Rapid Test to Establish Grading of Unbound Aggregate Products: Automation of Aggregate Characterization Using Laser Profiling and Digital Image Analysis

This final project report describes the development of a laser scanning device for measuring the gradation and other morphological characteristics of unbound construction aggregates. The device is called the LASS, for "Laser-based Aggregate Scanning System." The method of characterizing aggregate particles from three-dimensional (3D) laser profiling required the development of particle segmentation algorithms, particle measurement algorithms, and generalized particle descriptions. With the LASS, true 3D data of aggregate particles are obtained by laser profiling. This data is first transformed into digital images. Second, segmentation and particle measurement algorithms separate the particles and process each particle data individually with the aid of various digital image technologies. Finally, in order to provide a generalized, quantitative, and representative way to characterize aggregate particles, 3D particle descriptors were developed using the multi-resolution analysis feature of wavelet transforms. Verification tests show that this approach can characterize various aggregate properties in a fast, accurate, and reliable way. When implemented, this ability to automatically analyze multiple characteristics of an aggregate sample will lead to reduced labor costs in the laboratory, but more importantly, to better control of the quality of aggregate products. ICAT Project 503 was undertaken to study rapid, automated methods of determining the grain size distribution of unbound aggregate products. Automatic measurement of particle size and shape properties has the potential to overcome problems with manual measurements such as subjectivity, labor intensity, and slow speed. Testing machines that rely on 2D digital image analysis were evaluated as described earlier in Report ICAR 503-2.