A Method for Determining the Surface Area of Quarried Rocks
A coating method which used nickel powder to determine the surface area of angular rock particles was found to be reproducible and required no special equipment. The technique utilized the difference in weight between uncoated and coated rock particles. Four calibration methods were considered. Relationships between surface area and an estimate of the volume of individual rocks were obtained for graded rock having a mean diameter of 25.6 mm and for unisized rock having a mean diameter of 130 mm. The volume of each rock was estimated by measuring the three orthogonal axes of each rock. An analysis of covariance showed that whether or not a rock was spheroid in shape was statistically significant for the evaluation of surface area. Curves relating the hydraulic mean radius to porosity for a range of unisized rock sizes are presented. A procedure for estimating the hydraulic mean radius for a graded media is also discussed.