Volume 8, Issue 10 (November 2011)
Evaluation of Particle Shape and Surface Texture of Recycled Organic Aggregates
The size, shape, and texture of aggregate particles are important because these physical characteristics influence the engineering properties. Recycled organic aggregates have advantageous physical and mechanical properties for geoengineering applications, but the particle shapes and textures have not been well quantified and evaluated. Three pairs of recycled organic aggregates were studied in this investigation: nylon and polyethylene terephthalate (thermoplastics), ground and crumb rubber (elastomers), and pine and oak wood (natural organic materials). The particle flatness, elongation, and sphericity were calculated for representative samples of each aggregate. The particle index of the shape and texture was measured per ASTM D 3398, and this test method was determined to provide a meaningful assessment of irregular geometrical characteristics. With the exception of nylon chips, recycled organic aggregates contain a high percentage of flat and elongated particles with Lmax:Lmin ratios that are much greater than those observed in crushed stone, gravel, and sand. Void volumes are much higher, resulting in particle indices between 30 and 50, as compared to indices of less than 20 for natural, inorganic aggregate.