COMPOSITIONAL VARIATIONS ASSOCIATED WITH CARBONATE AGGREGATE REACTIONS
CHANGES IN THE COMPOSITION OF AGGREGATES AND CEMENT PASTES WERE STUDIED BY PLACING CUBES OF VARIOUS AGGREGATES IN CEMENT PASTE BARS AND REACTING THEM IN A WATER BATH AT 130 F FOR A 3-MONTH PERIOD. CHEMICAL AND X-RAY ANALYSES WERE MADE ON SAMPLES TAKEN AT SPECIFIED INTERVALS ACROSS THE AGGREGATE INTO THE CEMENT PASTE. THE DATA INDICATE THAT MUCH OF THE SILICA IN THE SHELL ZONE IS LOCALLY DERIVED FROM BREAKDOWN OF QUARTZ. SILICA CAN MIGRATE OUT OF THE ROCK INTO THE CEMENT PASTE OR FARTHER BACK INTO THE ROCK. DEDOLOMITIZATION IS A CONCURRENT REACTION. SILICA MIGRATION WAS POSTULATED TO REPRESENT AN EQUILIBRIUM REACTION CONTROLLED BY THE RELATIVE CONCENTRATION OF AVAILABLE SILICA IN ADJACENT CEMENT AND AGGREGATE AND THE LOCAL PH ENVIRONMENT. THE RESULTS INDICATE THAT CARBONATE AGGREGATE REACTIONS REPRESENT AN ATTEMPT OF AGGREGATES TO COME INTO EQUILIBRIUM WITH THE HIGH PH ENVIRONMENT OF CONCRETE. SILICA MIGRATION AND DEDOLOMITIZATION OCCUR CONCURRENTLY. RELEASED CALCIUM COULD REACT TO FORM CALCIUM CARBONATE. SILICA IN THE SHELL ZONES CAN BE LOCALLY DERIVED FROM THE AGGREGATE ITSELF WHEN A CEMENT PASTE MEDIUM IS USED FOR THE REACTION. CEMENT PASTES ARE NOT A SOURCE OF SILICA BUT MAY PROVIDE CALCIUM AND HIGH PH ENVIRONMENT. /AUTHOR/
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Supplemental Notes:
- No 3, pp 1-8, 8 FIG, 2 TAB, 12 REF 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
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Authors:
- Lemish, John
- Harwood, Robert J
- Hiltrop, Carl L
- Werner, Michael A
- Publication Date: 1963
Media Info
- Media Type: Print
- Pagination: pp 1-8
- Monograph Title: Properties of concrete
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Serial:
- Highway Research Record
- Issue Number: 3
- Publisher: Highway Research Board
Subject/Index Terms
- TRT Terms: Aggregates; Carbonates; Cement; Chemical analysis; Dolomite; Materials selection; Mechanical failure; Migration; Pastes; pH value; Quartz; Samples; Silica; Water; X ray analysis
- Uncontrolled Terms: Change
- Old TRIS Terms: Breakdown; Dedolimitization; Reaction
- Subject Areas: Geotechnology; Highways; Materials;
Filing Info
- Accession Number: 00212311
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Mar 2 1994 12:00AM