Use of small size bars placed properly, leads to closer cracks but of
smaller width. The risk of cracking due to temperature and shrinkage
effects may be minimized by limiting the changes in moisture content and
temperature to which the structure as a whole is subjected. The risk of
cracking can also be minimized by reducing the restraint on the free
expansion of the structure with long walls or slab founded at or below
ground level, restraint can be minimized by the provision of a sliding
layer. This can be provided by founding the structure on a flat layer of
concrete with interposition of some material to break the bond and
facilitate movement.
In case length of structure is large it should be subdivided into suitable
lengths separated by movement joints, especially where sections are
changed the movement joints should be provided.
Where structures have to store hot liquids, stresses caused by difference
in temperature between inside and outside of the reservoir should be taken
into account.
The coefficient of expansion due to temperature change is taken as 11 x
10-6 /° C and coefficient of shrinkage may be taken as 450 x 10-6 for initial
shrinkage and 200 x 10-6 for drying shrinkage.