DIGITAL IMAGE-PROCESSING FOR AGGREGATE ORIENTATION IN ASPHALT CONCRETE MIXTURES

Asphalt concrete is a composite material which consists of asphalt cem ent, voids, fine particles, sand, and coarse aggregates. Previous inve stigations of asphalt concrete mixtures have mainly concentrated on th e macroscopic properties of the composite materials based on the assum ption that the mixtures are homogeneous and isotropic. This paper appl ies an innovative digital image processing technique to quantify the o rientations of coarse aggregate particles (greater than or equal to 2 mm) in asphalt concrete mixtures such as hot mix asphalt, stone matrix asphalt, and large stone asphalt compacted in the laboratory or field . The results indicate quantitatively that asphalt concrete specimens compacted in the field or in the laboratory with gyratory compactor ha ve an oriented structure of aggregate particle distribution where the major cross sections of aggregate particles have the tendency to lie h orizontally, and that aggregate particles are more randomly oriented i n the asphalt concrete specimens compacted in the laboratory with the Marshall compactor.