Letteratura scientifica selezionata sul tema "Geopolymer (GEO)"
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Articoli di riviste sul tema "Geopolymer (GEO)":
1
Et. al., P. Suresh Chandra,. "Dynamic and Analysis of A Geo-Polymer Concrete Structure". INFORMATION TECHNOLOGY IN INDUSTRY 9, n. 2 (21 marzo 2021): 55–61. http://dx.doi.org/10.17762/itii.v9i2.303.
Abstract (sommario):
The standard portland cement (OPC) was traditionally used as the binding agent in concrete. However it is also important to find alternative emissions-free concrete binding agents to reduce environmental damage caused by cement manufacturing. Geopolymers, also known as inorganic polymers, use byproducts like fly ash rather than cement. Recent studies have shown that geopolymer concrete based on fly ash has enough properties for use. As the geopolymer strength mechanism is different from the OPC binder, an appropriate constituent model for geopolymer concrete must be obtained in order to predict the load-deflection behavior and strength of geopolymer concrete structural components. A number of problems faced with today's cement industry are addressed by geopolymer binders. These binders have similar or better engineering qualities in comparison with cement and can use many types of waste materials.
This project describes the seismic analysis of buildings with high-rise structures, the model of residential G+10 buildings with traditional concrete and geopolymer concrete properties is modelled and analysis is carried out using the response spectra method considering the position of the building in zone III, this analysis would generate the effect of higher vibration modes and real force distribution in elastic range. Test results include maximum story shifts, maximum story drifts, story shears and story stiffness, and an efficient lateral load resistance system, helping to establish whether geo-polymer concrete can be used in high-rise building construction as dynamic loads are included in the high-rise structures
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Kavya, M. Sri, R. Satyanarayana, N. Vamshi Krishna, T. Jayanth e G. Prem Kumar. "Experimental Investigation of Mechanical Properties of Geo–Polymer Concrete Using Flyash". International Journal for Research in Applied Science and Engineering Technology 12, n. 4 (30 aprile 2024): 2769–74. http://dx.doi.org/10.22214/ijraset.2024.60513.
Abstract (sommario):
Abstract: Geopolymer concrete (GPC) is a new material in the construction industry, with different chemical compositions and reactions involved in a binding material. The pozzolanic materials (industrial waste like fly ash, ground granulated blast furnace slag (GGBS), and rice husk ash), which contain high silica and alumina, work as binding materials in the mix. Geopolymer concrete is economical, low energy consumption, thermally stable, easily workable, ecofriendly, cementless, and durable. GPC reduces carbon footprints by using industrial solid waste like slag, fly ash, and rice husk ash. Around one tons of carbon dioxide emissions produced one tons of cement that directly polluted the environment and increased the world’s temperature by increasing greenhouse gas production. For sustainable construction, GPC reduces the use of cement and finds the alternative of cement for the material’s binding property. So, the geopolymer concrete is an alternative to Portland cement concrete and it is a potential material having large commercial value and for sustainable development in Indian construction industries. The comprehensive survey of the literature shows that geopolymer concrete is a perfect alternative to Portland cement concrete because it has better physical, mechanical, and durable properties. Geopolymer concrete is highly resistant to acid, sulphate, and salt attack. Geopolymer concrete plays a vital role in the construction industry through its use in bridge construction, high-rise buildings, highways, tunnels, dams, and hydraulic structures, because of its high performance. It can be concluded from the review that sustainable development is achieved by employing geopolymers in Indian construction industries, because it results in lower CO2 emissions, optimum utilization of natural resources, utilization of waste materials, is more cost-effective in long life infrastructure construction, and, socially, in financial benefits and employment generation.
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Sai Ketana, Nutakki, V. Srinivasa Reddy, M. V. Seshagiri Rao e S. Shrihari. "Mathematical model for predicting stress-strain behavior of low calcium fly-ash based geopolymer concrete". E3S Web of Conferences 309 (2021): 01103. http://dx.doi.org/10.1051/e3sconf/202130901103.
Abstract (sommario):
The focus of the study was to identify the stress strain behavior of geo polymer concrete and salient parameters that influence the mixture proportions and the properties of low calcium fly ash- based geo polymers concrete. To develop geopolymer concrete the chemical proportions are alkaline liquid solution/fly-ash ratio=0.5, Sodium silicate/sodium hydroxide ratio=2.5,16M NaOH and SiO2/Na2O ratio=2.0. The geopolymer concrete mixes have shown improved stress values for the same strain levels compared to that of controlled concrete mix. Normalized stress strain curves are used to compare the behaviours of geopolymer concrete. It can be observed that geopolymer concrete has improved strains for the same stress when compared to conventional concrete. Geopolymer concrete mixes have shown improved stress values for the same strain levels compared to that of controlled concrete mixes.
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Uthayakumar, Marimuthu, Ponnambalam Balamurugan, Kinga Korniejenko, Szymon Gądek e Dariusz Mierzwiński. "Abrasive water jet machining of fly ash and metakaolin based geo-polymers". MATEC Web of Conferences 322 (2020): 01020. http://dx.doi.org/10.1051/matecconf/202032201020.
Abstract (sommario):
In the present study, the abrasive water jet machining (AWJM) of geopolymers prepared from fly ash, metakaolin and sand is discussed. The samples were prepared from sodium promoter, fly ash / metakaolin and sand. The process of activation was made using a 10M sodium hydroxide solution combined with a sodium silicate solution (the ratio of liquid glass - 1:2.5). To produce geopolymers, flakes of technical sodium hydroxide were used and an aqueous solution of sodium silicate (R-145) with a molar module of 2.5 and a density of around 1.45 g/cm3 the tap water. The alkaline solution was prepared by means of pouring the aqueous solution of sodium silicate over the solid sodium hydroxide. The solution was mixed and left until its temperature stablised and the concentrations equalised, which took around 2 hours. The fly ash, sand and alkaline solution were mixed for around 10 minutes using a low-speed mixing machine (in order to obtain a homogeneous paste). The paste was allowed to dry in the shade. The paper investigates the AWJM studies on the prepared geopolymer specimens with varyied input parameters such as standoff distance (1.2 and 3 mm), water pressure (120, 140 and 160 MPa) and feed rate (5, 10 and 15 mm/min). The output parameters such as kerf angle and material removal rate (MRR) were studied with the varying combination of input parameters. From the results, the optimal parameters for machining the geopolymer composites were interpreted.
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Reddy, Gadikota Chennakesava, e KHK Reddy. "Strength and Durability Studies of Geo-Polymer Concrete in the presence of Marine Water". IOP Conference Series: Earth and Environmental Science 1280, n. 1 (1 dicembre 2023): 012022. http://dx.doi.org/10.1088/1755-1315/1280/1/012022.
Abstract (sommario):
Abstract Geopolymer concrete represents an innovative and eco-friendly alternative to conventional concrete, with the potential to significantly reduce the carbon footprint of the construction industry. Extensive research has explored the strength and durability properties of both geopolymer concrete and control concretes made with ordinary Portland cement. Compared to its traditional counterpart, geopolymer concrete exhibits a substantially lower carbon footprint by utilizing industrial byproducts - namely fly ash and ground granulated blast furnace slag (GGBS) - as replacements for traditional cement. The present study synthesized geopolymer concrete mixes using Class F fly ash alongside alkaline activators. Following heat-curing at 75°C for 24 hours, the geopolymer concrete had cured, enabling subsequent strength and durability testing to proceed. A comprehensive tests assessed key parameters including compressive strength, sulphate resistance, acid resistance, water absorption, and chloride ion permeability. Test results demonstrated that the inclusion of fly ash and GGBS to synthesize geopolymer concrete significantly enhanced the acid resistance and overall durability compared to control concretes, in addition to reducing the carbon footprint. The outcomes highlight the promise of geopolymer concrete as a sustainable construction material that retains mechanical strength while enhancing durability.
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Al-Ghouti, Mohammad A., Mariam Khan, Mustafa S. Nasser, Khalid Al Saad e OON Ee Heng. "Application of geopolymers synthesized from incinerated municipal solid waste ashes for the removal of cationic dye from water". PLOS ONE 15, n. 11 (5 novembre 2020): e0239095. http://dx.doi.org/10.1371/journal.pone.0239095.
Abstract (sommario):
In this study, municipal solid waste bottom ash (MSW-BA) and fly ash (MSW-FA) were used as a source of aluminosilicate to prepare geopolymer (GEO) adsorbents (GEO-MSWBA and GEO-MSWFA) for the removal of methylene blue (MB) from water. The effects of temperature, pH, and initial concentration on the MB adsorption onto GEO-MSWBA and GEO-MSWFA were evaluated. The adsorption isotherms parameters and thermodynamics were also determined. Detailed physical and chemical characterizations of the prepared adsorbents were carried out to further understand their impact on MB adsorption. The results from the scanning electron microscopy revealed a uniform granule-sphere like structure on both prepared geopolymers, which would facilitate the MB adsorption onto the adsorbents. The X-ray diffraction allowed observation of the microstructural transformations that occur after the alkaline activation. The surface areas of the GEO-MSWBA and the GEO-MSWFA were recorded as 32.78 m2/g and 4.5 m2/g, respectively. From the Fourier transform infrared, a stretching vibration of the aluminosilicate tetrahedral was observed, which indicated the success of geopolymerization. The prepared geopolymers showed a high capability of MB adsorption from an aqueous solution. The adsorption process was best suited and explained using the Langmuir isotherm model with a maximum adsorption capacity of 666.7 mg/g for the GEO-MSWBA (at 25°C) and 769.2 mg/g for the GEO-MSWFA (at 35°C). The positive value of the enthalpy (ΔHo) for the GEO-MSWBA suggested the reaction favored endothermic reaction while the negative value of entropy (ΔSo) indicated a solid/liquid random interaction. On the other hand, the negative ΔHo value for the GEO-MSWFA indicated the reaction followed an exothermic reaction causing energy to be released, the positive ΔSo value indicated a good affinity at the solid-liquid surface. The overall negative value for Gibbs free energy (ΔGo) for both adsorbents suggested the adsorption was spontaneous and feasible. It was also inferred that n- π interaction, direct and indirect hydrogen bond, and electrostatic interaction between the MB and the prepared geopolymers facilitated the adsorption process. The current study shows that the GEO-MSWBA and the GEO-MSWFA have a great potential of removing MB as a cationic dye from water without performing any sort of laborious pretreatments.
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Ndagi, Abubakar, e Mohd Saleh Jaafar. "Geo-Polymer Binder as Portland Cement Alternative: Challenges, Current Developments and Future Prospects". Jurnal Kejuruteraan 31, n. 2 (31 ottobre 2019): 281–86. http://dx.doi.org/10.17576/jkukm-2019-31(2)-12.
Abstract (sommario):
Ordinary Portland Cement (OPC), a material which built the world is now devastating it. Environmental impact has raised concerns over its continued usage while its multifaceted problems are also biting the production companies hard. Hence, alternative geopolymer binder has demonstrated excellent properties to stand ordinary Portland cement even though it is still being faced with technical drawbacks. Therefore, these paper reviews attempt made on improving discoveries and understanding about proper implementation of geopolymer binder. The geopolymer binder is curable at ambient temperature by the use of Fly Ash/Ground Granulated Blast Furnace Slag (GGBS) blend. This has been an alternative have been discovered for cheaper activating solutions rather than the expensive Sodium Hydroxide/Sodium Silicate solution. However, various of chemical composition known as Supplementary Cementitious Materials (SCMs) still an issues to fabricate a geopolymer binder.
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Subaer, Subaer, Hamzah Fansuri, Abdul Haris, Misdayanti, Resky Irfanita, Imam Ramadhan, Yulprista Putri e Agung Setiawan. "Pervaporation Membranes for Seawater Desalination Based on Geo–rGO–TiO2 Nanocomposites. Part 1: Microstructure Properties". Membranes 11, n. 12 (8 dicembre 2021): 966. http://dx.doi.org/10.3390/membranes11120966.
Abstract (sommario):
This is the first of two papers about the synthesis and microstructure properties of the Geo–rGO–TiO2 ternary nanocomposite, which was designed to suit the criteria of a pervaporation membrane for seawater desalination. The performance and capability of Geo–rGO–TiO2 as a seawater desalination pervaporation membrane are described in the second paper. A geopolymer made from alkali-activated metakaolin was utilized as a binder for the rGO-TiO2 nanocomposite. A modified Hummer’s method was used to synthesize graphene oxide (GO), and a hydrothermal procedure on GO produced reduced graphene oxide (rGO). The adopted approach yielded high-quality GO and rGO, based on Raman spectra results. The nanolayered structure of GO and rGO is revealed by Transmission Electron Microscopy (TEM) images. The Geo–rGO–TiO2 ternary nanocomposite was created by dispersing rGO nanosheets and TiO2 nanoparticles into geopolymer paste and stirring it for several minutes. The mixture was then cured in a sealed mold at 70 °C for one hour. After being demolded, the materials were kept for 28 days before being characterized. Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD) measurements revealed that the geopolymer matrix efficiently bonded the rGO and TiO2, creating nanocomposites. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) was used to examine the morphology of the outer layer and cross-sections of nanocomposites, and the results displayed that rGO were stacked on the surface as well as in the bulk of the geopolymer and will potentially function as nanochannels with a width of around 0.36 nm, while TiO2 NPs covered the majority of the geopolymer matrix, assisting in anti-biofouling of the membranes. The pores structure of the Geo–rGO–TiO2 were classified as micro–meso pores using the Brunauer–Emmet–Teller (BET) method, indicating that they are appropriate for use as pervaporation membranes. The mechanical strength of the membranes was found to be adequate to withstand high water pressure during the pervaporation process. The addition of rGO and TiO2 NPs was found to improve the hyropobicity of the Geo–rGO–TiO2 nanocomposite, preventing excessive seawater penetration into the membrane during the pervaporation process. The results of this study elucidate that the Geo–rGO–TiO2 nanocomposite has a lot of potential for application as a pervaporation membrane for seawater desalination because all of the initial components are widely available and inexpensive.
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Rathour, Toshan Singh. "Strength and Durability of Geo-Polymer Concrete with Mineral Admixture". International Journal for Research in Applied Science and Engineering Technology 10, n. 1 (31 gennaio 2022): 770–75. http://dx.doi.org/10.22214/ijraset.2022.39899.
Abstract (sommario):
Abstract: It is important to durable of structure and reduce co2 emission through the greater use of substitute of cement. The use of supplementry cementitious materials as partial replacement for the cement in concrete will play a significant role with respect to the environmental control of greenhouse and global temperature reduction. The development of geopolymer concrete (GPC) processing of geopolymer using black rice husk ash, GGBS in combination with sodium hydroxide and sodium silicate solutions, offers a promising alternative to ordinary portland cement concrete. This study compares the different ratio of black rice husk ash to GGBS where50:50 60:40 40:60 ratios and differing the molarities of alkaline solutions which are 8m , 10m and 12m and comparing the strength of the above ratios and conducting durability characteristics of fly ash and GGBS based geopolymer concrete by conducting test procedure like compressive strength , split tensile strength test, sorpitivity test. Keywords: Geo-polymer concrete ,Black rice husk ash (BRHA),Ground granulated blast furnace slag (GGBS).
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Srivathsav, Bitla, N. Prem Kumar, S. Shrihari e C. Vivek Kumar. "Proposed mathematical model for stress- strain behaviour of geopolymer concrete". E3S Web of Conferences 309 (2021): 01053. http://dx.doi.org/10.1051/e3sconf/202130901053.
Abstract (sommario):
In the present study, appropriate analytic stress-strain mathematical model is developed that can capture the real (observable) stress-strain behaviour of geo polymer concrete. The geo polymer concrete mixes have shown improved stress values for the same strain levels compared to that of controlled concrete mix in M20 grade. The analytical equations for the stress-strain response of conventional and geopolymer concrete mixes have been proposed in the form of y = Ax / (1+Bx+Cx2), both for ascending and descending portions of the curves with different set of values for constants. The proposed equations have shown good correlation with experimental values. The proposed empirical equations can be used as stress block in analyzing the flexural behavior of sections of controlled and geo polymer concrete. The stress-strain curves obtained in the experiment for M20 & G20 grades of controlled and geo polymer concrete exhibit a similar trend when compared to the empirical equations of modified Saenz model. So Saenz mathematical model is successfully evaluated and validated for geopolymer concrete.
Tesi sul tema "Geopolymer (GEO)":
1
Lee, William K. "Solid-gel interactions in geopolymers". Connect to thesis, 2002. http://repository.unimelb.edu.au/10187/1071.
Abstract (sommario):
This is partly because the requirements for such an ultimate material change with people’s perception about its properties as well as its environmental impact. Thus, the once-believed ultimate Portland cement binder is now becoming unacceptable for a number of reasons including poor durability as well as severe environmental impact during production. Thus, an improved mineral binder is required by modern society to serve the same purposes as the existing Portland cement binder, as well as to reduce the current environmental impact caused by Portland cement production.Geopolymerisation is such a ‘green’ technology capable of turning both natural ‘virginal’ aluminosilicates and industrial aluminosilicate wastes, such as fly ash and blast furnace slag, into mechanically strong and chemically durable construction materials. However, the source materials for geopolymer synthesis are less reactive than Portland cement clinkers and the chemical compositions of these source materials can vary significantly. Consequently, product quality control is a major engineering challenge for the commercialisation of geopolymers.
This thesis is therefore devoted to the mechanistic understanding of the interfacial chemical interactions between a number of natural and industrial aluminosilicates and the various activating solutions, which govern the reactivity of the aluminosilicate source materials. The effects of activating solution alkalinity, soluble silicate dosage and anionic contamination on the reactivity of the aluminosilicate source materials to produce geopolymeric binders, as well as their bonding properties to natural siliceous aggregates for concrete making, are examined. In particular, a new set of novel ‘realistic’ reaction models has been developed for such purposes. These reaction models have been further utilised to develop a novel analytical procedure, which is capable of studying geopolymerisation on ‘real’ geopolymers in situ and in real time. This novel procedure is invaluable for the total understanding of geopolymerisation, which is in turn vital for effective geopolymer mix designs.
2
Ercoli, Roberto. "Chemical neutralization of industrial by-products from the secondary aluminum industry: re-use as foaming agents for the synthesis of geopolymers and monitoring of the hydrogen-rich gas production". Doctoral thesis, Urbino, 2022. http://hdl.handle.net/11576/2698511.
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Reeb, Charles. "Synthèse et caractérisation de composites à base de matériaux alcali-activés incorporant des huiles minérales pour la gestion des huiles tritiées". Electronic Thesis or Diss., Centrale Lille Institut, 2022. http://www.theses.fr/2022CLIL0020.
Abstract (sommario):
Ce travail a pour but le conditionnement des huiles tritiées et s’inscrit dans la problématique des déchets nucléaires sans filière de gestion. La stratégie consiste à directement conditionner des huiles minérales modèles dans des matrices alcali-activés (MAA), également fonctionnalisées avec un piégeur à hydrogène/tritium γ-MnO2/Ag2O. Géopolymères (GEO) et laitiers de hauts fourneaux (LHF) sont considérés comme MAA. En présence de tensioactifs, l’huile est émulsionnée avec succès (gouttelettes fines et homogènes) dans les deux types de MAA. Deux modes d’actions des tensioactifs sont observés agissant par: 1) réduction de la tension interfaciale ou 2) promotion d’interactions huile-particules. Le mécanisme 1 doit être favorisé si l’ouvrabilité des coulis est requise alors que le mécanisme 2 doit être ciblé afin de permettre un meilleur confinement de l’huile grâce aux interactions huile-particules. Après durcissement, des composites MAA-Huile sont obtenus. Il n’y a pas d’influence de l’huile et des tensioactifs sur la prise et le développement des propriétés mécaniques des MAA. Les principaux produits de réaction (C-A-S-H pour LHF et N-A-S-H pour GEO) ne sont pas impactés. Néanmoins, l’addition de tensioactifs entraîne une porosité plus importante à cause de la stabilisation de bulles d’air. Les composites MAA-Huile contenant 20%vol. d’huile ont tous des résistances en compression supérieures à 20 MPa, ce qui est plus que les 8 MPa requis par l’ANDRA. Globalement, en accord avec les observations aux états frais et durci, les GEO possèdent de meilleures performances pour l’immobilisation d’huile que les LHF. L’efficacité du piégeur γ-MnO2/Ag2O a été caractérisée dans les MAA par production d’hydrogène in-situ par irradiations gamma et corrosion du magnésium. Les deux types d’expérience s’accordent sur la meilleure performance de piégeage dans le GEO que dans le LHF. Cela s’explique par la présence d’espèces soufrés réductrices dans le LHF qui réagissent avec les oxydants constituant le piégeur. Finalement, des mesures de mouillabilité ont démontré que les huiles industrielles ont une excellente affinité pour le GEO, démontrant qu’une exposition longue durée à de l’infiltration d’eau ne délogera pas l’huile des composites MAA-Huile. Dans le contexte du traitement des déchets nucléaires, les GEO fonctionnalisés avec un piégeur γ-MnO2/Ag2O semblent être une option intéressante pour le stockage des huiles tritiées. Néanmoins, des études complémentaires doivent être menées au sujet du confinement de l’HTO, ce qui pourrait faire renaitre l’intérêt d’utiliser le LHFThis work deals with the conditioning of tritiated industrial oils in the context of nuclear wastes that are still deprived of an appropriate treatment solution. The strategy consists in directly conditioning model mineral oils in alkali-activated materials (AAM), additionally functionalized with a γ-MnO2/Ag2O hydrogen/tritium getter. Geopolymer (GEO) and alkali-activated blast furnace slag (AABFS) are considered as AAM. In the presence of surfactants, the oil was successfully emulsified (small and homogeneous droplets) in both types of AAM. Two surfactant mechanisms are distinguished acting by: 1) decreasing the interfacial tension or 2) promoting oil-particles interactions. Mechanism 1 should be favored if workability of fresh mixtures is required, while mechanism 2 should be targeted to provide a better confinement of oil owing to strong oil-particles interactions. After curing, AAM-OIL composites are obtained. There is no influence of the oil and surfactants on the setting time and strength development of AAM. The main reaction products (C-A-S-H in AABFS and N-A-S-H in GEO) are not impacted. However, the addition of surfactants leads to increased porosity of AAM due to air bubbles stabilization. AAM-OIL composites immobilizing 20%vol. of oil all have compressive strengths higher than 20 MPa, which is a more than the 8 MPa required from ANDRA. Overall, according to both fresh and hardened states observations, GEO exhibit higher performances for the immobilization of oil than AABFS. The efficiency of the γ-MnO2/Ag2O getter was assessed in AAM via in-situ hydrogen production by gamma irradiations or magnesium corrosion. Both types of experiments agree to the higher performances of the getter in GEO than in AABFS. This is explained by reducing sulfur species present in AABFS, which react with the oxidizing getter components. Finally, wetting measurements demonstrated that industrial oils have an excellent affinity for GEO, testifying that long-term water seepage is not likely to dislodge them from GEO-OIL composites. In the context of nuclear waste management, GEO functionalized with γ-MnO2/Ag2O getter appears as a promising option for disposal of tritiated oils. However, additional investigations of HTO confinement need to be performed that could renew the interest of using AABFS
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Rincón, Acacio. "Development of low cost waste-derived sintered glass-ceramics for energy saving and recovery". Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426371.
Abstract (sommario):
A new technique for the production of cellular glass and glass-ceramics foams is the main goal of the hereby presented research activities. It is based on a combination of alkali-activation of silica-rich materials, with subsequent inorganic gel casting foaming by means of a surfactant and final heat treatment trough sinter-crystallisation process. This new process is less expensive and more environmentally sustainable than the current procedures based on mixtures of glass powders and foaming agents, which decompose and release gases at a temperature significantly above the softening glass point, and is conceived as an alternative route to valorise silica-rich waste materials
The alkali activation of glass waste allows to obtain well-dispersed concentrated suspensions, undergoing gelation by treatment at low temperature (40-80 °C), due to the formation of silicate hydrates. An extensive direct foaming was achieved by mechanical stirring of partially gelified suspensions, also comprising a surfactant. The final microstructure (total amount of porosity, cell size) can be directly correlated with the degree of gelation. A sintering treatment, at only 700 °C, was finally applied to stabilise the structures and limit the leaching of alkaline ions.
The approach proved to be extended to different glasses and industrial waste mixtures leading to different gels after alkali activation. Alkali activation of soda-lime waste glass was exploited through mixing with iron-rich inorganic waste from a copper slag and fly ash from coal combustion. The approach was also extended to different glass-based material coming from waste, such as an alumino-boro-silicate glass from the recycling of pharmaceutical vials, and vitrified bottom ashes from municipal solid waste incinerators. A considerable number of processing parameters combinations (such as surfactants, activating solution, curing times, conditions for heating treatments etc.) were explored and understood.
Apart from waste-derived materials and applications in the building industry, the technique was also applied to create highly porous bioactive glass-ceramics scaffolds; the successful production of highly homogeneous foams proves the versatility in the approach.
The progressive hardening associated with inorganic polymerisation configuring an ‘inorganic gel casting’ has also been used to produce advanced ceramics, such as mullite and cordierite foams and scaffolds. These materials were obtained through the thermal treatment of engineered alkali activated suspensions consisting of a Na-geopolymer enriched with reactive γ-Al2O3 powders in the case of mullite, and reactive γ-Al2O3 and talc in the synthesis of cordierite. The gelation was studied in order to have a proper viscosity for trapping air during vigorous mechanical stirring or maintaining the shape of the scaffold struts obtained by direct ink writing. After the hardened samples were obtained, sodium ions were extracted through ion exchange in ammonium nitrate solution. Finally, the ion-exchanged foams were successfully converted into pure mullite or cordierite foams and scaffolds with the application of a firing treatment.
Alkali activation was the basis for the manufacturing of lightweight granules according to a ‘spheroidisation technique’ consisting in the casting of fine glass powders on a rotary drum, before firing. The hardened suspensions of soda-lime glass obtained from alkaline activation, were reduced into fragments and cast on a rotary drum with dry glass. The firing of green granules was accompanied by a significant foaming, owing to the decomposition of hydrated compounds.L’obiettivo delle attività di ricerca presentate è l’individuazione di una nuova tecnica per la produzione di schiume di vetro e vetroceramiche, basata sulla combinazione di un processo di attivazione alcalina di materiali ricchi di silice e successiva schiumatura del gel inorganico mediante un tensioattivo e un trattamento termico finale mediante sinterizzazione e cristallizzazione (“sinter-crystallisation”). Si tratta di un processo più economico ed ecologicamente sostenibile rispetto alle attuali procedure, basate su miscele di polveri di vetro e agenti schiumogeni, che sono soggette a decomposizione e rilasciano gas a una temperatura significativamente superiore al punto di rammollimento (“softening point”) del vetro. Questa nuova tecnica offre una strategia alternativa per la valorizzazione di materiali di scarto ad alto contenuto di silice. L'attivazione alcalina degli scarti di vetro consente di ottenere sospensioni concentrate ben disperse, le quali subiscono una gelificazione mediante trattamento a bassa temperatura (40-80°C), ascrivibile alla formazione di idrati di silicato. Si è ottenuta una schiumatura diretta ed estesa mediante agitazione meccanica di sospensioni parzialmente gelificate, con l’ausilio di un tensioattivo. La microstruttura finale (livello totale di porosità, dimensione delle celle) può essere direttamente correlata al grado di gelificazione. È stato infine applicato un trattamento di sinterizzazione a soli 700°C, per stabilizzare le strutture e limitare la lisciviazione (“leaching”) di ioni alcalini. È stata dimostrata l’applicabilità di tale approccio a diverse tipologie di vetro e miscele di rifiuti industriali, ottenendo diversi gel in seguito all'attivazione alcalina. L'attivazione alcalina del vetro sodico-calcico di scarto è stata sfruttata attraverso la miscelazione con rifiuti inorganici ricchi di ferro da scorie di rame e ceneri volatili prodotte dalla combustione del carbone. L'approccio è stato esteso anche a diversi materiali a base di vetro provenienti da rifiuti, come il vetro borosilicato proveniente dal riciclaggio di fiale farmaceutiche e ceneri pesanti vetrificate provenienti dagli inceneritori di rifiuti solidi urbani. Sono state esplorate e comprese diverse combinazioni di parametri di processo (tensioattivi, soluzioni di attivazione, tempi di polimerizzazione, condizioni per il trattamento termico ecc.). Oltre che per la creazione di materiali derivati dai rifiuti e l’individuazione di possibili applicazioni nel settore dell'edilizia, la tecnica è stata utilizzata anche per creare scaffold vetroceramici bioattivi altamente porosi, a dimostrazione della versatilità dall'approccio. L'indurimento progressivo associato alla polimerizzazione inorganica che configura un "gel inorganico" è stato inoltre sfruttato per produrre ceramiche avanzate, come schiume e scaffold di mullite e cordierite. Questi materiali sono stati ottenuti mediante il trattamento termico di sospensioni ingegnerizzate attivate alcalinamente, costituite da un geopolimero a base di sodio arricchito con polveri reattive γ-Al2O3, nel caso della mullite, e γ-Al2O3 reattivo e talco, nella sintesi della cordierite. La gelificazione è stata studiata allo scopo di ottenere una viscosità appropriata per intrappolare l'aria in condizioni di vigorosa agitazione meccanica o per mantenere la forma dei filamenti negli scaffold ottenuti mediante stampa diretta. In seguito all’ottenimento dei campioni induriti, sono stati estratti gli ioni di sodio mediante scambio ionico in soluzione di nitrato di ammonio. Infine, le schiume sottoposte a scambio ionico sono state convertite in schiume e scaffold di mullite o cordierite pura con l'applicazione di un trattamento di cottura. L'attivazione alcalina è stata la base di partenza per la produzione di granuli leggeri tramite una "tecnica di sferoidizzazione" che consiste nella aggregazione di polveri di vetro sottili su un tamburo rotante, prima del tratamento termico. Una volta indurite, le sospensioni di vetro sodico-calcico ottenute dall’attivazione alcalina sono state ridotte in frammenti e collocate su un tamburo rotante con polvere di vetro secco. Il tratamento termico dei granuli verdi ha determinato una significativa formazione di schiuma, dovuta alla decomposizione dei composti idrati.
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Forsgren, Johan. "Functional Ceramics in Biomedical Applications : On the Use of Ceramics for Controlled Drug Release and Targeted Cell Stimulation". Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132377.
Abstract (sommario):
Ceramics are distinguished from metals and polymers by their inorganic nature and lack of metallic properties. They can be highly crystalline to amorphous, and their physical and chemical properties can vary widely. Ceramics can, for instance, be made to resemble the mineral phase in bone and are therefore an excellent substitute for damaged hard tissue. They can also be made porous, surface active, chemically inert, mechanically strong, optically transparent or biologically resorbable, and all these properties are of interest in the development of new materials intended for a wide variety of applications. In this thesis, the focus was on the development of different ceramics for use in the controlled release of drugs and ions. These concepts were developed to obtain improved therapeutic effects from orally administered opioid drugs, and to reduce the number of implant-related infections as well as to improve the stabilization of prosthetic implants in bone. Geopolymers were used to produce mechanically strong and chemically inert formulations intended for oral administration of opioids. The carriers were developed to allow controlled release of the drugs over several hours, in order to improve the therapeutic effect of the substances in patients with severe chronic pain. The requirement for a stable carrier is a key feature for these drugs, as the rapid release of the entire dose, due to mechanical or chemical damage to the carrier, could have lethal effects on the patient because of the narrow therapeutic window of opioids. It was found that it was possible to profoundly retard drug release and to achieve almost linear release profiles from mesoporous geopolymers when the aluminum/silicon ratio of the precursor particles and the curing temperature were tuned. Ceramic implant coatings were produced via a biomimetic mineralization process and used as carriers for various drugs or as an ion reservoir for local release at the site of the implant. The formation and characteristics of these coatings were examined before they were evaluated as potential drug carriers. It was demonstrated that these coatings were able to carry antibiotics, bisphosphonates and bone morphogenetic proteins to obtain a sustained local effect, as they were slowly released from the coatings.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 710
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Rees, Catherine Anne. "Mechanisms and kinetics of gel formation in geopolymers". 2007. http://repository.unimelb.edu.au/10187/3330.
Abstract (sommario):
Geopolymer chemistry governs the formation of an X-ray amorphous aluminosilicate cement material. Binders form at ambient temperatures from a variety of different raw material sources, including industrial wastes. Early research in this field was based around investigating binder material properties; however, more recently, geopolymer formation chemistry has been intensively studied. Better understanding of the chemical processes governing geopolymer curing reactions will allow a wider variety of waste materials to be utilised and also the tailoring of binder properties for specific applications. (For complete abstract open document).
Capitoli di libri sul tema "Geopolymer (GEO)":
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Law, D. W., C. Gunasekara e S. Setunge. "Use of Brown Coal Ash as a Replacement of Cement in Concrete Masonry Bricks". In Lecture Notes in Civil Engineering, 23–25. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-3330-3_4.
Abstract (sommario):
AbstractPortland cement production is not regarded as environmentally friendly, because of its associated high carbon emissions, which are responsible for 5% of global emissions. An alternative is to substitute fly ash for Portland cement. Australia has an abundance of brown coal fly ash, as it is the main source of primary energy in the State of Victoria. Currently, the majority of this material is stored in landfills and currently there is no commercial use for it in the cement industry because brown coal fly ash cannot be used as a direct replacement material for Portland cement due to the high sulfur and calcium content and low aluminosilicate content. However, the potential exists to use brown coal fly ash as a geopolymeric material, but there remains a significant amount of research needed to be conducted. One possible application is the production of geopolymer concrete bricks. A research project was undertaken to investigate the use of brown coal fly ash from Latrobe Valley power stations in the manufacture of geopolymer masonry bricks. The research developed a detailed understanding of the fundamental chemistry behind the activation of the brown coal fly ash and the reaction mechanisms involved to enable the development of brown coal fly ash geopolymer concrete bricks. The research identified suitable manufacturing techniques to investigate relationships between compressive strength and processing parameters and to understand the reaction kinetics and microstructural developments. The first phase of the research determined the physical, chemical, and mineralogical properties of the Loy Yang and Yallourn fly ash samples to produce a 100% fly ash-based geopolymer mortar. Optimization of the Loy Yang and Yallourn geopolymer mortars was conducted to identify the chemical properties that were influential in the production of satisfactory geopolymer strength. The Loy Yang mortars were able to produce characteristic compressive strengths acceptable in load-bearing bricks (15 MPa), whereas the Yallourn mortars produced characteristic compressive strengths only acceptable as non-load-bearing bricks (5 MPa). The second phase of the research transposed the optimal geopolymer mortar mix designs into optimal geopolymer concrete mix designs while merging the mix design with the optimal Adbri Masonry (commercial partner) concrete brick mix design. The reference mix designs allowed for optimization of both the Loy Yang and Yallourn geopolymer concrete mix designs, with the Loy Yang mix requiring increased water content because the original mix design was deemed to be too dry. The key factors that influenced the compressive strength of the geopolymer mortars and concrete were identified. The amorphous content was considered a vital aspect during the initial reaction process of the fly ash geopolymers. The amount of unburnt carbon content contained in the fly ash can hinder the reactive process, and ultimately, the compressive strength because unburnt carbon can absorb the activating solution, thus reducing the particle to liquid interaction ratio in conjunction with lowering workability. Also, fly ash with a higher surface area showed lower flowability than fly ash with a smaller surface area. It was identified that higher quantity of fly ash particles <45 microns increased reactivity whereas primarily angular-shaped fly ash suffered from reduced workability. The optimal range of workability lay between the 110–150 mm slump, which corresponded with higher strength displayed for each respective precursor fly ash. Higher quantities of aluminum incorporated into the silicate matrix during the reaction process led to improved compressive strengths, illustrated by the formation of reactive aluminosilicate bonds in the range of 800–1000 cm–1 after geopolymerization, which is evidence of a high degree of reaction. In addition, a more negative fly ash zeta potential of the ash was identified as improving the initial deprotonation and overall reactivity of the geopolymer, whereas a less negative zeta potential of the mortar led to increased agglomeration and improved gel development. Following geopolymerization, increases in the quantity of quartz and decreases in moganite correlated with improved compressive strength of the geopolymers. Overall, Loy Yang geopolymers performed better, primarily due to the higher aluminosilicate content than its Yallourn counterpart. The final step was to transition the optimal geopolymer concrete mix designs to producing commercially acceptable bricks. The results showed that the structural integrity of the specimens was reduced in larger batches, indicating that reactivity was reduced, as was compressive strength. It was identified that there was a relationship between heat transfer, curing regimen and structural integrity in a large-volume geopolymer brick application. Geopolymer bricks were successfully produced from the Loy Yang fly ash, which achieved 15 MPa, suitable for application as a structural brick. Further research is required to understand the relationship between the properties of the fly ash, mixing parameters, curing procedures and the overall process of brown coal geopolymer concrete brick application. In particular, optimizing the production process with regard to reducing the curing temperature to ≤80 °C from the current 120 °C and the use of a one-part solid activator to replace the current liquid activator combination of sodium hydroxide and sodium silicate.
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Wang, Huicong, Jialiang Yao, Yi Lin e Hua He. "Research of Geopolymer Deal with the Strength of Soft Soil and Microstructure Test". In New Developments in Materials for Infrastructure Sustainability and the Contemporary Issues in Geo-environmental Engineering, 204–14. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-95774-6_16.
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Ge, Xiaonan, e Guoping Zhang. "Mechanical Properties of Geopolymers Cured in Saline Water". In New Developments in Materials for Infrastructure Sustainability and the Contemporary Issues in Geo-environmental Engineering, 215–26. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-95774-6_17.
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Provis, John L., Jannie S. J. van Deventer e Grant C. Lukey. "A Conceptual Model for Solid-Gel Transformations in Partially Reacted Geopolymeric Systems". In Advances in Ceramic Matrix Composites X, 47–70. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118408353.ch6.
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Gluth, G. J. G., P. Sturm, S. Greiser, C. Jäger e H. C. Kühne. "One-Part Geopolymers and Aluminosilicate Gel-Zeolite Composites Based On Silica: Factors Influencing Microstructure and Engineering Properties". In Proceeding of the 42nd International Conference on Advanced Ceramics and Composites, 183–96. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2019. http://dx.doi.org/10.1002/9781119543381.ch17.
Atti di convegni sul tema "Geopolymer (GEO)":
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Alanqari, Khawlah, Abdullah Al-Yami e Vikrant Wagle. "Preparation of a Synthetic Geo-Polymer Based LCM Utilizing Saudi Arabian Volcanic Ash for a Sustainable Development: Method, Lab Testing and Applications". In ASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/omae2023-104959.
Abstract (sommario):
Abstract We successfully developed a novel geo-polymer based LCM to treat moderate to severe losses. Geopolymers can be prepared utilizing waste materials such as fly ash. In Saudi Arabia, we have enough volcanic ash to sustain the development of the geo-polymer based LCM. This novel LCM was prepared by utilizing a Saudi Arabian volcanic ash. The volcanic ash particles were activated with an alkali solution to undergo a geo-polymerization reaction. The geo-polymerization was designed to delay and successfully controlled to gel up and form the target geo-polymer barrier after the fluid goes inside the wellbore. This is very important to avoid an early setting of the fluid. The objective of this paper is to discuss the formulation and preparation of the geopolymer barrier as a lost circulation material. Also, to investigate the effect of both the addition amounts and concentration of the activating solution on the final geopolymer physical properties as well as to detail lab testing. Saudi Arabian volcanic ash particles were activated by a mixture of NaOH, sodium silicate and water to develop a geopolymer barrier. In this study, we prepared four different activating solutions by varying the alkali concertation and the addition amounts based on the volcanic ash chemical composition. The effect of these variations on the geo-polymerization in terms of setting time and rheological properties of the final geopolymer barrier were investigated. This was done to develop a geo-polymer barrier with a delayed and controlled setting to assure a right placement inside the wellbore. In addition, the chemical conditions were evaluated to simulate a variety of downhole conditions to prove the effectiveness of this novel geo-polymer composition as an LCM to treat moderate to severe losses. The lab testing includes thickening time, rheology, compressive strength and a chemical analysis of the Saudi Arabian volcanic ash. We found that thickening time and rheological properties of the final geo-polymer barrier are strongly affected by the alkali concentration and the addition amounts of the activating solution. This novel geo-polymer barrier can remain in a liquid phase from a few minutes to several hours based on the desired conditions. The final and target geo-polymer barrier will appear and gel as a solid thereby preventing loss circulation.
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Ren, Xin, e Lianyang Zhang. "The Complete Recycling of Waste Concrete to Produce Geopolymer Concrete". In Geo-Chicago 2016. Reston, VA: American Society of Civil Engineers, 2016. http://dx.doi.org/10.1061/9780784480151.011.
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Clements, Cara, Isabelle Goetz, Ahmadreza Hedayat e Lori Tunstall. "High Temperature Treatment to Improve Hydrolytic Stability of Mine Tailing-Based Geopolymer Bricks". In Geo-Congress 2024. Reston, VA: American Society of Civil Engineers, 2024. http://dx.doi.org/10.1061/9780784485330.011.
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Munthir, Hammad H., e Hasan M. Ahmed Albegmprli. "A Review of Shear Strength of Hybrid Fiber Reinforced Geopolymer Concrete under Ambient Condition". In 3rd International Conference of Engineering Sciences. Switzerland: Trans Tech Publications Ltd, 2023. http://dx.doi.org/10.4028/p-voj8ko.
Abstract (sommario):
Geopolymer is an innovative cement substitute constructed of alkali-activated cementitious materials (AACMs). Researchers interested in improving concrete's structural resistance, toughness, and flexure tensile strength have turned their focus to geo-polymer concrete binders. To completely understand how geopolymer binders act under these circumstances, it is necessary to investigate their behavior when exposed to multiaxial stress states. The purpose of this review is to examine geopolymer cement in depth and to get a better understanding of its mechanical characteristics. In this analysis, we see that Geopolymer concrete, in particular its compressive and tensile strengths, provides higher resilience. GPC is an eco-friendly material since it reduces emissions and requires less water for curing. Incorporating hybrid polypropylene and steel fibers to ternary mixed geopolymer concrete improves its mechanical qualities.
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Sanusi, O., B. Tempest e V. O. Ogunro. "Mitigating Leachability from Fly Ash Based Geopolymer Concrete Using Recycled Concrete Aggregate (RCA)". In Geo-Frontiers Congress 2011. Reston, VA: American Society of Civil Engineers, 2011. http://dx.doi.org/10.1061/41165(397)135.
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Nikvar-Hassani, Arash, e Lianyang Zhang. "Development of a New Geopolymer Based Cementitious Material for Pumpable Roof Supports in Underground Mining". In Geo-Congress 2020. Reston, VA: American Society of Civil Engineers, 2020. http://dx.doi.org/10.1061/9780784482797.032.
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Srinivasula Reddy, M., P. Dinakar, B. Hanumantha Rao, B. K. Satpathy e A. N. Mohanty. "A Study on the Effect of Oxide Compositions on the Compressive Strength Characteristics of Geopolymer Concrete". In Geo-Chicago 2016. Reston, VA: American Society of Civil Engineers, 2016. http://dx.doi.org/10.1061/9780784480151.001.
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Disu, Adedeji A., Prabir Kolay, Vijay Puri e Sanjeev Kumar. "Effect of Polypropylene Fiber and Curing on the Unconfined Compressive Strength of Geopolymer Stabilized Kaolin Clay". In Geo-Congress 2022. Reston, VA: American Society of Civil Engineers, 2022. http://dx.doi.org/10.1061/9780784484012.015.
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Inti, Sundeep, Megha Sharma e Vivek Tandon. "Ground Granulated Blast Furnace Slag (GGBS) and Rice Husk Ash (RHA) Uses in the Production of Geopolymer Concrete". In Geo-Chicago 2016. Reston, VA: American Society of Civil Engineers, 2016. http://dx.doi.org/10.1061/9780784480137.059.
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Pavithra, P., M. Srinivasula Reddy, P. Dinakar, B. Hanumantha Rao, B. K. Satpathy e A. N. Mohanty. "Effect of the Na 2 SiO 3 /NaOH Ratio and NaOH Molarity on the Synthesis of Fly Ash-Based Geopolymer Mortar". In Geo-Chicago 2016. Reston, VA: American Society of Civil Engineers, 2016. http://dx.doi.org/10.1061/9780784480151.034.