The Experts below are selected from a list of 4563 Experts worldwide ranked by ideXlab platform

Francis Claret - One of the best experts on this subject based on the ideXlab platform.

  • Quantitative X-ray pair distribution function analysis of nanocrystalline calcium silicate hydrates: a contribution to the understanding of Cement Chemistry
    Journal of Applied Crystallography, 2017
    Co-Authors: Sylvain Grangeon, Alejandro Fernandez-martinez, Alain Baronnet, Nicolas Marty, Agnieszka Poulain, Erik Elkaim, Cedric Roosz, Stéphane Gaboreau, Pierre Henocq, Francis Claret
    Abstract:

    The structural evolution of nanocrystalline calcium silicate hydrate (C-S-H) as a function of its calcium to silicon (Ca/Si) ratio has been probed using qualitative and quantitative X-ray atomic pair distribution function analysis of synchrotron X-ray scattering data. Whatever the Ca/Si ratio, the C-S-H structure is similar to that of tobermorite. When the Ca/Si ratio increases from similar to 0.6 to similar to 1.2, Si wollastonite-like chains progressively depolymerize through preferential omission of Si bridging tetrahedra. When the Ca/Si ratio approaches similar to 1.5, nanosheets of portlandite are detected in samples aged for 1 d, while microcrystalline portlandite is detected in samples aged for 1 year. High-resolution transmission electron microscopy imaging shows that the tobermorite-like structure is maintained to Ca/Si > 3

Sylvain Grangeon - One of the best experts on this subject based on the ideXlab platform.

  • Quantitative X-ray pair distribution function analysis of nanocrystalline calcium silicate hydrates: a contribution to the understanding of Cement Chemistry
    Journal of Applied Crystallography, 2017
    Co-Authors: Sylvain Grangeon, Alejandro Fernandez-martinez, Alain Baronnet, Nicolas Marty, Agnieszka Poulain, Erik Elkaim, Cedric Roosz, Stéphane Gaboreau, Pierre Henocq, Francis Claret
    Abstract:

    The structural evolution of nanocrystalline calcium silicate hydrate (C-S-H) as a function of its calcium to silicon (Ca/Si) ratio has been probed using qualitative and quantitative X-ray atomic pair distribution function analysis of synchrotron X-ray scattering data. Whatever the Ca/Si ratio, the C-S-H structure is similar to that of tobermorite. When the Ca/Si ratio increases from similar to 0.6 to similar to 1.2, Si wollastonite-like chains progressively depolymerize through preferential omission of Si bridging tetrahedra. When the Ca/Si ratio approaches similar to 1.5, nanosheets of portlandite are detected in samples aged for 1 d, while microcrystalline portlandite is detected in samples aged for 1 year. High-resolution transmission electron microscopy imaging shows that the tobermorite-like structure is maintained to Ca/Si > 3

Inés Joekes - One of the best experts on this subject based on the ideXlab platform.

  • Cement industry: sustainability, challenges and perspectives
    Environmental Chemistry Letters, 2011
    Co-Authors: F. A. Rodrigues, Inés Joekes
    Abstract:

    Cement-based materials, such as concrete and mortars, are used in extremely large amounts. For instance, in 2009 concrete production was superior to 10 billion tons. Cement plays an important role in terms of economic and social relevance since it is fundamental to build and improve infrastructure. On the other hand, this industry is also a heavy polluter. Cement production releases 5–6% of all carbon dioxide generated by human activities, accounting for about 4% of global warming. It can release huge amounts of persistent organic pollutants, such as dioxins and heavy metals and particles. Energy consumption is also considerable. Cement production use approximately 0.6% of all energy produced in the United States. On the other hand, the Chemistry underlying Cement production and its applications can be very helpful to overcome these environmental issues. In terms of manufacture, there are many alternative materials that can be used to minimize carbon dioxide production and reduce energy consumption, such as calcium sulfoaluminates and β-Ca_2SiO_4—rich Cements. Using residues from other industrial sectors can also improve the sustainability of Cement industry. Under adequate conditions, waste materials such as tyres, oils, municipal solid waste and solvents can be used as supplementary fuel in Cement plants. Concrete can be used for encapsulation of waste materials such as tyres, plastics and glasses. In this review, we discuss some aspects of the Cement industry associated with environmental science. Other issues such as economic aspects, the Chemistry of Cement manufacture and its properties are also presented. Special attention is given to the role that Cement Chemistry can play in terms of sustainability. The most relevant aspects are outlined, such as the use of alternative materials, new possibilities and also the recycling of materials. It is also argued that an important aspect is the role of research and development necessary to improve Cement sustainability.

H Takenouti - One of the best experts on this subject based on the ideXlab platform.

  • electrochemical behaviour of steel rebars in concrete influence of environmental factors and Cement Chemistry
    Electrochimica Acta, 2001
    Co-Authors: C Andrade, M Keddam, X R Novoa, M C Perez, C M Rangel, H Takenouti
    Abstract:

    Four series of reinforced concrete specimens have been studied over 3 years exposure in a 100% relative humidity atmosphere. Addition of CaCl2, NaNO2, and a mixture of CaCl2 and NaNO2 changed the Cement Chemistry with respect to an ordinary portland Cement series of samples used as reference series. The study, based on low-scan rate cyclic voltammetry and electrochemical impedance spectroscopy, confirms previous results obtained in alkaline medium, i.e. the redox activity in the rebar’s oxides layer greatly influences the electrochemical behaviour of rebars in the passivity potential domain. Different redox processes also influence the active and cathodic protection domains that make corrosion rate estimations very difficult. The possibilities of estimating corrosion rate are discussed in terms of Cement Chemistry and corrosion potential of the system. © 2001 Elsevier Science Ltd. All rights reserved.

  • electrochemical behaviour of steel rebars in concrete influence of environmental factors and Cement Chemistry
    International symposium on Electrochemical methods in Corrosion Research, 2001
    Co-Authors: C Andrade, M Keddam, X R Novoa, M C Perez, C M Rangel, H Takenouti
    Abstract:

    Four series of reinforced concrete specimens have been studied over 3 years exposure in a 100% relative humidity atmosphere. Addition of CaCl 2 , NaNO 2 , and a mixture of CaCl 2 and NaNO 2 changed the Cement Chemistry with respect to an ordinary portland Cement series of samples used as reference series. The study, based on low-scan rate cyclic voltammetry and electrochemical impedance spectroscopy, confirms previous results obtained in alkaline medium, i.e. the redox activity in the rebar's oxides layer greatly influences the electrochemical behaviour of rebars in the passivity potential domain. Different redox processes also influence the active and cathodic protection domains that make corrosion rate estimations very difficult. The possibilities of estimating corrosion rate are discussed in terms of Cement Chemistry and corrosion potential of the system.

Alejandro Fernandez-martinez - One of the best experts on this subject based on the ideXlab platform.

  • Quantitative X-ray pair distribution function analysis of nanocrystalline calcium silicate hydrates: a contribution to the understanding of Cement Chemistry
    Journal of Applied Crystallography, 2017
    Co-Authors: Sylvain Grangeon, Alejandro Fernandez-martinez, Alain Baronnet, Nicolas Marty, Agnieszka Poulain, Erik Elkaim, Cedric Roosz, Stéphane Gaboreau, Pierre Henocq, Francis Claret
    Abstract:

    The structural evolution of nanocrystalline calcium silicate hydrate (C-S-H) as a function of its calcium to silicon (Ca/Si) ratio has been probed using qualitative and quantitative X-ray atomic pair distribution function analysis of synchrotron X-ray scattering data. Whatever the Ca/Si ratio, the C-S-H structure is similar to that of tobermorite. When the Ca/Si ratio increases from similar to 0.6 to similar to 1.2, Si wollastonite-like chains progressively depolymerize through preferential omission of Si bridging tetrahedra. When the Ca/Si ratio approaches similar to 1.5, nanosheets of portlandite are detected in samples aged for 1 d, while microcrystalline portlandite is detected in samples aged for 1 year. High-resolution transmission electron microscopy imaging shows that the tobermorite-like structure is maintained to Ca/Si > 3