Does the use of larger coarse aggregate in a mix tend to produce concrete of higher strength?
A recent report by the National Ready Mixed Concrete Association reached the following conclusions: 1. At a given water ratio, within the range employed in most structural concrete, smaller maximum sizes of aggregate will tend to produce higher concrete strengths than larger ones. 2. The larger sizes will require less mixing water and hence, for a given cement factor, will produce concrete of lower water-ratio than the smaller sizes. 3. The advantage of small aggregate in the water-ratio strength relationship may or may not be sufficient to offset the effects of its higher mixing water demand. It appears that optimum maximum size, so far as strength is concerned, will vary for different aggregates, different cement factors, different test ages and probably other conditions. 4. A realistic appraisal of the recent data for several different aggregates must lead to the conclusion that size of aggregate, within a reasonable range, is of less importance to concrete strength than other aggregate characteristics. Even in the leaner mix, where the larger aggregate gave higher strength, the advantage was inconsequential in relation to strength differences between aggregates of the same size from different sources.