PROBING THE EFFECT OF SUPERPLASTICIZER ADSORPTION ON THE SURFACE FORCES USING THE COLLOIDAL PROBE AFM TECHNIQUE

Superplasticizers are used to improve the flowability of cementitious systems; recent advancements in superplasticizers have focused on good flowability, extended working time, and an increased need for a reduction in concrete porosity. This article reports on a study of the interactions between adsorbed superplasticizer layers. The study used direct force measurements, with an atomic force microscope (AFM). In the study, MgO was used as a nonreactive model system for cement, and a new freeze granulation method was used for the production of spherical particles suitable for the colloidal probe AFM. Direct measurements of the forces between the spherical probe and a flat MgO substrate showed that the surfaces attract each other in an electrolyte that mimics cement water at pH 10. However, the adsorption of superplasticizers eliminates the attraction and induces a repulsive force between the surfaces. The authors found that the interactions induced by the adsorption of the anionic acrylic ester-ethylene oxide (AAE-EO) copolymers can be described as electrosteric, with an electrostatic and steric contribution. The lignosulfonate also induced a significant steric contribution that could be related to a dense coil conformation of the adsorbed superplasticizer.

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  • Corporate Authors:

    Elsevier

    The Boulevard, Langford Lane
    Kidlington, Oxford  United Kingdom  OX5 1GB
  • Authors:
    • Kauppi, A
    • Andersson, K M
    • Bergstrom, L
  • Publication Date: 2005-1

Language

  • English

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  • Accession Number: 00988991
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 18 2005 12:00AM