Detailed petrographic examinations and X-ray diffraction analyses were made of carbonate aggregates that had been tested by ASTM Methods C227 and C586. It was found that the most expansive mortar bars exhibited more external cracks and deposits of reaction products than did the less expansive bars. Any reaction rims were within the aggregate particles, and etching with various strengths of hydrochloric acid showed that they were negative. Rim- forming aggregates within the mortar bars appear in thin section to have undergone dedolomitization in the rim zone at the paste-aggregate interface. X-ray examination of the most expansive aggregates from these mortar bars failed to detect any brucite. However, comparison of the diffractograms generated by X-ray reflection from these reacted aggregates with diffractograms generated by the fresh, unused portions of these aggregates indicated that some type of dedolomitization reaction had occurred. The information obtained indicates that, under conditions found when testing rock for expansion by ASTM C586, the minerals of the hydrotalcite-sjogrenite mineral groups (complex magnesium carbonate hydroxides) can be the chief products of alkali dedolomitization near the surface of the test prisms of dolomite carbonate aggregate and that brucite can be the major dedolomitization product in the interior of the aggregate.

Media Info

  • Media Type: Print
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 28-37
  • Monograph Title: Cement-aggregate reactions
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00097197
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 30 1975 12:00AM