CONCRETE PERFORMANCE AS RELATED TO BEHAVIOR OF CARBONATE AGGREGATES

THE MAJORITY OF CARBONATE ROCKS MAKE EXCELLENT AGGREGATE FOR CONCRETE, HOWEVER, THERE ARE CERTAIN DOLOMITIC LIMESTONES WHICH CAUSE EXCESSIVE EXPANSION AND CRACKING OF CONCRETE WHEN USED AS COARSE AGGREGATE WITH HIGH ALKALI CEMENT. FIELD INVESTIGATIONS ARE REPORTED ON THIS ALKALI-AGGREGATE REACTION. LABORATORY TESTS WERE CONDUCTED BY MAKING CONCRETE PRISMS USING JOB MATERIALS AND MIX DESIGNS AND EXPOSING THESE TO CONTINUOUS FOGROOM CONDITIONS. MEASUREMENTS OF LENGTH CHANGES WERE MADE ON A COMPARATOR WHICH CONTAINED A MICROMETER AT THE TOP WHICH MEASURED TO THE NEAREST 0.0001 INCH. EXPANSIONS OF THE ORDER OF 0.1 PERCENT OR MORE WERE MEASURED AFTER A PERIOD OF A FEW MONTHS. TEST RESULTS WITH VARIOUS COMBINATIONS OF DIFFERENT COARSE AND FINE AGGREGATES REVEALED THAT DOLOMITIC LIMESTONE COARSE AGGREGATE WAS THE EXPANSIVE COMPONENT. THE DURABILITY OF CONCRETES MADE WITH SPECIAL LOW-ALKALI CEMENT WAS INVESTIGATED IN THE LABORATORY USING AGGREGATE FROM VARIOUS BEDS. FREEZE-THAW TESTS AND DRYING CYCLING TESTS WERE CONDUCTED. IT IS CONCLUDED THAT: (1) THE ALKALI-CARBONATE ROCK REACTION IS DIFFERENT FROM THE ALKALI-SILICA REACTION, (2) IT RESULTS FROM REACTION BETWEEN A SPECIAL TYPE OF DOLOMITIC LIMESTONE AND THE ALKALIS DERIVED FORM HIGH-ALKALI CEMENT, (3) MOISTURE IS NECESSARY FOR THE REACTION, (4) POZZOLANIC MATERIALS WHICH CONTROL THE SILICA REACTIONS ARE NOT EFFECTIVE IN THIS CASE, AND (5) THE ACTION MAY BE CONTROLLED BY USE OF LOW-ALKALI CEMENT BUT THE TOTAL ALKALI CONTENT SHOULD BE LIMITED TO ABOUT 0.40 TO 0.45 PERCENT. THE PROCEDURES FOUND NECESSARY FOR FIELD USE FOR RECONGNITION OF POTENTIALLY EXPANSIVE CARBONATE ROCKS ARE: (1) PETROGRAPHIC METHODS, (2) ROCK PRISM OR ROCK CYLINDER TEST, AND (3) CONCRETE BEAM TEST WHICH IS THE MOST DIRECT METHOD OF EVALUATION. THE MOST IMPORTANT MINERALOGICAL CHANGE WHICH TAKES PLACE WHEN FINE-GRAINED DOLOMITIC LIMESTONE IS PLACED IN STRONG ALKALI IS KNOWN AS DEDOLOMITIZATION. THE MINERAL DOLOMITE IS REPLACED BY MAGNESIUM HYDROXIDE, CALCIUM CARBONATE AND ALKALI CARBONATE.

• Supplemental Notes:
  • pp 133-139, 5 FIG, 3 REF
• Authors:
  • Gillott, J E
• Conference:
  • Highway Geology Symposium, Iowa State U
• Publication Date: 1968-7

Subject/Index Terms

• TRT Terms: Alkali aggregate reactions; Alkalinity; Beams; Carbonate rocks; Cement; Coarse aggregates; Concrete; Concrete aggregates; Concrete tests; Cracking; Dolomite; Durability; Expansion; Flexural strength; Freeze thaw tests; Laboratory tests; Limestone aggregates; Petrography; Prisms; Structural tests
• Uncontrolled Terms: Concrete cracking; Low alkali cement
• Old TRIS Terms: Dedolomitization
• Subject Areas: Bridges and other structures; Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00213345
• Record Type: Publication
• Report/Paper Numbers: pp 128-129
• Files: TRIS
• Created Date: Jul 7 1994 12:00AM