Concrete Corrosion Prediction from gaseous H2S concentration

[sewerratt]

I'm looking for formulas, research papers, nomographs, etc. that can be used to help predict the pH on concrete manhole walls due to microbially induced corrosion from thiobacillus reduction of h2s to H2SO4. I presume the resultant pH and corrosion effects can be or have been correlated to gaseous H2S concentration. A little guidance to some previous research will be greatly appreciated.

 

[chicopee]

where is your hydrogen sulfide coming from? are you working in a landfill? About doing some air sampling for concentration levels. Since wet concrete is alkali, a little coating of acid should somewhat become meutralized-wouldn't it?

 

[sewerratt]

H2S is coming from the sewage in wastewater. Manholes are on sanitary sewer lines. Stopping the H2S generation is not an option. It is bacterially produced. Successive generations of differing bacteria produce by-products from wastewater constituents that eventually result in a bacteria that produces H2SO4 as a wasteproduct and progressively lower the pH level of the concrete surface, allowing progressively more aggressive bacteria strains to live there. I'm trying to find some studies that have correlated those concentrations into observed levels of corrosion, or measured levels of pH on the walls

 

[chicopee]

Is this a problem that you are facing or is this an academic exercise? I worked in the construction field for over a dozen years on State bridge and highway contracts and I dont ever remember such problem ever came up whereby we had to protect concrete manholes and sewer lines from this chemical reaction. We had jobs in areas that had previously being identified as landfills perhaps decades old and closed, yet hydrogen sulfide and its byproducts were never an issue eventho we had air samplings tests for such contaminants.

 

[LittleWheels]

It is quite common to epoxy-coat or HDPE-line sewerage maholes, wet wells and suchlike, either during remediation or construction, for increased service life.

The amount of oxygen (ventilation), washing/drying cycles and the composition of upstream sewage generators seem to have a significant effect on H2S attack, in my experience, but there are probably other major influences too.

Neutralisation of concrete never seems to have progressed very far when I have checked, perhaps due to progressive erosion of the concrete as a result of H2S attack. Some of the wet wells I've inspected have lost over 50 mm of concrete over 30 years or so but neutralisation has only progressed a few millimetres into the remaining concrete. I have found similar results with wet wells that have lost less than 20 mm of concrete over the same period.