Manufacture of Concrete Pipes Using CPL Technology

In many developed countries, population density in the cities is increasing where urban renewal is preferred to the urban spread of previous decades. Existing trunk sewer systems in these urban areas are often undersized to cope with the increased flows and authorities are faced with the construction of new gravity sewer lines. Reinforced concrete pipes are the most cost effective means of building these pipelines in the diameter range of DN900 to DN2400. Cast-in corrosion protection liners (CPLs) offer an effective means of preventing internal corrosion of these concrete structures and assuring a 100 year service life in aggressive sewer environments. Australia has a long history in thermoplastic cast-in liners in concrete pipes and plasticised PVC has been installed into spun concrete pipes since the 1960's. More recently, high Density Polyethylene (HDPE) linings have become the preferred lining material. This paper investigates successful design and use of HDPE CPL in lining of reinforced concrete pipes and structures. The paper looks at lining material selection, material thickness, knob shape and spacing, sheet sizes and configuration. Lining materials and production processes will be compared. Joint welding using purpose built machines is another key aspect as well as testing requirements, both in the factory and for joint welding on site. Embedment of the knobs in the concrete and the integrity of welds at joints are two key quality issues. Comparisons of cost and performance are made between CPL reinforced concrete pipe and spray applied linings in pipes and with other inert pipe material types. The paper demonstrates that CPL's are an effective corrosion protection method in reinforced concrete pipes and that the inherent strength and robustness of a rigid concrete pipe combined with the assured quality of a CPL can provide a sound solution that overcomes construction and service life issues.