A New Classification Method for High-Volume Fly Ash: Performance Based on Coal Source and Particle Size

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Fly ash utilization in cement systems is key for sustainable construction.
• Variations in fly ash properties, influenced by coal source and particle size, affect its performance.
• Effective classification methods are needed to optimize fly ash for concrete applications.

Purpose of the Study:

• To investigate the impact of fly ash particle size on fly ash-cement systems.
• To evaluate a novel flotation classification method for optimizing fly ash properties.
• To understand the relationship between particle size, pozzolanic activity, and cement performance.

Main Methods:

• Flotation classification for physical property analysis of fly ash.
• Thermal analysis to determine calcium hydroxide content and its impact.
• Selective dissolution and X-ray Diffraction (XRD) analysis to assess reaction rates and hydration.
• Testing of high-volume fly ash (50% replacement) concrete systems.

Main Results:

• Flotation classification effectively optimizes fly ash properties, improving activity and flow.
• Smaller fly ash particles demonstrate superior performance in cement systems, enhancing hydration and pozzolanic reactions.
• High-volume fly ash replacement (50%) shows sustained pozzolanic reactions, particularly with finer ash fractions.
• Reaction rates decrease significantly with increasing particle size, highlighting the importance of classification.

Conclusions:

• Particle size is a critical factor influencing fly ash performance in cementitious materials.
• The developed flotation classification method is effective in producing optimized fly ash fractions.
• Utilizing classified, smaller fly ash particles is essential for maximizing the benefits of high-volume fly ash replacement in concrete.