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Component

http://onlinepubs.trb.org...s/hrr/1973/430/430-002.pdf

THE TRANSFORMATION OF A CLAY MINERAL INTO AN INERT, STABLE, AMORPHOUS SILICATE UNDER THE COMBINED ACTION OF HEAT AND TIME IS AN EXTREMELY COMPLEX PHENOMENON THAT OCCURS UNDER NONEQUILIBRIUM CONDITIONS. ESSENTIALLY WHAT OCCURS IS, FIRST, THE LOSS OF FREE AND ABSORBED WATER AND, THEN, THE LOSS OF HYDROXYLATED WATER COUPLED WITH THE DECOMPOSITION OF MINERALS SUCH AS CALCITE, PYRITE, AND DOLOMITE. THESE CHEMICAL TRANSFORMATIONS TAKE TIME; THEREFORE, DEPENDING ON THE AMOUNT OF HEAT AND SIZE OF THE PARTICLE, DIFFERENT DEGREES OF TRANFORMATION CAN OCCUR. AN INTERESTING SPECIAL PHENOMENON IS THE PROCESS OF "BLOATING" WHERE SOME CLAYS "PUFF UP" SLIGHTLY. EXAMINATION UNDER THE MICROSCOPE OF A PROPERLY BLOATED CLAY REVEALS A SPONGE-LIKE STRUCTURE WHERE THE HOLES, OR "BLEBS" AS THEY ARE TERMED, ARE NUMEROUS BUT SMALL. THE DRY UNIT WEIGHT OF THIS AGGREGATE (COARSE SIZES) IS OFTEN IN THE RANGE OF 35 TO 45 LB/CUFT. WITH SUCH A SMALL "BLEB" STRUCTURE, THE RESULTANT AGGREGATE CAN BE STRONG AND DURABLE. TO FULLY DEVELOP THE CRITERIA FOR PERFORMANCE, OR DURABILITY, THE RESEARCH WAS CONSIDERED FROM FOUR ASPECTS: PHYSICAL PERFORMANCE, CHEMICAL PERFORMANCE, MECHANICAL PERFORMANCE, AND VOLUME CHANGE PERFORMANCE. THE FOLLOWING FINDINGS RELATE TO THE LIMITATIONS IMPOSED ON THIS STUDY, AND FURTHER GENERALIZATIONS MAY NOT BE WARRANTED: SOUND, DURABLE, HIGH-QUALITY HIGHWAYS AND BRIDGES CAN BE CONSTRUCTED WITH SYNTHETIC AGGREGATES, PROVIDED THE AGGRAGATES MEET CERTAIN REQUIREMENTS; NOT ALL FUNCTIONAL USES OF SYNTHETIC AGGREGATES REQUIRE AGGREGATE OF THE SAME QUALITY; AND LABORATORY EVALUATIONS CAN, WITH REASONABLE ASSURANCE, PREDICT FIELD PERFORMANCE OF SYNTHETIC AGGREGATES.

Sponsored by Commitee on Mineral Aggregates. 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

01410346

pp 9-15

1973

Highway Research Record

52nd Annual Meeting of the Highway Research Board

0309021596

Print

Figures (4) ; References (13) ; Tables (3)

Artificial aggregates; Chemical reactions; Clay; Durability; Evaluation; Performance; Shale; Strength of materials

Geotechnology; Highways

TRIS, TRB

Dec 22 1973 12:00AM

• RECYCLED CONCRETE
• USE OF ZINC SMELTER WASTE AS HIGHWAY CONSTRUCTION MATERIAL
• UTILIZATION OF ASH FROM COAL-BURNING POWER PLANTS IN HIGHWAY CONSTRUCTION