Modeling the relationship between the shape and flowing characteristics of processed sands

• The quality of processed sands is important for many construction applications.
• High accuracy video equipment can be used to characterize the shape of sand.
• A simple shape factor describing the shape of sand particles has been proposed.
• A simple relationship between shape factor and actual shape has been proposed.
• The empirical relationship has been validated using the ASTM 1252 flow test.

The quality of processed sands is a critical issue for several construction applications (asphalt mixes, concrete, granular layers). The sand flow test is commonly used to control this quality. High accuracy video-capturing equipment is now also used to characterize the shape of aggregates. The objective of this study is to model the relationship between the actual shape of sand particles, measured using a video-capturing equipment, to the sand’s flowing time in a hopper, in order to eliminate the need for sand flow laboratory measurements.Several samples of processed and natural sands were tested using on the sand flow test equipment used in the European standards. The shape of the particles was then analyzed using a video-capturing equipment. A simple empirical relation was found between the shape factor of particles by Beverloo’s law and the actual shape of particles, characterized by a shape index defined in this study. The results were then confronted with the sand test equipment specified in the ASTM standards, to validate this empirical relation.The coefficients in this new relation had to be experimentally determined according to definition of the particle’s diameter, the video system, and the sand flow test equipment. The discharge coefficient was also taken into consideration. This is mainly experimental work; the physical explanation of this relation would have to be analyzed in greater depth in the future.

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