Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...

4.3.6 Specific Gravity and Porosity
4.3.6.1 Introduction. Specific gravity was measured by the displacement method in accordance with
ASTM D792. The standard specifies that any convenient size specimen can be used for this testing. A
weighing scale (Figure 4-30) fitted with a hook at the bottom was placed on a bench having a circular
hole in the middle. A small wire basket was hung from the hook (Figure 4-31). A thermometer to
measure the water temperature was hung from the bottom of the bench.
Figure 4-30. Weighing Scale, Model
Mettler PM200
50
Figure 4-31. Wire Basket and Thermometer
A bucket full of water was placed on top of a screw jack. The screw jack helped in elevating the bucket
and immersing the specimen in water. A sinker was also used to sink the specimens. Details of the
instrumentation are shown in Figure 4-32.
Thermometer
Bucket
Screw
jack
Scale
Figure 4-32. ASTM D792 Setup
Bench
The weight of each specimen was measured in air and water. The weight of the wire basket was also
measured in water. Each time the immersed depth for the wire basket was kept identical. Specific gravity
was calculated for each specimen using the equation provided in ASTM D792.
The bulk specific gravity of the liner comprises a mixture of resin, fabric, coating, and air. It is a useful
measure to check whether the liner meets the theoretical specific gravity based on the weighted
contribution of its components. Low specific gravities typically indicate higher porosities in the liner.
The results of the specific gravity measurements across all of the liners tested are discussed in Section 6.