INELASTIC BEHAVIOR AND FRACTURE OF CONCRETE

ELEMENTS OF A UNIFIED THEORY OF THE MECHANICAL BEHAVIOR OF CONCRETE ARE DEVELOPED FROM NO-LOAD TO FRACTURE UNDER SHORT-TIME LOADING BASED ON OBSERVED MICROCRACK BEHAVIOR AND ON A STATISTICAL DISTRIBUTION OF MORTAR STRENGTH. IT IS KNOWN THAT IN UNIAXIAL COMPRESSION, AGGREGATE AND HARDENED CEMENT PASTE, THE TWO CONCRETE CONSTITUENTS, ARE ALMOST WHOLLY ELASTIC TO FRACTURE. FOR MORTAR THE STRESS-STRAIN CURVE IS MORE PRONOUNCED AND THE STRENGTH IS LESS THAN FOR PASTE OF THE SAME WATER-CEMENT RATIO. CONCRETE IN TURN HAS A STRESS-STRAIN CURVE WHICH IS STILL MORE CURVED AND THE STRENGTH BECOMES LESS THAN FOR MORTAR OF THE SAME WATER-CEMENT RATIO. FROM THIS IT IS SHOWN THAT CONCRETE'S INELASTICITY AND STRENGTH ARE GOVERNED BY PASTE-AGGREGATE INTERACTION, CONDITIONED BY THE FACT THAT IN AGREEMENT WITH PREVIOUS FINDINGS, THE AGGREGATE-MORTAR INTERFACE CONSTITUTES THE WEAK LINK. BASED ON THESE STATISTICAL FINDINGS REGARDING THE ELASTICITY OF AGGREGATE AND HARDENED CONCRETE PASTE, IT IS DEMONSTRATED THAT A PROGRESSIVELY INELASTIC CONDITION DEVELOPS IN CONCRETE UNDER SHORT-TIME LOADING AND CONTINUES UP TO THE CRITICAL LOAD OF 85 TO 90 PERCENT OF ULTIMATE INELASTICITY. IT IS DESCRIBED THAT THIS INELASTICITY RESULTS CHIEFLY FROM BOND CRACKING AT THE AGGREGATE-MORTAR INTERFACE. IT IS SHOWN THAT IN THIS RANGE A REALISTIC STRESS-STRAIN CURVE CAN BE CALCULATED ENTIRELY ON THE BASIS OF SEPARATELY OBSERVED MICROCRACK BEHAVIOR AND INDEPENDENTLY MEASURED MATERIALS CONSTANTS. IT IS CONCLUDED THAT THE CRITICAL LOAD IS THE POINT AT WHICH INCREASINGLY EXTENSIVE MORTAR CRACKING CAUSES VOLUME EXPANSION AND THE HITHERTO ESSENTIALLY CONTINUOUS MATERIAL CHANGES TO AN ESSENTIALLY DISCONTINUOUS ONE. INCREASED INTERFACIAL FRICTION AND THE REDUCTION OF MORTAR TENSILE STRESSES, AS SHOWN STATISTICALLY IN THIS PAPER, CONFIRM THE HYPOTHESIS OF HIGHER BIAXIAL AND TRIAXIAL RATHER THAN UNIAXIAL CONCRETE COMPRESSION STRENGTH. IT IS FURTHER CONCLUDED THAT THE BEHAVIOR THEORY DEMONSTRATES THAT CONCRETE'S SHORT-TIME INELASTICITY CAN BE EXPLAINED ENTIRELY ON THE BASIS OF BRITTLE MICROBEHAVIOR WITHOUT INVOKING ANY EXPERIMENTALLY UNOBSERVED FLOW-PROCESSES. /ACIJP/

  • Corporate Authors:

    American Concrete Institute

    38800 Country Club Drive
    Farmington Hills, MI  USA  48331
  • Authors:
    • Shah, S P
    • Winter, G
  • Publication Date: 1968

Subject/Index Terms

Filing Info

  • Accession Number: 00213804
  • Record Type: Publication
  • Source Agency: Am Concrete Inst Journal & Proceedings
  • Report/Paper Numbers: Title No Sp 20-1
  • Files: TRIS
  • Created Date: Sep 28 1970 12:00AM