CONCRETE PRODUCING PROPERTIES OF NORTH DAKOTA PIT-RUN AGGREGATES

INVESTIGATION WAS CONDUCTED TO DETERMINE THE STRENGTH CAPABILITIES OF AGGREGATES TAKEN DIRECTLY FROM GRAVEL PITS LOCATED AT VARIOUS POINTS WITHIN THE STATE OF NORTH DAKOTA. THE RESULTS SOUGHT WERE TO OBTAIN COMPRESSIVE STRENGTH VALUES OF 2,000 PSI, OR GREATER, FOR CONCRETE CAST FROM THE VARIOUS MIXES AND MOIST CURED FOR 28 DAYS. THE CEMENT CONTENT VARIED FROM 3 SACKS/CU.YD. TO 7 1/2 SACKS/CU.YD. IN INCREMENTS OF 1 1/2 SACKS AND THE ENTRAINED AIR CONTENT VARIED FROM 4% TO 10%. PREDETERMINED PHYSICAL TESTS WERE USED TO CLASSIFY THE QUALITY OF THE AGGREGATE AND PROVIDE A CRITERIA FOR THE SELECTION OF FOUR AGGREGATES REPRESENTATIVE OF THE MATERIAL IN THE 10 SELECTED GRAVEL PITS. LATER AN ADDITIONAL 4 AGGREGATES WERE TESTED. SIXTEEN CONCRETE MIXES WERE ALSO MADE USING A STANDARD AGGREGATE. THE COARSE AND FINE AGGREGATE COMPOSITION WAS SELECTED TO AGREE CLOSELY WITH THE GRADATION OF THE PIT-RUN MATERIAL. TWENTY-EIGHT-DAY MOIST-CURE COMPRESSIVE AND FLEXURE STRENGTH, 28-DAY AND 90- DAY DRY-CURE FLEXURE STRENGTH WERE DETERMINED. THE CHANGE OF LENGTH AT 7 DAYS, 28 DAYS, AND 90 DAYS WAS MEASURED. THE DURABILITY OF THE CONCRETE WAS DETERMINED FROM THE-RESULTS OF 300 CYCLES OF RAPID FREEZING IN AIR AND THAWING IN WATER, ASTM METHOD C-291. THE COMPRESSIVE STRENGTH OF 2,000 PSI AFTER 28 DAYS OF MOIST CURING WAS OBTAINED FOR FOUR OF THE EIGHT AGGREGATES TESTED WITH 4 1/2 SACKS/CU.YD. AND 6% ENTRAINED AIR, FOR FIVE WITH 4 1/2 SACKS AND 8% AIR, FOR SEVEN WITH 6 SACKS AND 6% AIR, AND FOR SIX WITH 6 SACKS AND 8% AIR. THIS MINIMUM COMPRESSIVE STRENGTH WAS REACHED WITH THE STANDARD AGGREGATE USING 3 SACKS/CU.YD. AND 4 AND 10% AIR. THE ONLY AGGREGATE OF THE EIGHT AGGREGATES TESTED WHICH MET THE PROPOSED COMPRESSIVE STRENGTH CRITERIA WITH 3 SACKS/CU.YD. ALSO SHOWED THE HIGHEST OVERALL COMPRESSIVE STRENGTH. THIS CONCRETE, HOWEVER, EXHIBITED THE HIGHEST STRENGTH LOSS DURING THE DURABILITY TEST BEING AS GREAT AS 44% FOR ONE OF THE CONCRETE MIX PROPORTIONS RECOMMENDED FOR USE. FIVE OF THE EIGHT AGGREGATES SELECTED FOR TESTING MAINTAINED THEIR STRENGTH WITH A LOSS IN FREEZING AND THAWING OF LESS THAN 11.5%. ALLOWING STRENGTH LOSS OF 15% QUALIFIES AN ADDITIONAL TWO AGGREGATES. /AUTHOR/

  • Supplemental Notes:
    • I-65,
  • Corporate Authors:

    University of North Dakota

    Grand Forks, ND  USA  58202

    Bureau of Public Roads /US

    400 7th Street, SW
    Washington, DC  USA  20590
  • Authors:
    • Dahlgren, C E
  • Publication Date: 1968-6

Subject/Index Terms

Filing Info

  • Accession Number: 00212041
  • Record Type: Publication
  • Source Agency: Bureau of Public Roads /US
  • Files: TRIS
  • Created Date: Nov 29 1994 12:00AM