00217587

Component

http://onlinepubs.trb.org...rbbulletin/355/355-002.pdf

THE DISCOVERY THAT CONCRETE AGGREGATES WERE NOT INERT BUT COULD PARTICIPATE IN CHEMICAL REACTIONS WITH CERTAIN CEMENT COMPOUNDS STIMULATED AN INTERNATIONAL RESEARCH EFFORT THAT HAS RESULTED IN THE RECOGNITION OF SEVERAL DISTINCT MECHANISMS BY WHICH THESE REACTIONS MAY REDUCE THE DURABILITY OF CONCRETE. RECENTLY, ATTENTION HAS BEEN DRAWN TO A REACTION INVOLVING THE CEMENT ALKALIES AND A TYPE OF ARGILLACEOUS DOLOMITIC LIMESTONE. AGGREGATES SUSCEPTIBLE TO THIS TYPE OF REACTION WERE FOUND IN ILLINOIS AND INDIANA. THE REACTION DIFFERS FROM WELL-KNOWN ALKALI-SILICA REACTION IN THAT NO VISIBLE GEL OR REACTION PRODUCT IS FORMED NOR IS ANY RIM FORMATION APPARENT ON THE REACTED AGGREGATE PARTICLES AS IS THE CASE WITH THE SILIFICATION REACTION. THE PERFORMANCE IN CONCRETE OF AN AGGREGATE FROM KINGSTON, ONTARIO, MET ALL PHYSICAL AND CHEMICAL TESTS AND YET WAS SHOWN TO BE ALKALI REACTIVE. PATTERN CRACKING DEVELOPED IN FIELD CONCRETE CONTAINING THIS AGGREGATE COMPARATIVELY SOON AFTER PLACING. THE CRACKS SURROUNDED AREAS FROM 2 TO 4 INCHES ACROSS AND THE CONCRETE BETWEEN THE CRACKS WAS RELATIVELY SOUND. THE EXPANSION DECREASED WITH MAXIMUM AGGREGATE SIZE, A BEHAVIOR CONTRARY TO OTHER TYPES OF CEMENT-AGGREGATE REACTIONS. THE CONCLUSION WAS THAT ROCKS COMPOSED OF NEAR EQUAL PROPORTIONS BY WEIGHT OF DOLOMITE AND CALCITE COULD BE REGARDED AS SUSPECT AND THAT A POSSIBLE CONNECTION EXISTED BETWEEN THE EXPANSIVE REACTIVITY AND THE DEDOLOMITIZATION REACTION (REPLACEMENT OF DOLOMITE BY CALCITE AND BRUCITE). IN CONCRETE, THE ALKALI CARBONATE WOULD REACT WITH HYDRATION PRODUCTS OF CEMENT TO REGENERATE ADDITIONAL ALKALI. THE EXPANSIVE TENDENCY OF ROCKS WAS MEASURED BY LABORATORY TEST. /AUTHOR/

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01410733

pp 27-44

1962

Highway Research Board Bulletin

41st Annual Meeting of the Highway Research Board

Digital/other

Appendices (2) ; Figures (14) ; References (16) ; Tables (6)

Alkali; Alkali aggregate reactions; Calcites; Clastic rocks; Concrete; Concrete aggregates; Cracking; Dolomite; Durability; Gels; Hydration; Laboratory tests; Measurement; Rocks

Concrete cracking

Geotechnology; Highways; Materials

TRIS, TRB, ATRI

Jun 3 1994 12:00AM

• STEAM CURING OF PORTLAND CEMENT AT ATMOSPHERIC PRESSURE