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Low
Heat Cement is specially engineered cement for use where the heat evolved
during the cement hydration process needs to be reduced. In mass
concrete or in thick structural elements using normal cements, this heat of
hydration can cause significant temperature gradients within the structure and
thermal cracking may result. The use of Low Heat Cement can minimize this
effect. As the name indicates, it produces less heat than other ordinary
types of cement and it is slow in hardening.
Specified minimum early strength is little lower than that the ordinary
Portland
cements. This cement is mostly used
for gravity retaining walls, large dams and similar massive
concrete structures where temperature rise in the mass concrete and subsequent
shrinkage in cooling stage can be reduced.
Low Heat Cement can also be used in soil stabilization,
underground mining and marine concrete applications where
engineering properties such as re-workability and durability are required.
Low heat evolution is achieved by reducing the
contents of C3S & C3A (which are the compounds
evolving maximum heat of hydration) and increasing C2S. Low
heat evolution would result in reduction in temperature which will retard the
chemical reaction of hardening. A retarded chemical reaction of hardening will
further reduce the rate of evolution of heat. Thus evolution of heat will
extend over a longer period now with reduced rate of evolution of heat .
This results in slow rate of gain of strength though the ultimate strength
is same as that of OPC.
In some applications a very low early strength may be
a disadvantage. For this reason so called modified (Type II) cement was
developed in US. This modified cement
successfully combines a somewhat higher rate of heat development than that of
low heat cement with a rate of gain of strength similar to that of OPC.
Modified cement is recommended for use where a moderately low heat
generation is desirable.
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