PARTICLE SIZE ANALYSIS AS A MEANS TO BETTER UNDERSTAND THE INFLUENCE OF FLY ASH VARIABILITY IN CONCRETE

摘要

Fly ash is generated from thermal power stations as an industrial by-product of coal combustion materials. Its particles are generally glassy, spherical in shape, and typically range in size from 0.5-300 fim. Coal fly ash is widely used as a partial cementitious material in concrete, which not only offers economic and environmental benefits but also improves concrete performance. However, variability of the physical description and chemical composition of fly ash has been considered to be a major barrier to its increased use in cement and concrete. In this study the variability and properties of fly ash are characterized with an emphasis on particle size analysis as a means for fly ash producers to better understand material properties in relation to the process of production, classification, and potential modes of utilization. Fly ash samples were collected from different coal-fired power plants from certain Indian and Canadian sources. The particle size analysis results using Laser Diffraction Technique showed a wide variation between the particle size distributions of the studied sources. However, no correlation between the varied size distributions and chemical compositions of fly ash samples was found. Laboratory experiments on the selected fly ash samples are being undertaken to correlate fly ash characteristics and their effects on the performance of concrete mixtures with cementitious replacement level up to 50%.