EVALUATION OF SHRINKAGE-CRACKING CHARACTERISTICS OF STRUCTURAL LIGHTWEIGHT CONCRETE

TESTS WERE CONDUCTED TO DETERMINE THE EFFECT OF COARSE AGGREGATE TYPE, CEMENT CONTENT AND CURING ENVIRONMENT ON UNRESTRAINED VOLUME CHANGES AND RESTRAINED SHRINKAGE CRACKING BEHAVIOR. MEASUREMENTS OF RESTRAINED SHRINKAGE STRESS AND ULTIMATE TENSILE STRENGTH WERE MADE FOR PURPOSES OF COMPARING THESE PROPERTIES WITH THE ABOVE CHARACTERISTICS. TWO SYNTHETIC LIGHTWEIGHT AGGREGATES, COMMERCIALLY PRODUCED IN TEXAS AND HAVING WIDELY DIFFERENT SATURATION CHARACTERISTICS WERE USED ALONG WITH A NATURAL SILICEOUS RIVER GRAVEL AS COARSE AGGREGATES. AFTER A FIVE-DAY INITIAL MOIST CURING PERIOD, THE SPECIMENS WERE PLACED IN FOUR DIFFERENT CURING ENVIRONMENTS, (1) 140 DEGREE F 25 PERCENT R.H., (2) 73 DEGREE F 50 PERCENT R.H., (3) 73 DEGREE F 95 PERCENT R.H., AND (4) 40 DEGREE F 92 PERCENT R.H. CEMENT CONTENTS OF 5.0, 6.0 AND 6.5 SACKS/CUBIC YARD WERE USED. UNRESTRAINED VOLUME CHANGES WERE MEASURED ON STANDARD TYPE SPECIMENS (3 X 3 X 11.25 IN.). CRACKING WAS EVALUATED AS THE NUMBER OF CRACKS OCCURRING ON A SPECIMEN 4 X 4 X 48 IN. WITH A NO. 8 REINFORCING BAR THROUGH THE CENTER. USING CONCRETE MADE WITH ONE OF THE LIGHTWEIGHT COARSE AGGREGATES, SPECIMENS WERE CAST FOR MEASUREMENT OF RESTRAINED SHRINKAGE STRESS. AFTER 60 DAYS, THESE SPECIMENS WERE LOADED TO CONCRETE FAILURE IN TENSION AND ULTIMATE TENSILE STRENGTH WAS DETERMINED. THE EFFECTIVE OR USABLE TENSILE STRENGTH WAS GREATLY AFFECTED BY THE CURING ENVIRONMENT. RESULTS INDICATED THAT BOTH UNRESTRAINED SHRINKAGE AND CONCRETE WATER LOSS RELATE TO RESTRAINED SHRINKAGE STRESS. UNRESTRAINED SHRINKAGE DID NOT INDICATE CRACKING TENDENCY WHILE WATER LOSS PROVIDED AN INDICATION OF CRACKING TENDENCY. /AUTHOR/

  • Supplemental Notes:
    • Res Rept 81-11, 20PP, 19FIG, 11TAB, 60REF
  • Corporate Authors:

    Texas Transportation Institute

    Texas A&M University System, 1600 E Lamar Boulevard
    Arlington, TX  United States  76011
  • Authors:
    • McKeen, R G
    • Ledbetter, W B
  • Publication Date: 1969-10

Subject/Index Terms

Filing Info

  • Accession Number: 00213781
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 26 1970 12:00AM