The Use of Epoxy and Polymer Modified Cementitious Coatings to Re-Line Old Concrete and Brick Manholes and Sewer Structures

Paper No. 144
Mr. David Johnstone, Australasian Product Manager – Linings, Akzo Nobel Pty Limited, 2 Capelli Road, Wingfield, South Australia, 5013

Abstract

Concrete man holes and sewer pipes are an integral part of all sewerage systems. They are however exposed to corrosion from Hydrogen Sulfide (H2S) and Chloride diffusion which, if not addressed, lead to sectional loss of concrete and can ultimately lead to a failure of the system.

Sewage Infrastructure Corrosion is estimated to cost around $91 million per year in Australia. (Report commissioned by the Australasian Corrosion Association (ACA), the report, Corrosion Challenges – Urban Water Industry)

Protective coatings such as Polyurea and, Novolac epoxies provide excellent barrier protection when applied correctly, however these systems are difficult to apply as often the application environment has very high humidity, with the host concrete being damp and/or subject to negative water pressure.

Extending the long term durability of the structures and providing chemical resistance from  Hydrogen Sulfide (H2S) attack is very challenging, particularly when the expected design life of the structure can be 50 years.

Issues such as reinstating the effective concrete cover, fast return to service capabilities, the presence of surface moisture and high atmospheric humidity during coating application all contribute to the complexity, cost and overall result of the coating application.

This paper explores the issues of applying protective coatings  to degraded manholes and sewer pipes and reviews the use of advanced, two-component cementitious coatings as an environmentally friendly, cost saving solution providing long term protection from Hydrogen Sulfide (H2S) attack and chloride protection.

Keywords

Concrete, Sectional loss of Concrete, Long Term Durability, Design Life, Chloride Diffusion, Cementitious Coatings