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Sotiris Tsivilis - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of chloride-penetration resistance of Metakaolin concrete by means of a diffusion – Binding model and of the k-value concept
Cement & Concrete Composites, 2015Co-Authors: E Badogiannis, E. Aggeli, Vagelis G. Papadakis, Sotiris TsivilisAbstract:Abstract In this paper, the effect of the addition of Metakaolin on chloride-penetration resistance of concrete is investigated. Greek kaolin thermally treated at defined conditions and a commercial Metakaolin were used. Eight mixture proportions were used to produce high performance concrete, where Metakaolin replaced either cement or sand in percentages 10% or 20% by weight of the control cement content. The specimens were placed in a NaCl solution for 90 days and the concentration of total and free (unbound) chloride was determined. The chloride penetration was studied by means of a fundamental model taking into account diffusion and binding (adsorption & desorption) processes. The efficiency factors (k-values) for the studied Metakaolins were determined. Both Metakaolins present a considerable chloride-penetration resistance, depending on active silica and alumina contents, and their addition significantly decreases chloride penetration leading to improved concrete durability.
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Exploitation of poor Greek kaolins: Durability of Metakaolin concrete
Cement & Concrete Composites, 2009Co-Authors: E Badogiannis, Sotiris TsivilisAbstract:In this paper the effect of Metakaolin on concrete durability is investigated. A Greek kaolin of low kaolinite content was thermally treated at defined conditions and the produced Metakaolin was finely ground. In addition, a commercial Metakaolin of high purity was used. Eight mixture proportions were used to produce high performance concrete, where Metakaolin replaced either cement or sand in percentages 10% or 20% by weight of the control cement content. Durability of Metakaolin concrete was evaluated by means of resistance to chloride penetration, air permeability, sorptivity, porosity and pore size distribution. Metakaolin concrete exhibits significantly lower chloride permeability, gas permeability and sorptivity. The addition of Metakaolin refines the pore system of concrete, leading to a decreased mean pore size and improved uniformity of the pore size distribution. The produced Metakaolin, derived from the poor Greek kaolin, imparts similar behavior to that of the commercial Metakaolin, with respect to the concrete durability.
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Metakaolin as supplementary cementitious material optimization of kaolin to Metakaolin conversion
Journal of Thermal Analysis and Calorimetry, 2005Co-Authors: E Badogiannis, G Kakali, Sotiris TsivilisAbstract:In this paper the optimization of the kaolin calcination is studied, aiming at using the produced Metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of Metakaolins and finally by strength development analysis of cement-Metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive Metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO3. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive Metakaolins.
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Metakaolin as supplementary cementitious material
Journal of Thermal Analysis and Calorimetry, 2005Co-Authors: E Badogiannis, G Kakali, Sotiris TsivilisAbstract:In this paper the optimization of the kaolin calcination is studied, aiming at using the produced Metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of Metakaolins and finally by strength development analysis of cement-Metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive Metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO3. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive Metakaolins.
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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.
E Badogiannis - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of chloride-penetration resistance of Metakaolin concrete by means of a diffusion – Binding model and of the k-value concept
Cement & Concrete Composites, 2015Co-Authors: E Badogiannis, E. Aggeli, Vagelis G. Papadakis, Sotiris TsivilisAbstract:Abstract In this paper, the effect of the addition of Metakaolin on chloride-penetration resistance of concrete is investigated. Greek kaolin thermally treated at defined conditions and a commercial Metakaolin were used. Eight mixture proportions were used to produce high performance concrete, where Metakaolin replaced either cement or sand in percentages 10% or 20% by weight of the control cement content. The specimens were placed in a NaCl solution for 90 days and the concentration of total and free (unbound) chloride was determined. The chloride penetration was studied by means of a fundamental model taking into account diffusion and binding (adsorption & desorption) processes. The efficiency factors (k-values) for the studied Metakaolins were determined. Both Metakaolins present a considerable chloride-penetration resistance, depending on active silica and alumina contents, and their addition significantly decreases chloride penetration leading to improved concrete durability.
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Exploitation of poor Greek kaolins: Durability of Metakaolin concrete
Cement & Concrete Composites, 2009Co-Authors: E Badogiannis, Sotiris TsivilisAbstract:In this paper the effect of Metakaolin on concrete durability is investigated. A Greek kaolin of low kaolinite content was thermally treated at defined conditions and the produced Metakaolin was finely ground. In addition, a commercial Metakaolin of high purity was used. Eight mixture proportions were used to produce high performance concrete, where Metakaolin replaced either cement or sand in percentages 10% or 20% by weight of the control cement content. Durability of Metakaolin concrete was evaluated by means of resistance to chloride penetration, air permeability, sorptivity, porosity and pore size distribution. Metakaolin concrete exhibits significantly lower chloride permeability, gas permeability and sorptivity. The addition of Metakaolin refines the pore system of concrete, leading to a decreased mean pore size and improved uniformity of the pore size distribution. The produced Metakaolin, derived from the poor Greek kaolin, imparts similar behavior to that of the commercial Metakaolin, with respect to the concrete durability.
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Metakaolin as supplementary cementitious material optimization of kaolin to Metakaolin conversion
Journal of Thermal Analysis and Calorimetry, 2005Co-Authors: E Badogiannis, G Kakali, Sotiris TsivilisAbstract:In this paper the optimization of the kaolin calcination is studied, aiming at using the produced Metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of Metakaolins and finally by strength development analysis of cement-Metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive Metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO3. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive Metakaolins.
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Metakaolin as supplementary cementitious material
Journal of Thermal Analysis and Calorimetry, 2005Co-Authors: E Badogiannis, G Kakali, Sotiris TsivilisAbstract:In this paper the optimization of the kaolin calcination is studied, aiming at using the produced Metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of Metakaolins and finally by strength development analysis of cement-Metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive Metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO3. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive Metakaolins.
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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.
Yuping Zhang - One of the best experts on this subject based on the ideXlab platform.
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investigation of the properties of high porosity cement foams based on ternary portland cement Metakaolin silica fume blends
Construction and Building Materials, 2016Co-Authors: Jun Jiang, Yunhui Niu, Zhongyuan Lu, Jun Li, Yuping ZhangAbstract:Abstract High-porosity cement foams based on ternary blends of Portland cement, Metakaolin and silica fume were prepared by the pre-foaming method. The effects of ternary blends on the early-age properties, air-void structure and hardened state properties of cement foams were investigated. The effect of Metakaolin and silica fume on stabilizing air-voids was observed, and the collapse of cement foams during the hardening process was avoided by addition of Metakaolin. Moreover, the compressive strength of the prepared 91% high-porosity cement foams was enhanced by addition of Metakaolin and silica fume. The compressive strength and thermal conductivity reached 0.74 MPa and 0.054 W/m K, respectively. However, Metakaolin and silica fume had a negative impact on the workability of the cement foam.
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Investigation of the properties of high-porosity cement foams based on ternary Portland cement–Metakaolin–silica fume blends
Construction and Building Materials, 2016Co-Authors: Jun Jiang, Yunhui Niu, Zhongyuan Lu, Jun Li, Yuping ZhangAbstract:Abstract High-porosity cement foams based on ternary blends of Portland cement, Metakaolin and silica fume were prepared by the pre-foaming method. The effects of ternary blends on the early-age properties, air-void structure and hardened state properties of cement foams were investigated. The effect of Metakaolin and silica fume on stabilizing air-voids was observed, and the collapse of cement foams during the hardening process was avoided by addition of Metakaolin. Moreover, the compressive strength of the prepared 91% high-porosity cement foams was enhanced by addition of Metakaolin and silica fume. The compressive strength and thermal conductivity reached 0.74 MPa and 0.054 W/m K, respectively. However, Metakaolin and silica fume had a negative impact on the workability of the cement foam.
Kimberly E. Kurtis - One of the best experts on this subject based on the ideXlab platform.
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assessment of binary and ternary blends of Metakaolin and class c fly ash for alkali silica reaction mitigation in concrete
Cement and Concrete Research, 2010Co-Authors: Robert D Moser, Amal R Jayapalan, Victor Y Garas, Kimberly E. KurtisAbstract:Abstract The potential for binary and ternary blends of Metakaolin, with two differing particle size distributions, and Class C fly ash to mitigate alkali-silica reactions (ASR) with a highly reactive fine aggregate were evaluated using accelerated mortar bar test (AMBT) and concrete prism test (CPT) methods. Binary blends of Metakaolin or Class C fly ash reduced expansion by 55–90% and 25–37% compared to the control, respectively. When incorporating Metakaolin with a lower mean particle size, binary blends showed a greater reduction in expansion compared with Class C fly ash. Ternary blends of Metakaolin and Class C fly ash resulted in a marginally higher expansion than binary blends incorporating the same amount of Metakaolin. Correlation between AMBT and CPT results was good at high levels of expansion but poor for those compositions producing expansions near the acceptable limits corresponding to increased addition rates of Metakaolin and/or Class C fly ash.
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influence of portland cement composition on early age reactions with Metakaolin
Cement and Concrete Research, 2007Co-Authors: Fabien Lagier, Kimberly E. KurtisAbstract:Abstract The reactivity of two Metakaolins, which vary principally in their surface area, and Portland cements of varying composition were examined via isothermal calorimetry for pastes at water-to-cementitious materials ratio of 0.50 containing 8% cement replacement by weight of Metakaolin. Both Metakaolins examined appear to have a catalysing effect on cement hydration. Calorimetry showed accelerated hydration, a slight increase in cumulative heat evolved during early hydration, and – for some cements examined – apparently an increased intensity of the heat evolved, particularly during the period typically associated with hydration of calcium aluminates. The higher surface area Metakaolin had a greater effect. It is proposed that the presence of Metakaolin may enhance dissolution of cementitious phases and/or provide additional, well-dispersed sites for nucleation of hydration products, in addition to increasing the early age concentration of solubilized aluminium (due to Metakaolin dissolution). The increased intensity of some of the calorimetry data also suggests that some additional exothermic reactions are occurring, which may be related to an increased reactivity of calcium aluminate phases in the cement as well as the reaction of the Metakaolin. This effect is apparently increased as the cement equivalent alkali content increases.
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influence of Metakaolin surface area on properties of cement based materials
Journal of Materials in Civil Engineering, 2007Co-Authors: J.m. Justice, Kimberly E. KurtisAbstract:Two Metakaolins, with similar mineralogical composition but which vary in their surface area (11.1 versus 25.4 m2 ∕g ), were evaluated for use as supplementary cementitious materials through measurements of workability, setting time, strength, elastic modulus, heat evolution, calcium hydroxide (CH) content, and surface area. Compressive and flexural strength of concrete were greater and increased at a faster rate when the finer Metakaolin was used, as expected. The addition of Metakaolin increased early age (i.e., 1–3 days ) flexural strength by as much as 60%. The effect of Metakaolin surface area on compressive strength was particularly evident at the lower water-to-cementitious materials ratios (w/cms) examined and generally at later ages (i.e., 7 days or later). However, although greater in the Metakaolin–cement concretes than the ordinary concretes (particularly at the lowest w/cm examined, 0.40) elastic modulus measured at 28 days , was not affected by the Metakaolin surface area. The greater surfac...
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Comparision of Two Metakaolins and a Silica Fume Used as Supplementary Cementitious Materials
2005Co-Authors: J.m. Justice, L.h. Kennsion, B.j. Mohr, S.l. Beckwith, L.e. Mccormick, B. Wiggins, Kimberly E. KurtisAbstract:The performance of two Metakaolins as supplementary cementitious materials (SCMs) were evaluated at 8% by weight cement replacement. The Metakaolins varied by their surface area. Performance of Metakaolin mixtures was compared to control measures at water-to-cement ratios of 0.40, 0.50, and 0.60 where no SCM has been used and to mixtures where silica fume had been used as partial replacement for cement. In both mixtures containing Metakaolins, compressive, splitting tensile, and flexural strengths increased, as well as elastic modulus, as compared to control mixtures. Setting time was reduced in the pastes with both Metakaolins. Additionally, considering durability, both Metakaolins reduced rapid chloride ion permeability and expansion due to alkali-silica reaction when compared to control and silica fume mixtures. In general, the finer of the two Metakaolins proved more effective in improving concrete properties, although both performed superior to silica fume.
Yunhui Niu - One of the best experts on this subject based on the ideXlab platform.
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investigation of the properties of high porosity cement foams based on ternary portland cement Metakaolin silica fume blends
Construction and Building Materials, 2016Co-Authors: Jun Jiang, Yunhui Niu, Zhongyuan Lu, Jun Li, Yuping ZhangAbstract:Abstract High-porosity cement foams based on ternary blends of Portland cement, Metakaolin and silica fume were prepared by the pre-foaming method. The effects of ternary blends on the early-age properties, air-void structure and hardened state properties of cement foams were investigated. The effect of Metakaolin and silica fume on stabilizing air-voids was observed, and the collapse of cement foams during the hardening process was avoided by addition of Metakaolin. Moreover, the compressive strength of the prepared 91% high-porosity cement foams was enhanced by addition of Metakaolin and silica fume. The compressive strength and thermal conductivity reached 0.74 MPa and 0.054 W/m K, respectively. However, Metakaolin and silica fume had a negative impact on the workability of the cement foam.
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Investigation of the properties of high-porosity cement foams based on ternary Portland cement–Metakaolin–silica fume blends
Construction and Building Materials, 2016Co-Authors: Jun Jiang, Yunhui Niu, Zhongyuan Lu, Jun Li, Yuping ZhangAbstract:Abstract High-porosity cement foams based on ternary blends of Portland cement, Metakaolin and silica fume were prepared by the pre-foaming method. The effects of ternary blends on the early-age properties, air-void structure and hardened state properties of cement foams were investigated. The effect of Metakaolin and silica fume on stabilizing air-voids was observed, and the collapse of cement foams during the hardening process was avoided by addition of Metakaolin. Moreover, the compressive strength of the prepared 91% high-porosity cement foams was enhanced by addition of Metakaolin and silica fume. The compressive strength and thermal conductivity reached 0.74 MPa and 0.054 W/m K, respectively. However, Metakaolin and silica fume had a negative impact on the workability of the cement foam.