The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform

Denis Damidot - One of the best experts on this subject based on the ideXlab platform.

  • Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: Cement hydration, strength development and volume stability
    Journal of Hazardous Materials, 2011
    Co-Authors: S. Berger, Patrick Le Bescop, Céline Cau Dit Coumes, Denis Damidot
    Abstract:

    Abstract The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5 mol/L ZnCl 2 mixing solution was characterized over one year as a function of the Gypsum Content of the binder and the thermal history of the material. Blending the CSA clinker with 20% Gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, stratlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the Gypsum Content of the binder), and possibly C–(A)–S–H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes.

  • Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: Cement hydration, strength development and volume stability
    Journal of Hazardous Materials, 2011
    Co-Authors: Stéphane Berger, Céline Cau Dit Coumes, Patrick Le Bescop, Denis Damidot
    Abstract:

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5mol/L ZnCl2 mixing solution was characterized over one year as a function of the Gypsum Content of the binder and the thermal history of the material. Blending the CSA clinker with 20% Gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, strätlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the Gypsum Content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes. © 2011 Elsevier B.V.

  • Hydration of calcium sulfoaluminate cement by a ZnCl2 solution: Investigation at early age
    Cement and Concrete Research, 2009
    Co-Authors: Stéphane Berger, Patrick Le Bescop, Céline Cau Dit Coumes, Denis Damidot
    Abstract:

    Abstract Hydration of calcium sulfoaluminate cement at early age was investigated as a function of the Gypsum Content of the binder, the thermal history of the material, and the ZnCl2 concentration in the mixing solution. Early hydration was strongly accelerated by the presence of Gypsum, but lower percentages of reaction were reached after 24 h. The slowing down effect induced by ZnCl2, even at a concentration as high as 0.5 mol/L, was moderated compared to OPC but had a greater intensity in the absence of Gypsum. Unlike what would have been expected for Portland cement, it was shown that the delay of a Gypsum-free calcium sulfoaluminate cement resulted from the strong retardation caused by chloride anions, which was partly compensated by the accelerating effect of Zn2+ cations. The mineralogical observations revealed the precipitation of chloro–AFm phases such as Friedel's and Kuzel's salts, but no crystallized zinc-containing phases could be identified by XRD. The thermal history of the samples proved to be a key parameter. Applying a thermal cycle which reproduced the temperature rise and decrease occurring in a massive mortar block accelerated the rate of hydration and mainly modified the proportion of AFt versus AFm hydrates, especially when the binder had a Gypsum Content below 20%.

  • Hydration of calcium sulfoaluminate cement by a ZnCl2 solution: Investigation at early age
    Cement and Concrete Research, 2009
    Co-Authors: Stéphane Berger, Céline Cau Dit Coumes, Patrick Le Bescop, Denis Damidot
    Abstract:

    Hydration of calcium sulfoaluminate cement at early age was investigated as a function of the Gypsum Content of the binder, the thermal history of the material, and the ZnCl2 concentration in the mixing solution. Early hydration was strongly accelerated by the presence of Gypsum, but lower percentages of reaction were reached after 24 h. The slowing down effect induced by ZnCl2, even at a concentration as high as 0.5 mol/L, was moderated compared to OPC but had a greater intensity in the absence of Gypsum. Unlike what would have been expected for Portland cement, it was shown that the delay of a Gypsum-free calcium sulfoaluminate cement resulted from the strong retardation caused by chloride anions, which was partly compensated by the accelerating effect of Zn2+ cations. The mineralogical observations revealed the precipitation of chloro-AFm phases such as Friedel's and Kuzel's salts, but no crystallized zinc-containing phases could be identified by XRD. The thermal history of the samples proved to be a key parameter. Applying a thermal cycle which reproduced the temperature rise and decrease occurring in a massive mortar block accelerated the rate of hydration and mainly modified the proportion of AFt versus AFm hydrates, especially when the binder had a Gypsum Content below 20%. © 2009 Elsevier Ltd. All rights reserved.

Stéphane Berger - One of the best experts on this subject based on the ideXlab platform.

  • Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: Cement hydration, strength development and volume stability
    Journal of Hazardous Materials, 2011
    Co-Authors: Stéphane Berger, Céline Cau Dit Coumes, Patrick Le Bescop, Denis Damidot
    Abstract:

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5mol/L ZnCl2 mixing solution was characterized over one year as a function of the Gypsum Content of the binder and the thermal history of the material. Blending the CSA clinker with 20% Gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, strätlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the Gypsum Content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes. © 2011 Elsevier B.V.

  • Hydration of calcium sulfoaluminate cement by a ZnCl2 solution: Investigation at early age
    Cement and Concrete Research, 2009
    Co-Authors: Stéphane Berger, Patrick Le Bescop, Céline Cau Dit Coumes, Denis Damidot
    Abstract:

    Abstract Hydration of calcium sulfoaluminate cement at early age was investigated as a function of the Gypsum Content of the binder, the thermal history of the material, and the ZnCl2 concentration in the mixing solution. Early hydration was strongly accelerated by the presence of Gypsum, but lower percentages of reaction were reached after 24 h. The slowing down effect induced by ZnCl2, even at a concentration as high as 0.5 mol/L, was moderated compared to OPC but had a greater intensity in the absence of Gypsum. Unlike what would have been expected for Portland cement, it was shown that the delay of a Gypsum-free calcium sulfoaluminate cement resulted from the strong retardation caused by chloride anions, which was partly compensated by the accelerating effect of Zn2+ cations. The mineralogical observations revealed the precipitation of chloro–AFm phases such as Friedel's and Kuzel's salts, but no crystallized zinc-containing phases could be identified by XRD. The thermal history of the samples proved to be a key parameter. Applying a thermal cycle which reproduced the temperature rise and decrease occurring in a massive mortar block accelerated the rate of hydration and mainly modified the proportion of AFt versus AFm hydrates, especially when the binder had a Gypsum Content below 20%.

  • Hydration of calcium sulfoaluminate cement by a ZnCl2 solution: Investigation at early age
    Cement and Concrete Research, 2009
    Co-Authors: Stéphane Berger, Céline Cau Dit Coumes, Patrick Le Bescop, Denis Damidot
    Abstract:

    Hydration of calcium sulfoaluminate cement at early age was investigated as a function of the Gypsum Content of the binder, the thermal history of the material, and the ZnCl2 concentration in the mixing solution. Early hydration was strongly accelerated by the presence of Gypsum, but lower percentages of reaction were reached after 24 h. The slowing down effect induced by ZnCl2, even at a concentration as high as 0.5 mol/L, was moderated compared to OPC but had a greater intensity in the absence of Gypsum. Unlike what would have been expected for Portland cement, it was shown that the delay of a Gypsum-free calcium sulfoaluminate cement resulted from the strong retardation caused by chloride anions, which was partly compensated by the accelerating effect of Zn2+ cations. The mineralogical observations revealed the precipitation of chloro-AFm phases such as Friedel's and Kuzel's salts, but no crystallized zinc-containing phases could be identified by XRD. The thermal history of the samples proved to be a key parameter. Applying a thermal cycle which reproduced the temperature rise and decrease occurring in a massive mortar block accelerated the rate of hydration and mainly modified the proportion of AFt versus AFm hydrates, especially when the binder had a Gypsum Content below 20%. © 2009 Elsevier Ltd. All rights reserved.

Aly Ahmed - One of the best experts on this subject based on the ideXlab platform.

  • investigation of recycled Gypsum in conjunction with waste plastic trays for ground improvement
    Construction and Building Materials, 2011
    Co-Authors: Keizo Ugai, Aly Ahmed, Takeshi Kamei
    Abstract:

    Abstract During the three stages of production, construction and demolition, approximately 15 million tons of Gypsum waste plasterboard is generated annually in the world. It is considered a serious problem due to scarcity of land-filling space, increasing the cost of disposal and increasing environmental regulations. Investigations of using recycled Gypsum “bassanite” which is derived from Gypsum waste plasterboard and waste plastic trays for ground improvement were studied. Recycled Gypsum was used as a stabilizing agent to improve the compressive strength while the waste plastic trays were used to improve the tensile strength. Recycled Gypsum Content, curing time and frost heave property throughout capillary rise test were investigated to determine the behavior of treated soil with recycled Gypsum. In addition, size, Content and aspect ratio of strips of waste plastic trays were investigated. Test results showed that increasing recycled Gypsum Content has a more significant effect on compressive strength compared to the tensile strength. The effect of curing time on the strength of treated soil samples with recycled Gypsum is much pronounced in the early curing days compared to later ages. Adding strips of waste plastic trays to samples treated with recycled Gypsum enhanced both splitting tensile and compressive strengths as well increased the value of secant modulus. Capillary rise rate was reduced with the increase of recycled Gypsum Content, which helps to reduce the formation of ice lenses; hence the susceptibility of treated soil against frost heave is increased. The size and Content of strips of waste plastic trays have significant effect on the potential of capillary rise and the enhancement of strength and stiffness of tested soil.

  • Application of Gypsum Waste Plasterboard and Waste Plastic Trays to Enhance the Performance of Sandy Soil
    Ground Improvement and Geosynthetics, 2010
    Co-Authors: Aly Ahmed, Keizo Ugai, Takeshi Kamei
    Abstract:

    This paper presents the results of a research project that evaluated the use of recycled Gypsum obtained from waste plasterboard along with strips of waste plastic trays to enhance the performance of tested soil. Recycled Gypsum was used as a stabilizing agent for stabilized soil to improve the compressive strength, whereas the waste plastic trays were used to improve the tensile strength. The effects of waste Gypsum Content, size, aspect ratio and waste plastic trays Content were investigated to determine the mechanical behavior of soil treated with such waste materials. Experimental test results showed that unconfined compressive and splitting tensile strengths increased with increasing waste Gypsum Content. The increase in waste Gypsum has a more significant effect on the unconfined compressive strength than on the tensile strength. Adding strips of waste plastic trays to samples treated with waste Gypsum enhanced the splitting tensile strength. The size, aspect ratio and Content of waste plastic trays have significant effect on the enhancement of soil strength.

Patrick Le Bescop - One of the best experts on this subject based on the ideXlab platform.

  • Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: Cement hydration, strength development and volume stability
    Journal of Hazardous Materials, 2011
    Co-Authors: S. Berger, Patrick Le Bescop, Céline Cau Dit Coumes, Denis Damidot
    Abstract:

    Abstract The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5 mol/L ZnCl 2 mixing solution was characterized over one year as a function of the Gypsum Content of the binder and the thermal history of the material. Blending the CSA clinker with 20% Gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, stratlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the Gypsum Content of the binder), and possibly C–(A)–S–H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes.

  • Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: Cement hydration, strength development and volume stability
    Journal of Hazardous Materials, 2011
    Co-Authors: Stéphane Berger, Céline Cau Dit Coumes, Patrick Le Bescop, Denis Damidot
    Abstract:

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5mol/L ZnCl2 mixing solution was characterized over one year as a function of the Gypsum Content of the binder and the thermal history of the material. Blending the CSA clinker with 20% Gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, strätlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the Gypsum Content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes. © 2011 Elsevier B.V.

  • Hydration of calcium sulfoaluminate cement by a ZnCl2 solution: Investigation at early age
    Cement and Concrete Research, 2009
    Co-Authors: Stéphane Berger, Patrick Le Bescop, Céline Cau Dit Coumes, Denis Damidot
    Abstract:

    Abstract Hydration of calcium sulfoaluminate cement at early age was investigated as a function of the Gypsum Content of the binder, the thermal history of the material, and the ZnCl2 concentration in the mixing solution. Early hydration was strongly accelerated by the presence of Gypsum, but lower percentages of reaction were reached after 24 h. The slowing down effect induced by ZnCl2, even at a concentration as high as 0.5 mol/L, was moderated compared to OPC but had a greater intensity in the absence of Gypsum. Unlike what would have been expected for Portland cement, it was shown that the delay of a Gypsum-free calcium sulfoaluminate cement resulted from the strong retardation caused by chloride anions, which was partly compensated by the accelerating effect of Zn2+ cations. The mineralogical observations revealed the precipitation of chloro–AFm phases such as Friedel's and Kuzel's salts, but no crystallized zinc-containing phases could be identified by XRD. The thermal history of the samples proved to be a key parameter. Applying a thermal cycle which reproduced the temperature rise and decrease occurring in a massive mortar block accelerated the rate of hydration and mainly modified the proportion of AFt versus AFm hydrates, especially when the binder had a Gypsum Content below 20%.

  • Hydration of calcium sulfoaluminate cement by a ZnCl2 solution: Investigation at early age
    Cement and Concrete Research, 2009
    Co-Authors: Stéphane Berger, Céline Cau Dit Coumes, Patrick Le Bescop, Denis Damidot
    Abstract:

    Hydration of calcium sulfoaluminate cement at early age was investigated as a function of the Gypsum Content of the binder, the thermal history of the material, and the ZnCl2 concentration in the mixing solution. Early hydration was strongly accelerated by the presence of Gypsum, but lower percentages of reaction were reached after 24 h. The slowing down effect induced by ZnCl2, even at a concentration as high as 0.5 mol/L, was moderated compared to OPC but had a greater intensity in the absence of Gypsum. Unlike what would have been expected for Portland cement, it was shown that the delay of a Gypsum-free calcium sulfoaluminate cement resulted from the strong retardation caused by chloride anions, which was partly compensated by the accelerating effect of Zn2+ cations. The mineralogical observations revealed the precipitation of chloro-AFm phases such as Friedel's and Kuzel's salts, but no crystallized zinc-containing phases could be identified by XRD. The thermal history of the samples proved to be a key parameter. Applying a thermal cycle which reproduced the temperature rise and decrease occurring in a massive mortar block accelerated the rate of hydration and mainly modified the proportion of AFt versus AFm hydrates, especially when the binder had a Gypsum Content below 20%. © 2009 Elsevier Ltd. All rights reserved.

Takeshi Kamei - One of the best experts on this subject based on the ideXlab platform.

  • investigation of recycled Gypsum in conjunction with waste plastic trays for ground improvement
    Construction and Building Materials, 2011
    Co-Authors: Keizo Ugai, Aly Ahmed, Takeshi Kamei
    Abstract:

    Abstract During the three stages of production, construction and demolition, approximately 15 million tons of Gypsum waste plasterboard is generated annually in the world. It is considered a serious problem due to scarcity of land-filling space, increasing the cost of disposal and increasing environmental regulations. Investigations of using recycled Gypsum “bassanite” which is derived from Gypsum waste plasterboard and waste plastic trays for ground improvement were studied. Recycled Gypsum was used as a stabilizing agent to improve the compressive strength while the waste plastic trays were used to improve the tensile strength. Recycled Gypsum Content, curing time and frost heave property throughout capillary rise test were investigated to determine the behavior of treated soil with recycled Gypsum. In addition, size, Content and aspect ratio of strips of waste plastic trays were investigated. Test results showed that increasing recycled Gypsum Content has a more significant effect on compressive strength compared to the tensile strength. The effect of curing time on the strength of treated soil samples with recycled Gypsum is much pronounced in the early curing days compared to later ages. Adding strips of waste plastic trays to samples treated with recycled Gypsum enhanced both splitting tensile and compressive strengths as well increased the value of secant modulus. Capillary rise rate was reduced with the increase of recycled Gypsum Content, which helps to reduce the formation of ice lenses; hence the susceptibility of treated soil against frost heave is increased. The size and Content of strips of waste plastic trays have significant effect on the potential of capillary rise and the enhancement of strength and stiffness of tested soil.

  • Application of Gypsum Waste Plasterboard and Waste Plastic Trays to Enhance the Performance of Sandy Soil
    Ground Improvement and Geosynthetics, 2010
    Co-Authors: Aly Ahmed, Keizo Ugai, Takeshi Kamei
    Abstract:

    This paper presents the results of a research project that evaluated the use of recycled Gypsum obtained from waste plasterboard along with strips of waste plastic trays to enhance the performance of tested soil. Recycled Gypsum was used as a stabilizing agent for stabilized soil to improve the compressive strength, whereas the waste plastic trays were used to improve the tensile strength. The effects of waste Gypsum Content, size, aspect ratio and waste plastic trays Content were investigated to determine the mechanical behavior of soil treated with such waste materials. Experimental test results showed that unconfined compressive and splitting tensile strengths increased with increasing waste Gypsum Content. The increase in waste Gypsum has a more significant effect on the unconfined compressive strength than on the tensile strength. Adding strips of waste plastic trays to samples treated with waste Gypsum enhanced the splitting tensile strength. The size, aspect ratio and Content of waste plastic trays have significant effect on the enhancement of soil strength.