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Sotiris Tsivilis - One of the best experts on this subject based on the ideXlab platform.
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sulfate resistance of limestone Cement concrete exposed to combined chloride and sulfate environment at low temperature
Cement & Concrete Composites, 2012Co-Authors: Konstantinos Sotiriadis, Elena Nikolopoulou, Sotiris TsivilisAbstract:Abstract Concrete durability was investigated, taking under consideration the limestone content of the Cement used, as well as the effect of chlorides on concrete’s deterioration due to the thaumasite form of sulfate attack. A normal Portland Cement and two Portland limestone Cements (15% and 35% w/w limestone content) were used for concrete preparation. The specimens were immersed in two corrosive solutions (chloride-sulfate; sulfate) and stored at 5 ± 1 °C. Visual inspection of the specimens, mass measurements and compressive strength tests took place for 24 months. Concretes containing limestone, as Cement Constituent and/or as aggregate, suffered from the thaumasite form of sulfate attack, which was accompanied by brucite and secondary gypsum formation. Limestone Cement concretes exhibited higher deterioration degree compared to the concrete made without limestone Cement. The disintegration was more severe and rapid, the higher the limestone content of the Cement used. Chlorides inhibit sulfate attack on concrete, thus delaying and mitigating its deterioration.
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metakaolin as a main Cement Constituent exploitation of poor greek kaolins
Cement & Concrete Composites, 2005Co-Authors: E. Badogiannis, G Kakali, G Dimopoulou, Emmanouil Chaniotakis, Sotiris TsivilisAbstract:Abstract In this work, the properties and the hydration procedure of Cements containing metakaolin were monitored for periods up to 180 days. Four metakaolins, derived from poor Greek kaolins, as well as a commercial metakaolin of high purity were used. Cement mortars and pastes, with 0%, 10% and 20% replaCement of Cement with the above metakaolins, were examined. Strength development, water demand and setting time were determined in all samples. In addition, XRD and TGA were applied in order to study the hydration products and the hydration rate in the Cement–metakaolin pastes. It is concluded that metakaolin has a very positive effect on the Cement strength after 2 days and specifically at 28 and 180 days. The blended Cements demand significantly more water than the relatively pure Cement and the water demand increase is higher, the higher the metakaolin content. The produced metakaolins as well as the commercial one give similar hydration products after 28 days and the pozzolanic reaction is accelerated between 7 and 28 days, accompanied by a steep decrease of Ca(OH)2 content. Finally, it is concluded that a 10% metakaolin content seems to be, generally, more favorable than 20%. The produced metakaolins, derived from poor Greek kaolins, as well as the commercial one impart similar properties with respect to the Cement strength development, the setting and the hydration.
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Portland-limestone Cements. Their properties and hydration compared to those of other composite Cements
Cement & Concrete Composites, 2005Co-Authors: N. Voglis, G Kakali, Emmanouil Chaniotakis, Sotiris TsivilisAbstract:Abstract The new European Standard EN 197-1 emphasizes the development of composite Cements. In Greece a variety of pozzolanic and/or hydraulic materials are used as Cement main Constituents. Until now, limestone could be used only as a filler (up to 3% w/w), but since 2001 (application of EN 197-1) it can also be used as a main Cement Constituent. In this work a comparison between limestone and some of the materials that are already used in Greece is presented. An ordinary Portland Cement and three Portland-composite Cements containing limestone, natural pozzolana or fly ash were produced. The grinding process was designed in order to produce Cements of the same 28 day compressive strength. The mechanical and physical properties of the Cements were measured and hydrated products, formed after 1–28 days, were identified by means of XRD. The composite Cements present significant differences as far as the clinker fineness, the development of the strength, the water demand and the hydration rate is concerned. The production of Portland-limestone Cements seems to be very challenging, due to the satisfactory properties of the limestone Cements as well as the low cost and the high availability of limestone in Greece.
Cristina Argiz - One of the best experts on this subject based on the ideXlab platform.
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Coal bottom ash natural radioactivity in building materials
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: Miguel Ángel Sanjuán, Begona Quintana, Cristina ArgizAbstract:The viability of ground coal bottom ash as a potential Portland Cement Constituent to be used in building materials is assessed. Currently, coal fly ash is used to produce Portland Cements and concretes. However, coal bottom ash is mainly landfilled. Gamma spectrometry analysis, compressive strength, physical and chemical testing were performed. The ground coal bottom ash activity concentration index (I = 1.03) was compared to that of the coal fly ash (I = 1.11) provided from the same thermo-electrical power plant. Ground coal bottom ash could be used in building materials in the same way as coal fly ash as a Portland Cement Constituent.
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use of ground coal bottom ash as Cement Constituent in concretes exposed to chloride environments
Journal of Cleaner Production, 2018Co-Authors: Cristina Argiz, A Moragues, E. MenéndezAbstract:Abstract Coal bottom ash waste obtained from thermoelectric power plants could be recycled like any other new Cement Constituent when sufficiently ground. Such a proposal would result in a reduction of both energy consumption and CO 2 emissions from Cement production, while minimising the environmental impact of disposing of the coal bottom ash in landfill sites. The new Cement Constituent must guarantee at least the same durability than that of Cements in current use. In order to assess the viability of using the coal bottom ash as the new main Constituent of Portland Cements, a comparative study with coal fly ash supplied by the same power plant was conducted. Coal fly as and ground coal bottom ash were used to replace 10% and 25% of the weight of the Portland Cement. Natural chloride diffusion and chloride migration, as well as electrical resistivity, were determined in the concrete. Concretes made with 25% of coal bottom ash result in lower migration and diffusion coefficients (Dnssm = 0.98·10 −12 and De = 0.42·10 −12 ) than concretes with 10% (Dnssm = 4.12·10 −12 and De = 1.33·10 −12 ). These coefficients are lower than those for coal fly ash for the same ash content of 25% (Dnssm = 3.82·10 −12 and De = 1.26·10 −12 ) or 10% (Dnssm = 7.06·10 −12 and De = 3.80·10 −12 ). In addition, concretes made of Cements with 25% of ground coal bottom ash showed significant higher resistivity values than coal fly ash concretes with ages over 28 days. These results can be explained by considering the higher fineness of the ground coal bottom ash.
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Coal Bottom Ash for Portland Cement Production
Advances in Materials Science and Engineering, 2017Co-Authors: Cristina Argiz, Miguel Ángel Sanjuán, E. MenéndezAbstract:Because of industrialization growth, the amount of coal power plant wastes has increased very rapidly. Particularly, the disposal of coal bottom ash (CBA) is becoming an increasing concern for many countries because of the increasing volume generated, the costs of operating landfill sites, and its potential hazardous effects. Therefore, new applications of coal bottom ash (CBA) have become an interesting alternative to disposal. For instance, it could be used as a Portland Cement Constituent leading to more sustainable Cement production by lowering energy consumption and raw material extracted from quarries. Coal fly and bottom ashes are formed together in the same boiler; however, the size and shape of these ashes are very different, and hence their effect on the chemical composition as well as on the mineralogical phases must be studied. Coal bottom ash was ground. Later, both ashes were compared from a physical, mechanical, and chemical point of view to evaluate the potential use of coal bottom ash as a new Portland Cement Constituent. Both ashes, produced by the same electrical power plant, generally present similar chemical composition and compressive strength and contribute to the refill of mortar capillary pores with the reaction products leading to a redistribution of the pore size.
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Coal fly ash alkalis content characterization by means of a full factorial design
Materials Letters, 2016Co-Authors: Miguel Ángel Sanjuán, Cristina ArgizAbstract:Abstract Concrete structures durability is affected by the alkali ions amount in the pore solution when potentially reactive aggregates are employed. Then, a long-term durability indicator of concrete could be the coal fly ash alkali content. Such alkali ions are provided by the Portland Cement, but also by the coal fly ash when is used as a main Cement Constituent. In this work, fly ashes from the combustion of a South African coal were investigated. The scope of this paper is to deep in the knowledge of coal fly ash alkalis content and, in particular, how it is affected by free CaO and reactive silica content and fineness. Evaluation of variables was done by using a 2 3 full factorial design. The maximum Na 2 O equ of 1.68% was obtained at 1% free CaO, 40% reactive silica and 30% residue on 45 µm (fineness). Reactive silicon is the main parameter influencing Na 2 O equivalent amount in coal fly ash.
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Recent Advances in Coal Bottom Ash Use as a New Common Portland Cement Constituent
Structural Engineering International, 2014Co-Authors: Cristina Argiz, E. Menéndez, A MoraguesAbstract:Cement new Constituents can contribute to improve the sustainable of the construction materials and also, in many cases, enhance their durability. Coal bottom ash could be one of such new Portland Cement Constituents. Currently, they are dumped because are considered as wastes in some countries leading to generate an environmental problem. Therefore, in this paper, coal bottom ash used as a main Constituent of Portland Cements when it is mixed in an optimized proportion with fly ashes is studied. Mechanical and durable characteristics of standardized mortars made of mixes of coal combustion bottom and fly ashes are compared to mortars made of CEM I 42.5 N (EN 197-1:2011). Ash and Cement mixes were designed in order to get similar compositions of CEM II/A-V, CEM II/B-V and CEM IV/A (V) Cements according to the European standard EN 197-1:2011. Summing up, it can be said that bottom ash and fly ash mixes perform in the same way than common Portland Cements made of fly ash.
E. Menéndez - One of the best experts on this subject based on the ideXlab platform.
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use of ground coal bottom ash as Cement Constituent in concretes exposed to chloride environments
Journal of Cleaner Production, 2018Co-Authors: Cristina Argiz, A Moragues, E. MenéndezAbstract:Abstract Coal bottom ash waste obtained from thermoelectric power plants could be recycled like any other new Cement Constituent when sufficiently ground. Such a proposal would result in a reduction of both energy consumption and CO 2 emissions from Cement production, while minimising the environmental impact of disposing of the coal bottom ash in landfill sites. The new Cement Constituent must guarantee at least the same durability than that of Cements in current use. In order to assess the viability of using the coal bottom ash as the new main Constituent of Portland Cements, a comparative study with coal fly ash supplied by the same power plant was conducted. Coal fly as and ground coal bottom ash were used to replace 10% and 25% of the weight of the Portland Cement. Natural chloride diffusion and chloride migration, as well as electrical resistivity, were determined in the concrete. Concretes made with 25% of coal bottom ash result in lower migration and diffusion coefficients (Dnssm = 0.98·10 −12 and De = 0.42·10 −12 ) than concretes with 10% (Dnssm = 4.12·10 −12 and De = 1.33·10 −12 ). These coefficients are lower than those for coal fly ash for the same ash content of 25% (Dnssm = 3.82·10 −12 and De = 1.26·10 −12 ) or 10% (Dnssm = 7.06·10 −12 and De = 3.80·10 −12 ). In addition, concretes made of Cements with 25% of ground coal bottom ash showed significant higher resistivity values than coal fly ash concretes with ages over 28 days. These results can be explained by considering the higher fineness of the ground coal bottom ash.
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Coal Bottom Ash for Portland Cement Production
Advances in Materials Science and Engineering, 2017Co-Authors: Cristina Argiz, Miguel Ángel Sanjuán, E. MenéndezAbstract:Because of industrialization growth, the amount of coal power plant wastes has increased very rapidly. Particularly, the disposal of coal bottom ash (CBA) is becoming an increasing concern for many countries because of the increasing volume generated, the costs of operating landfill sites, and its potential hazardous effects. Therefore, new applications of coal bottom ash (CBA) have become an interesting alternative to disposal. For instance, it could be used as a Portland Cement Constituent leading to more sustainable Cement production by lowering energy consumption and raw material extracted from quarries. Coal fly and bottom ashes are formed together in the same boiler; however, the size and shape of these ashes are very different, and hence their effect on the chemical composition as well as on the mineralogical phases must be studied. Coal bottom ash was ground. Later, both ashes were compared from a physical, mechanical, and chemical point of view to evaluate the potential use of coal bottom ash as a new Portland Cement Constituent. Both ashes, produced by the same electrical power plant, generally present similar chemical composition and compressive strength and contribute to the refill of mortar capillary pores with the reaction products leading to a redistribution of the pore size.
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Coal bottom ash studies as a new Cement Constituent
2015Co-Authors: E. Menéndez, Cristina Argiz Lucio, Amparo Moragues Terrades, Miguel Angel Sanjuán BarbudoAbstract:Future Cements will require new Constituents in order to become a more sustainable construction product. Therefore, the durability of the Cements made with them must be checked. In this respect, coal bottom ash is proposed as a new Portland Cement Constituent and thus chemical durability as well as mechanical strength have been tested in mortar and concrete to evaluate its capability to be an adequate Cement Constituent. Coal bottom ash is tested in mortars made of mixes of coal combustion bottom and fly ashes. The results are compared to those performed in mortars made of CEM I 42.5 N (EN 197-1:2011). These bottom ash-fly ash mixes are incorporated in the common Portland Cement in the needed proportions to produce CEM II/A-V, CEM II/B-V and CEM IV/A (V) Cements according to the European standard EN 197-1:2011. Natural carbonation is the only durable property considered in the present work. Blended Cements perform well with regard to the chloride diffusion. On the contrary, the higher amount of ashes, the deeper carbonation fronts regardless of the type of ash, bottom ash, fly ash or mixes of them. This effect could be explained because the bottom ash has a content of Fe2O3, TiO2, P2O5, SrO2 and so on, quite similar to that of the fly ash. The presence of such oxides might have a significant effect on pore solution concentration and then it is expected that they will play a significant role in the Cement properties related to mortar and concrete durability. Summing up, it is possible to say that the utilization of bottom ash, in comparison to fly ash, does not modify the compressive strength, carbonation resistance and pozzolanicity characteristics of the mortars studied in the present work. The final result invites to propose the use of this new Cement Constituent for some applications in the appropriate Cement standard
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Recent Advances in Coal Bottom Ash Use as a New Common Portland Cement Constituent
Structural Engineering International, 2014Co-Authors: Cristina Argiz, E. Menéndez, A MoraguesAbstract:Cement new Constituents can contribute to improve the sustainable of the construction materials and also, in many cases, enhance their durability. Coal bottom ash could be one of such new Portland Cement Constituents. Currently, they are dumped because are considered as wastes in some countries leading to generate an environmental problem. Therefore, in this paper, coal bottom ash used as a main Constituent of Portland Cements when it is mixed in an optimized proportion with fly ashes is studied. Mechanical and durable characteristics of standardized mortars made of mixes of coal combustion bottom and fly ashes are compared to mortars made of CEM I 42.5 N (EN 197-1:2011). Ash and Cement mixes were designed in order to get similar compositions of CEM II/A-V, CEM II/B-V and CEM IV/A (V) Cements according to the European standard EN 197-1:2011. Summing up, it can be said that bottom ash and fly ash mixes perform in the same way than common Portland Cements made of fly ash.
Teng-hung Huang - One of the best experts on this subject based on the ideXlab platform.
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Leaching characteristics of a model solidification/stabilization system: Tricalcium silicate and copper oxide
Journal of Hazardous Materials, 1994Co-Authors: Cheng-fang Lin, Teng-hung HuangAbstract:Abstract The major Cement Constituent, i.e. tricalcium silicate (C 3 S), and copper oxide were used in this study as a model solidification/stabilization system for investigating the leaching characteristics of a solidified waste form. The semi-dynamic leaching process was employed for simulating the dynamic nature of the relevant conditions. The primary objective of this work lies in assessing the long-term stability of a waste matrix which would experience acidic leaching at a disposal site. The changes in the matrix Constituents, pore size, pore volume, physical strength, as well as the pH of the matrix were closely related with each other for interpretation of the leaching mechanism. The dissolution of calcium compounds was found to be critical to the leaching of solidified hazardous materials. Dissolution of calcium compounds in the matrix would increase the number of pores and pore size and, therefore, enhance the dissolution reactions and solute transport within the matrix. Dissolution of the hydration products was promoted by the proton-controlled surface reactions.
G Kakali - One of the best experts on this subject based on the ideXlab platform.
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metakaolin as a main Cement Constituent exploitation of poor greek kaolins
Cement & Concrete Composites, 2005Co-Authors: E. Badogiannis, G Kakali, G Dimopoulou, Emmanouil Chaniotakis, Sotiris TsivilisAbstract:Abstract In this work, the properties and the hydration procedure of Cements containing metakaolin were monitored for periods up to 180 days. Four metakaolins, derived from poor Greek kaolins, as well as a commercial metakaolin of high purity were used. Cement mortars and pastes, with 0%, 10% and 20% replaCement of Cement with the above metakaolins, were examined. Strength development, water demand and setting time were determined in all samples. In addition, XRD and TGA were applied in order to study the hydration products and the hydration rate in the Cement–metakaolin pastes. It is concluded that metakaolin has a very positive effect on the Cement strength after 2 days and specifically at 28 and 180 days. The blended Cements demand significantly more water than the relatively pure Cement and the water demand increase is higher, the higher the metakaolin content. The produced metakaolins as well as the commercial one give similar hydration products after 28 days and the pozzolanic reaction is accelerated between 7 and 28 days, accompanied by a steep decrease of Ca(OH)2 content. Finally, it is concluded that a 10% metakaolin content seems to be, generally, more favorable than 20%. The produced metakaolins, derived from poor Greek kaolins, as well as the commercial one impart similar properties with respect to the Cement strength development, the setting and the hydration.
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Portland-limestone Cements. Their properties and hydration compared to those of other composite Cements
Cement & Concrete Composites, 2005Co-Authors: N. Voglis, G Kakali, Emmanouil Chaniotakis, Sotiris TsivilisAbstract:Abstract The new European Standard EN 197-1 emphasizes the development of composite Cements. In Greece a variety of pozzolanic and/or hydraulic materials are used as Cement main Constituents. Until now, limestone could be used only as a filler (up to 3% w/w), but since 2001 (application of EN 197-1) it can also be used as a main Cement Constituent. In this work a comparison between limestone and some of the materials that are already used in Greece is presented. An ordinary Portland Cement and three Portland-composite Cements containing limestone, natural pozzolana or fly ash were produced. The grinding process was designed in order to produce Cements of the same 28 day compressive strength. The mechanical and physical properties of the Cements were measured and hydrated products, formed after 1–28 days, were identified by means of XRD. The composite Cements present significant differences as far as the clinker fineness, the development of the strength, the water demand and the hydration rate is concerned. The production of Portland-limestone Cements seems to be very challenging, due to the satisfactory properties of the limestone Cements as well as the low cost and the high availability of limestone in Greece.