ASTM Designation: C20 (Apparent Porosity, Water Absorption, Apparent Specific Gravity, and Bulk Density )

These test methods cover the determination of the
following properties of burned refractory brick:
1.1.1 Apparent porosity,
1.1.2 Water absorption,
1.1.3 Apparent specific gravity, and
1.1.4 Bulk density.
1.2 These test methods are not applicable to refractories
attacked by water.
1.3 The values stated in inch-pound units are to be regarded
as the standard. The values given in parentheses are for
information only.

When testing 9-in. (228-mm) straight brick, use a
quarter-brick specimen by halving the brick along a plane
parallel to the 9 by 2-1⁄2 or 3-in. (228 by 64 or 76-mm) face and
along a plane parallel to the 4-1⁄2 by 2-1⁄2 or 3-in. (114 by 64 or
76-mm) face. Four of the surfaces of the resultant quarter-brick
specimen include part of the original molded faces.

When testing other refractory shapes, cut, drill, or break
from each shape a specimen having volume of approximately
25 to 30 in.3 (410 to 490 cm3
). The specimen shall include
interior and exterior portions of the shape.

Remove all loosely adhering particles from each specimen.

• Dry Weight, D
• Dry the test specimens to constant weight by heating
  to 220 to 230°F (105 to 110°C) and determine the dry weight,
  D, in grams to the nearest 0.1 g.
•  The drying procedure may be omitted only when the
  test specimens are known to be dry, as may be the case with
  samples taken directly from kilns.
• The drying of the specimens to constant weight and
  the determination of their dry weight may be done either before
  or after the saturation operation (Section 6). Usually, the dry
  weight is determined before saturation. However, if the specimens are friable or evidence indicates that particles have
  broken loose during the saturating operation, dry and weigh the
  specimens after the suspended weight, S, and the saturated
  weight, W, have been determined, as described in Sections 5.3
  and 5.4. Use this second dry weight in all appropriate calculations

Saturation:

• Place the test specimens in water and boil for 2 h.
  During the boiling period, keep them entirely covered with
  water, and allow no contact with the heated bottom of the
  container
• After the boiling period, cool the test specimens to
  room temperature while still completely covered with water.
  After boiling keep the specimens immersed in water for a
  minimum of 12 h before weighing.

Suspended Weight, S:

•  Determine the weight, S, of each test specimen after
  boiling and while suspended in water in grams to the nearest
  0.1 g
• This weighing is usually accomplished by suspending
  the specimen in a loop or halter of AWG Gage 22 (0.643-mm)
  copper wire hung from one arm of the balance. The balance
  shall be previously counter-balanced with the wire in place and
  immersed in water to the same depth as is used when the
  refractory specimens are in place.
• Saturated Weight, W—After determining the suspended weight, blot each specimen lightly with a moistened
  smooth linen or cotton cloth to remove all drops of water from
  the surface and determine the saturated weight, W, in grams by
  weighing in air to the nearest 0.1 g. Perform the blotting
  operation by rolling the specimen lightly on the wet cloth,
  which has previously been saturated with water, and then press
  only enough to remove such water as will drip from the cloth.
  Excessive blotting will induce error by withdrawing water
  from the pores of the specimen.

 Calculation

• Exterior Volume, V—Obtain the volume, V, of the test
  specimens in cubic centimetres by subtracting the suspended
  weight from the saturated weight, both in grams, as follows:
•                                                               V =  W – S