DETERMINATION OF THE FREE CHLORIDE IN CONCRETE IS NOT THAT SIMPLE

Two methods have been used to determine the 'free' and 'water soluble' chloride ion concentration in five differing strength grades or compositions of concretes of low, medium and high strength. Each grade of concrete had varying concentration of Cl admixed as NaCl. In all, 36 different batches of concretes were made with admixed Cl concentration varying from 0.2 to 4%, by weight of cement. The first method was the analysis of the pore solution expressed from specimens and second by the analysis of the decanted solution of pulverised specimens. The results suggest that the decanted solutions of concretes overestimate the Cl concentration, and give erroneously high values for OH concentrations. The concentration of both the expressed and the solutions was found to depend on the (i) concentration of the admixed Cl ions; (ii) strength of the concrete; (iii) presence or absence of fly ash; and (iv) presence or absence of a superplasticiser. Accordingly, there does not seem to be a simple relationship between total Cl content and the Cl concentration as found in decanted and expressed pore solutions. Whereas the presence of flyash improves the chloride binding capacity of a concrete, the presence of superplasticisers tends to lower it. The paper concludes that in order to limit the damage caused by Cl in a concrete, an upper limit on the total Cl content of the chloride existing in the mix ingredients rather than the percentage of Cl by the weight of cement should be prescribed. (a)

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  • Corporate Authors:

    N/A

    ,   United States 
  • Authors:
    • Haque, M N
    • Kayyali, O A
  • Publication Date: 1995-5

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00717838
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ITRD, ATRI
  • Created Date: Mar 20 1996 12:00AM