| Abstract | voids, fine particles, sand, and coarse aggregates. A review of the literature reveals that the investigations of AC have mainly concentrated on the macroscopic behavior of the material based on the assumption that the mixture is homogeneous. This assumption is mainly due to the extreme difficulty associated with the quantitative measurements of AC microstructure and the random nature of the aggregate distribution. This paper applies an innovative digital image-processing technique to quantify the distribution, orientation, and shape of coarse aggregates (=2 mm) in AC mixtures. Results of the quantitative measurements of coarse aggregate distribution and shape in AC mixture are then presented and analyzed. The quantitative results of AC microstructure clearly indicate the following findings : (a) the microstructure characteristics of coarse aggregates in AC mixtures can be accurately measured using the digital image-processing technique ; (b) the area gradation of aggregate cross sections by the Feret diameter gives an excellent prediction of the sieve gradation of coarse aggregates (=2 mm) used in the design of AC mixtures ; (c) the major cross sections of coarse aggregate particles have the tendency to lie horizontally in the mixtures ; and (d) comparison among two laboratory and two field compaction techniques provides valuable information related to compaction quality in terms of favorable aggregate distribution within the mixtures. |
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