Air-classified fly ash at 4500 cm2/g Blaine - noticeably more reactive than standard ash at the same dosage.
Air classification removes the coarse, largely inert fraction and leaves the fine, glassy, genuinely reactive particles. The result is a material that behaves less like a filler and more like a binder: higher early strength, better particle packing and a measurably denser paste.
MFA 450 is the practical starting point for high-performance concrete where standard ash is not quite delivering.