00097197

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http://onlinepubs.trb.org...s/trr/1974/525/525-004.pdf

https://scholar.google.co...lker&publication_year=1974

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.

Publication of this paper sponsored by Committee on Performance of Concrete-Chemical Aspects. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.

01411388

pp 28-37

1974

Transportation Research Record

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Figures (5) ; Photos (4) ; References (10) ; Tables (2)

Alkali; Alkali aggregate reactions; Carbonate rocks; Diffraction; Dolomite; Expansion; Mineral aggregates; Petrography; Reactive aggregates; X rays

X-ray diffraction

Geotechnology; Highways

TRIS, TRB

Sep 30 1975 12:00AM

• 15 YEARS OF LIVING AT KINGSTON WITH A REACTIVE CARBONATE ROCK
• BRIDGE DECK DETERIORATION PROMOTED BY ALKALI-CARBONATE REACTION: A DOCUMENTED EXAMPLE
• DEVELOPMENTS IN SPECIFICATION AND CONTROL
• EXPANSION OF REACTIVE CARBONATE ROCKS UNDER RESTRAINT
• KANSAS CONCRETE PAVEMENT PERFORMANCE AS RELATED TO D-CRACKING
• THE UHTHOFF QUARRY ALKALI-CARBONATE ROCK REACTION: A LABORATORY AND FIELD PERFORMANCE STUDY