In order to prevent the disintegration of concrete structures in the presence of severe chemical and physical abuse, concrete pipe, tunnels, tanks, and other structures have incorporated plastic linings made of polyvinyl chloride resins or other suitable materials to form an extremely dense, impervious and chemically resistant liner. These liners may be cast into place so that they are mechanically locked into concrete surfaces or adhesive bonded to other surfaces to become a permanent and integral part of the structure.
When sections of lined concrete pipe are joined, it is necessary that the plastic liners be sealed in a manner that maintains the integrity of the lining at the joint. Various methods have heretofore been proposed for joining the liners at the joints to form a seal. One such method utilizes a liner which is allowed to extend beyond the end of the pipe so that the liner of one pipe section can telescope inside the liner of the adjoining pipe section in overlapping relationship. Where the liners overlap, they can be either fused, cemented, or otherwise joined to form a fluid-tight junction. This requires special casting techniques and the extended lining is susceptible to damage during the pipe casting and installation operations. An alternative arrangement is to use a joint strip which overlaps the liners on either side of the joint. This of course in effect doubles the length of seam which must be sealed. One method heretofore employed has been to fuse a polyvinyl chloride strip over the pipe joint using an electrically-heated air gun. This has proved much too slow and expensive in providing a doublewelded joint.