Double corrosion protection of sewage tunnel linings

ABSTRACT In sewer environments, there are complex chemical and microbiological processes with a reaction between the hydrogen sulphide, a gas produced by the used water, and aerobic feeding microorganism. This resulted in production of sulphuric acid which would cause long-term corrosion on cement based concrete structures. This corrosion process is known as “Microbiologically Influenced Corrosion“. Generally, the ordinary Portland cement-based concrete is not considered as a suitable material for direct exposure to acidic sewer environments. As such, it is necessary to prevent the aggressive environments from developing, as well as to prevent the corrosive environments from coming in contact with the concrete elements. A robust corrosion protection system must be specified and provided for the tunnels and underground structures to ensure the durability of these structures under the aggressive sewer environments and able to withstand a design life span of 100 years. Case example with discussion on seven proven corrosion protection lining systems based on current technology. Past experience of the tunnels is provided with further exploratory study in terms of cost effectiveness and quantity analysis for these seven lining systems to be investigated. A technical specification for Portland cement–based Microbiologically Influenced Corrosion resistant concrete is provided.