MECHANICAL DAMAGE TO CONCRETE BY EARLY REMOVAL OF FORMWORK

In this experimental investigation of the mechanical damage to concrete caused by the early removal of formwork, controlled removal of formwork both perpendicular and parallel to the concrete face was carried out at various times after concreting. The form material has a major influence upon the striking stresses and risk of mechanical damage. Provided the concrete has achieved an in situ cube strength of 2 N/mm (square), unsealed plywood with a release agent can be struck after an equivalent age at 20 deg C of 12 h with an acceptable risk of mechanical damage. With impremeable formwork and a release agent, the minimum equivalent age at striding can be reduced to 9 h. The types of mechanical damage are described, a mathematical relationship for equivalent age is set forth, experiments are outlined, and details are given of the preparation of moulds. Descriptions of the test rig, concrete and test procedure are detailed, and the results are discussed. Conclusions based on the study are presented which relate to unsealed plywood formwork's striking properties, release agents, internal and external vibration, the reaction between the wood sugars and cement, and the applicability of the equivalent age concept.

  • Corporate Authors:

    Cement and Concrete Association

    52 Grosvenor Gardens
    London SW1W 0AQ,   England 
  • Authors:
    • HARRISON, T A
  • Publication Date: 1975-2

Media Info

  • Features: Appendices; References; Tables;
  • Pagination: 28 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00096474
  • Record Type: Publication
  • Report/Paper Numbers: 42.505
  • Files: TRIS
  • Created Date: Aug 13 1975 12:00AM