A new generation of concrete has been created to satisfy the needs of civil engineering companies to face new architectural requirements and the constraints of shorter deadlines. The authors of this article first discuss the use of large (up to 20-m-high) formworks that are filled in one pour only at a very high pouring rate, and the resulting mechanics and conditions of high pressure related to the depth of poured material. The authors report on their research study on fresh cement paste which was carried out in order to establish a relationship between the intrinsic properties of the cement-based mixtures and fresh concrete pressure exerted on the surface of the formwork; and to explain the process of maturation of cement-based materials between casting and striking phases of the form. Three types of cement paste mixtures with a water/cement (W/C) ratio of 0.30, 0.36 and 0.45, respectively, were tested in 1-m to 10-m formworks. In addition, temperature and setting kinetics were also examined. The results show that the kinetics of the pore water pressure and the total lateral pressure were strongly affected by the W/C ratio, the vibration, and the level of stress to which the fresh cement paste is subjected. These parameters have a particular influence on the compactness of the material and, consequently, on the size of the capillaries and on the depression level. For the cement paste, the profiles of the pore water pressures and the total lateral pressures are hydrostatic, from the initial state until cancellation. Once the total lateral pressure is null, the pore water pressure passes to a depression state. The autogenous shrinkage test shows that the contraction of the paste is activated from the beginning because of the formation of the interstitial depression state related to the capillarity phenomenon.

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    The Boulevard, Langford Lane
    Kidlington, Oxford  United Kingdom  OX5 1GB
  • Authors:
    • Andriamanantsilavo, N R
    • Amziane, S
  • Publication Date: 2004-11


  • English

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  • Accession Number: 00986448
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 8 2005 12:00AM