INFLUENCE OF NATURAL SAND FINE AGGREGATE ON SOME PROPERTIES OF HARDENED CONCRETE MORTAR

MOST MODERN CONCRETE SPECIFICATIONS INCLUDE REQUIREMENTS FOR QUALITY OF THE FINE AGGREGATE PORTION TO INSURE THAT IT DOES NOT DETRACT FROM THE QUALITY OF THE HARDENED CONCRETE. THE SIGNIFICANCE OF MANY OF THE TESTS USED TO MEASURE FINE AGGREGATE QUALITY, HOWEVER, IS ONLY POORLY UNDERSTOOD. THIS PAPER REPORTS A LABORATORY STUDY OF 25 NEW YORK NATURAL SANDS AND THE EFFECT THAT VARIATIONS IN THEIR CHARACTERISTICS HAVE ON THE FREEZE-THAW DURABILITY, DRYING SHRINKAGE AND WATER REQUIREMENT OF CONCRETE MORTAR. THE PURPOSE OF THIS STUDY WAS TO DEFINE SIGNIFICANT AGGREGATE PROPERTIES AND TO SUGGEST PRACTICAL METHODS OF MEASURING THEM. IT IS CONCLUDED THAT EXCEPT FOR VARYING AMOUNTS OF SURFACE DAMAGE IN THE FORM OF SMALL PITS OR POPOUTS, EVEN EXTREMELY LOW QUALITY FINE AGGREGATE, IN ITSELF, WILL CAUSE NO FREEZE-THAW DETERIORATION OF AIR-ENTRAINED CONCRETE. THE DIFFERENT FINE AGGREGATES, HOWEVER, DID CAUSE VARIATIONS IN MORTAR SHRINKAGE AND WATER REQUIREMENT. MODULUS OF ELASTICITY WAS FOUND TO BE THE MOST SIGNIFICANT AGGREGATE PROPERTY AFFECTING SHRINKAGE. BOTH AGGREGATE ELASTICITY AND WATER REQUIREMENT CORRELATED EMPIRICALLY WITH RESULTS OF THE MAGNESIUM SULFATE SALT SOUNDNESS TEST. /AUTHOR/