Ductile Iron Pipe and Fittings

In most cases, ductile iron pipe and fittings are mortar-lined at the factory. Field application of a mortar lining is normally done on older, in-service pipe for rehabilitation purposes. Ductile iron pipe can be supplied with protective linings other than cement mortar lining. Some of the other protective linings may be more appropriate, depending upon the fluid being transported. For instance, ductile iron pipe transmitting raw sewage under gravity flow conditions might be lined with a protective material since sulfuric acid, which may form in the space above the flow, can severely attack portland cement mortar linings and ferrous pipe materials. For most non-aggressive raw water and potable water transmission situations, cement mortar linings are very economical and the most common means of protection.

Table A summarizes the mortar lining application methods, curing methods, and mix proportions used in the manufacturing plant and in the field for ductile iron pipe and fittings.

		Applied at manufacturing plant	Applied in the field
Pipe	Application	Centrifugal casting or pneumatic placement	Mechanical placement and troweling
	Curing	Asphaltic seal coat, steam, or water	Water
	Mix proportions	1 part portland cement, not more than 2 parts fine aggregate, and sufficient water to achieve required workability	1 part portland cement to 1–1¹⁄₂ parts fine aggregate, and sufficient water to achieve required workability
Fittings	Application	Hand-placed or pneumatic placement	Hand-placed if not by mechanical placement and troweling
	Curing	Asphaltic seal coat, steam, or water	Water
	Mix proportions	1 part portland cement, not more than 2 parts fine aggregate, and sufficient water to achieve required workability	1 part portland cement to 1–1¹⁄₂ parts fine aggregate, and sufficient water to achieve required workability

Table A: Cement Mortar Lining Application, Curing, and Mix Proportions for Ductile Iron Pipe

Table B summarizes the factory-applied mortar lining thickness requirements for ductile iron pipe and fittings. Linings with twice the thicknesses shown in Table B (known as double thickness) can be supplied for extra protection if requested by the purchaser. 

Pipe size range	Mortar lining thickness
NPS 3–NPS 12 (DN 75–DN 300)	0.0625 in (1.6 mm)
NPS 14–NPS 24 (DN 350–DN 600)	0.0938 in (2.4 mm)
NPS 30–NPS 64 (DN 750–DN 1600)	0.125 in (3.2 mm)

Table B: Factory-Applied Mortar Lining Thickness for Ductile Iron Pipe and Fittings

Table C shows the field-applied mortar lining thickness requirements for ductile iron pipe and fittings.

Pipe size range	Mortar lining thickness for old and new ductile iron
4–10 in (100–250 mm)	0.1875 in (4.8 mm)
11–23 in (280–580 mm)	0.25 in (6.4 mm)
24–36 in (600–900 mm)	0.3125 in (8 mm)
36 in (900 mm)	0.3125 in (8 mm)

Table C: Field-Applied Mortar Lining Thickness for Ductile Iron Pipe and Fittings

Joint Protection

As with the concrete pressure pipe joint, in the case of factory-applied mortar linings, a small annular gap between the lining of adjoining pipe sections results after assembly of a ductile iron bell and spigot joint in the field. Depending on the nature of the water being transported and the protective coating applied to the joint surfaces by the pipe manufacturer, it may be necessary for the installing contractor to mortar this annular recess to protect the joint. In the case of field applied mortar lining, the lining is continuous across the joint, and no further work is needed at the joint.

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