ABSTRACT
This paper reviews certain equations that are used for calculating key parameters influencing micro-bially-induced concrete corrosion in sewers These equations form the basis of the so-called Life Factor Method (LFM) that is widely used by practising engineers for corrosion prediction in Portland Cement (PC) based concrete outfall sewers that flow partly full. The LFM quantifies sulphide (H2S) build-up in stale sewage (US EPA 1985). Under certain conditions H2S is readily released into the sewer headspace where it is biologically converted to sulphuric acid (H2SO4) on the moist pipe walls This acid attacks the concrete matrix. Thus, the key parameters in this method are the rate of H2S oxidation on the sewer walls and the alkalinity of the concrete matrix. In effect, this alkalinity amounts to the neutralisation capacity of the concrete matrix (Alexander & Fourie 2011). It therefore follows that the microbially-induced corrosion of the concrete sewer pipe is dependent on the rate at which the attacking acid forms and the effectiveness of the pipe binder system in neutralising the aggressiveness of this acid.
