Components of Cement

Components of Cement Comparison of Chemical and Physical Characteristicsa[23][24][25]
Property	Portland Cement	Siliceous (ASTM C618 Class F) Fly Ash	Calcareous (ASTM C618 Class C) Fly Ash	Slag Cement	Silica Fume
SiO2 content (%)	21.9	52	35	35	85–97
Al2O3 content (%)	6.9	23	18	12	—
Fe2O3 content (%)	3	11	6	1	—
CaO content (%)	63	5	21	40	< 1
MgO content (%)	2.5	—	—	—	—
SO3 content (%)	1.7	—	—	—	—
Specific surfaceb (m2/kg)	370	420	420	400	15,000– 30,000
Specific gravity	3.15	2.38	2.65	2.94	2.22
General use in concrete	Primary binder	Cement replacement	Cement replacement	Cement replacement	Property enhancer
aValues shown are approximate: those of a specific material may vary.
bSpecific surface measurements for silica fume by nitrogen adsorption (BET) method, others by air permeability method (Blaine).