TENSILE STRENGTH REDUCTION OF MORTAR AND CONCRETE DUE TO MOISTURE GRADIENTS

BECAUSE OF THE TENDENCY OF HYDRATED PORTLAND CEMENT TO SHRINK OR SWELL WITH LOSS OR GAIN OF WATER, MOISTURE GRADIENTS PRODUCED BY RAPID DRYING MAY INDUCE STRESSES IN CONCRETE AND MORTAR. THE RESEARCH DESCRIBED HERE SHOWS THAT THESE STRESSES CAN BE OF SUFFICIENT MAGNITUDE TO REDUCE SIGNIFICANTLY THE TENSILE STRENGTH OF CONCRETE AND MORTAR. THE FOLLOWING SPECIFIC CONCLUSIONS ARE REPORTED: (1) THE TENSILE STRENGTHS OF MORTAR AND CONCRETE ARE SIGNIFICANTLY LOWER DURING THE INTERMEDIATE STAGES OF RAPID DRYING THAN FOR THE SATURATED CONDITION. (2) THE MAXIMUM STRENGTH REDUCTIONS OCCUR WHEN ABOUT HALF OF THE EVAPORABLE WATER HAS BEEN REMOVED. (3) THE MAGNITUDE OF THE MAXIMUM STRENGTH REDUCTIONS, AS COMPARED WITH THE SATURATED STATE, ARE 30--35%. (4) ABOVE 100 DEGREES C DRYING-TEMPERATURE VARIATIONS DO NOT SIGNIFICANTLY AFFECT THE MAGNITUDE OF STRENGTH REDUCTION. (5) THE STRENGTH REDUCTION OBSERVED AT INTERMEDIATE MOISTURE CONTENTS IS APPARENTLY DUE TO THE PRESENCE OF STEEP MOISTURE GRADIENTS LEADING TO INDUCED TENSION FROM DIFFERENTIAL SHRINKAGE. (6) THE TENSILE STRENGTH OF COMPLETELY DRY CONCRETE IS SIGNIFICANTLY LESS THAN THAT OF SATURATED CONCRETE, PROBABLY AS A RESULT OF RESIDUAL TENSILE STRESSES IN THE PAST OF THE DRY CONCRETE. (7) THE TENSILE STRENGTH OF COMPLETELY DRY CONCRETE IS SIGNIFICANTLY GREATER THAN THAT AT INTERMEDIATE SATURATION LEVELS DURING DRYING.

  • Authors:
    • Cady, P D
    • CLEAR, K C
    • Marshall, L G
  • Publication Date: 1972-11

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  • Accession Number: 00214199
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 15 1973 12:00AM