Scope
This Part of this British Standard describes two
methods for determination of air content of
compacted fresh concrete, made with normal weight
or relatively dense aggregate having a nominal
maximum size of 40 mm or less.
Neither of the
methods is applicable to aerated concrete, very stiff
concrete which cannot be compacted by vibration
alone nor to concrete made with lightweight
aggregates, air cooled blast-furnace slag or
aggregates of high porosity.
NOTE The titles of publications referred to in this standard are
listed on the inside back cover.
Apparatus
Sampling tray, minimum
dimensions 900 mm × 900 mm × 50 mm deep of
rigid construction and made from a non-absorbent
material not readily attacked by cement paste.
4.1.2 Square mouthed shovel, size 2 in accordance
with BS 3388.
4.2 Procedure. Empty the sample from the
container(s) on to the sampling tray. Ensure that no
more than a light covering of slurry is left adhering
to the container(s).
Thoroughly mix the sample by shovelling it to form
a cone on the sampling tray and turning this over
with the shovel to form a new cone, the operation
being carried out three times.
When forming the
cones deposit each shovelful of the material on the
apex of the cone so that the portions which slide
down the sides are distributed as evenly as possible
and so that the centre of the cone is not displaced.
Flatten the third cone by repeated vertical insertion
of the shovel across the apex of the cone, lifting the
shovel clear of the concrete after each insertion.