ALKALI-SILICA-REACTIVE ROCKS IN THE CANADIAN SHIELD

SANDS, GRAVEL, AND ROCK FROM AN AREA OF THE CANADIAN SHIELD, SOME 200 MILES NORTH OF TORONTO, CONSISTED MAINLY OF GRAYWACKES, ARGILLITES, AND RELATED ROCKS. ON THE BASIS OF THE QUICK CHEMICAL TEST (ASTM C 289), THESE ROCKS APPEARED ACCEPTABLE FOR USE AS CONCRETE AGGREGATES. MORTAR BARS, HOWEVER, DEVELOP ALKALI-SILICA GEL AND SHOW EXPANSION GREATER THAN 0.10 PERCENT AFTER BEING TESTED FOR MORE THAN ONE YEAR. A CONCRETE DAM IN THE AREA CONTAINING SIMILAR ROCKS AS AGGREGATE ALSO SHOWED SIGNS OF ALKALI-SILICA REACTIONS WITH GEL FORMATION, PATTERN CRACKING, AND WIDE- OPEN CRACKS. MORTAR BARS MADE WITH SELECTED VARVED ARGILLITES USED AS PART OF THE COARSE AGGREGATE IN THIS DAM EXPANDED MORE THAN 0.10 PERCENT IN 24 WEEKS. ASTM METHOD C 586-66T APPEARS APPLICABLE FOR DETERMINATION OF EXPANSION OF THESE SILICA ROCKS. LIKE CARBONATE ROCKS, THE SEEMINGLY UNIFORM VARVED ARGILLITES DO NOT RESPOND UNIFORMLY TO IMMERSION IN SODIUM HYDROXIDE. MOST ROCK CYLINDERS SHRINK SLIGHTLY BEFORE STARTING TO EXPAND. THE MAXIMUM EXPANSION OBSERVED IN ONE CYLINDER WAS 0.152 PERCENT IN 36 WEEKS. A COMPARISON OF THE CYLINDERS WITH MORTAR BARS MADE FROM THE SAME TYPE OF ARGILLITE AND FROM OTHER SAMPLES CONTAINING SOME ARGILLITE SHOWS THAT THE RANGE OF EXPANSION OF CYCIN- DERS IS GREATER THAN THAT OF MORTAR BARS. THIN SECTIONS AND CYLINDER TESTS INDICATE THAT THE LESS METAMORPHOSED GRAY ARGILLITE VARIETY IS GENERALLY MORE EXPANSIVE THAN THE MORE METAMORPHOSED GREENISH GRAY VARIETY. THIS IS THE FIRST KNOWN INDICATION THAT ARGILLITES ARE ALKALI-SILICA REACTIVE, ALTHOUGH THESE ROCKS ARE CLOSELY RELATED TO PHYLLITES AND SLATES, SOME OF WHICH ARE KNOWN TO BE REACTIVE. THERE ARE INDICATIONS THAT CERTAIN TYPES OF GRAYWACKE OCCURRING IN THE AREA ARE REACTIVE TO A LESSER DEGREE. /AUTHOR/

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/hrr/1969/268/268-008.pdf
• Supplemental Notes:
  • Paper sponsored by Committee on Performance of Concrete--Chemical Aspects. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
• Authors:
  • Dolar-Mantuani, L
• Publication Date: 1969

Media Info

• Media Type: Digital/other
• Features: Appendices; Figures; References; Tables;
• Pagination: pp 99-117
• Monograph Title: Portland cement concrete - sealers, durability creep, reactivity, and cement determination
• Serial:
  • Highway Research Record
  • Issue Number: 268
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Aggregates; Alkali aggregate reactions; Chemical tests; Concrete aggregates; Concrete dams; Expansion; Materials tests; Mortar; Rocks; Silica
• Uncontrolled Terms: Aggregate testing; Cylinders
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00213389
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Sep 22 1994 12:00AM