The fly ash used as SCM has the specific gravity within which range?

• A. 1.9 - 2.8
• B. 1.0 - 1.5
• C. 2.8 - 3.8
• D. 0.9 - 1.3

Answer: (A)

Specific gravity tells you how dense a material is compared with water. Fly ash used as a supplementary cementitious material is a fine, glassy powder with a density around 2.0 to 2.8 times that of water. That’s why the range 1.9 to 2.8 fits the typical values you’ll encounter for fly ash. Values much below water, like 0.9–1.3 or 1.0–1.5, are too light for fly ash, and a range as high as 2.8–3.8 is at the upper extreme and not representative of standard fly ashes. Knowing this helps with mix design calculations when converting weights to volumes for cementitious materials.