PRETESTING CONCRETE QUALITY BY GAMMA-RAY BACKSCATTERING.

A PROTOTYPE PORTABLE NUCLEAR GAGE WITH THE POTENTIAL FOR CONDUCTING RAPID, ACCURATE, AND NONDESTRUCTIVE FIELD TESTS TO DETERMINE THE CEMENT CONTENT OF WET (PLASTIC) PORTLAND CEMENT CONCRETE HAS BEEN DEVELOPED, AND HAS PROVEN APPLICABLE WHERE THE AGGREGATE IS ESSENTIALLY SILICEOUS IN NATURE. ACCURACY DECLINES RAPIDLY, HOWEVER, WITH AGGREGATE MIXES CONTAINING LIMESTONE. THE DEVICE EMPLOYS AN INNOVATIVE GAMMA RAY BACKSCATTER TECHNIQUE IN A SUBMISSIBLE PROBE. TWO RADIOISOTOPE SOURCES, AMERICIUM AND CESIUM, ARE USED WITH A SCINTILLATION COUNTER DEVICE. AMERICIUM EMITS A LOW-ENERGY RADIATION AND CESIUM EMITS A HIGH-ENERGY RADIATION. THE ELECTRONIC UNIT SIMULTONEOUSLY REGISTERS THE TWO BACKSCATTER INTENSITIES AND THE CEMENT CONTENT IS INTERPRETED FROM A CALIBRATION CURVE. COMPARATIVE TESTS ON SURFACE AND SUBSURFACE BACKSCATTER ARRANGEMENTS SHOWED THE LATTER TO BE SUPERIOR. ERRORS IN DETERMINATIONS WITH THE DEVICE ARE CAUSED BY AGGREGATE TYPE, AND WATER CONTENT AND THE ACCOMPANYING CHANGE IN BULK DENSITY. FURTHER LABORATORY EVALUATION IS NEEDED TO INVESTIGATE THE MAJOR TECHNICAL PROBLEMS OF AGGREGATE HETEROGENEITY OF BATCH SAMPLES AND BULK DENSITY DETERMINATION.

  • Availability:
  • Supplemental Notes:
    • Vol 36, No 9, 180-183, 4 FIG, 2 REF
  • Publication Date: 1971-8

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Filing Info

  • Accession Number: 00214042
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Nov 15 1971 12:00AM