29 resultados para Geopolymer mortar

em Deakin Research Online - Australia


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Deregulation, innovations in mobile and wireless technologies and media convergence, together with the rapid diffusion of the Internet, have opened up strategic business opportunities in the financial sector. With deregulation removing entry barriers, an increasing number of online banks are threatening the market share of ‘bricks and mortar’ banks. To survive this competition, and to leverage the new opportunities of online and mobile banking facilitated by the Internet, many banks have adapted a hybrid, ‘clicks and mortar’ model, to increase their profitability while reducing transaction costs. In this paper, we report the results of a preliminary analysis based on a few major banks in Australia and India, two diverse economies, to reveal some interesting insights.

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Fly ash is generated from combustion of brown coal in power stations. The majority of fly ash is removed by electrostatic precipitators (ESP) and finally disposed into the landfill as prescribed wastes. A method was studied to add clay materials to the brown coal fly ash in order to form the so-called geopolymer network, which is effective at stopping the metal contents from leaching, and have minimum impact to the environment. The experiments were conducted parallel on leached fly ash and dry precipitator fly ash. The ratios of fly ash and added clay materials were varied to determine the effects of different compositions on leaching rates. Both X-ray diffraction analysis and scanning electron microscopy images showed that as the percentage of fly ash was increased, the formation of geopolymer is reduced. Eighteen metals and heavy metals were targeted during the leaching tests and the leachate samples were analysed using ICP-AES and ICP-MS. It was found that the reduction of metal leaching was achieved by adding up to 60% of fly ash to form the geopolymer like structure. Significant reductions were observed for calcium, strontium and barium. Leached fly ash achieved better stabilisation than dry precipitator fly ash for major elements. It's hard to quantify its effects on trace metals leaching due to their ultra low concentration in the fly ash. The samples spiked with trace metals of lead, zinc, mercury and barium showed remarkable reduction in leaching.

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Through experimentation, we establish a causal relationship between trust and the expansion of a retailer from online to brick-and-mortar and vice versa. Trust is multidimensional and contingent on the distribution path first chosen. Vendor trustworthiness (knowledge-based) and technological trustworthiness (institution-based) have different effects depending on the initial and new distribution channel. Expanding from brick-and-mortar to online negatively affects technology-based trust, while transfers from an online to a physical location maintain the same level of technology-based trust. Vendor-based trust is positively affected by transfer from online to the brick-and-mortar location, and is not significantly unaffected by transfers from brick and-mortar to online locations. The perceived “permanence” of a physical location influences consumer beliefs about the location’s trustworthiness.

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Geopolymer cement utilises industrial by-products and is associated with low CO2 emissions. The use of dune sand as fine aggregate could reduce the environmental impact of mining activities. The present study is to examine the feasibility of using dune sand in geopolymer-based construction materials. The geopolymer mortars made with dune sand (DSM) were prepared by using alkali activators of different cations(Na, K and Na/K). In order to compare, the corresponding geopolymer mortars made with normal sand (NSM) were also prepared. It was found that dune sand has little influence on the strength of geopolymer mortars, especially for K based mortars. However, the alkali cation has significant influence on the compressive strength of geopolymer mortars. This influence was found to be correlated to porosity. Low compressive strength is associated with high porosity. For all investigated alkali cations, the tensile strengths of DSM compare favourably to those predicted by the relevant Standards for construction materials. Based on the experimental results, Australian dune sand can be used as fine aggregate for the production of geopolymer based construction materials.

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The effects of strain rate on compressive and tensile strength of fly ash based geopolymer concrete were investigated experimentally. Four mixes of geopolymer concrete using different alkaline solutions and under vary curing conditions were prepared. One mix of ordinary Portland cement (OPC) concrete was prepared for comparison. Both Quasi-Static tests using standard MTS and dynamic tests using Split-Hopkinson pressures bar (SHPB) were conducted, which were giving varying strain rate loadings from 10‾⁷ to 103 per second. The strain rate effect is presented as the ratio of dynamic compressive strength to static compressive strength (DIF). Results show that DIFs of geopolymer concrete are generally higher than those of OPC concrete at strain range of 187/s to 346/s (compression tests) and 7/s to 13/s (splitting tensile tests), respectively. This tendency is independent on loading regimes (compression or tension). This suggests that geopolymer concrete can be used as an alternative construction material to OPC concrete for the structures which has a high risk of being subjected to impact loadings.

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As environmentally-friendly materials, geopolymers have the potential to replace ordinary Portland cement (OPC) for the construction of railway sleepers and multi-flue chimneys, where the vibration control capabilities of the material must be considered. The critical damping value (ξ) is the main parameter in relation to vibration reduction. In this study, the traditional logarithmic decrement technique was used to measure the ξ of geopolymers. Geopolymers were prepared by activating fly ash using alkali solutions with different SiO2/Na2O ratios. The results show that the ξ of the geopolymers is similar to that of the OPC counterpart. Finite element analysis (FEM) based on the Rayleigh damping model was conducted to replicate the test results, and scanning electron microscopy and mercury-intrusion porosimetry were used to study the microstructure of the geopolymers. A discussion of the possible damping mechanisms based on the microstructural investigation and the FEM analysis is presented.

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When fly ash based geopolymer mortars were exposed to an elevated temperature of 800oC, it was found that the strength after the exposure sometimes decreased, but at other times increased compared to the original strength. The aim of this investigation is to find the reason for this contrasting behaviour. Fol-lowing exposure to high temperature, residual strengths of specimens prepared with two different fly ashes, with initial strengths ranging from 5MPa to 60MPa, were investigated. The parameter that was found to have a major influence on the contrasting behaviour was the ductility of the mortars. The results indicate that the higher the ductility the lower the strength loss. This correlation is attributed to the fact that mortars with high ductility could provide higher capacity to accommodate thermal incompatibility than mortars with low ductil-ity. Beyond the particular threshold of ductility, some mortars even increased strength after the exposure, pos-sibly due to sintering.

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This paper reports the properties of fly ash based geopolymer mortars made with dune sand. The geopolymer mortars of different cation type, namely sodium based (Na), potassium based (K) and a mixed Na/K, were prepared with dune sand (DS) and river sand (RS). The corresponding geopolymer pastes were also prepared. A series of tests including compressive strength, modulus of elasticity, splitting tensile strength, microanalysis (using scanning electron microscopy), porosity (using mercury intrusion porosimetry), sorptivity and air void (using section analysis method) were carried out. The results showed a strong correlation between strength and porosity of geopolymeric materials. The addition of DS had influences on the chemical compositions and physical properties of geopolymer mortars. These influences were dependent on the type of cation. Based on the results of mechanical properties, DS can be utilised as the fine aggregate for the production of geopolymer based construction material.

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Tailoring the nanostructures of electrode materials is an effective way to enhance their electrochemical performance for energy storage. Herein, an ice-templating "bricks-and-mortar" assembly approach is reported to make ribbon-like V2O5 nanoparticles and CNTs integrated into a two-dimensional (2D) porous sheet-like V2O5-CNT nanocomposite. The obtained sheet-like V2O5-CNT nanocomposite possesses unique structural characteristics, including a hierarchical porous structure, 2D morphology, large specific surface area and internal conducting networks, which lead to superior electrochemical performances in terms of long-term cyclability and significantly enhanced rate capability when used as a cathode material for LIBs. The sheet-like V2O5-CNT nanocomposite can charge/discharge at high rates of 5C, 10C and 20C, with discharge capacities of approximately 240 mA h g-1, 180 mA h g-1, and 160 mA h g-1, respectively. It also retains 71% of the initial discharge capacity after 300 cycles at a high rate of 5C, with only 0.097% capacity loss per cycle. The rate capability and cycling performance of the sheet-like V2O5-CNT nanocomposite are significantly better than those of commercial V2O5 and most of the reported V2O5 nanocomposite.

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The High Court, in the 1995 landmark case of Bryan v Maloney, held a builder of a residential house liable to a subsequent owner for economic loss suffered by way of the reduction in value of the house caused by its defective foundations. Since that decision, several cases in state courts have indicated that any extension of the principle in Bryan to commercial properties is a matter for the High Court. This year, Woolcock Street Investments Pty Ltd v CDG Pty Ltd provided the vehicle for the High Court to revisit the Bryan principle in a commercial context. Faced with the question 'can a subsequent owner of a commercial property who discovers faulty foundations sue the builder for the costs of fixing the problem before it causes any physical damage to person or property?', the resounding response from the High Court has been 'no'. Gleeson CJ, Gummow, Hayne and Heydon JJ in a joint judgment and McHugh J and Callinan J in separate judgements rejected any 'extension' of the Bryan principle to commercial premises. Much to the relief of the construction industry, the Court made it clear that it will be difficult for a subsequent owner to make out a case in negligence against the original builder unless it can show special vulnerability to the risk of injury. Kirby J, in a dissenting judgment, suggested that the extension of liability to commercial builders fits quite comfortably with general principles and lamented the 'incremental' approach to liability presently favoured by the Court. Consequent upon the retirement of Gaudron J, Kirby J appears to be a lonely light on the hill, shining a solitary beacon on matters of principle.

The revisitation of Bryan has long been anticipated. However, Woolcock does not provide the solid bricks and mortar craved by the construction industry. Close examination of the reasoning of the Court suggests that it may itself rest on faulty foundations. In his dissenting judgment, Kirby J questions some of the assumptions made by the majority and highlights the deficiencies of the 'stated case' procedure for a re-examination of this particular area of law, thus suggesting that Woolcock may not be completely sound.

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Current regulations classify fly ash as a prescribed waste and prohibit its disposal in regular landfill. Treatment of the fly ash can reduce the leach rate of metals, and allow it to be disposed in less prescribed landfill. A geopolymer matrix was investigated as a potential stabilisation method for brown coal fly ash. Precipitator fly ash was obtained from electrostatic precipitators and leached fly ash was collected from ash disposal ponds, and leaching tests were conducted on both types of geopolymer stabilised fly ashes. The ratio of fly ash to geopolymer was varied to determine the effects of different compositions on leaching rates.

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The burning of brown coal for electricity generation produces thousands of tonnes of fly ash each year. Treatment of the fly ash can reduce leach rates of metals and allow it to be disposed in less prescribed landfill. A geopolymer matrix was investigated as a potential stabilisation method for fly ash obtained from electrostatic precipitators and ash disposal ponds. The ratio of fly ash and geopolymer was varied to determine the effects of different compositions on leaching rates. The major element leachate concentrations obtained from pond ash were lower than that of precipitator fly ash. Conversely, precipitator ash-geopolymers were better for trace heavy metal stabilisation. Effective reduction of elemental concentrations in the leachate has been achieved, particularly for calcium, arsenic, selenium, strontium and barium. Scanning electron microscopy revealed the distribution of metals originated from fly ash and from added geopolymer material. It also showed that some elements are leached from ash particles to the geopolymer phase and others remained as undissolved particles. Qualitative analysis showed that fly ash particles interacted with the geopolymers phase through surface reactions.