CONCRETE PIPE Joint Gaskets and Sealants Gaskets and sealants vary in cost and inherent performance characteristics, but field performance is always dependent upon installation procedures. The most common are: • • • • Cement, paste or mortar Rubber, attached or separate External bands, cement mortar or rubber Mastic, bulk or preformed Cement Cement sealants consist of cement paste made with water. The joint surfaces should be clean and soaked with water immediately before the joint is made. A layer of cement paste or mortar is placed in the lower portion of the bell or groove of the installed pipe and on the upper portion of the tongue or spigot of the pipe section to be installed. The tongue or spigot is then inserted into the bell or groove of the installed pipe until the sealant material is squeezed out on the interior or exterior surfaces. The annular joint space should be completely filled and the abutting joint sections flush and even. Rubber Rubber gaskets are of three basic types; flat gaskets which may be cemented to the pipe tongue or spigot, O-ring gaskets which are recessed in a groove on the pipe tongue or spigot and then confined by the bell or groove after the joint is completed, and roll-on gaskets which are placed around the tongue or spigot and rolled into position as the joint is assembled. Except for the roll-on gasket, the gasket and joint surfaces should be lubricated with a lubricant recommended by the manufacturer. At Lafarge, rubber gaskets are distributed with concrete pipe as required. The performance of the gasket system is very installation sensitive and the importance of lubrication cannot be understated. Please refer to page 62 of this manual for proper installation procedures. Alternatively, contact your local Lafarge representative for additional information. Mastic Mastic sealants consist of bitumen and inert mineral fillers. The sealant is applied to the tongue or spigot and inserted into the bell or groove. A sufficient amount of sealant should be used to fill the annular joint space with some squeeze out. External Bands Cement mortar bands are placed around the exterior of the pipe joint. A slight depression is excavated in the bedding material to enable the mortar to be placed underneath the pipe and the external joint surface cleaned and soaked with water. Canvas or cloth wrapping is used to hold the mortar as it is placed. Backfill material should be placed around the pipe immediately after the mortar band is in place. PAGE 58 LAFARGE PIPE eMANUAL