The significance of chlorides in concrete trial mixes

The concentration of acid-soluble chlorides in concrete has been used to determine the risk of corrosion of reinforcing steel despite indications that the level of free chloride ions may be overestimated by this test, which may result in the rejection of otherwise suitable aggregates. To assess the influence of sample size on the test results, 100mm diameter x 200mm long concrete cylinders were ground to 150 micrometres and analysed for acid-soluble chloride in accordance with AS 1012.20, modified to improve accuracy. The concrete was found to contain between 0.03 and 0.04 per cent chloride by weight. The same concrete was extracted in boiling water. The water soluble chloride content was no more than 1/35 of that measured by acid extraction. The constituents of the concrete mix were then analysed by acid extraction and total chlorides determined. Hardened concrete samples of the mix were made and analysed for chloride by acid extraction, with the quantity of chloride found to be within 0.1 per cent of the quantity of chloride in the constituents. Water extraction found nil chlorides. Additional samples of the concrete mix were prepared containing an added known quantity of sodium chloride and analysed. The chloride was recovered quantitatively using acid and water extraction, with water extraction finding nil chlorides. This testing and its implications for testing concrete trial mixes for chlorides are discussed. (a) For the covering record of this conference, please refer to ITRD abstract no E218284.

  • Authors:
    • FORSTER, G J
  • Publication Date: 2009-9


  • English

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  • Accession Number: 01153004
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ITRD, ATRI
  • Created Date: Mar 23 2010 9:10AM