11-08-2012, 05:10 PM
METHODS OF PHYSICAL TESTS FOR HYDRAULIC CEMENT
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Compacted Cement Bed
The compacted cement bed comprises a reproducible
arrangement of cement particles with a specified
volume of air included between the particles. This air
volume is defined as a fraction of the total volume of
the bed and is termed the porosity, e.
It follows that the volume fraction occupied by the
cement particles is (l-e). If Vis the total volume of the
bed, the absolute volume of cement is V( l-e) (cm3),
and the mass of cement m is pV(l-e) (g) where p is
the solid density of the cement particles p (g/cm3).
Calibration of Apparatus
Determination of the Bed Volume
Owing to the need for clearance between the cell and
the plunger, the volume of the compacted cement bed
varies for each cell-plunger combination. The volume
of the compacted cement bed shall be established for
a given cell-plunger clearance, this volume is to be
determined as follows.
Apply a very thin film of light mineral oil to the cell
interior. Place the perforated disc on the ledge in the
cell. Place two new filter paper discs on the perforated
disc and ensure that each covered the base of the cell
whilst lying flat by pressing with a rod.