The Experts below are selected from a list of 6267 Experts worldwide ranked by ideXlab platform

Pierre Claude Aïtcin - One of the best experts on this subject based on the ideXlab platform.

  • the adsorption behavior of pns superplasticizer and its relation to fluidity of cement paste
    Cement and Concrete Research, 2000
    Co-Authors: Shiping Jiang, Carmel Jolicoeur, Pierre Claude Aïtcin
    Abstract:

    The adsorption behavior of a polynaphthalenesulfonate (PNS) superplasticizer and its relation to the fluidity of cement paste has been investigated for six cements at a given dosage of PNS superplasticizer. The results show that incompatible cements have a higher adsorption capacity of PNS superplasticizer because of a lack of Soluble Alkali sulfates. There is an inverse relationship between the amount of PNS adsorbed and the mini-slump area value of the cement pastes at 30 min, that is, the higher the amount of PNS adsorbed, the lower the initial slump value, and the higher the slump loss. The addition of some Na2SO4 contributes to increase the slump area by reducing the amount of PNS adsorbed. Moreover, it has been found that additional calcium sulfate does not prevent the adsorption of PNS on cement particles as sodium sulfate does in cement pastes having W/C=0.35. The contribution of Alkali sulfate on dispersing mechanism of PNS superplasticized cement pastes is explained in relation with initial slump and its loss.

  • importance of adequate Soluble Alkali content to ensure cement superplasticizer compatibility
    Cement and Concrete Research, 1999
    Co-Authors: Shiping Jiang, Pierre Claude Aïtcin
    Abstract:

    Abstract The effect of Soluble Alkalis on cement/superplasticizer compatibility has not yet been thoroughly understood. This paper establishes the impact that Soluble Alkalis have on the compatibility of cement and polynaphthalene sulfonate superplasticizer during the first few minutes of hydration. The amount of Soluble Alkalis that go into solution during the first few minutes is a key parameter in controlling fluidity and fluidity loss of a cement paste made with superplasticizer. The optimum Soluble Alkali content for increasing initial fluidity and decreasing fluidity loss with time was found to be on the order of 0.4%–0.5% Na 2 O equivalent in the six cements under study. Furthermore, this optimum Alkali content is independent of the superplasticizer dosage and cement type. In cement with an optimum amount of Soluble Alkalis, the C 3 A content has practically no effect on fluidity loss.

Hjh Jos Brouwers - One of the best experts on this subject based on the ideXlab platform.

  • Chemical speciation, distribution and leaching behavior of chlorides from municipal solid waste incineration bottom ash.
    Chemosphere, 2019
    Co-Authors: Qadeer Alam, A. Lazaro, K. Schollbach, Hjh Jos Brouwers
    Abstract:

    Abstract Municipal solid waste incineration (MSWI) bottom ash is an environmentally harmful solid waste that cannot be recycled without pre-treatment. The chloride content in bottom ash (BA) is a major obstacle that restricts its application as secondary building materials. Here, the chemical speciation of the chlorides in BA is systematically studied with multiple analytical techniques, i.e., quantitative XRD, microanalysis and XPS. In addition to halite (NaCl), several chloride-rich minerals are present in BA. These phases are hydrous metal oxides, ettringite, decomposed hydration products (C4A3) and incineration slag with a chloride content of 3.2%, 1.4%, 2.1% and 1.3%, respectively. For the first time, the real-time leaching profiles of chloride (up to 80 h) from BA were obtained with a chloride-ion specific electrode to explain the leaching mechanism. In the initial stage of leaching, highly Soluble Alkali salts (NaCl) and physisorbed chlorides (especially those adsorbed on hydrous metal oxides) are released, which is controlled by diffusion. Later, the leaching is controlled by the solubility/reactivity of the chloride-containing phases, such as ettringite and incineration slag. The results show that the release of chloride is not only a diffusion-controlled process, as reported in the literature, but also a reaction-controlled phenomenon, during which the chloride-rich phases decompose and release chlorides that are associated with them via sorption/incorporation.

Shiping Jiang - One of the best experts on this subject based on the ideXlab platform.

  • the adsorption behavior of pns superplasticizer and its relation to fluidity of cement paste
    Cement and Concrete Research, 2000
    Co-Authors: Shiping Jiang, Carmel Jolicoeur, Pierre Claude Aïtcin
    Abstract:

    The adsorption behavior of a polynaphthalenesulfonate (PNS) superplasticizer and its relation to the fluidity of cement paste has been investigated for six cements at a given dosage of PNS superplasticizer. The results show that incompatible cements have a higher adsorption capacity of PNS superplasticizer because of a lack of Soluble Alkali sulfates. There is an inverse relationship between the amount of PNS adsorbed and the mini-slump area value of the cement pastes at 30 min, that is, the higher the amount of PNS adsorbed, the lower the initial slump value, and the higher the slump loss. The addition of some Na2SO4 contributes to increase the slump area by reducing the amount of PNS adsorbed. Moreover, it has been found that additional calcium sulfate does not prevent the adsorption of PNS on cement particles as sodium sulfate does in cement pastes having W/C=0.35. The contribution of Alkali sulfate on dispersing mechanism of PNS superplasticized cement pastes is explained in relation with initial slump and its loss.

  • importance of adequate Soluble Alkali content to ensure cement superplasticizer compatibility
    Cement and Concrete Research, 1999
    Co-Authors: Shiping Jiang, Pierre Claude Aïtcin
    Abstract:

    Abstract The effect of Soluble Alkalis on cement/superplasticizer compatibility has not yet been thoroughly understood. This paper establishes the impact that Soluble Alkalis have on the compatibility of cement and polynaphthalene sulfonate superplasticizer during the first few minutes of hydration. The amount of Soluble Alkalis that go into solution during the first few minutes is a key parameter in controlling fluidity and fluidity loss of a cement paste made with superplasticizer. The optimum Soluble Alkali content for increasing initial fluidity and decreasing fluidity loss with time was found to be on the order of 0.4%–0.5% Na 2 O equivalent in the six cements under study. Furthermore, this optimum Alkali content is independent of the superplasticizer dosage and cement type. In cement with an optimum amount of Soluble Alkalis, the C 3 A content has practically no effect on fluidity loss.

Yingzu Liu - One of the best experts on this subject based on the ideXlab platform.

  • characteristics of Alkali species release from a burning coal biomass blend
    Applied Energy, 2018
    Co-Authors: Yingzu Liu, Zhihua Wang, Jun Xia, Kaidi Wan, Ronald Whiddon, Kefa Cen
    Abstract:

    Abstract Solvent fractionation, Laser induced breakdown spectroscopy (LIBS), X-ray Diffraction (XRD) and chemical analysis were applied to binary fuel mixtures of Zhundong coal and cornstalk agricultural class to investigate the release characteristics of Alkali species during co-firing of coal and biomass. As the biomass proportion increases, the water-Soluble, NH4Ac-Soluble and HCl-Soluble Alkali species interconvert; the extent of the conversion depends on the composition of the blend. From LIBS measurements, it was found that adding the biomass accelerates combustion and outgassing processes. The higher the proportion of the biomass in the blend, the earlier the peak concentrations of Alkali appear, and the magnitude of peak concentrations of sodium and potassium decrease and increase, respectively. Furthermore, the interaction between coal and biomass can generate crystals causing the eutectic melting phenomenon (similar to feldspar in XRD results), which results in a sharp decline of the ash fusion temperatures (AFTs). The results not only provide the information of fundamental transformation but also guide industrial co-firing applications of lignite and agricultural class biomass to reduce the risk of ash deposition.

Qadeer Alam - One of the best experts on this subject based on the ideXlab platform.

  • Chemical speciation, distribution and leaching behavior of chlorides from municipal solid waste incineration bottom ash.
    Chemosphere, 2019
    Co-Authors: Qadeer Alam, A. Lazaro, K. Schollbach, Hjh Jos Brouwers
    Abstract:

    Abstract Municipal solid waste incineration (MSWI) bottom ash is an environmentally harmful solid waste that cannot be recycled without pre-treatment. The chloride content in bottom ash (BA) is a major obstacle that restricts its application as secondary building materials. Here, the chemical speciation of the chlorides in BA is systematically studied with multiple analytical techniques, i.e., quantitative XRD, microanalysis and XPS. In addition to halite (NaCl), several chloride-rich minerals are present in BA. These phases are hydrous metal oxides, ettringite, decomposed hydration products (C4A3) and incineration slag with a chloride content of 3.2%, 1.4%, 2.1% and 1.3%, respectively. For the first time, the real-time leaching profiles of chloride (up to 80 h) from BA were obtained with a chloride-ion specific electrode to explain the leaching mechanism. In the initial stage of leaching, highly Soluble Alkali salts (NaCl) and physisorbed chlorides (especially those adsorbed on hydrous metal oxides) are released, which is controlled by diffusion. Later, the leaching is controlled by the solubility/reactivity of the chloride-containing phases, such as ettringite and incineration slag. The results show that the release of chloride is not only a diffusion-controlled process, as reported in the literature, but also a reaction-controlled phenomenon, during which the chloride-rich phases decompose and release chlorides that are associated with them via sorption/incorporation.