Three-dimensional laser scanning technique to quantify aggregate and ballast shape properties

• CSIR using laser-based technique to evaluate aggregate/ballast shape properties.
• Improvements in aggregate/ballast shape properties measurement demonstrated.
• 3-D laser scanning method provides accurate aggregates aggregates/ballast shape properties.
• Volume-based flakiness index equation validated for aggregates/ ballast particles.
• Reliable flakiness data can now be obtained for aggregates and ballast materials.

There is a need to improve the measurements of shape characteristics of aggregates and ballast materials used in the construction of road, airfield, and railway track infrastructures. The fundamental shape properties of aggregate and ballast, including form (roundness, flatness, elongation, sphericity), angularity, and surface texture (roughness) have not been accurately quantified because of their irregular and non-ideal shapes. Current developments are shifting from manual and subjective methods towards a more accurate and automated techniques to quantify aggregate shape properties. This paper validates a new flakiness index equation using three-dimensional (3-D) laser scanning data of aggregate and ballast materials obtained from different sources (quarries) in South Africa. The new equation uses volume ratio instead of the traditional mass ratio to determine flakiness index of aggregates and ballast materials. It is concluded that the validated equation can be used with confidence to determine flakiness index of aggregate and ballast materials.