The scanning electron microscope was used to investigate the difference between the appearance, dimension and distribution of entrained-air following the addition of several agents available on the market. These agents cause the formation of 300-micron bubbles, the latter sometimes reaching 1000-microns for some agents in mortar. Attention is drawn to microcracks present in the cement paste round the air bubbles. These microcracks are numerous and varied in shape. They seem to have been formed during hardening, perhaps as a result of stresses created at the interface of the entrained air. The appearance of these microcracks in the paste or mortar seems to be accompanied by an increase in capillary absorption and a reduction in shrinkage. Moreover, cracking of air-entrained concrete is slightly delayed. The maximum size of the bubbles appears to influence the physical characteristics of mortars. Similarly, their distribution in the mortar plays an important role in the strength. The coalescence or regrouping of a large number of small bubbles (30, 40 microns) round a large bubble (200, 300 microns) leads to greater reductions in strength. /TRRL/

  • Corporate Authors:

    Laboratoire Central des Ponts et Chausees (LCPC)

    Boulevard Lefebvre 58
    Paris Cedex 15,   France  F-75732
  • Authors:
    • Paillere, A M
    • Gonzalez, J C
  • Publication Date: 1977-9-10


  • French

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00194111
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Jun 13 1979 12:00AM