cement, viz., compressive strength and dimensional stability arises from the surface
properties and porosity of the cement gel. The principal constituent of this gel is
tobermotite, a calcium silicate hydrate (CSH) obtained by the hydration of C3S and C2S.
Ca(OH)2 (15-25% by weight of cement) formed during hydration does not contribute to
the strength and durability of the concrete rather it has diverse effects in the form of
retrogression in strength and stiffness of concrete. Inclusion of an additive like silica
fume can reduce the bad effect of Ca(OH)2. Microsilica is supposed to react with
Ca(OH)2 formed during hydration of cement and forms CSH. Thus the content of
Ca(OH)2 will decrease, while the content of CSH which provides strength and durability
will increase.