Page 276 - Buried Pipe Design

Chapter
5

Rigid Pipe Products

Chapter 5 deals with various generic rigid pipe products. For each
product, selected standards and material properties are listed. The
standards are from standard organizations such as the American
Water Works Association (AWWA) and American Society for Testing
and Materials (ASTM). Actual design examples for the various prod-
ucts are given in this chapter.

Asbestos-Cement Pipe
Asbestos-cement (AC) pipes are available for both gravity and pressure
applications (see Tables 5.1 and 5.2). Because of the health risks asso-
ciated with the handling of asbestos, AC pipe production in the United
States has come to a complete halt. It is still produced in some coun-
tries and is available in some parts of the United States. This product
has some flexibility, especially for lower classes (thinner walls).
However, it is generally considered to be a rigid pipe product; therefore,
the rigid pipe design method should be used for AC pipe installations.
Asbestos-cement pipes are manufactured from asbestos, cement,
silica, and water. The pipe-making machine places this mixture on a
polished steel mandrel, and it is pressure-steam-treated (autoclaved)
to achieve curing with less than 1 percent uncombined calcium
hydroxide (free lime). AC pipes which have less than 1 percent free
lime are designated as type 2. Type 2 AC pipes are generally resistant
to all levels of soluble sulfates, but will be attacked by acids with a pH
level of 5.0 or less. Type 1 pipes have more than 1 percent free lime and
are generally not resistant to either soluble sulfates or acids.
Asbestos-cement pipes are joined via rubber-gasketed cou-
plings. The pipe has a hard and fairly smooth internal surface.

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