EFFECT OF ENTRAINED AIR ON THE BOND STRENGTH OF CONCRETE

THE TESTS WERE LIMITED TO EVALUATING THE EFFECT OF AIR- ENTRAINMENT ON THE BOND STRENGTH OF CONCRETE HAVING A QUALITY SIMILAR TO THAT USED FOR HIGHWAY STRUCTURES IN ILLINOIS. THE AGGREGATES USED CONSISTED OF TORPEDO SAND AND A 1-IN. MAXIMUM SIZE GRAVEL. THREE MAIN CONCRETE MIXTURES WERE USED: (1) A BASIC MIX WITHOUT AIR-ENTRAINMENT, (2) A MIXTURE CONTAINING ABOUT 4 PERCENT OF AIR, AND (3) A MIXTURE CONTAINING ABOUT 6 PERCENT OF AIR. TWO TYPES OF DEFORMED BARS WERE USED; NAMELY, THE NEW LACLEDE AND THE HI- BOND BAR, AND TWO SIZES OF EACH TYPE; NAMELY, 1/2-IN. AND 7/8-IN. DIAMETERS. THE VARIABLES CONSIDERED INCLUDED THREE NOMINAL AIR CONTENTS, THREE POSITIONS OF CASTING (VERTICAL, HORIZONTAL TOP AND BOTTOM), AND THREE COMPANION SPECIMENS. ALL TESTS WERE OF THE PULL-OUT TYPE IN WHICH EACH BAR WAS PULLED FROM A CONCRETE CUBE HAVING SIDE DIMENSIONS, OR BAR EMBEDMENT, 12 TIMES THE DIAMETER OF THE BAR. THE SPECIMENS AS CAST FOR THE HORIZONTAL BARS WERE 12 BAR DIAMETERS SQUARE AND 36 DIAMETERS TALL. DEFORMATIONS OF THE REINFORCING BARS WERE GIVEN CAREFUL CONSIDERATION. SLIP BETWEEN THE BAR AND THE CONCRETE CUBE WAS MEASURED AT BOTH THE FREE END AND THE LOADED END OF THE BAR BY MEANS OF AMES DIALS. LOADING WAS CONTINUED UNTIL THE BAR HAD PASSED ITS YIELD POINT. THE RESULTS OF THE TESTS SHOW THAT FOR BOTH TYPES OF BARS WHEN CAST VERTICALLY THE BOND FOR A SPECIFIED SLIP, WHEN COMPARED TO NONAIR-ENTRAINED CONCRETE, WAS REDUCED BY 10 PERCENT AT 4.5 PERCENT OF ENTRAINED AIR. THIS REDUCTION WAS ABOUT THE SAME AS THE CORRESPONDING REDUCTION IN COMPRESSIVE STRENGTH AND MODULUS OF RUPTURE OF THE CONCRETE. FOR AIR CONTENTS ABOVE 4.5 PERCENT THE RESULTS FOR THE TWO TYPES OF BARS WERE DIFFERENT. FOR THE HORIZONTALLY CAST BARS 4 PERCENT OF ENTRAINED AIR CAUSED PRACTICALLY NO CHANGE IN BOND AS COMPARED TO NONAIR-ENTRAINED CONCRETE, EXCEPT THAT IN ONE CASE THE BOND INCREASED. FOR AN AIR-ENTRAINMENT OVER 4 PERCENT, HOWEVER, A REDUCTION IN BOND TOOK PLACE. THIS REDUCTION IN TERMS OF THE VALUES AT 4 PERCENT AIR WAS 5 TO 15 PERCENT FOR EACH PERCENT AIR OVER 4, WHILE THE COMPRESSIVE STRENGTH WAS REDUCED ABOUT 6.5 PERCENT FOR EACH PERCENT AIR OVER 4. /AUTHOR/

  • Supplemental Notes:
    • Vol 28, pp 195-210, 15 FIG, 3 TAB, 15 REF
  • Authors:
    • Russell, H W
  • Publication Date: 1949

Media Info

  • Monograph Title: Proceedings of the Twenty-Eighth Annual Meeting of the Highway Research Board Held at Washington, D.C. December 7-10, 1948
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00213937
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Oct 3 1971 12:00AM