Modified calcium aluminate cement coating for sewage applications

 
The problem of corrosion due to internal attack from aggressive fluids such as sewage and industrial waste is pervasive in many countries. As liquid waste is becoming more and more concentrated, chemically resistant coatings are required. Calcium Aluminate Cement (CAC) based mortars and concretes are an extremely suitable material for sewage coatings and have been successfully placed in waste water systems as in liner of ductile iron pipes, manholes, repair mortars and in wastewater treatment plants. CAC mortar linings have a high abrasion resistance in combination with good resistance against chemical attack and a substantially better resistance against Biogenic Sulphuric Acid Corrosion (BSAC) compared to normal concrete pipes. The term "biogenic sulphuric acid corrosion" is used for those processes in certain well known areas of waste water systems, where micro-organisms form sulphuric acid and subsequently exert an aggressive attack on the hardened cement paste matrix through its dissolution.