Use of Modified Cementitious Coatings to Re Line Manholes and Sewerage Infrastructure From H2S Attack

Concrete man holes are an integral part of all sewerage systems, however they are exposed to corrosion from Hydrogen Sulfide (H2S) gas which, if not addressed leads to sectional loss of concrete and can ultimately lead to catastrophic failure of the structure.

The economic impact of corrosion and it’s degradation of sewage infrastructure and assets in Australasia is estimated to be 3 to 5 per cent of GDP each year, which represents an estimated annual cost of approximately AUD$982 million (Report commissioned by the Australasian Corrosion Association (ACA), the report, Corrosion Challenges – Urban Water Industry).

Other protective linings such as Polyurea, Vinyl Ester and Novolac epoxies provide excellent barrier protection when applied correctly, however these technologies have specific challenges with application as often the environment has very high humidity, with the concrete structure being damp and/or subject to water pressure from the outside face of the structure.

Extending the long-term durability of structures and providing a chemical resistant solution from Hydrogen Sulfide (H2S) attack is very challenging, particularly when the expected design life of the structure can be >25 years. Issues such as reinstating the effective concrete cover, fast return to service capabilities, the presence of substrate moisture and high atmospheric humidity during coating application all contribute to the complexity, cost and overall performance of the lining application.

This paper explores the challenges and issues with applying protective coatings to degraded manholes and sewerage infrastructure and explores the use of advanced, two-component cementitious coatings as an environmentally friendly and cost-efficient solutions providing long term protection from Hydrogen Sulfide (H2S) attack.