CHLORIDE-BINDING IN CEMENT AND THE CL/OH-RATIO OF THE PORE SOLUTION

Although it is generally recognized that only the free chloride can damage the steel in concrete it is the total chloride content which is normally used for the assessment for the corrosion risk. Thus it is worth while to have precise information on chloride concentration in the pore solution of hardened cement paste as well as of the factors influencing chloride binding. The investigations showed that the residual chloride concentration in the pore solution of samples prepared with the addition of chloride, made with the same cement and with 1 % total chloride content varied on dependency of the w/c-ratio (between 0.4 and 1.0) and the used chloride compound (sodium chloride or calcium dichloride) up to a factor of over 8. Therefore the total chloride content alone can not be a reliable indicator. Results of different authors show that the Cl/OH-ratio of the pore water is the significant value. Although the Cl/OH-ratio allows without any doubt a much better assessment than the total chloride content alone but it is also not the indicator which gives an absolutely sure information. This because the results showed that with increasing w/c-ratio both the Cl- and OH-concentration in the pore water of samples with otherwise identical composition decrease continuously, however, at different rates. The Cl/OH-ratio was therefore the higher the lower the w/c-ratio. That would mean that the corrosion risk increases with decreasing w/c-ratio. This is in contradiction to all practical experiences probably because of the influence of other corrosion relevant factors such as oxygen diffusion, moisture, electrical resistivity etc. For the covering abstract of the conference see IRRD 9006VT004E. (A)

Language

  • English

Media Info

  • Pagination: p. 129-142
  • Serial:
    • VTI Rapport
    • Issue Number: 352A
    • Publisher: Swedish National Road and Transport Research Institute (VTI)
    • ISSN: 0347-6030

Subject/Index Terms

Filing Info

  • Accession Number: 00607084
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS, ATRI
  • Created Date: Mar 31 1991 12:00AM