Hydrates
are composed with water of crystallization in their structures. When a hydrate
is thermally exposed, it absorbs enormous quantity of heat (endothermic) and
forms anhydrous mineral. When an anhydrate is immersed into water; it absorbs
water and releases huge quantity of heat transforming into a hydrate mineral 6.
In other way, it can be expressed that a hydrate is formed by releasing
enormous quantity of heat from its anhydrous product. For an example; the
formation snow from freezing water releases heat and snowfalls warms up the
atmosphere may be cited. The heat released into the pore space might promote
further evaporation of pore fluids. Most of the hydrates are stable and soluble
in water at room temperature.  Efflorescence
may cause spontaneous loss of water of crystallization in some hydrates.   Others
absorb water into their structure forming hydroscopic hydrates. Deliquescent
mineral like sodium hydroxide absorb huge quantities of water and form as
liquid. The decomposition of carbohydrates generally releases water. Thus water
of crystallization in a hydrate minerals play critical role on their changes in
specific gravities and volumes 7. Hydration is not a reversible reaction;
however, the environment crystallization of hydrates plays critical role for
the formation of hydrates and anhydrates 8. 
The repeated hydration and dehydration changes the volume of saline
minerals which in turn affects the volume of pore spaces and hairline cracks
are induced. Most pores are partially or completely filled with saline pore
fluids and repeated influxes of saline fluids and evaporations play critical
role on the evolution of saline precipitates 9.  The evaporation of saline fluids precipitates
saline minerals initially at peripheral portions of saline droplets inside the
pores. The ionic components of chloride, carbonate and sulphate, hydroxide and
water play critical role in the formation of mixed crystals of mineral
components rather than individual minerals. The scope of the investigation
mainly lies to trace the trend of changes of chemical composition during
successive crystallization of chloride components from the primary carbonate
source. Generally, the composition of groundwater is enriched with bicarbonates
and depleted in carbonates. Similar condition is true in the case of saline
waters interlocked in the pore spaces of lime-mortars.

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