STUDIES RELATING TO THE TESTING OF FLY ASH FOR USE IN CONCRETE

THE EFFECT OF FLY ASH ON THE STRENGTH OF PORTLAND CEMENT- FLY ASH MORTARS IS CONSIDERED TO INDICATE THE PROBABLE EFFECT ON THE STRENGTH OF CONCRETE AND IS USED IN THIS INVESTIGATION AS A CRITERION FOR EVALUATING OTHER TESTS OF FLY ASH. THE EFFECT OF FLY ASH ON THE EXPANSION RESULTING FROM THE ALKALI-AGGREGATE REACTION IS ALSO CONSIDERED. TO DETERMINE THE VARIATIONS IN PROPERTIES WHICH MAY BE EXPECTED AND THE EFFECT OF THESE VARIATIONS ON THE BEHAVIOR OF THE FLY ASH IN MORTAR, 34 FLY ASHES FROM 19 DIFFERENT SOURCES WERE EXAMINED. THE RESULTS OF THE TESTS INDICATE THAT GENERALLY THE STRENGTH DEVELOPED IN PORTLAND CEMENT-FLY ASH MORTARS IS RELATED TO THE CARBON CONTENT OF THE FLY ASH, THE FINENESS OF FLY ASH AS MEASURED BY THE AMOUNT PASSING THE NO. 325 SIEVE, AND THE WATER REQUIRED FOR MORTARS CONTAINING FLY ASH AS COMPARED TO THE WATER REQUIRED FOR SIMILAR MORTARS WITHOUT FLY ASH. NO WELL-DEFINED RELATION BETWEEN THE INDIVIDUAL INORGANIC CONSTITUENTS OF THE FLY ASH AND THE DEVELOPMENT OF STRENGTH OF THE MORTAR WAS OBTAINED. THESE TESTS ALSO INDICATE THAT THE EFFECT ON THE STRENGTH OF MORTAR OF REPLACING A PORTION OF THE CEMENT WITH FLY ASH VARIES ACCORDING TO THE CEMENT USED. TESTS OF MORTAR BARS SHOW THAT FLY ASH MAY BE USED TO INHIBIT THE EXPANSION RESULTING FROM THE ALKALI-AGGREGATE REACTION. THESE TESTS INDICATE THAT THE AMOUNT OF FLY ASH REQUIRED TO REDUCE EXPANSION BELOW A SAFE LIMIT VARIES FOR DIFFERENT FLY ASHES. /AUTHOR/