Methodology for Determining Particle-Size Distribution Characteristics of Fly Ashes

Particle size of the fly ash governs its utilization in various engineering projects. This could be obtained by either conducting dry- and wet-sieving or hydrometer analysis. Though, for a material with a particle size less than $75\mu \text{m}$ , the hydrometer analysis is best suited, difficulties associated with it are well known. This necessitates application of advanced techniques such as laser particle analysis, soft imaging, etc. However, not only are these techniques cost intensive, but they also fail to yield reliable results, particularly, if the material is heterogeneous and the particles are coarser. This calls for resorting to dry or wet sieving for accurate determination of particle-size distribution characteristics. However, not many studies have been conducted that critically evaluate and compare the results obtained from these methodologies in relation to those obtained from the hydrometer tests. With this in view, investigations were conducted on different fly ashes by conducting dry sieving. In addition, the fraction of fly ash retained on $45\mu \text{m}$ sieve was determined by employing wet sieving. Results obtained from these methodologies are critically examined. It has been demonstrated that dry-sieving with plastic balls yields reliable results in less time as compared to the wet sieving and hence this methodology would be better suited for pozzolanic materials.