DETERMINATION OF SLAG AND FLY ASH CONTENT IN HARDENED CONCRETE

A need exists to be able to quantify the slag content of hardened concretes to show conformance to agency specifications. Two methods are proposed: x-ray diffraction (XRD) of ignited mixtures and optical microscopy on thin sections. The XRD method involves ignition of the mortar fraction of concrete at 950 to 1050 deg C to devitrify the unreacted slag. The resulting crystalline melilite component is then compared to that in an ignited sample of slag from the same source. The optical method involves preparation of thin sections of the concrete and point counting to determine the number of unhydrated slag grains. These are compared to a set of calibration standard sections. The optical procedure can be used to estimate fly ash content and similarly, grain mounts have been used to detect the presence of fly ash and slag substitution in portland cements. This paper describes the two methods in detail and discusses limitations. Either technique, when properly calibrated, can be useful in estimating the slag replacement level. Case histories demonstrate the usefulness of the procedures proposed.

Language

  • English

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Filing Info

  • Accession Number: 00715288
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 1 1996 12:00AM