Asbestos Cement Pipe

Applicable Technologies

Leak & Gas Pocket

Acoustic Monitoring

RTPM

Video Inspection

Asbestos cement (AC) pressure pipe is used primarily for potable water, as well as for sewer force mains and industrial effluent and process piping. AC pipe was first introduced in North America in the late 1920s and became a common choice for potable water main construction from the 1940s to the 1970s. The use of AC pipe was largely discontinued in North America in the early 1980s but AC pipe is still a significant portion of the water distribution systems in many North American cities.

Asbestos cement (AC) pipe is manufactured from a mixed slurry of portland cement (80-85%) and a mixture of chrysotile asbestos fibres (15-20%). The slurry is dewatered using a rotary sieve cylinder and a very thin layer of asbestos cement is produced. This thin layer is wrapped around a mandrel under pressure until a pipe with the desired wall thickness is made. After curing, the ends of the pipe lengths are cut and finished to receive couplings that are produced by cutting larger diameter pipe into sections.

Advantages	Disadvantages
Inexpensive to manufacture Very durable Capable to withstand the transverse stress arising out of internal pressure Resistent to corrosion and tuberculation Ease of installation and tapping Lighter than iron pipe	Potential health concerns on potable lines and worker safety Difficult to repair (cut & splice) Pipe is brittle and tends to crack under stress from trench loads

Main Forms Failure in Asbestos Cement Pipes

Form of Failure	Causes of Failure	Indicators of Failure
Break failure	Soil differential movement or inadequate bedding support	Circumferential cracks
	Internal pressure and external loads (soil cover, live loads, frost)	Longitudinal cracks
	Manufacturing defects	Cracks in body
Structural Failure	Movements from thermal, seismic, external loading	Joint leaks, poor bedding, and pipe movements
Structural Failure	Internal pressures, external loadings, thermal stresses	Longitudinal cracks and changed internal/external loads
Leaks	Loss of soil support and bending failure	Leak noise, wet areas, and pressure variations