Explanations for the good behaviour in sewer networks of calcium aluminate cement materials

Sewer networks are subjected to many corrosion agents leading to deterioration of variant magnitude. One type of damage can be ascribed to concrete corrosion by biogenic sulfuric acid. According to field data, cementitious materials have different behaviours depending more especially on cement type. Those made with calcium aluminate cement (CAC) offer better performance than those made of ordinary Portland cement (OPC). This difference of durability may have three origins that can be combined. The first one is due to the oxidation of hydrogen sulfide at the surface of each materials leading to a lower amount of elemental sulfur deposited on CAC materials due to the difference of matrix composition (chemical composition and mineralogy). Elemental sulfur is then oxidized into sulfuric acid by microorganisms and leads to cementitious materials corrosion. The second one, the alumina content of CAC materials stabilizes the surface pH at around 3-4 and therefore limits the development of the most deleterious sulfur oxidizing bacteria. The last one, the aluminium content of CAC has a bacteriostatic effect on some microorganisms, limiting biofilm development. All that results are participating at the good performances of CAC materials