Effect of size fraction and glass structure of siliceous fly ashes on fly ash cement hydration

Paper presents effect of size fraction and glass structure of fly ashes on cement hydration. Fly ashes below 16 μm and 16–32 μm, both from the 1st and 3rd section of electro-filter, were applied. Hydration heat, content of Ca(OH)2 and unreacted C3S were studied and compressive strength and microstructure were analysed. Results show that finer ashes have higher depolymerization degree of SiO4 units in glass what increases pozzolanic reactivity. Incorporation of fly ashes below 16 μm from the 3rd section gives cement class 52.5 N. At 180 day, Ca(OH)2 content decreases by 67% and C3S hydration degree increases by 50% relative to control sample.