Quantification of Specific Surface Area of Aggregates Using an Imaging Technique

Abstract

An imaging method is proposed to quantify the specific surface area of aggregates of different sieve sizes. The procedure for determining the specific surface areas of aggregate particles by the proposed method includes the following steps: (1) separating the aggregates into different standard sieve sizes, (2) placing the aggregate particles in a container and injecting a resin to bind them, (3) sawing the aggregate/resin specimen to obtain one to four cut planes, (4) using an image analyzer to take the aggregate particles images from the cut planes, (5) determining the specific surface areas and other aggregate particle properties, such as the slenderness ratio and the roughness from the images. The proposed method was used to determine the specific surface area of a crushed granite aggregate sample with the particle size ranging from passing 19mm to #50 sieve. The results were compared with the approximate specific surface areas for different aggregate sizes commonly used by the aggregate industry. The approximate specific surface areas were based on the average specific surface areas of the spheres having the diameters equal to the corresponding passing and retaining sieve opening sizes. The specific surface areas determined by the proposed method are higher, particularly for the aggregates passing #16, #30, and #50 sieve sizes, than those of the approximate values. The reason for the higher specific surface areas determined by the proposed method was primarily due to the irregular shapes and the rough textures of the crushed aggregate particles. The proposed method can be used for quantifying the aggregate properties, including the specific surface area, roundness, slenderness ratio, and roughness in the laboratory for the quality control of aggregate properties.