ALKALI-AGGREGATE REACTION IN CONCRETE - A PROBLEM IN NEW ZEALAND. NEW ZEALAND ROADING SYMPOSIUM 1987. VOLUME 4

This paper describes the problem of alkali-aggregate reaction in concrete overseas and in New Zealand. Alkali-aggregate reaction may take place when the following are all present in concrete: (a) there is a reactive siliceous constituent in the aggregate; (b) there are sufficient alkalies in the pore solution; and (c) there is water present. The reaction produces an alkali-silica gel which swells when it absorbs water, producing expansive forces sufficient to crack the surrounding concrete. This may lead to corrosion of the steel reinforcement and subsequent spalling of the cover concrete. Overall, expansion may close up joints, misalign associated details and locally overstress individual structural members. Overseas, detailed surveys of concretes containing suspect aggregates have invariably revealed affected structures in various conditions of distress. Similarly, cases in New Zealand have been uncovered by recent surveys carried out by Central Laboratories, MWD. There is no practical way to stop the reaction in a structure, although in some cases the reaction stops itself by running out of reactive materials. In theory, drying the concrete will stop the reaction. While surface coatings may slow the ingress of water many concretes retain sufficient internal water for the reaction to proceed. Irrespective of the repair techniques used, overseas experience indicates that costs are considerable. New Zealand has investigated and employed preventive measures to reduce the effects of alkali-aggregate reaction for over forty years. Thus, compared with many other countries, alkali-aggregate reactions are not widespread in New Zealand. For the covering abstract of the symposium see IRRD 810782. (TRRL)

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0477071562
• Corporate Authors:

  National Roads Board, New Zealand

  P.O. Box 12-041
  Wellington,   New Zealand 
• Authors:
  • SMITH, L M
  • St John, D A
  • Freitag, S A
• Publication Date: 1987

Media Info

• Features: References;
• Pagination: p. 821-826
• Serial:
  • Publication of: UNITED NATIONS
  • Publisher: United Nations
  • ISSN: 0252-4392

Subject/Index Terms

• TRT Terms: Alkali aggregate reactions; Concrete; Conferences; Prevention
• Geographic Terms: New Zealand
• ITRD Terms: 4577: Aggregate; 7353: Alkali; 4755: Concrete; 8525: Conference; 5252: Corrosion; 5211: Cracking; 1614: Damage; 4123: Quartz; 7156: Reaction (chem); 4355: Water
• Subject Areas: Highways; Materials; Security and Emergencies;

Filing Info

• Accession Number: 00476439
• Record Type: Publication
• Source Agency: Transport Research Laboratory
• ISBN: 0-477-07156-2
• Files: ITRD, TRIS
• Created Date: Sep 30 1988 12:00AM