The Influence of Natural Sand Fine Aggregate on Some of the Properties of Hardened Concrete Mortar

摘要

The report summarizes a laboratory study of twenty-five natural sands and the effect that variations in their characteristics have on the freeze-thaw durability, drying shrinkage and water requirement of concrete mortar. It was shown that except for the possibility of slight surface damage in the form of small pits or 'popouts,' even extremely poor quality fine aggregate will cause no freeze-thaw deterioration of air entrained concrete. Variations in sands, however, were associated with significant variations in mortar shrinkage and water requirement. The effective modulus of elasticity of the sands was found to correlate to a high degree with mortar shrinkage. The outstanding fact concluded from this research is that results of the sulfate salt soundness test bear little relationship to the effect of fine aggregate, per se, on the frost resistance of concrete. Such results, however, do correlate to a high degree with two very significant properties, modulus of elasticity and water requirement. It was also concluded that the measures of 'quartz and feldspar' and 'kaolin' of the New York rational analysis are less precise indicators of quality than sulfate salt soundness.