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overburned oxides can slowly hydrate and cause expansion of the hardened
cement paste.
the soundness test is conducted by using either Le Chatelier apparatus or
Autoclave method. Le Chatelier method determines the unsoundness due to free
lime. The apparatus consists of a small brass cylinder split along its generatrix.
Two indicators with pointed ends are attached to the cylinder on either side of
the split.
A cement paste of normal consistency is placed in Le Chatelier mould and
covered with glass plate. After being cured at 98%RH for 24 hrs, the distance
(A) between the indicator points is measured and then the mould is heated
gradually to boiling during (30±5) min and the water bath is maintained at
boiling temperature for 3h ± 5 min.
At the end of the boiling period and after cooling to 20oC the distance (C)
between the indicator points is measured again
For each specimen, the measurements A and C and the difference C-A are
calculated.
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