7. Geotechnical characteristics of fly ash

7.1 Granularity

The material takes the form of a powder with a particle size ranging from 0.5 to 315 µ .m. Blaine fineness (specific surface area) is high, generally in excess of 2,000 cm ² /g (not far from conventional cements), and even in excess of 10,000 cm ² /g in the case of certain CFL ashes.

In the case of silica-alumina ashes, it should be noted that, in order to be used in road construction, the passings at 40 and 80 µ.m (cf. standard XP P 18-545 March 2008, which replaces the experimental standard XP P 18-545, February 2004 edition, fascicule NF X 11-640 is still current) must be respectively greater than 40 and 70% (cf. standard NF EN 14 227 – Part 3, February...