Abstract
Summary
Experimental evidence is used to show that, despite certain weaknesses, the fineness modulus method is applicable within wide practical limits. Then aspects of the fineness modulus and the specific surface not generally known are discussed. These include two mathematical expressionsfor thefineness modulus as afunction of the particle size distribution, which show that the fineness modulus is a measure of the (logarithmic) average particle size of the grading. This, in turn, provides a new interpretation for the relationship between the grading and workability. Similar mathematical expressions are presentedfor the specific surface, and they show that this is also a measure of an average particle size. Specifically, it represents the reciprocal value of the ‘harmonic’ average particle size. However, experimental evidence suggests it is inferior to the fineness modulus where aggregates for concrete are concerned. A further item is the ‘D-m-s method’ in which the fineness modulus and specific surface are both used for grading evaluation, to combine the advantages of the two methods. Finally, an analogy is used in an attempt to explain why the logarithmic average particle size is the parameter which is the most suitable for the grading evalulation of concrete aggregate.