geopolymer. Results from the test shows maximum compressive strength of 33 MPa when 20% of the metakaolin was substituted with mineral wool. Further substitution was observed to reduce the mechanical properties of the geopolymer.
Also, optimization of glasswool and rockwool in different compositional mixes was done to select a particular mineral wool to be used further in the course of the study. Glasswool precursor with metakaolin showed better compressive strength using the chosen SiO₂/Al₂O₃ and Na₂O/Al₂O₃-ratios, compared to rockwool and was continued as the co-binder with metakaolin during reinforcement with fibres. Additionally, during the investigation the matrices were cured at various temperatures (50, 60, 80 and 100 °C). Results showed best mechanical strength was achieved when the geopolymer matrices were cured at 50 °C. XRD and TGA where used to characterize the behaviour of the raw materials and geopolymer samples and to verify geopolymer formations and its thermal stability respectively.
Geopolymers in general during testing experiences brittle failure, this limitation can be corrected using fibre reinforcement. Geopolymer composites with glass, carbon and cotton/polyester fibres were investigated using a simple layering method. Data from these preliminary tests showed that cotton/polyester blend fibre exhibited better ductility and flexural strength than glass and carbon fibre.
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Lo, Xin Yin. "Analysis and reproduction of geopolymer concrete." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127289.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (page 36).
Geopolymers are inorganic polymers based on aluminosilicates that are produced from synthesizing pozzolanic compounds or aluminosilicate source materials with highly alkaline solutions. Geopolymer concrete is a stronger, more durable and more environmentally friendly alternative to ordinary Portland cement (OPC) concrete. Based on Joseph Davidovits' recipe for geopolymer concrete, we varied the ratios of the materials in an attempt to produce the ideal formula for the concrete that withstands maximum compressive strength. Through our iterations, we found the optimum texture was produced when the amount of sodium carbonate and lime are proportionally increased relative to the rest of the materials.
by Xin Yin Lo.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Matenda, Amanda Zaina. "GEOPOLYMER CONCRETE PRODUCTION USING COAL ASH." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1654.
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Coal powered power plants account for more than 40 percent of the electricity production of the United States. The combustion of coal results in a large number of solid waste materials, or coal combustion byproducts (CCBs). These waste materials are stored in landfill or ponds. The construction industry is heavily reliant on concrete which is used to make the building blocks for any type of structures, bricks. Concrete is a composite material made of a binder and coarse and fine aggregate. The most widely used binder in concrete production is Ordinary Portland Cement (OPC). Since cement manufacture is costly and environmentally damaging, research has increased in recent years to find a more readily available binder. This study aims at investigating the properties of Illinois fly ash as a binder in the production of geopolymer concrete. Geopolymer concrete is an innovative material made by using Alumina and Silica rich materials of geological origins as a binder as well as an alkali activated solution. Sodium Silicate and Sodium Hydroxide were used to make the activator solution of two different ratios. Geopolymer Concrete with a ratio of 1:1 of Sodium Silicate to Sodium Hydroxide reached a compressive strength above 6000 psi while samples made with a ratio of 1:2 reached a compressive strength above 4000 psi. This environmentally-friendly, green concrete was also found to have a cost comparable to conventional concrete.
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Shadnia, Rasoul, and Rasoul Shadnia. "Green Geopolymer with Incorporated PCM for Energy Saving in Buildings." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/622931.
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This research studies the green geopolymer incorporated with phase change material (PCM) for energy saving in buildings. First class F fly ash (FA) based-geopolymer binder was studied. In order to improve the mechanical properties, low calcium slag (SG) was added to the FA to produce geopolymer. The effect of different factors including SG content (at different relative amounts FA/SG = 0/100, 25/75, 50/50, 75/25 and 100/0), NaOH solution at different concentrations (7.5, 10 and 15 M), various curing times (1, 2, 4, 7, 14 and 28 days) and curing temperatures (25 (ambient), 45, 60, 75 and 90°C) was investigated. The unit weight and uniaxial compressive strength (UCS) of the geopolymer specimens were measured. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD) were also performed to characterize the microstructure and phase composition of the geopolymer specimens. The results show that the incorporation of SG not only improves the strength of the geopolymer specimens but also decreases the initial water content and thus the NaOH consumption at the same NaOH concentration required for geopolymer production. In addition, the inclusion of SG increases the unit weight of the geopolymer specimens, simply because SG has a much greater specific gravity than FA. The results also show that the strength of the FA/SG-based geopolymer develops rapidly within only 2 days and no obvious gain of the strength after 7 days. The optimum curing temperature (the curing temperature at which the maximum UCS is obtained) at a FA/SG ratio of 50/50 is around 75°C. Second, FA-based geopolymer concrete was synthesized and the effect of different factors including sodium silicate to sodium hydroxide (SS/SH) ratio, aggregate shape, water to fly ash (W/FA) ratio, curing time, water exposure and PCM inclusion on the compressive strength of the geopolymer concrete specimens cured at different ambient temperatures was studied. The results show that the UCS of the specimens increases with higher SS/SH and W/FA ratios up to a certain level and then starts to decrease at higher ratios. The results also indicate that a major portion of the strength of the specimens cured at ambient temperatures develops within the first four weeks. In addition the strength of the FA-based geopolymer concrete is slightly decreased with water exposure and PCM incorporation. Third, the mechanical and thermal properties of geopolymer mortar synthesized with FA and different amount of PCM were studied and the effect of incorporated PCM on the unit weight and UCS of geopolymer mortar was evaluated. SEM imaging was performed to identify the change of micro structure of the geopolymer mortar after incorporation of PCM. The thermal properties of the geopolymer mortar containing different amount of PCM were also characterized using differential scanning calorimetry (DSC) analysis. In addition model tests were performed using small cubicles built with geopolymer mortar slabs containing different amount of PCM to evaluate the effectiveness of geopolymer mortar wall with incorporated PCM in controlling the heat flow and internal temperature. The results indicate that both the unit weight and UCS of the geopolymer mortar decrease slightly after PCM is incorporated, mainly due to the small unit weight and low strength and stiffness of the PCM, respectively. However, the compressive strength of geopolymer mortar containing up to 20% PCM is still sufficiently high for applications in buildings. The results also show that the incorporation of PCM leads to substantial increase of heat capacity and decrease of thermal conductivity of the geopolymer mortar and is very effective in decreasing the temperature inside the cubicles. Finally, a numerical study on the thermal performance of geopolymer with incorporated PCM was carried out. In order to simulate the heat transfer through geopolymer containing PCM, a simplified method was first presented. The influence of phase transition was linked to the energy balance equation through variable specific heat capacity of the PCM-geopolymer. The thermal properties of the geopolymer containing PCM for the numerical analysis were determined using DSC and guarded heat flow (GHF) tests. The simplified method was validated based on the good agreement between the numerical and experimental results. With the validated model, the effect of various factors including the specific heat capacity, thermal conductivity and wall thickness on the thermal performance of PCM-geopolymer walls was studied. Then a modified numerical method was proposed for simulating the whole thermal transfer processes and the simulation results were used to conduct the economic evaluation of PCM-geopolymer walls for energy savings in buildings.
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Hardjito, Djwantoro. "Studies of fly ash-based geopolymer concrete." Thesis, Curtin University, 2005. http://hdl.handle.net/20.500.11937/634.
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The use of Portland cement in concrete construction is under critical review due to high amount of carbon dioxide gas released to the atmosphere during the production of cement. In recent years, attempts to increase the utilization of fly ash to partially replace the use of Portland cement in concrete are gathering momentum. Most of this by-product material is currently dumped in landfills, creating a threat to the environment. Geopolymer concrete is a ‘new’ material that does not need the presence of Portland cement as a binder. Instead, the source of materials such as fly ash, that are rich in Silicon (Si) and Aluminium (Al), are activated by alkaline liquids to produce the binder. Hence concrete with no Portland cement. This thesis reports the details of development of the process of making fly ash-based geopolymer concrete. Due to the lack of knowledge and know-how of making of fly ashbased geopolymer concrete in the published literature, this study adopted a rigorous trial and error process to develop the technology of making, and to identify the salient parameters affecting the properties of fresh and hardened concrete. As far as possible, the technology that is currently in use to manufacture and testing of ordinary Portland cement concrete were used. Fly ash was chosen as the basic material to be activated by the geopolimerization process to be the concrete binder, to totally replace the use of Portland cement. The binder is the only difference to the ordinary Portland cement concrete. To activate the Silicon and Aluminium content in fly ash, a combination of sodium hydroxide solution and sodium silicate solution was used. Manufacturing process comprising material preparation, mixing, placing, compaction and curing is reported in the thesis.Napthalene-based superplasticiser was found to be ii useful to improve the workability of fresh fly ash-based geopolymer concrete, as well as the addition of extra water. The main parameters affecting the compressive strength of hardened fly ash-based geopolymer concrete are the curing temperature and curing time, the molar H2O-to-Na2O ratio, and mixing time. Fresh fly ash-based geopolymer concrete has been able to remain workable up to at least 120 minutes without any sign of setting and without any degradation in the compressive strength. Providing a rest period for fresh concrete after casting before the start of curing up to five days increased the compressive strength of hardened concrete. The elastic properties of hardened fly ash-based geopolymer concrete, i,e. the modulus of elasticity, the Poisson’s ratio, and the indirect tensile strength, are similar to those of ordinary Portland cement concrete. The stress-strain relations of fly ash-based geopolymer concrete fit well with the expression developed for ordinary Portland cement concrete.
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Hardjito, Djwantoro. "Studies of fly ash-based geopolymer concrete." Curtin University of Technology, Dept. of Civil Engineering, 2005. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=18580.
Full textAbstract:
The use of Portland cement in concrete construction is under critical review due to high amount of carbon dioxide gas released to the atmosphere during the production of cement. In recent years, attempts to increase the utilization of fly ash to partially replace the use of Portland cement in concrete are gathering momentum. Most of this by-product material is currently dumped in landfills, creating a threat to the environment. Geopolymer concrete is a ‘new’ material that does not need the presence of Portland cement as a binder. Instead, the source of materials such as fly ash, that are rich in Silicon (Si) and Aluminium (Al), are activated by alkaline liquids to produce the binder. Hence concrete with no Portland cement. This thesis reports the details of development of the process of making fly ash-based geopolymer concrete. Due to the lack of knowledge and know-how of making of fly ashbased geopolymer concrete in the published literature, this study adopted a rigorous trial and error process to develop the technology of making, and to identify the salient parameters affecting the properties of fresh and hardened concrete. As far as possible, the technology that is currently in use to manufacture and testing of ordinary Portland cement concrete were used. Fly ash was chosen as the basic material to be activated by the geopolimerization process to be the concrete binder, to totally replace the use of Portland cement. The binder is the only difference to the ordinary Portland cement concrete. To activate the Silicon and Aluminium content in fly ash, a combination of sodium hydroxide solution and sodium silicate solution was used. Manufacturing process comprising material preparation, mixing, placing, compaction and curing is reported in the thesis.Napthalene-based superplasticiser was found to be ii useful to improve the workability of fresh fly ash-based geopolymer concrete, as well as the addition of extra water. The main parameters affecting the compressive strength of hardened fly ash-based geopolymer concrete are the curing temperature and curing time, the molar H2O-to-Na2O ratio, and mixing time. Fresh fly ash-based geopolymer concrete has been able to remain workable up to at least 120 minutes without any sign of setting and without any degradation in the compressive strength. Providing a rest period for fresh concrete after casting before the start of curing up to five days increased the compressive strength of hardened concrete. The elastic properties of hardened fly ash-based geopolymer concrete, i,e. the modulus of elasticity, the Poisson’s ratio, and the indirect tensile strength, are similar to those of ordinary Portland cement concrete. The stress-strain relations of fly ash-based geopolymer concrete fit well with the expression developed for ordinary Portland cement concrete.
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Chen-Tan, Nigel W. "Geopolymer from a Western Australian fly ash." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1900.
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Ordinary Portland cement is utilised worldwide as a mainstay construction material. Worldwide consumption of cement in 2009 was estimated to be 2.8 billion tonnes, which unfortunately equates to the production of 2.8 billion tonnes of CO[subscript]2 via the sintering procedure required to produce cement clinkers. With worldwide concern over climate change, this value is a substantial contribution to greenhouse gas emission.Fly ash is a by-product of coal combustion from thermoelectric power stations. World production of fly ash was estimated at 600 million tonnes with only 9% utilisation (Kayali 2007). The remainder is typically disposed of in landfills or ash ponds. This takes up usable land for development, introduces environmental hazards and can lead to undesirable events with an example being the rupture of a fly ash pond barrier at the Kingston Fossil Plant, Tennessee in 2008 (Reilly 2008) known as the TVA Spill.Geopolymer is a cementitious binder and is considered an environmentally friendly alternative to cement as it emits no CO[subscript]2 during production. Production of geopolymer is a simple process that involves mixing an amorphous aluminosilicate feedstock with alkaline activating solution. In addition this process is able to utilise low cost industrial by-products such as blast furnace slag and fly ash as feedstock.Although fly ash is suitable as a feedstock for synthesis of geopolymer its inherent heterogeneity limits development of a general formulation for processing geopolymer. Beneficiation of fly ash can be considered a method for alleviating this limitation, leading to a more homogeneous geopolymer with improved properties.Collie fly ash from Western Australia was selected as the fly ash to investigate as it is the dominant fly ash in the State and had been successfully used previously to make geopolymer. The amorphous content of Collie fly ash was determined by dissolution and a combination of QXRD and XRF. Collie fly ash was thoroughly characterised by QXRD and XRF, revealing a reactive amorphous content of 54.5 wt.% and secondary phases of carbon, hematite, maghemite, magnetite, mullite and quartz. The amorphous component was found to contain a modest amorphous iron oxide (5.5 wt.%) which after dissolution studies and subsequent analysis by QEMSCAN, was determined not to play a direct role in geopolymerisation. Crystalline quartz was found to exist as primary quartz separate from the fly ash spheres and secondary quartz embedded in the spheres believed to have exsolved from the decomposition of clay in the production of mullite.Beneficiation of the fly ash was conducted in a three stage procedure using sieving, milling and magnetic separation to improve fly ash homogeneity and reactivity. Sieving was effective in reducing large carbon and free primary quartz content. Interestingly most of the carbon was found to be small and finely dispersed throughout the material making it unfeasible to remove by sieving. Sieving in conjunction with milling increased surface area from 9.83 m[superscript]2/g to 10.7 m[superscript]2/g. Magnetic separation revealed that the amorphous iron was not magnetic though the complete removal of crystalline iron phases is not possible without a robust separation technique. The removal of magnetic phases increased the surface area of the sieved and milled fly ash to 12.9 m[superscript]2/g.At each stage of beneficiation the proportion of reactive amorphous material increases resulting in increased reactivity. This increase in reactivity necessitated changes in solids:liquids ratio to maintain a workable geopolymer mixture. The least beneficiated fly ash (sieved < 45 μm) produced the strongest geopolymer with a compressive strength of 132 MPa. The most beneficiated fly ash (sieved/milled/magnetically separated) produced geopolymer with the same compressive strength as geopolymer from unmodified fly ash (100 MPa). However, the highly beneficiated fly ash geopolymer proved to be highly resistant to high temperature cracking even after exposure to 900 ºC. The outcomes from this project clearly identifies that different levels of fly ash beneficiation lead to different geopolymer properties which in turn extend the range of applications for which geopolymers can be used.
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Deb, Partha Sarathi. "Durability of fly ash based geopolymer concrete." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/2126.
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Inclusion of ground granulated blast furnace slag (GGBFS) together with fly-ash can have significant effects on the development of mechanical and durability properties of geopolymer concrete when cured at normal temperature. The slag blended geopolymer concretes showed durability properties comparable to those of the control OPC concrete. In general, the results show that it is possible to design fly ash and slag blended geopolymer concrete suitable for ambient curing with similar or better durability properties of conventional OPC concrete.
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Vickers, Les. "Development of Geopolymer Systems for High Temperature Applications." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/1453.
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Geopolymers are amorphous, inorganic structures based on silicate and aluminate tetrahedrons and could be beneficial in thermal and fire resistant applications. The outcomes from this work suggest that fly ash geopolymer composites suitable for thermal applications can be produced. When compared to OPC based systems geopolymers showed extended thermal resistance (from 500 °C to 800 °C). Improved thermal properties were achieved with increases in compressive strength after firing to 1000 °C and the near elimination of expansive events at high temperature.
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Subaer. "Influence of aggregate on the microstructure of geopolymer." Thesis, Curtin University, 2004. http://hdl.handle.net/20.500.11937/1695.
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Inorganic geopolymers or simply geopolymers based on silico-aluminate are relatively novel materials with a wide range of potential applications. The mAln purpose of the present study was to experimentally investigate the compositionmicrostructure- property relationship of these new materials. These must be understood in order to optimise the performance of geopolymers. Geopolymers with different chemical compositions (Si:Al and Na:Al atomic ratios) were prepared by thermally assisted alkali-activation of metakaolinite at 70ºC. Metakaolinite was obtAlned by dehydroxylation of kaolinite at 750ºC for 6 hours. Measurements indicated that the compositions of geopolymers influence the microstructural character as well as the physical and mechanical properties of these materials. Geopolymers prepared with an atomic ratio of Si:Al = 1.04 and 1.25 are categorised as sodium-poly(sialate) (Na-PS) geopolymers. These materials were found to be composed of zeolite-A or zeolite-X in conjunction with amorphous geopolymer. These materials are relatively soft, with low density and high apparent porosity, and have low hardness and compressive strength. Geopolymers prepared with an atomic ratio of Si:Al = 1.50, 1.75 and 2.00 are categorised as sodium-poly(sialate-siloxo) (Na-PSS) geopolymers. The structure of these geopolymers is amorphous as observed by X-ray diffraction (XRD) with no evidence of zeolite formation. A broad amorphous hump in the X-ray diffraction patterns suggests that the Na-PSS geopolymers consist of disordered frameworks with short-range order. The thermal analysis of Na-PSS by means of thermogravitmetric-differential thermal analysis (TG-DTA) revealed that about 15% of the initial reaction water remAlns in the geopolymer framework. The DTA curves for Na-PSS show a single endothermic peak around 135ºC due to water evolution.Na-PSS geopolymers exhibit substantial shrinkage and cracking after heating up to 950ºC. Geopolymers with aggregate also suffer extensive cracking due to heating although the shrinkage was less than that of geopolymers without aggregate Dilatometer results show that geopolymer pastes shrink about 2% below 300ºC and remAln dimensionally stable up to 800ºC. The coefficient of thermal expansion of geopolymers is comparable to that of Portland cement paste. The presence of aggregate was found to reduce the shrinkage of geopolymer by 50%. Quartz aggregate, however, limits the useful working temperature range of geopolymers to below 500ºC due to a sudden expansion of quartz at 574ºC. The thermal conductivity of geopolymers was measured using a hot-wire method. The results indicated that thermal conductivity of geopolymers was similar to those of Portland cement paste. As with Portland cement, the addition of quartz was found to increase the thermal conductivity. The compressive strength of Na-PSS geopolymers is significantly influenced by the hardness, apparent porosity and the atomic ratio of Si:Al. It was found that geopolymers with an atomic ratio of Si:Al = 1.5, Na:Al = 0.6 have the highest compressive strength and hardness. It was also observed that the addition of aggregate (quartz and granite) has negligible effect on the strength of geopolymers. The bond strength between geopolymer and aggregate was measured by using a tensile test. The results indicated that sandstone aggregate provides the strongest interfacial bond with geopolymer, followed by granite and quartz. The mechanical interlocking due to the rough surface of the sandstone was believed to be responsible for the relatively high interfacial bond strength.The microstructural characterisation of Na-PSS by means of SEM (scanning electron microscopy) and TEM (transmission electron microscopy) revealed that the morphology of Na-PSS consists of aluminosilicate matrix, unreacted metakaolinite, pores and microcracks. The presence of microcracks observed by SEM and TEM are categorised as secondary microcracks formed during sample preparation. Computed Tomography Imaging (CT-Scan) results for as prepared geopolymers with and without the inclusion of aggregate did not reveal any resolvable cracks. Optical microscopy observations on polished and vacuum evacuated samples also shows the formation of cracks on the surface of geopolymers. The presence of unreacted metakaolinite was confirmed by energy dispersive spectroscopy (EDS), X-ray mapping and electron diffraction. It was also found that Na-PSS geopolymers prepared with Si:Al = 2.0, Na:Al = 1.0 are more homogeneous (less unreacted metakaolinite) than Na-PSS geopolymers prepared with Si:Al = 1.5, Na:Al = 0.6. SEM and TEM observations revealed that the interfacial zone between geopolymer paste and aggregate has the same chemical composition as the rest of the geopolymer matrix. As a result of this study there is a better understanding of the composition-microstructure-property relationship of geopolymers paving the way to the production of geopolymers with improved performance in a variety of applications.
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Subaer. "Influence of aggregate on the microstructure of geopolymer." Curtin University of Technology, Department of Applied Physics, 2004. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=15824.
Full textAbstract:
Inorganic geopolymers or simply geopolymers based on silico-aluminate are relatively novel materials with a wide range of potential applications. The mAln purpose of the present study was to experimentally investigate the compositionmicrostructure- property relationship of these new materials. These must be understood in order to optimise the performance of geopolymers. Geopolymers with different chemical compositions (Si:Al and Na:Al atomic ratios) were prepared by thermally assisted alkali-activation of metakaolinite at 70ºC. Metakaolinite was obtAlned by dehydroxylation of kaolinite at 750ºC for 6 hours. Measurements indicated that the compositions of geopolymers influence the microstructural character as well as the physical and mechanical properties of these materials. Geopolymers prepared with an atomic ratio of Si:Al = 1.04 and 1.25 are categorised as sodium-poly(sialate) (Na-PS) geopolymers. These materials were found to be composed of zeolite-A or zeolite-X in conjunction with amorphous geopolymer. These materials are relatively soft, with low density and high apparent porosity, and have low hardness and compressive strength. Geopolymers prepared with an atomic ratio of Si:Al = 1.50, 1.75 and 2.00 are categorised as sodium-poly(sialate-siloxo) (Na-PSS) geopolymers. The structure of these geopolymers is amorphous as observed by X-ray diffraction (XRD) with no evidence of zeolite formation. A broad amorphous hump in the X-ray diffraction patterns suggests that the Na-PSS geopolymers consist of disordered frameworks with short-range order. The thermal analysis of Na-PSS by means of thermogravitmetric-differential thermal analysis (TG-DTA) revealed that about 15% of the initial reaction water remAlns in the geopolymer framework. The DTA curves for Na-PSS show a single endothermic peak around 135ºC due to water evolution.Na-PSS geopolymers exhibit substantial shrinkage and cracking after heating up to 950ºC. Geopolymers with aggregate also suffer extensive cracking due to heating although the shrinkage was less than that of geopolymers without aggregate Dilatometer results show that geopolymer pastes shrink about 2% below 300ºC and remAln dimensionally stable up to 800ºC. The coefficient of thermal expansion of geopolymers is comparable to that of Portland cement paste. The presence of aggregate was found to reduce the shrinkage of geopolymer by 50%. Quartz aggregate, however, limits the useful working temperature range of geopolymers to below 500ºC due to a sudden expansion of quartz at 574ºC. The thermal conductivity of geopolymers was measured using a hot-wire method. The results indicated that thermal conductivity of geopolymers was similar to those of Portland cement paste. As with Portland cement, the addition of quartz was found to increase the thermal conductivity. The compressive strength of Na-PSS geopolymers is significantly influenced by the hardness, apparent porosity and the atomic ratio of Si:Al. It was found that geopolymers with an atomic ratio of Si:Al = 1.5, Na:Al = 0.6 have the highest compressive strength and hardness. It was also observed that the addition of aggregate (quartz and granite) has negligible effect on the strength of geopolymers. The bond strength between geopolymer and aggregate was measured by using a tensile test. The results indicated that sandstone aggregate provides the strongest interfacial bond with geopolymer, followed by granite and quartz. The mechanical interlocking due to the rough surface of the sandstone was believed to be responsible for the relatively high interfacial bond strength.
The microstructural characterisation of Na-PSS by means of SEM (scanning electron microscopy) and TEM (transmission electron microscopy) revealed that the morphology of Na-PSS consists of aluminosilicate matrix, unreacted metakaolinite, pores and microcracks. The presence of microcracks observed by SEM and TEM are categorised as secondary microcracks formed during sample preparation. Computed Tomography Imaging (CT-Scan) results for as prepared geopolymers with and without the inclusion of aggregate did not reveal any resolvable cracks. Optical microscopy observations on polished and vacuum evacuated samples also shows the formation of cracks on the surface of geopolymers. The presence of unreacted metakaolinite was confirmed by energy dispersive spectroscopy (EDS), X-ray mapping and electron diffraction. It was also found that Na-PSS geopolymers prepared with Si:Al = 2.0, Na:Al = 1.0 are more homogeneous (less unreacted metakaolinite) than Na-PSS geopolymers prepared with Si:Al = 1.5, Na:Al = 0.6. SEM and TEM observations revealed that the interfacial zone between geopolymer paste and aggregate has the same chemical composition as the rest of the geopolymer matrix. As a result of this study there is a better understanding of the composition-microstructure-property relationship of geopolymers paving the way to the production of geopolymers with improved performance in a variety of applications.
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Conte, Alberto. "Development of brake components: geopolymer based brake pads." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3424930.
Full textAbstract:
The brake disc technology is the most used on commercial vehicle. The main focus of this project was the substitution of the phenolic resin, which is normally used as matrix in brake pads, with inorganic matrix, and in particular with geopolymer.
The inspiration comes from their inorganic structure. Geopolymers have better thermal properties than organic resins, which typically decompose by oxidation starting from 400°C. In fact, during the braking events temperature in the order of 600°C-800°C can be reached.
The research has been financed by ITT Italia s.r.l a world company leader on the production of brake pads. On the base of the guidelines of the company, the goal of the project has been the substitution of the phenolic resin with the geopolymer matrix and without any modification on the production process of brake pads.
Brake pads were produced using a warm press technology in dry conditions. During the pressing step occurs the phenolic resin’s crosslinking which could be completed through a post-curing in oven.
Based on the fact which the geopolymer are synthesized in solution, the first part of the project was focused on the development of geopolymer matrices suitable to be processed in the same conditions used to produce phenolic resin-based brake pads.
Two geopolymer system have been developed:
1. the hydrothermal dry synthesis of hydrosodalite from the reaction of kaolin and sodium hydroxide;
2. the cold sintering of geopolymer powder based on metakaolin and sodium silicate.
The best pressing conditions for the two system were evaluated on the base of their effect on mechanical properties and physical proprieties of geopolymer matrix. To evaluate the feasibility of the production in large scale of the geopolymer based brake pads, for the geopolymer matrices two goals have been followed at the same time:
1. The scale up at an industrial level for the geopolymer matrix production. Tests were carried out before at lab scale and subsequently with industrial technologies.
2. The optimization of the brake formulations has been done in ITT Italia s.r.l. on the base of physical properties and friction characterization of geopolymer based brake pads.La tecnologia di frenata basata sui dischi freno è la più utilizzata sui veicoli commerciali. L'obiettivo principale di questo progetto ha riguardato la sostituzione della resina fenolica, che viene normalmente utilizzata come matrice nelle pastiglie freno, con una matrice inorganica e in particolare con geopolimeri. L'idea deriva dalla loro struttura inorganica. I geopolimeri possiedono infatti proprietà termiche migliori delle resine organiche, le quali si decompongono in genere per ossidazione a partire dai 400 °C. Infatti, in fase di frenata frenata si possono raggiungere temperature dell'ordine di 600 °C - 800 °C. La ricerca è stata finanziata da ITT Italia s.r.l, un'azienda leader mondiale nella produzione di pastiglie freno. Sulla base delle linee guida dell'azienda, l'obiettivo del progetto è stato la sostituzione della resina fenolica con la matrice geopolimerica, e con il vincolo di non introdurre alcuna modifica sul processo di produzione delle pastiglie freno a base di resina fenolica. Le pastiglie freno sono state prodotte utilizzando una tecnologia di pressatura a caldo e a secco. Durante la fase di pressatura, avviene la reticolazione della resina fenolica, che può essere completata successivamente attraverso un post-curing in forno. Sulla base del fatto che il geopolimero è prodotto in soluzione acquosa, la prima parte del progetto, si è concentrata sullo sviluppo di matrici geopolimeriche adatte ad essere lavorate nelle stesse condizioni utilizzate per la produzione di pastiglie freno a base di resine fenoliche. Sono stati sviluppati due sistemi geopolimerici: 1. La sintesi idrotermale a secco di idrosodalite dalla reazione di caolino e idrossido di sodio; 2. La sinterizzazione a freddo della polvere di geopolimero ottenuto dalla reazione tra metacaolino e silicato di sodio. Le migliori condizioni di pressatura per i due sistemi, sono state valutate sulla base del loro effetto sulle proprietà meccaniche e sulle proprietà fisiche della matrice geopolimerica. Per valutare la fattibilità della produzione su larga scala delle pastiglie freno a matrice geopolimerica, per le matrici geopolimeriche sono stati perseguiti due obiettivi allo stesso tempo: 1. L’industrializzazione della produzione delle matrici geopolimeriche. I test sono stati effettuati prima su scala di laboratorio e successivamente con tecnologie industriali. 2. L'ottimizzazione delle formulazioni per pastiglie freno, che è stata effettuata presso il centro ricerche di ITT Italia s.r.l., sulla base delle proprietà fisiche e della caratterizzazione del comportamento ad usura delle pastiglie freno basate sui geopolimeri.
17
Chang, Ee Hui. "Shear and bond behaviour of reinforced fly ash-based geopolymer concrete beams." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/468.
Full textAbstract:
Concrete is by far the most widely used construction material worldwide in terms of volume, and so has a huge impact on the environment, with consequences for sustainable development. Portland cement is one of the most energy-intensive materials of construction, and is responsible for some emissions of carbon dioxide — the main greenhouse gas causing global warming. Efforts are being made in the construction industry to address these by utilising supplementary materials and developing alternative binders in concrete; the application of geopolymer technology is one such alternative. Indeed, geopolymers have emerged as novel engineering materials with considerable promise as binders in the manufacture of concrete. Apart from their known technical attributes, such as superior chemical and mechanical properties, geopolymers also have a smaller greenhouse footprint than Portland cement binders.Research on the development, manufacture, behaviour and applications of low calcium fly ash-based geopolymer concrete has been carried out at Curtin University of Technology since 2001. Past studies of the structural behaviour of reinforced fly ash-based geopolymer concrete members have covered the flexural behaviour of members. Further studies are needed to investigate other aspects of the structural behaviour of geopolymer concrete. Design for both shear and bond are important in reinforced concrete structures. Adequate shear resistance in reinforced concrete members is essential to prevent shear failures which are brittle in nature. The performance of reinforced concrete structures depends on sufficient bond between concrete and reinforcing steel. The present research therefore focuses on the shear and bond behaviour of reinforced low calcium fly ash-based geopolymer concrete beams.For the study of shear behaviour of geopolymer concrete beams, a total of nine beam specimens were cast. The beams were 200 mm x 300 mm in cross section with an effective length of 1680 mm. The longitudinal tensile reinforcement ratios were 1.74%, 2.32% and 3.14%. The behaviour of reinforced geopolymer concrete beams failing in shear, including the failure modes and crack patterns, were found to be similar to those observed in reinforced Portland cement concrete beams. Good correlation of test-to-prediction value was obtained using VecTor2 Program incorporating the Disturbed Stress Field Model proposed by Vecchio (2000). An average test-to-prediction ratio of 1.08 and a coefficient of variation of 8.3% were obtained using this model. It was also found that the methods of calculations, including code provisions, used in the case of reinforced Portland cement concrete beams are applicable for predicting the shear strength of reinforced geopolymer concrete beams.For the study of bond behaviour of geopolymer concrete beams, the experimental program included manufacturing and testing twelve tensile lap-spliced beam specimens. No transverse reinforcement was provided in the splice region. The beams were 200 mm wide, 300 mm deep and 2500 mm long. The effect of concrete cover, bar diameter, splice length and concrete compressive strength on bond strength were studied. The failure mode and crack patterns observed for reinforced geopolymer concrete beams were similar to those reported in the literature for reinforced Portland cement beams. The bond strength of geopolymer concrete was observed to be closely related to the tensile strength of geopolymer concrete. Good correlation of test bond strength with predictions from the analytical model proposed by Canbay and Frosch (2005) were obtained when using the actual tensile strength of geopolymer concrete. The average ratio of test bond strength to predicted bond strength was 1.0 with a coefficient of variation of 15.21%. It was found that the design provision and analytical models used for predicting bond strength of lapsplices in reinforced Portland cement concrete are applicable to reinforced geopolymer concrete beams.
18
Neupane, Kamal. "Investigation of Structural Behaviour of Geopolymer Prestressed Concrete Beam." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/24951.
Full textAbstract:
Production of ordinary Portland cement (OPC) is a carbon-intensive process that generates significant amounts of carbon dioxide (CO2) gas from the combustion of fossil fuels and thermal decomposition of limestone. Overall, cement industries are responsible for around 7% of global CO2 emissions which poses a considerable threat to global climate change because of its greenhouse effects. Geopolymer is an inorganic polymer material having similar binding properties to OPC which can be produced from aluminosilicate compounds, such as fly ash when activated by alkaline solution. The recent advent of geopolymer technology shows great potential to reduce carbon footprints by utilising industrial by-products, such as fly ash and ground granulated blast furnace slag (GGBS), and convert into effective binding material.
The setting and hardening process of geopolymer binder is different from hydration of OPC, called “geopolymerisation” which is the condensation process of aluminate and silicate monomers to form a polymer chain. Generally, fly ash-based geopolymer concrete attains relatively lower early-age strength at ambient temperature due to the slow rate of reaction. However, geopolymer concrete based on GGBS or a combination of fly ash and GGBS can set and harden in ambient temperature with comparable early age strength to OPC concrete of same grade. In the recent past, several studies were carried out to investigate mechanical, serviceability, durability and microstructural properties of geopolymer concrete using different aluminosilicate materials. However, limited research has been carried out on applications of geopolymer binder in structural concrete, such as reinforced concrete beam, column and prestressed concrete beam.
Prestressed concrete is a construction technique in which flexural tensile stress generated in the concrete member due to imposed load is counteracted by applying an initial prestressing compressive force. The use of prestressed concrete structures has been increasing in modern construction practices because they can withstand significantly higher flexural load with minimal deflection and cracks than conventional reinforced concrete (RC) members of similar cross-section. Generally, tensile strength of concrete is ignored in the design of conventional RC structures. However, tensile or flexural strengths of concrete are significant in the design of prestressed concrete structures where tensile strength of concrete limits the maximum permissible prestressing load according to ACI 318. Application of higher prestressing load can increase the load-carrying capacity of prestressed concrete structures and minimize their deflection under service load. Previous results showed that geopolymer concrete possesses higher indirect-tensile and flexural strength than OPC concrete for the same compressive strength. In addition, time-dependent losses of prestressing stress are the major serviceability problems of prestressed concrete structure which reduce the load-carrying capacity of structures and increase the deflection under service loads. The time-dependent losses of prestressing stress are directly proportional to the amount of shrinkage and creep strains of concrete. Having smaller drying shrinkage and creep strains, geopolymer concrete can result in better serviceability than OPC concrete in prestressed concrete structures. Thus, this study investigates the application of geopolymer concrete in the prestressed concrete beam which may be a worthwhile utilization of geopolymer concrete in concrete structures.
Despite having higher mechanical strengths and durability properties than conventional OPC concrete, geopolymer concrete has not been widely used in structural grade concrete, so far. The safety hazards in mixing and handling of concrete due to the use of liquid sodium hydroxide in geopolymer binder is one of the barriers to the adaptation of geopolymer in concrete industry. In this study, the mechanical and serviceability properties of grade 50 MPa geopolymer concrete from sodium hydroxide-free one-part geopolymer binder are investigated under ambient temperature curing and compared against same grade OPC concrete. Development of strengths at an early age under accelerated curing is investigated to study the suitability of geopolymer concrete in precast prestressed concrete structures. Finite element models of prestressed concrete beams of three different lengths and sizes are analysed to investigate their load-deflection behaviours under imposed load for short-term and long-term durations using the Abaqus program. The effects of tensile strength of concrete in load-deflection behaviours of prestressed concrete beams are studied by comparing the results between identical geopolymer and OPC prestressed concrete beams.
This study finds that geopolymer concrete has around 27% higher indirect-tensile and flexural strengths than OPC concrete of same strength grade which contributes to geopolymer prestressed concrete beams to withstand around 20% higher first-crack load than OPC concrete beams of same span. In addition, geopolymer prestressed concrete beams show a relatively smaller loss in prestressing stress which results in a smaller loss in flexural capacity of beams over the service life of the structure.
19
Assaedi, Hasan Suliman. "Characterization and Development of Flax Fibre Reinforced Geopolymer Nanocomposites." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/57344.
Full text
20
Chang, Ee Hui. "Shear and bond behaviour of reinforced fly ash-based geopolymer concrete beams." Curtin University of Technology, Department of Civil Engineering, 2009. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=120482.
Full textAbstract:
Concrete is by far the most widely used construction material worldwide in terms of volume, and so has a huge impact on the environment, with consequences for sustainable development. Portland cement is one of the most energy-intensive materials of construction, and is responsible for some emissions of carbon dioxide — the main greenhouse gas causing global warming. Efforts are being made in the construction industry to address these by utilising supplementary materials and developing alternative binders in concrete; the application of geopolymer technology is one such alternative. Indeed, geopolymers have emerged as novel engineering materials with considerable promise as binders in the manufacture of concrete. Apart from their known technical attributes, such as superior chemical and mechanical properties, geopolymers also have a smaller greenhouse footprint than Portland cement binders.Research on the development, manufacture, behaviour and applications of low calcium fly ash-based geopolymer concrete has been carried out at Curtin University of Technology since 2001. Past studies of the structural behaviour of reinforced fly ash-based geopolymer concrete members have covered the flexural behaviour of members. Further studies are needed to investigate other aspects of the structural behaviour of geopolymer concrete. Design for both shear and bond are important in reinforced concrete structures. Adequate shear resistance in reinforced concrete members is essential to prevent shear failures which are brittle in nature. The performance of reinforced concrete structures depends on sufficient bond between concrete and reinforcing steel. The present research therefore focuses on the shear and bond behaviour of reinforced low calcium fly ash-based geopolymer concrete beams.
For the study of shear behaviour of geopolymer concrete beams, a total of nine beam specimens were cast. The beams were 200 mm x 300 mm in cross section with an effective length of 1680 mm. The longitudinal tensile reinforcement ratios were 1.74%, 2.32% and 3.14%. The behaviour of reinforced geopolymer concrete beams failing in shear, including the failure modes and crack patterns, were found to be similar to those observed in reinforced Portland cement concrete beams. Good correlation of test-to-prediction value was obtained using VecTor2 Program incorporating the Disturbed Stress Field Model proposed by Vecchio (2000). An average test-to-prediction ratio of 1.08 and a coefficient of variation of 8.3% were obtained using this model. It was also found that the methods of calculations, including code provisions, used in the case of reinforced Portland cement concrete beams are applicable for predicting the shear strength of reinforced geopolymer concrete beams.
For the study of bond behaviour of geopolymer concrete beams, the experimental program included manufacturing and testing twelve tensile lap-spliced beam specimens. No transverse reinforcement was provided in the splice region. The beams were 200 mm wide, 300 mm deep and 2500 mm long. The effect of concrete cover, bar diameter, splice length and concrete compressive strength on bond strength were studied. The failure mode and crack patterns observed for reinforced geopolymer concrete beams were similar to those reported in the literature for reinforced Portland cement beams. The bond strength of geopolymer concrete was observed to be closely related to the tensile strength of geopolymer concrete. Good correlation of test bond strength with predictions from the analytical model proposed by Canbay and Frosch (2005) were obtained when using the actual tensile strength of geopolymer concrete. The average ratio of test bond strength to predicted bond strength was 1.0 with a coefficient of variation of 15.21%. It was found that the design provision and analytical models used for predicting bond strength of lapsplices in reinforced Portland cement concrete are applicable to reinforced geopolymer concrete beams.
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Santos, Gessica Zila Batista dos. "Argamassa geopolimérica à base de lodo de estação de tratamento de água calcinado." Universidade Federal do Amazonas, 2016. http://tede.ufam.edu.br/handle/tede/5532.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
In the process of water treatment for public supply, which is made in the water treatment plants (WTPs), a waste conventionally called sludge is formed. As in the soil, the main components of WTP sludge are silicon (Si), aluminum (Al) and iron (Fe). This composition allowed to suggest that this waste could be used in the production of inorganic polymers - the geopolymers. While conventional polymers are formed by carbon structures, geopolymers are composed of Si and Al structures. They are obtained by dissolving aluminosilicates materials in highly alkaline solution. Among the possible applications, they can be used as pastes, mortars and concretes, in replacement of Portland cement, which is the most used binder in civil construction worldwide. To verify the suitability of the sludge as a geopolymer precursor, this waste was properly benefited by means of mechanical grinding and calcination at 750 °C for 6 hours, being characterized before and after its processing. The results of chemical and mineralogical analyzes proved the adequacy of calcined WTP sludge as a geopolymeric raw material. To check the influence of the sources of raw water abstraction intake on the WTP sludge characteristics and consequently in the properties of materials produced from sludge-based, samples of this waste were collected under the influence of two different water sources. With these samples it produced of two geopolymeric mortars. The final products were properly characterized and the results proved that regardless of the peculiarities of water sources, WTP sludge can be used as a geopolymeric raw material. In the thermal tests the two mortars produced showed indications of refractory bahavior and have been free of calcium hydroxide, therefore, it can be inferred that they are free matrices of deleterious actions of this compound. In the mechanical tests, at 28 days of cure, they reached mechanical strengths of 57 and 79 MPa, on average. Some results evidenced the need for improvements in the formulation of mortars, but in general, it was verified that the use of WTP sludge as a geopolymer precursor material is a very promising alternative for the destination of this waste, making it valuable and useful product for society.
No processo de tratamento de água para abastecimento público, realizado em estações de tratamento de água – ETAs, gera-se um resíduo convencionalmente chamado de lodo. Da mesma forma que acontece no solo, os principais constituintes do lodo de ETA são o silício (Si), o alumínio (Al) e o ferro (Fe). Tal composição permitiu sugerir que este resíduo poderia ser usado na produção de polímeros inorgânicos – os geopolímeros. Enquanto os polímeros convencionais são formados por estruturas de carbono, geopolímeros são constituídos de estruturas de Si e Al. São obtidos através da dissolução de materiais aluminossilicatos em solução altamente alcalina. Dentre as possíveis aplicações, podem ser empregados como pastas, argamassas e concretos, em substituição ao cimento Portland, o material ligante mais utilizado mundialmente na construção civil. Para verificar a adequação do lodo de ETA como material precursor geopolimérico, este resíduo foi devidamente beneficiado por meio de moagem mecânica e calcinação a 750 ° C por 6 horas, sendo caracterizado antes e após seu beneficiamento. Os resultados de análises químicas e mineralógicas comprovarem a adequação do lodo de ETA calcinado como matéria-prima geopolimérica. A fim de avaliar a influência dos mananciais de captação de água bruta nas características do lodo de ETA e, consequentemente, nas propriedades de materiais produzidos à base deste resíduo, foram coletadas amostras de lodo sob influência de dois diferentes mananciais. Com estas amostras produziu-se duas argamassas geopoliméricas. Os produtos finais foram devidamente caracterizados e os resultados comprovaram que, independentemente das peculiaridades dos mananciais, o lodo de ETA pode ser utilizado como material precursor geopolimérico. Nos ensaios térmicos, as duas argamassas produzidas exibiram indícios de comportamento refratário e se mostraram isentas de hidróxido de cálcio, portanto, pode-se inferir que são matrizes livres das ações deletérias ocasionadas por este composto. Nos ensaios de resistência mecânica, aos 28 dias de cura, atingiram 57 e 79 MPa, em média. Alguns resultados evidenciaram a necessidade de melhorias na formulação das argamassas, mas de uma forma geral, constatou-se que o aproveitamento do lodo de ETA como matéria-prima geopolimérica é uma alternativa bastante promissora para a destinação deste resíduo, podendo torná-lo um produto com valor agregado e útil para a sociedade.
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Sadat, Mohammad Rafat, and Mohammad Rafat Sadat. "Using Molecular Dynamics and Peridynamics Simulations to Better Understand Geopolymer." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626361.
Full textAbstract:
Geopolymer is a novel cementitious material which can be a potential alternative to ordinary Portland cement (OPC) for all practical applications. However, until now research on this revolutionary material is limited mainly to experimental studies, which have the limitations in considering the details of the atomic- and meso-scale structure and atomic scale mechanisms that govern the properties at the macro-scale. Most experimental studies on geopolymer have been conducted focusing only on the macroscopic properties and considering it as a single-phase material. However, research has shown that geopolymer is a composite material consisting of geopolymer binder (GB), unreacted source material, and, in the presence of Ca in the source material, calcium silicate hydrate (CSH). Therefore, in this research, a multiscale/multiphysics modeling approach has been taken to understand geopolymer structure and mechanical properties under varying conditions and at different length scales. First, GB was prepared at the atomic scale using molecular dynamics (MD) simulations with varying Si/Al ratios and water contents within the nano voids. The MD simulated geopolymer structure was validated based on comparison with experiments using X-ray pair distribution function (PDF), infra-red (IR) spectra, coordination of atoms, and density. The results indicate that the highest strength occurs at a Si/Al ratio of 2-3 and the presence of molecular water negatively affects the mechanical properties of GB. The loss of strength for GB with increased water content is linked to the diffusion of Na atoms and subsequent weakening of Al tetrahedra. The GB was also subjected to nanoindentation using MD and the effect of indenter size and loading rate was investigated at an atomic scale. A clear correlation between the indenter size and observed hardness of GB was observed which proves indentation size effects (ISE). Realizing the composite nature of geopolymer, the presence of unreacted and secondary phases such as quartz and CSH in geopolymer was also investigated. To do that, the mechanical properties of GB, the secondary phases and their interfaces was first determined from MD simulations. Using the MD generated properties, a meso-scale model of geopolymer composite was prepared in Peridynamics (PD) framework which considered large particles of GB and secondary phases of nanometers in size which cannot be easily modeled in MD. The meso-scale model provides a larger platform to study geopolymer in the presence of large nano-voids and multiple phases. Results from the PD simulations were directly comparable to experimentally observed mechanical properties. Findings of this study can be directly used in future to construct more advanced and sophisticated models of geopolymer and will be instrumental in designing the synthesis condition for geopolymer with superior mechanical properties.
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Safari, Samira. "Early-age mechanical properties and electrical resistivity of geopolymer composites." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/13379.
Full textAbstract:
Cement-less and/cement-like geopolymer mortars were made with pulverised fuel ash (PFA) or ground granulated blast furnace slag (GGBS) activated by alkali with different alkali moduli (AM) and alkali dosage (AD). Once synthesised the samples were cured at 20°C and 70°C up to 28 days. The flexural and compressive strengths of these samples at early ages up to 28 days were tested conforming to BS EN196-1:2005. The electrical resistivity of these materials was monitored using a set of non-contacting electrodes to the age up to 7 days to characterise the geopolymerisation process from a physical phenomenon point of view. The effects of AD and AM on the early-age mechanical strengths and electrical resistivity of geopolymer materials were examined from the experimental results. The correlation between strength development and electrical resistivity was studied. The geopolymerisation process was characterised by a 5-stage model, based on electrical resistivity, analogue to hydration process of Portland cement. This research therefore proposes an alternative method for characterisation of geopolymerisation of geopolymers different from traditional methods based on chemistry. It is expected that such a physical phenomenon model will be better accepted by structural engineers for better promotion of usage of geopolymer composites, a type of low carbon and more sustainable binder-based materials, in construction.
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Zhang, Mo. "Geopolymer, Next Generation Sustainable Cementitious Material − Synthesis, Characterization and Modeling." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/455.
Full textAbstract:
Geopolymers have received increasing attention as a promising sustainable alternative to ordinary Portland cement (OPC). However, the relationship among the synthesis, geopolymerization process, microstructures, molecular strucutres and mechanical properties of geopolymers remains poorly understood. To fill this knowledge gap, this dissertation focuses on the correlation of chemical composition-reaction kinetics-microstructure-mechanical properties of geopolymers. This study also sheds light on the durability, environmental impact and engineering applications of geopolymers from practical perspectives. The first part of this dissertation presents a comprehensive study on red mud-class F fly ash based geopolymers (RFFG). Firstly, RFFG with a high 28-day mechanical strength were successfully synthesized under the ambient condition of 23°C and 40 to 50% relative humidity. A nominal Na/Al molar ratio of 0.6 ~ 0.8 with a Si/Al ratio of 2 was found to be a good starting chemical composition for RFFG synthesis. Secondly, the reaction kinetics and its relation to the mechanical properties of RFFG were investigated by monitoring the development of geopolymer gels, reaction rate, porosity and mechanical properties of RFFG samples cured at room temperature, 50°C and 80°C for up to 120 days. The asymmetric stretching FTIR band of Si-O-T (T is Si or Al) centered around 960-1000 cm-1, which is the characteristic band of geopolymer gels, was observed to shift to a lower wavenumber at the early stage of the synthesis and shift to a higher wavenumber later on during the synthesis. The shift of Si-O-T band indicates that the geopolymerization took place in three stages: dissolution to Al-rich gels at Stage I, Al-rich gels to Si-rich gels at Stage II and Si-rich gels to tectosilicate networks at Stage III. The mechanical strength of RFFG barely increased, increased slowly by a limited amount and developed significantly at these three stages, respectively. An elevated curing temperature enhanced the early strength of RFFG, whereas an excessively high curing temperature resulted in a higher pore volume that offset the early-developed strength. Lastly, the remaining mechanical properties of the RFFG samples after soaking in a pH = 3.0 sulfuric acid solution for up to 120 days and the concentration of heavy metals leached from RFFG samples after the soaking were measured. The RFFG samples’ resistance against sulfuric acid was found to be comparable to that of OPC, and leaching concentrations of heavy metals were much lower than the respective EPA limits for soil contaminations. The degradation in mechanical properties of the RFFG samples during soaking in the acid was attributed primarily to the depolymerization and dealumination of geopolymer gels. The second part of this dissertation is devoted to the investigation of nano-scale mechanical properties and molecular structures of geopolymer gels with grid-nanoindentation and molecular modeling. Four phases (e.g., porous phase, partially developed geopolymer gels, geopolymer gels and unreacted metakaolin or crystals) and their nano-mechanical properties were identified in metakaolin based geopolymers (MKG) with grid-nanoindentation technique. It was found that the proportion of geopolymer gels largely determines the mechanical strength of the resulting geopolymers while other factors (e.g., pores and cracks) also play some roles in macro-scale mechanical strength of geopolymers. The final setting time of the geopolymers increased with the increase in Si/Al ratio and the decrease in Na/Al ratio, while the proportion of geopolymer gels and macro-mechanical strength of geopolymers increased with the increase in both Si/Al and Na/Al molar ratios, within the range of 1.2~1.7 and 0.6~1.0, respectively. In the molecular modeling, a combined density function theory (DFT)-molecular dynamic (MD) modeling simulation was developed to “synthesize� geopolymers. DFT simulation was used to optimize reactive aluminate and silicate monomers, which were subsequently used in reactive MD simulations to model the polymerization process and computationally synthesize geopolymer gels. The influence of Si/Al ratio and simulation temperatures on geopolymerization and resulting molecules of geopolymer gels was also examined. The computationally polymerized molecular structures of geopolymer gels were obtained. The distribution of Si4(mAl) and radial distribution fuctions of Si-O, Al-O, O-O and Na-Al for the models were compared and qualitatively agreed well with the experimental results from nuclear magnetic resonance (NMR) and neutron/X-ray pair distribution function in previous literature. Three polymerization stages: oligomerization, ring formation and condensation, were identified based on the nature of polymerization process, which were found to be affected by the temperature and Si/Al ratio. A higher temperature enhanced the reaction rate while a lower Si/Al ratio resulted in more compact geopolymer networks. The final part of this dissertation presents an experimental feasibility study of using geopolymer in shallow soil stabilization, in which a lean clay was stabilized with MKG at different concentrations. The study confirmed that MKG can be used as a soil stabilizer for clayey soils and the unconfined compressive strength, Young’s modulus and failure strain are comparable to or even better than OPC when the MKG’s concentration is higher than 11%. The binding effect of geopolymer gels on the soil particles was confirmed as the main mechanism for the improvement in mechanical properties of the stabilized soils with the scanning electron microscopy imaging, energy dispersive X-ray spectroscopy analyses and X-ray diffractometry characterization.
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Alanazi, Hani Mohammed. "Explore Accelerated PCC Pavement Repairs Using Metakaolin-Based Geopolymer Concrete." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27633.
Full textAbstract:
In order to adopt geopolymer concrete as a pavement repair material due to its better durability, splitting and slant shear tests are performed. Effect of curing time, degradation of the pavement concrete under different acid conditions on the bond strength of geopolymer with conventional concrete, and comparison of the metakaolin geopolymer with other pavement repair materials are analyzed. It was found curing time affects the interface bond strength greatly and the interface bond strength degrades quickly in an acid environment. Effect of molar ratio of SiO2/Na2O, calcium aluminate cement, and slag on early strength of the geopolymer have been studied. It was found molar ratio of SiO2/Na2O of 1.0 gave the highest early strength in 24 hours. Also, freeze-thaw durability of geopolymer concrete are investigated by exposing the specimens to rapid freeze-thaw cycles. Based on these research results, adopting metakaolin geopolymer in accelerated PCC pavement repairs is a feasible option.
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Chen, Rui. "Bio Stabilization for Geopolymer Enhancement and Mine Tailings Dust Control." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/319999.
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The first part of the thesis investigates the enhancement of fly ash-based geopolymer with alkali pretreated sweet sorghum fiber. The unconfined compression, splitting tensile and flexural tests were conducted to investigate the mechanical properties of geopolymer composite. The results indicate that the inclusion of sweet sorghum fiber slightly decreases the unconfined compressive strength (UCS), however, the splitting tensile and flexural strengths as well as the post-peak toughness increase with the fiber content up to 2% and then decrease thereafter. A durability test program containing 10 wet/dry cycles was performed to evaluate the long-term performance of the geopolymer composite related to wet/dry cycling. The results indicate that both the UCS and the splitting tensile strength of the geopolymer composite progressively decrease with the number of wet/dry cycles. The second part of the thesis investigates the utilization of biopolymers to stabilize MT for dust control. First, a fall cone method was adopted to evaluate the Atterberg limits and undrained shear strength of MT stabilized with biopolymers. The results indicate that the inclusion of biopolymers increases both the liquid limit and the undriained shear strength of MT. Two new equations are proposed for predicting the undrained shear strength of MT based on liquid limit and water content, and liquidity index. Second, an experimental program including moisture retention, wind tunnel and surface strength tests was performed to evaluate the effectiveness of biopolymer stabilization for dust control. The results indicate that biopolymers are effective in enhancing the moisture retention capacity, improving the dust resistance, and increasing the surface strength of MT. Third, a durability test program containing 10 wet/dry cycles was applied to MT samples treated with biopolymer solutions of different concentrations. The results show that the dust resistance of MT samples progressively decreases with the number of wet/dry cycles. Finally, experimental and numerical studies on the unconfined compressive strength (UCS) of MT stabilized with biopolymer were carried out. It is found that inclusion of biopolymer into MT favors the increase of adhesion between MT particles and thus the increase of the UCS of MT.
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Paija, Navin. "FEASIBILITY STUDY OF USING GROUND BOTTOM ASH IN GEOPOLYMER CONCRETE." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2134.
Full textAbstract:
AN ABSTRACT OF THE THESIS OF NAVIN PAIJA, for the Master of Science degree in CIVIL ENGINEERING, presented on 04/06/2017, at Southern Illinois University Carbondale. FEASIBILITY STUDY OF USING GROUND BOTTOM ASH IN GEOPOLYMER CONCRETE MAJOR PROFESSOR: Dr. Sanjeev Kumar Dr. Manoj K. Mohanty United States alone has about three quarters of the accessible worldwide reserve of coal. There are about 511 coal-powered electric plants and generates about 33% of the nation’s electricity. The combustion of coal results in a large number of solid waste materials known as coal combustion byproducts (CCBs) that are stored in landfill or ponds. These are easily accessible and with proper research it can be put into beneficial use. Today concrete is the second most consumed substance after water. Concrete, a composite material made of a binder in combination with coarse and fine aggregate, is used in foundations and structures of buildings, bridges, roads, dams. Cement is the most widely used binder for concrete, however, research has shown that a single cement industry produces approximately 5% of global CO2 emissions, and one ton of Portland cement emits approximately one ton of CO2. This emission of CO2 is one of the main reasons for global warming and has detrimental impacts on environment. The possibility of using fly ash and bottom ash as an alternative to cement as a binder to produce sustainable concrete is investigated in this study. The process of geopolymerization includes the reaction of ash and an alkali activated solution made of diluted sodium silicate and sodium hydroxide. The initial objective of this study was to produce fly ash geopolymer concrete which has a strength comparable to that of cement concrete. However, later the possibility of bottom ash as a binder material for geopolymer production was also studied. During this study, the strength of conventional mortar with 10%, 20%, and 30% cement replacement with fly ash and bottom ash was experimented and compared with strength of cement mortar. The test results showed that with increase in the fly ash and bottom ash replacement the strength of the mortars decreased, moreover, the mortars that was replaced by bottom ash produced better results than that of the fly ash replacement. Also, the effect of increase in the ratio of sodium silicate to sodium hydroxide ratio on the strength of geopolymer mortar is studied. Sodium silicate to sodium hydroxide ratio of 1.5, 2.5, and 3 is used in this ratio, and the test results showed that with the increase in this ratio the compressive strength of geopolymer mortar also increased. Similarly, different combinations of fly ash and bottom ash is used to produce geopolymer mortars. The results showed that geopolymer mortar with higher bottom ash content produced better results. The effect of ground fly ash and bottom ash on the compressive strength of geopolymer mortar is also studied. The test result showed that with increase in fineness of fly ash and bottom ash, there was slight improvement in the strength.
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Rahman, Muhammad Motiur. "Geopolymer concrete columns subjected to axial load and biaxial bending." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/1410.
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This thesis focuses on the behaviour of fly ash based geopolymer concrete columns under axial load and biaxial bending. Tests showed that failure load of columns increased with the increase of concrete compressive strength and longitudinal reinforcement ratio, and decreased with the increase of load eccentricity. Use of the Bresler’s reciprocal load formula with an iterative procedure for slender columns in uniaxial bending conservatively predicted the strength of the test columns.
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Khan, Musaad Zaheer Nazir. "Development of Ambient Cured High-Strength Fiber Reinforced Geopolymer Composites." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75405.
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This research focused on the development of high-strength and ductile geopolymer composites cured in ambient conditions, followed by characterization of the material properties under quasi-static, dynamic, and multiaxial stress conditions. The research findings encourage using geopolymer materials in actual constructions and applications requiring high-energy absorption capacity. The research data also provides significant input for developing the corresponding material model for predicting the behaviour of structures made of geopolymer materials subjected to static and dynamic loads.
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Deb, Partha Sarathi. "Properties of Geopolymer Concrete Using Ultrafine Fly Ash and Nanosilica." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75529.
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This study investigated the effects of ultrafine fly ash and nanosilica in geopolymers cured at room temperature. It was found that the optimum percentages of ultrafine fly ash and nanosilica with fly ash alone or that blended with 15% GGBFS or 10% OPC significantly improved strength and durability of geopolymers. The properties of geopolymer improved by enhancement of the hydrated phases and microstructure that reduced porosity.
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Karmokar, Trijon R. "Tensile performance of cast-in headed anchors in geopolymer concrete." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2023. https://ro.ecu.edu.au/theses/2657.
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Geopolymer concrete is an ecofriendly alternative to normal concrete and its use in construction industry is growing due to the increased awareness of global warming. The relationships between the mechanical properties, such as the compressive strength, elastic modulus and mode I fracture energy of geopolymer concrete are not similar to those of normal concrete; these are specifically important for the prediction of the tensile capacity of structural anchors in a concrete substrate. As there are limited studies on the fracture energy of ambient-temperature cured geopolymer concrete, experiments are conducted to study the fracture energy and compressive strength of geopolymer concrete and compare the results with the respective properties of normal concrete. The results show that the ambient-temperature cured geopolymer concrete provides approximately 85% lower fracture energy than normal concretes of comparable compressive strengths. Based on the experimental results, a new fracture energy prediction equation is proposed for ambient-temperature cured geopolymer concrete.
In the current research study, the tensile behaviour of cast-in headed anchors in ambient-temperature cured geopolymer concrete is studied using the results of over 100 experimental tests and over 90 numerical simulations. There are 3 sets of experiments on anchors, which are differentiated based on the mix design of concrete. In each set of experiments, cast-in headed anchors of sizes 1.3T, 2.5T and 5T are embedded at effective embedment depths of 40 mm, 70 mm and 90 mm. In addition to the above sets, anchors of 2.5T and 5T sizes at embedment depths of 40 mm and 70 mm are also installed in normal concrete for comparison purposes. The difference in the capacity of anchors due to the variations in fracture energy of geopolymer concretes of the same compressive strength as well as the influence of anchor head size ratio is investigated using experimental tests.
Numerical simulations are used to complement and expand the results from the experimental study. Nonlinear Finite-Element analyses are conducted to study the influence of surface cracking of the substrate material and the effect of anchor head profile on the tensile capacity of anchors.
The experimental and numerical results are compared with two of the currently available prediction models namely: Concrete Capacity Design (CCD) and Linear Fracture Mechanics (LFM) models. It is shown that on average, the CCD model overestimated the tensile capacities by 10% to 40%, depending on the anchor embedment depth, and the LFM model accurately predicted the capacity of anchors at 40 mm embedment depth, and underestimated the results by 40% at 90 mm embedment depth.
In comparison to similar anchors embedded in a normal concrete of a comparable compressive strength, the capacity of anchors in geopolymer concrete is on average 35% lower. Hence, new modification factors are proposed to extend the application of CCD and LFM models to anchors installed in geopolymer concrete. The modification factors are validated using 60 numerical simulations whereby the effective embedment depth ranges between 40 mm and 180 mm.
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Harb, Ramzi. "Asymmetric metakaolin-based geopolymer membranes for microfiltration: synthesis and first characterizations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
In this preliminary study, metakaolin-based geopolymer samples were synthesized. For the synthesis of support samples, casting and pressing shaping methods were considered. Moreover, the deposition of a layer by dipping was carried out. Support and selective layer samples produced by casting were made of an aqueous sodium silicate solution, sodium hydroxide, foaming and stabilizing agents, as well as metakaolin precursor, and supports obtained by pressing involved the addition of solid-state anhydrous sodium metasilicate and water to the metakaolin precursor. Both pressed and cast samples were cured at 70°C for 24h and then left at room temperature for 6 days. Initial characterization experiments were conducted on the support samples. Concerning pressed samples, increases in both pressure loads and water concentrations led to increases in their mechanical performance, and decreases in their hydraulic permeabilities and total open porosities. It was therefore concluded that increases in both pressure load and water content leads to a higher compaction of the sample prepared, resulting in lower open porosity and higher mechanical properties. The study of porosity and pore size distribution has revealed that the pressed support pressed sample with 12% of water content at 2 MPa has an open porosity of 40% and a modal pore size value of 23.45 µm and meets the typical porosity of a ceramic membrane support. Results concerning cast samples were less satisfying with respect to pressed samples.The addition of foaming agents resulted in a heterogeneous distribution of pores. The addition of stabilizing agent improved the formation of a more homogeneous pore size distribution. An increase in liquid/precursor ratio led to an increase of the total open porosity. Finally, the slurry prepared with a high liquid/precursor ratio (L/P > 100) proved to produce a selective layer with a thickness of about 100 μm and a relatively good adhesion.
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Król, Maciej R. "Studies of concrete properties based on geopolymer binders : PhD thesis summary." Rozprawa doktorska, [s.n.], 2017. http://dlibra.tu.koszalin.pl/Content/1039.
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Nath, Pradip. "Study of fly ash based geopolymer concrete cured in ambient condition." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/190.
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This research studied the properties of concrete using fly ash geopolymer as a low-emission alternative of Portland cement. Inclusion of small quantity of additives enabled curing in normal ambience eliminating the need for elevated heat. Mixtures suitable for curing in ambient condition were found that provided the setting time, workability and strength comparable to those of traditional cement concrete. Blending of additives with fly ash resulted in enhanced engineering and durability properties of geopolymer concrete.
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Olivia, Monita. "Durability related properties of low calcium fly ash based geopolymer concrete." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/506.
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Geopolymer material using by-products can lead to a significant reduction of the carbon footprint and have positive impact on the environment. Geopolymer is recognized as an alternative construction material for the Ordinary Portland Cement (OPC) concrete. The mechanical properties of geopolymer concrete are superior for normal exposure environments. In terms of durability in the seawater, a limited number of publications were available. The seawater environment contains chloride ions and microorganisms that are harmful for reinforced concrete structures. Hence, a study of the durability of fly ash geopolymer concrete is essential when this material is to be used in a real application. The present study aims to investigate the durability of fly ash geopolymer concrete mixture in a seawater environment such as seawater resistance and corrosion of steel reinforcement bars. The development of mixtures and their mechanical properties were also presented.The concrete mixtures were developed using the Taguchi optimization method. Three mixtures, labelled T4, T7, T10 and a control mix were investigated further. Mechanical properties such as compressive strength, tensile strength, flexural strength, Young’s Modulus of Elasticity were determined for each mix. In addition the water absorption/AVPV and drying shrinkage were also measured. The seawater resistance study comprises chloride ion penetration, change in strength, change in mass, change in Young’s Modulus of Elasticity, change in effective porosity and change in length. The corrosion performance of steel reinforcement bars in fly ash geopolymer concrete was determined by measuring the corrosion potential by half-cell potential, accelerated corrosion test by impressed voltage method and microbiologically influenced corrosion incorporating algae. The microstructure of the samples was also investigated using SEM and microscope.It can be summarized that the fly ash geopolymer concrete has an equivalent or higher strength than the OPC concrete. The seawater resistance revealed a high chloride ion penetration into the fly ash geopolymer concrete due to lack of a chloride binding ability and continuous hydration under aqueous medium. The geopolymer concrete had a higher strength and small expansion following exposure to wetting-drying cycles. There was a rapid depassivation of steel reinforcement bars in fly ash geopolymer concrete, although it has a smaller corrosion rate than the OPC concrete. This could delay the pressure in generating cracks in the concrete cover which is not favourable in the long term, due to a sudden loss of load carrying capacity. A novel study on the corrosion performance in algae medium demonstrated a risk of steel bar corrosion in fly ash geopolymer concrete due to the low alkalinity of this concrete. It can be concluded that the low calcium fly ash geopolymer offers some advantages in durability for reinforced concrete in seawater environments.
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Cheema, Didar Singh. "Low calcium fly ash based geopolymer concrete: Long term durability properties." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/2146.
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Alkaline activated low-calcium fly ash geopolymer (LCFG) was investigated for durability compared to conventional concrete. The investigation involved simulated laboratory testing mimicking the severe field environments and in-situ field observations of commercially produced culverts. Laboratory test data: pore structure, porosity, chloride diffusion, scaling, strength and electrochemical testing supported and explained the observed field data. Research investigated the impact of slag and reinforcing pre-treatment. Geopolymer binder being non-cement one using by-products, can be significantly sustainable.
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Alomayri, Thamer Salman. "Development and characterization of cotton and cotton fabric reinforced geopolymer composites." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/2388.
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Sustainable geopolymer composites reinforced with natural cotton fibres have been developed and their mechanical and durability properties are evaluated in this research. Results showed that the mechanical properties (flexural strength, flexural modulus, fracture toughness, compressive strength, impact strength and hardness) of woven cotton fabric-reinforced geopolymer composites were superior to those of geopolymer composites with short cotton fibres. Exposure to water and elevated temperatures (200 to 1000°C) severely reduced the mechanical properties of the composites.
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Soltaninaveh, Kaveh. "The properties of geopolymer concrete incorporating red sand as fine aggregate." Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/2481.
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Concrete is the most common building material in the world and its use has been increasing during the last century as the need for construction projects has escalated. Traditionally, concrete uses Ordinary Portland Cement (OPC) as binder, water as the activator of cement and aggregate. Finding an appropriate replacement for traditional concrete is a desirable solution to obviate the environmental problems caused by cement production. The use of fly ash as a partial replacement for Portland cement is a method to maintain the properties of concrete and reduce the need for cement. Fly ash is a by-product from coal-fired power plants and is abundantly available. The percentage of cement replacement can be varied according to application and mix design. One of the potential materials to substitute for conventional concrete is geopolymer concrete (introduced by Davidovits in 1979). Geopolymer concrete is an inorganic alumino-silicate polymer synthesized from predominantly silicon, aluminum and byproduct materials such as fly ash. Geopolymer properties have been investigated for several years and it is still a major area of interest among researchers and industry partners as it does not contain cement and uses fly ash and alkali liquids as binders to produce a paste to consolidate aggregates. Furthermore, the aggregate comprises a substantial portion of concrete. Including coarse and fine aggregates it is normally obtained from natural sources. Fine aggregate in Australia is usually mined from sand quarries. As the demand for concrete production increases, more natural sand is needed. The need for fine aggregate should be addressed in an environmentally friendly manner, considering the diminishing sources of natural sand. Red sand is a by-product generated from the manufacture of alumina from bauxite by the Bayer process.Previous studies on properties of red sand have shown that it has the potential to be used in concrete as a fine aggregate. While the use of red sand in traditional concrete has been investigated by some researchers, no research has been reported regarding the use of this by-product in manufacturing geopolymer concrete. This research looks into the replacement of natural sand fine aggregates with red sand in geopolymer concrete. Initially, an extensive series of mixtures was prepared and tested. The objective of the research was to identify the salient parameters affecting the properties of geopolymer concrete when natural sand is replaced by red sand. At the next stage, attempts were made to enhance the mechanical and durability features of red sand geopolymer concrete. The final stage consisted of testing red sand geopolymer concrete to find out the various properties of this novel construction material.
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Soltaninaveh, Kaveh. "The properties of geopolymer concrete incorporating red sand as fine aggregate." Curtin University of Technology, Curtin Engineering Faculty, Department of Civil Engineering, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=115093.
Full textAbstract:
Concrete is the most common building material in the world and its use has been increasing during the last century as the need for construction projects has escalated. Traditionally, concrete uses Ordinary Portland Cement (OPC) as binder, water as the activator of cement and aggregate. Finding an appropriate replacement for traditional concrete is a desirable solution to obviate the environmental problems caused by cement production. The use of fly ash as a partial replacement for Portland cement is a method to maintain the properties of concrete and reduce the need for cement. Fly ash is a by-product from coal-fired power plants and is abundantly available. The percentage of cement replacement can be varied according to application and mix design. One of the potential materials to substitute for conventional concrete is geopolymer concrete (introduced by Davidovits in 1979). Geopolymer concrete is an inorganic alumino-silicate polymer synthesized from predominantly silicon, aluminum and byproduct materials such as fly ash. Geopolymer properties have been investigated for several years and it is still a major area of interest among researchers and industry partners as it does not contain cement and uses fly ash and alkali liquids as binders to produce a paste to consolidate aggregates. Furthermore, the aggregate comprises a substantial portion of concrete. Including coarse and fine aggregates it is normally obtained from natural sources. Fine aggregate in Australia is usually mined from sand quarries. As the demand for concrete production increases, more natural sand is needed. The need for fine aggregate should be addressed in an environmentally friendly manner, considering the diminishing sources of natural sand. Red sand is a by-product generated from the manufacture of alumina from bauxite by the Bayer process.Previous studies on properties of red sand have shown that it has the potential to be used in concrete as a fine aggregate. While the use of red sand in traditional concrete has been investigated by some researchers, no research has been reported regarding the use of this by-product in manufacturing geopolymer concrete. This research looks into the replacement of natural sand fine aggregates with red sand in geopolymer concrete. Initially, an extensive series of mixtures was prepared and tested. The objective of the research was to identify the salient parameters affecting the properties of geopolymer concrete when natural sand is replaced by red sand. At the next stage, attempts were made to enhance the mechanical and durability features of red sand geopolymer concrete. The final stage consisted of testing red sand geopolymer concrete to find out the various properties of this novel construction material.
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Novotný, Radoslav. "Chemická kotva do zdiva na bázi rychletuhnoucích geopolymerních pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2012. http://www.nusl.cz/ntk/nusl-216862.
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The aim of this work is to develope fast-setting geopolymeric binders applicable in the chemical wall clamp. This clamping systems are big trend because of easy application, ability to transfer big forces and short setting time. Binders of this systems are based on polymeric resin. Their raw materials are expensive, toxic and flammable substances. Based on this consideration an anorganic fast-setting geopolymeric binder was developed. This binders consist of mixture of metakaolin and precipitated silica activated by potassium hydroxide. Binder were characterized by suitable analytic methods (XRD, SEM, DTA). The results of this metods were used for optimalization of binder properties.
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Zheng, Yong Chu. "Shrinkage behaviour of geopolymer." 2009. http://repository.unimelb.edu.au/10187/7157.
Full textAbstract:
Geopolymer cements offer an alternative to, and potential replacement for, ordinary Portland cement (OPC). Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. There is already a considerable amount of work and research conducted on geopolymers in the past decades, and it is now possible to implement this technology commercially. However, to ensure that geopolymer becomes commercially available and able to be used in the world, further understanding of its ability to provide durable and long lasting materials is required. One main property which is still relatively unexplored compared to other properties is its shrinkage properties. The objective of this thesis is therefore to examine the shrinkage of geopolymers and factors which might influence it.The factors which influence geopolymer strength were investigated as being the factors which may influence shrinkage. The selection of the activating solution is an important factor in forming the final product of a geopolymer. Activating solution SiO2/Na2O ratio is determined to be an important influence on the shrinkage of geopolymer. SEM images of the samples enable observation of the sample topology and microstructure. An important observation was the existence of a ‘knee point’ which also occurs in OPC shrinkage. The ‘knee point’ is the point where the shrinkage goes from rapid shrinkage to slow shrinkage. From SEMs it is noted that the samples past the knee point are shown to have a smoother topology which means it is more reacted.
Autogenous shrinkage is an important issue for OPC containing a high amount of silica, and is also a key factor in geopolymer shrinkage. Autogenous shrinkage is tested by keeping samples in a sealed environment where water lost to drying is kept to a minimum. It is noted that sealing and bagging the samples reduces the shrinkage considerably. The water to cement ratio, which is an important factor in OPC shrinkage, is also explored for the case of geopolymers. Water content plays an important role in determining early stage shrinkage, and has little to no effect on the later stage shrinkage. The water loss from the samples during drying on exposure to environment is noted and compared. The addition of more water did not necessary means that more water was lost.
Addition of slag is known to be beneficial to geopolymers by giving early structural strength and faster setting time. Commercial geopolymer concrete will also include the use of slag. However, the addition of slag up to a certain extent gives a deleterious affect on shrinkage.
A different type of Class F fly ash source with different composition data was used to see its effect on shrinkage, with only a slight influence observed between the two ashes tested. Fly ash was also ground for different lengths of time before use in geopolymerization, with grinding for less than 12 hours giving higher shrinkage than an unground sample, but shrinkage the decreasing with grinding for 18 or 24 hours. This initial higher shrinkage has been attributed to the mechanism of grinding which resulted in unevenly shaped fly ash particles taking up a larger initial volume resulting in higher shrinkage. The sample grinded for 24 hours showed higher shrinkage due to the particle size to be so fine that agglomerates may have form during mixing which would result in a lower reaction rate which increases the shrinkage. Elevated curing temperatures also reduce geopolymer shrinkage.
Thus, it is clear that the shrinkage of geopolymers is influenced by a wide range of variables, and more notably by a few important variables: activating solution ratio, addition of water, grinding and bagging. The shrinkage of geopolymers can be correlated to the strength to a certain extent. However, the understanding of the shrinkage of geopolymers is still at a very initial phase, and further research is required.
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Lin, Jia-Jyun, and 林家均. "Geopolymer as Aggragate of CLSM." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2698kz.
Full textAbstract:
碩士國立臺北科技大學
土木工程系土木與防災碩士班
106
Taiwan has poor terrain geological conditions,which included serious scouring problems, whenever the heavy rain, there’s large number of sediment from top to the bottom into the downstream reservoir, resulting serious siltation, affecting the life time of the reservoir. So the maintenance of the reservoir must be effective dredging, and dredging produces a lot of silt. How to consume these sludge, need to face the subject for the current urgent.In this study, used the recovered sludge was taken as the main solid raw material, and some fly ash was added to make Geopolymer, and it’s mechanical properties were discussed.It is also tried simulating an solid model with Geopolymer by the unbaked sludge of watery,at the same time.Because it’s strength isn’t expected,so the targer is placed in a non-structural product.CLSM doesn’t need high strength,in order to slove the current problems of late strength is too high in our country,this study attempts to break up the consolidated reservoir sludge with Geopolymer into aggragate, making CLSM instead of gravel.The results show that they conform to domestic regulations.The strength is below the upper limit of 90 kgf/cm2,showing nice potential.
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Acharya, Indra Prasad. "Synthesis and Characterization of Geopolymers as Construction Materials." Thesis, 2014. http://etd.iisc.ac.in/handle/2005/2988.
Full textAbstract:
Geopolymers are a relatively new class of materials that have many broad applications, including use as substitute for ordinary Portland cement (OPC), use in soil stabilisation, fire resistant panels, refractory cements, and inorganic adhesives. Geopolymers are an alternative binder to Portland cement in the manufacture of mortars and concrete, as its three-dimensional alumino silicate network develops excellent strength properties. Use of geopolymers in place of ordinary Portland cement is also favoured owing to the possible energy and carbon dioxide savings. Geopolymer is typically synthesized by alkali activation of pozzolanas at moderate temperatures (< 1000C).
The focus of the thesis is synthesis and characterization of geopolymers as construction materials. In this context, the role of compositional factors, such as, pozzolana type (fly ash, kaolinite, metakaolinite, ground granulated blast furnace slag, red soil), alkali (sodium hydroxide is used in this study) activator concentration, Si/Al (Si= silicon, Al = aluminium) ratio of the pozzolana and environmental factors, namely, curing period and temperature are examined. Besides synthesizing geopolymers that could be an alternate to concrete as construction material, sand-sized aggregates were synthesized using geopolymer reactions. This was done as river sand is becoming scarcer commodity for use as construction material.
Several compositional and environmental factors were varied in geopolymer synthesis in order to identify the optimum synthesis conditions that yield geopolymers with maximum compressive strength. Besides varying external (compositional and environmental) factors, the role of internal microstructure in influencing the compressive strength of the geopolymer was examined. Micro-structure examinations were made using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) studies.
The studies on compositional and environmental factors in geopolymer synthesis brought out several interesting results. The results firstly brought out that amongst the pozzolanas studied, ASTM class F fly ash is most suited for maximum compressive strength mobilization upon geopolymer reactions. Moderate temperature (75-1000C) was adequate to mobilize large compressive strengths. Room temperature curing needed more than 7 days before the pozzolana-NaOH paste began to develop strength. Curing period of 56 days was needed for the geopolymer to develop significant strength (19.6MPa). A similar range of compressive strength could be developed by the pozzolana-NaOH paste upon curing for 3 days at 1000C. Likewise curing the pozzolana-NaOH paste at temperatures > 1000C led to reduction in compressive strength from shrinkage and breakage of bonds. A caustic soda (NaOH) concentration of 10 M was adequate to develop maximum compressive strength of the geopolymer. Caustic soda concentrations in excess of 10 M did not result in further improvement of strength. The Si/Al ratio also contributes to strength mobilization. The Si/Al ratio of the geopolymer was enhanced by mixing commercially obtained silica gel with the pozzolana. Maximum strength mobilization was observed at Si/Al ratio = 2.45 corresponding to 6.5 % silica gel addition to the pozzolana (on dry mass basis). Comparing compressive strengths of geopolymers with varying silica gel contents, geopolymer specimens with least water content and largest dry density did not exhibit maximum compressive strength indicating that the physico-chemical (bond strength, micro-structure) played a pivotal role than physical parameters (dry density, water content) in dictating the strength of the geopolymer. MIP results showed that bulk of the porosity in fly ash geopolymer specimens is contributed by macro pores and air voids. Geopolymerization leads to bulk consumption of cenospheres in fly ash and forms polymerized matrix with network of large pores. After geopolymerization, all the main characteristic peaks of Al–Si minerals observed in fly ash persisted, suggesting that no new major crystalline phases were formed.
Presence of small amount of inorganic contaminants in fly ash can drastically reduce the strength of the fly ash geopolymer. For example, 5-20 % presence of red soil reduces the strength of fly ash geopolymer by 16 to 59 %. Presence of unreacted clay coupled with less porous structure is responsible for the reduction in compressive strength of fly ash geopolymer subjected to red soil addition.
MIP studies with geopolymers also revealed that there is good bearing between compressive strengths and maximum intruded volume (from MIP test) of geopolymers. For example, fly ash geopolymer specimen exhibits highest total intruded volume (0.3908 cc/g) and largest compressive strength of 29.5 MPa, while red soil geopolymer specimen exhibit least intruded volume (0.0416 cc/g) and lowest compressive strength (5.4 MPa). Further, analysis showed that specimens with larger airvoids+macropores volume had larger compressive strength, suggesting that geopolymers with more porous microstructure develop larger compressive strength. All geopolymer specimens exhibited tri-modal nature of pores i.e. macro-pore mode (entrance pore radius: 25-5000 nm), mesopore mode (entrance pore radius: 1.25 to 25 nm) and air void mode (entrance pore radius >5000 nm). The micro pores (entrance pore radius < 1.25 nm) do not contribute to porosity of the geopolymer specimens.
Sand particles prepared from geopolymer reactions (FAPS or fly ash geopolymer sand) predominated in medium sized (2mm to 0.425 mm) sand particles. Their particle size distribution characteristics (uniformity coefficient and coefficient of curvature) classified them as poorly graded sand (SP). Dissolution, followed by polymerization reactions led to dense packing of the Si–O–Al–O– units that imparted specific gravity of 2.59 to FAPS particles which is comparable to that of river sand (2.61). Dissolution in strongly alkaline medium imparted strongly alkaline pH (12.5) to the FAPS particles. The river sand is characterized by much lower pH (7.9). Despite being characterized by rounded grains, the FAPS particles mobilized relatively high friction angle of (35.5o) than river sand (∅ = 28.9o).
The river sand-mortar (RS-M) and fly ash geopolymer sand-mortar (FAPS-M) specimens developed similar 28-day compressive strengths, 11.6 to 12.2 MPa. Despite its higher water content, FAPS-mortar specimens developed similar compressive strength and initial tangent modulus (ITM) as river sand-mortar specimens. The FAPS-M specimen is more porous (larger intruded volume) with presence of larger fraction of coarser pores. Total porosity is majorly contributed by macro-pores (67.92%) in FAPS-M specimen in comparison to RS-M specimen (macro-pores = 33.1%).
Mortar specimens prepared from FAPS and river sand exhibit similar pH of 12.36 and 12.4 respectively. FAPS-mortar specimens have lower TDS (1545 mg/L) than river sand-mortar specimens (TDS = 1889 mg/L). The RS-M and FAPS-M specimens exhibit leachable sodium levels of 0.001 g Na/g RS-M and 0.007 g Na/g-FAPS-M respectively in the water leach tests. The larger leachable sodium of FAPS-M specimen is attributed to residual sodium hydroxide persisting in the FAPS even after washing. The ultra-accelerated mortar bar test (UAMBT) shows that the percentage expansion of FAPS-M and RS-M specimens are comparable and range between 0.07 to 0.08 %.
44
Acharya, Indra Prasad. "Synthesis and Characterization of Geopolymers as Construction Materials." Thesis, 2014. http://etd.iisc.ernet.in/handle/2005/2988.
Full textAbstract:
Geopolymers are a relatively new class of materials that have many broad applications, including use as substitute for ordinary Portland cement (OPC), use in soil stabilisation, fire resistant panels, refractory cements, and inorganic adhesives. Geopolymers are an alternative binder to Portland cement in the manufacture of mortars and concrete, as its three-dimensional alumino silicate network develops excellent strength properties. Use of geopolymers in place of ordinary Portland cement is also favoured owing to the possible energy and carbon dioxide savings. Geopolymer is typically synthesized by alkali activation of pozzolanas at moderate temperatures (< 1000C).
The focus of the thesis is synthesis and characterization of geopolymers as construction materials. In this context, the role of compositional factors, such as, pozzolana type (fly ash, kaolinite, metakaolinite, ground granulated blast furnace slag, red soil), alkali (sodium hydroxide is used in this study) activator concentration, Si/Al (Si= silicon, Al = aluminium) ratio of the pozzolana and environmental factors, namely, curing period and temperature are examined. Besides synthesizing geopolymers that could be an alternate to concrete as construction material, sand-sized aggregates were synthesized using geopolymer reactions. This was done as river sand is becoming scarcer commodity for use as construction material.
Several compositional and environmental factors were varied in geopolymer synthesis in order to identify the optimum synthesis conditions that yield geopolymers with maximum compressive strength. Besides varying external (compositional and environmental) factors, the role of internal microstructure in influencing the compressive strength of the geopolymer was examined. Micro-structure examinations were made using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) studies.
The studies on compositional and environmental factors in geopolymer synthesis brought out several interesting results. The results firstly brought out that amongst the pozzolanas studied, ASTM class F fly ash is most suited for maximum compressive strength mobilization upon geopolymer reactions. Moderate temperature (75-1000C) was adequate to mobilize large compressive strengths. Room temperature curing needed more than 7 days before the pozzolana-NaOH paste began to develop strength. Curing period of 56 days was needed for the geopolymer to develop significant strength (19.6MPa). A similar range of compressive strength could be developed by the pozzolana-NaOH paste upon curing for 3 days at 1000C. Likewise curing the pozzolana-NaOH paste at temperatures > 1000C led to reduction in compressive strength from shrinkage and breakage of bonds. A caustic soda (NaOH) concentration of 10 M was adequate to develop maximum compressive strength of the geopolymer. Caustic soda concentrations in excess of 10 M did not result in further improvement of strength. The Si/Al ratio also contributes to strength mobilization. The Si/Al ratio of the geopolymer was enhanced by mixing commercially obtained silica gel with the pozzolana. Maximum strength mobilization was observed at Si/Al ratio = 2.45 corresponding to 6.5 % silica gel addition to the pozzolana (on dry mass basis). Comparing compressive strengths of geopolymers with varying silica gel contents, geopolymer specimens with least water content and largest dry density did not exhibit maximum compressive strength indicating that the physico-chemical (bond strength, micro-structure) played a pivotal role than physical parameters (dry density, water content) in dictating the strength of the geopolymer. MIP results showed that bulk of the porosity in fly ash geopolymer specimens is contributed by macro pores and air voids. Geopolymerization leads to bulk consumption of cenospheres in fly ash and forms polymerized matrix with network of large pores. After geopolymerization, all the main characteristic peaks of Al–Si minerals observed in fly ash persisted, suggesting that no new major crystalline phases were formed.
Presence of small amount of inorganic contaminants in fly ash can drastically reduce the strength of the fly ash geopolymer. For example, 5-20 % presence of red soil reduces the strength of fly ash geopolymer by 16 to 59 %. Presence of unreacted clay coupled with less porous structure is responsible for the reduction in compressive strength of fly ash geopolymer subjected to red soil addition.
MIP studies with geopolymers also revealed that there is good bearing between compressive strengths and maximum intruded volume (from MIP test) of geopolymers. For example, fly ash geopolymer specimen exhibits highest total intruded volume (0.3908 cc/g) and largest compressive strength of 29.5 MPa, while red soil geopolymer specimen exhibit least intruded volume (0.0416 cc/g) and lowest compressive strength (5.4 MPa). Further, analysis showed that specimens with larger airvoids+macropores volume had larger compressive strength, suggesting that geopolymers with more porous microstructure develop larger compressive strength. All geopolymer specimens exhibited tri-modal nature of pores i.e. macro-pore mode (entrance pore radius: 25-5000 nm), mesopore mode (entrance pore radius: 1.25 to 25 nm) and air void mode (entrance pore radius >5000 nm). The micro pores (entrance pore radius < 1.25 nm) do not contribute to porosity of the geopolymer specimens.
Sand particles prepared from geopolymer reactions (FAPS or fly ash geopolymer sand) predominated in medium sized (2mm to 0.425 mm) sand particles. Their particle size distribution characteristics (uniformity coefficient and coefficient of curvature) classified them as poorly graded sand (SP). Dissolution, followed by polymerization reactions led to dense packing of the Si–O–Al–O– units that imparted specific gravity of 2.59 to FAPS particles which is comparable to that of river sand (2.61). Dissolution in strongly alkaline medium imparted strongly alkaline pH (12.5) to the FAPS particles. The river sand is characterized by much lower pH (7.9). Despite being characterized by rounded grains, the FAPS particles mobilized relatively high friction angle of (35.5o) than river sand (∅ = 28.9o).
The river sand-mortar (RS-M) and fly ash geopolymer sand-mortar (FAPS-M) specimens developed similar 28-day compressive strengths, 11.6 to 12.2 MPa. Despite its higher water content, FAPS-mortar specimens developed similar compressive strength and initial tangent modulus (ITM) as river sand-mortar specimens. The FAPS-M specimen is more porous (larger intruded volume) with presence of larger fraction of coarser pores. Total porosity is majorly contributed by macro-pores (67.92%) in FAPS-M specimen in comparison to RS-M specimen (macro-pores = 33.1%).
Mortar specimens prepared from FAPS and river sand exhibit similar pH of 12.36 and 12.4 respectively. FAPS-mortar specimens have lower TDS (1545 mg/L) than river sand-mortar specimens (TDS = 1889 mg/L). The RS-M and FAPS-M specimens exhibit leachable sodium levels of 0.001 g Na/g RS-M and 0.007 g Na/g-FAPS-M respectively in the water leach tests. The larger leachable sodium of FAPS-M specimen is attributed to residual sodium hydroxide persisting in the FAPS even after washing. The ultra-accelerated mortar bar test (UAMBT) shows that the percentage expansion of FAPS-M and RS-M specimens are comparable and range between 0.07 to 0.08 %.
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Chen, Zih-Cian, and 陳子謙. "Engineering Properties of Composite Geopolymer Mortar." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/5q6e4w.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
100
In this study, the slag and metakaolin which contain rich elements of silica and aluminium were used to manufacture three types of composite geopolymer: Type A (70% metakaolin and 30% slag), Type B (30% metakaolin and 70% slag) and Type C (100% slag). Both the sodium hydroxide and sodium silicate solution were used as the activators. Type A composite geopolymer uses three water glass moduli of 0.6, 0.8 and 1.0, three concentrations of alkali activator (11, 13 and 15%) and three water-to-solid ratios (0.55, 0.60 and 0.65), while Types B and C use the water glass moduli of 0.6 and 0.7, the e amount of alkali activator of 9% and 7%, and the water-to-solid ratios of 0.45 and 0.33, respectively. The engineering properties of flowability, initial and final setting times and polymerization temperature at the fresh state and the compressive strength, dynamic elastic and shear moduli, ultrasonic pulse speed, dry shrinkage and thermal properties at hardened for Type A composited geopolymer were studied. But only the engineering properties at hardened state for Types B and C were investigated. The results of study show that: 1. The flowablity of Type A composite geopolymer increases with the increase of the concentration of activator and water-to-solid ratio to reach a best flowability ratio of 125%. The increase of water glass modulus and activator concentration and decrease of water-to-solid ratio tend to reduce the setting times and increase the polymerization temperature with a shortest final setting time of 1.8 hours and a highest temperature of 81oC. 2. The dynamic elastic and shear moduli, ultrasonic pulse speed and thermal conductivity of Types A, B and C geopolymer increase with the increase of sand content with 15%, 96%, 74%, and 11%, 110%, 73%, and 21%, 16%, 9%, and 100%, 48%, 65%, respectively. But both the compressive strength and dry shrinkage decrease with the increase of sand content with 23%, 10%, 22%, and 74%, 35%, 62%, respective. 3. Type A composite geopolymer exhibits a state of uniform shrinkage, but Types B and C show a state of uneven shrinkage.
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Huang, Chiu-sung, and 黃秋松. "Development of Clay Bricks Adding Geopolymer." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/w555ph.
Full textAbstract:
碩士國立臺北科技大學
土木與防災研究所
100
The raw material of the traditional clay bricks is clay. They are manufactured by mixing and compacting into blocks, and after drying out then put into a 900 ~ 1000℃ brick furnace for few days. The compressive strength of regular clay bricks is about 300 kgf/cm2. A recent developed material, namely geopolymer, has performed quite well in replacing adhesive materials such as cement and epoxy. The present research is attempting to add a certain percentage of the geopolymer into clay. It is expected that the temperature and the duration of the furnace can be reduced to achieve or increase the strength of clay brick in order to save energy. The results showed that when the ratio of kaolin used in the geopolymer and clay was 1:1, the compressive strength could be up to 383kgf/cm2 even under room temperature. Further put it under temperature of 300 °C for one hour, the compressive strength was increased to 430 kgf/cm2, the increment is approximately 12.27%. While increase the ratio to 1:6, the compressive strength was 23kgf/cm2 under room temperature, and calcinated 12 hours under temperature of 1000℃, its compressive strength jumped to 213 kgf/cm2, with a increment of 826%. It is seemed that the heat energy required is much lower than the traditional clay bricks, revealing the potential of saving energy and carbon dioxide..
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Hsieh, Yi-Jui, and 謝宜叡. "Fire resistance Investigation of foamed Geopolymer." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/4ej676.
Full textAbstract:
碩士國立臺北科技大學
土木工程系土木與防災碩士班
104
The present research added aluminum powder to the geopolymer to form an uniformly distributed pores. It would not only help in reducing the weight, but also effectively isolating the heat and hopefully would satisfy the requirement of CNS12514-1 specification. A preliminary study was made by taking the ratio of aluminum powder as well as the times of mixing as parameters. 20cm hollow cylinder were made to testify the performance in forming and cracking process and a data bank was established accordingly. Improve the heating device to regulate the heating curve by the standard test body internally heated to high temperatures, measured one hour in vitro test measuring the temperature of the non-heated surface. The results showed that the mixture was stirred for 15 minutes and section was Notch, the test inside the most uniform pore distribution, thermal insulation effect is the best. The outer side of any position does not exceed a temperature 200℃, the average temperature has not exceeded 160℃, regulatory compliance requirements have practical application value filling fire doors.
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"New Nanostructured Aluminosilicates from Geopolymer Chemistry." Doctoral diss., 2015. http://hdl.handle.net/2286/R.I.28552.
Full textAbstract:
abstract: Geopolymers, a class of X-ray amorphous, ceramic-like aluminosilicate materials are produced at ambient temperatures through a process called geopolymerization. Due to both low energy requirement during synthesis and interesting mechanical and chemical properties, geopolymers are grabbing enormous attention. Although geopolymers have a broad range of applications including thermal/acoustic insulation and waste immobilization, they are always prepared in monolithic form. The primary aim of this study is to produce new nanostructured materials from the geopolymerization process, including porous monoliths and powders.
In view of the current interest in porous geopolymers for non-traditional applications, it is becoming increasingly important to develop synthetic techniques to introduce interconnected pores into the geopolymers. This study presents a simple synthetic route to produce hierarchically porous geopolymers via a reactive emulsion templating process utilizing triglyceride oil. In this new method, highly alkaline geopolymer resin is mixed with canola oil to form a homogeneous viscous emulsion which, when cured at 60 °C, gives a hard monolithic material. During the process, the oil in the alkaline emulsion undergoes a saponification reaction to decompose into water-soluble soap and glycerol molecules which are extracted to yield porous geopolymers. Nitrogen sorption studies indicates the presence of mesopores, whereas the SEM studies reveals that the mesoporous geopolymer matrix is dotted with spherical macropores. The method exhibits flexibility in that the pore structure of the final porous geopolymers products can be adjusted by varying the precursor composition.
In a second method, the geopolymerization process is modified to produce highly dispersible geopolymer particles, by activating metakaolin with sodium silicate solutions containing excess alkali, and curing for short duration under moist conditions. The produced geopolymer particles exhibit morphology similar to carbon blacks and structured silicas, while also being stable over a wide pH range.
Finally, highly crystalline hierarchical faujasite zeolites are prepared by yet another modification of the geopolymerization process. In this technique, the second method is combined with a saponification reaction of triglyceride oil. The resulting hierarchical zeolites exhibit superior CO2-sorption properties compared to equivalent commercially available and currently reported materials. Additionally, the simplicity of all three of these techniques means they are readily scalable.Dissertation/Thesis
Doctoral Dissertation Chemistry 2015
49
邱俊萍. "Geopolymer Produced Using Blast Furnace Slag." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/73726583962801188322.
Full textAbstract:
碩士國立臺北科技大學
材料及資源工程系碩士班
90
Blast furnace slag is formed in the process of pig iron manufacture from iron ore, combustion residue of coke, fluxes and other materials. Generally, the way to utilize granulated blast furnace slag is to partially replace Portland cement. There are at least 4 million tons/year granulated blast furnace slag used in Taiwan. Granulated blast furnace slag is a non-toxic material, and can be a good raw material to making high-value geopolymer for fire resistance utilization. Geopolymers, a kind of inorganic polymers, have been gradually got attention of the world as potentially revolutionary materials. Similar to natural zeolite minerals, geopolymer is a class of three-dimensionally networked alumino-silicate materials. The aim of this research work is trying to fabricate a granulated blast furnace slag-based geopolymer for fire-resistance purpose and hope to understand the mechanism of geopolymerisation. Granulated blast furnace slag has been used for the active filler to make geopolymer in this research work. It was found that using metakaolinte as the inactive filler, the geopolymer have obtained the best physical and mechanical properties. For fire resistant tests, a 10 mm thick geopolymer panel exposed to a 1100℃ flame, the measured back-side temperatures only reach 240℃ after 35 minutes. The products can be fabricated for construction purposes and have great application potential.
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Chiu, Wei-Ting, and 邱緯婷. "Development of FA/GGBFS Geopolymer Concrete." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/5e48n3.
Full textAbstract:
碩士國立臺北科技大學
土木工程系土木與防災碩士班
106
Iron blast-furnace slag is a by-product produced by the steel plant during the iron making process, and fly ash is a major by-product of coal-fired power plants. Every year, a large amount of blast-furnace slag and fly ash produced. With great difficulty, if it is disposed of as waste, it will not only be environmentally unfriendly, but will also cost a lot of costs. If blast-furnace slag is water-quenched cooling, grinding into fine powder and adding to concrete can replace part of the cement, it is generally considered that the concrete can be made denser and the durability is increased. The same is true for fly ash, which saves cement consumption. However, in order to make fuller and more efficient use of waste resources, this study attempted to produce geopolymer based on fly ash and blast-furnace slag, it is expected to develop cement-free concrete. According to the experimental results, a slurry of fly ash and geopolymer material ratio of 1, the strength of it can be up to 253.9 kgf/cm2 in 28 days. A slurry of blast-furnace slag and geopolymer material ratio of 1 and the performance is better, the strength of it can be up to 578.2 kgf/cm2. However, when gravel was separately added to make fly ash and blast-furnace slag geopolymer concrete specimens, the 28-day strength was only 148.8 kgf/cm2 and 229.7 kgf/cm2, respectively. It is initially known that the key factors may be in the gradation of coarse aggregates and will be discussed in subsequent research.