Testing and Performance Criteria for Stabilized/Solidified Waste Forms - Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes - page 291

11.4.3 P ARTICLE S IZE D ISTRIBUTION

Characterization of particle size distribution 53, 54 is carried out by sieving to determine
the grading of the untreated material. Particle size distribution affects the workability
of the material and the compaction of the material. It is desirable to achieve the
maximum density with a reasonable amount of work. 55

11.4.4 B ULK D ENSITY

Bulk density 56-59 is the mass per unit volume of the material. It can be used together
with moisture content and specific gravity to calculate S/S material porosity and
degree of saturation. These properties are related to durability and leachability,
although the relationship is not simple. It can also be used to assess the homogeneity
of the S/S material, and monitor volume or moisture changes during curing. Bulk
density can also be used together with the mass change factor to calculate volume
increase due to treatment.

11.4.5 S PECIFIC G RAVITY

Specific gravity 56,60,61 is a measure of the solids density of a material relative to the
density of water. This property is generally needed to calculate other physical
properties.

11.4.6 W ATER A BSORPTION

Water absorption 56,60,62 is a measure of water penetrating into the pores of a material,
but not including water adhering to the outside surface of the material. It is related
to the volume and characteristics of the porosity of the material, and its saturation.
It is determined by immersing a dried sample of known weight in water and obtaining
its mass after removing the free water from the sample's surface. The water absorp-
tion of an untreated material relates to its water demand in treatment by S/S; the
water absorption of a treated material may be related to durability with respect to
weathering.

11.4.7 P OROSITY

Porosity 63-65 is a measure of the proportion of the total volume of the material
occupied by pores and is useful in understanding results from other tests, such as
hydraulic conductivity.

11.4.8 M OISTURE C ONTENT

Moisture content 66-68 is a measure of the amount of free water in a material and is
necessary for determining the water mass balance in S/S treatment and in calculating
the L/S ratio in leaching tests. The moisture content of S/S materials is often
determined by drying at 60°C, or at a specified humidity, to avoid driving off the
water of hydration. 15