Variations in particle size distributions also were observed among the different materials (Fig. 1). The largest mean particle size and broadest distribution was in the GB fillers for both size ranges. CFA had the smallest mean particle size for both macro and micro size ranges. These discrepancies have important implications in the final characteristics of the composites. Particles in the size range of 38 µm or smaller were present in the macro sized particle distributions and were considered in the interpretations of the results. However, these small portions of material did not seem to drastically affect the overall composite properties.