Indirect Determination of Particle Shape of Fine Aggregate

About the report:

Three methods developed by various agencies for measuring indirectly the particle shapes of fine aggregates were used along with a visual classification procedure to study aggregates from eight commercial sources along with a reference sand. The methods were (1) measurement of void content of individual size fractions as originally developed by the National Crushed Stone Association and as currently used by the Virginia Department of Highways, (2) measurement of void content of a graded sample as more recently developed by Wills, and (3) determination of the rate of flow of aggregate through a standard orifice as suggested by Rex and Peck. Based upon the application of these methods to the fine aggregates studied, the following conclusions were drawn: (1) All methods, including visual classification, reflected the differences in particle shape among the sands. (2) The correlation between the test methods was high. (3) The high correlation among the three methods would permit utilization of data from either of the three methods. (4) Many natural sands have poorer particle shapes than some manufactured sands. (5) The variation in particle shape of fine aggregates used in Virginia, when compared with reported studies, was sufficient to indicate that this property would exercise a significant influence upon important properties of concrete such as water requirement, strength, slump, etc. (6) The variation is sufficient to warrant consideration of particle shape as a variable in any broader study of fine aggregate. (7) As far as time requirements are concerned, the Crushed Stone Method, which is currently used by the Virginia Department of Highways, appears to be not only the quickest but the easiest method.

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