NUCLEAR AND RADIOGRAFIC METHODS FOR THE STUDY OF CONCRETE

INVESTIGATIONS WERE MADE TO STUDY THE FACTORS, WHICH CAUSE THE VARIATION IN THE STRENGTH OF VERTICALLY CAST CONCRETE STRUCTURES. NUCLEAR TECHNIQUES WERE USED TO STUDY THE VARIATION IN DENSITY AND WATER-CEMENT RATIO OF THE CONCRETE IN THE TOP AND THE BOTTOM PART OF A COLUMN. MICROSTRUCTURE OF UNLOADED CONCRETE AND THE CRACKING OF CONCRETE DURING LOADING WERE ALSO STUDIED BY RADIOGRAPHY. THE SETTLING OF CONCRETE IN COLUMNS WAS STUDIED BY GAMMA-RAY TRANSMISSION. A SCINTILLATION DETECTOR WAS USED FOR THE DETECTION OF GAMMA- RAYS. THE GAMMA-RAY READINGS WERE TAKEN DURING SUCCESSIVE STAGES OF CONCRETE AND AT EVERY HALF HOUR DURING THE PERIOD OF SETTLEMENT. AN INCREASE IN DENSITY, DUE TO SETTLING WAS OBSERVED AT ALL LEVELS; THE INCREASE IN DENSITY AT THE BOTTOM WAS 2 TO 25%. FOR DETERMINING THE VARIATION IN WATER- CEMENT RATIO, THE VARIATION IN CEMENT CONTENT WAS STUDIED BY TRACER ANALYSIS AND THE VARIATION IN MOISTURE CONTENT WAS DETERMINED BY A NEUTRON MOISTURE GAUGE. THE MOISTURE CONTENT OF THE CONCRETE WAS 4 TO 5 PERCENT HIGHER IN THE TOP PART THAN IN THE BOTTOM PART OF A COLUMN. THERE WAS NO SIGNIFICANT DIFFERENCE IN CEMENT CONTENT BETWEEN THE TOP AND THE BOTTOM SLICES, SO THAT IT COULD BE CONCLUDED THAT THE WATER-CEMENT RATIO WAS 4 TO 5 PERCENT HIGHER IN THE TOP AS COMPARED TO THE BOTTOM, WHICH CORRESPONDS TO ABOUT 7 PERCENT DECREASE IN STRENGTH. THE MICROSTRUCTURE OF HARDENED CONCRETE WAS STUDIED BY CONTACT RADIOGRAPHY AND SHOWED THAT THE VARIATION IN STRENGTH BETWEEN THE TOP AND BOTTOM OF COLUMNS ARE CAUSED BY A COMBINATION OF SEVERAL FACTORS, WHICH MAY BE, (1) EFFECT OF THE MICROCRACKS, (2) EFFECT OF THE STRENGTHENING OF PASTE, (3) EFFECT OF WATER ON THE STRENGTH. SOME LIMITED INVESTIGATIONS WERE MADE TO STUDY THE NATURE OF WATER HARDENED CONCRETE SPECIMENS, USING THE NUCLEAR MAGNETIC RESONANCE METHOD. THESE STUDIES SHOWED THREE DIFFERENT STATES OF WATER IN THE HYDRATED CEMENT PASTE. CERTAIN DIFFERENCES IN THE CHARACTER AND BINDING OF WATER TO THE HYDRATES WERE OBSERVED, WHICH ALSO CONTRIBUTE TO THE DIFFERENCES IN STRENGTH BETWEEN THE TOP AND THE BOTTOM OF COLUMNS.

  • Supplemental Notes:
    • Summary, 2 PP, 2 FIG
  • Corporate Authors:

    Nat Swedish Inst Building Research

    ,    
  • Authors:
    • Bhargava, J
  • Publication Date: 1969

Subject/Index Terms

Filing Info

  • Accession Number: 00213800
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 5 1970 12:00AM