CORRELATION BETWEEN CONCRETE DURABILITY AND AIR-VOID CHARACTERISTICS

Abstract

THE THEORY OF THE ACTION OF ENTRAINED AIR IN PRODUCING FROST-RESISTANT CONCRETE DEMONSTRATES THE IMPORTANCE OF THE SIZE AND DISTRIBUTION OF THE AIR VOIDS IN THE PORTLAND CEMENT PASTE. THE CHARACTERISTICS INVESTIGATED WERE (1) AIR CONTENT, (2) NUMBER OF VOIDS INTERSECTED PER UNIT LENGTH OF TRAVERSE, (3) SPECIFIC SURFACE OF THE AIR VOIDS, (4) NUMBER OF HYPOTHETICAL SPHERES OF EQUAL RADIUS HAVING THE SAME VOLUME OF AIR PER UNIT VOLUME OF CONCRETE AND THE SAME SPECIFIC SURFACE AS THE ACTUAL SYSTEM OF RANDOM SIZED VOIDS AND (5) SPACING FACTOR. STATISTICAL METHODS WERE APPLIED TO THE STUDY OF THE VARIABILITY OF THE AIR CONTENT AND NUMBER OF VOIDS PER INCH WITHIN A CONCRETE BEAM. THE ANALYSIS SHOWED THAT THE MEASUREMENT OF THESE CHARACTERISTICS FOR A PARTICULAR BEAM MAY BE CONSIDERED AS ONE LONG TRAVERSE WITHOUT REGARD TO THE POSITION OR LENGTH OF THE INDIVIDUAL TRAVERSES. THIRTY-EIGHT BEAMS FROM 19 MIXES WERE USED TO STUDY THE CORRELATION BETWEEN EACH OF THE FIVE AIR-VOID CHARACTERISTICS AND DURABILITY. A DURABILITY FACTOR WAS USED TO EXPRESS THE RESISTANCE OF EACH BEAM TO DETERIORATION IN A LABORATORY FREEZE-THAW TEST. THE FIVE AIR-VOID CHARACTERISTICS RANKED IN ORDER OF THEIR CORRELATION WITH DURABILITY ARE (1) SPACING FACTOR, (2) SPECIFIC SURFACE, (3) NUMBER OF VOIDS PER INCH, (4) HYPOTHETICAL NUMBER OF VOIDS PER CUBIC INCH AND (5) TOTAL AIR CONTENT. THE SPACING FACTOR AND THE SPECIFIC SURFACE WERE FOUND TO BE OF ALMOST EQUAL IMPORTANCE IN PRODUCING DURABLE CONCRETE. HENCE, EITHER OF THESE TWO CHARACTERISTICS MAY BE USED AS A CRITERION FOR DETERMINING THE AIR REQUIREMENTS FOR FROST-RESISTANT CONCRETE. /AUTHOR/