EFFECT OF CORE DIAMETER ON MEASURED CONCRETE STRENGTH

Abstract

A 16 INCH DEEP SLAB AND A 16 INCH THICK WALL WERE CONSTRUCTED, MOIST-CURED FOR 3 MONTHS, AND THEN CORED TO OBTAIN 2, 4, AND 6 INCH DIAMETER SPECIMENS. THE 16 INCH LONG CORES WERE SAWED INTO 2 BY 4, 4 BY 8, AND 6 BY 12 INCH SPECIMENS FOR COMPRESSION TESTS. PRIOR TO BEING TESTED, HALF OF THE CORES WERE SOAKED IN WATER 40 TO 44 HOURS, THE OTHERS WERE IMMERSED FOR 28 DAYS BEFORE TESTING. AS A SUPPLEMENT TO THE MAIN SERIES OF TESTS, 4 INCH DIAMETER CORES WERE DRILLED 10 INCHES INTO THE WALL SPECIMEN AND BROKEN OUT, THE RESULTING CORES WERE TRIMMED TO 4 BY 8 INCH, SOAKED 40 TO 44 HOURS, AND THEN TESTED IN COMPRESSION. IN ALL, ABOUT 115 CORES WERE TESTED. NEITHER THE DIFFERENCE IN CORE SIZE NOR THE BREAKING OUT OF CORES AFFECTED THE MEASURED STRENGTH SIGNIFICANTLY. CORE STRENGTHS AT 3 AND 4 MONTHS AGE AVERAGED ABOUT 77 PER CENT OF THE STRENGTH OBTAINED FOR 28-DAY STANDARD CURED 6 BY 12 INCH CYLINDERS MADE FROM THE SAME CONCRETE. /AUTHOR/