Corrosion of biological origin observed on concrete digestors

The mechanism of hydrogen sulfide in an effluent, and the biological corrosion phenomena within concrete are recalled. The concrete digesters examined have shown, after 3 years in service, gas leaks and important deterioration on the top of the concrete shell. Investigation of the structure from the inside showed that the joint between the shell and the dome, which consists of a sealant and a resin coating, was cracked and therefore causing gas leakage outside the tank, Physico-chemical analyses (scanning electron microscope, and X-ray diffraction) showed that the development of gas leaks and the deterioration of concrete originated front biological phenomena. The cause of cracking and the biological corrosion mechanism are described. To repair the structure a technical solution was devised using a joint tape anchored in the resin, once the shell's top had been stripped and finished off with epoxy resin. (C) 1997 Published by Elsevier Science Ltd.