Field performance of concrete exposed to sulphate and low pH conditions from natural and industrial sources

Laboratory investigations have been used to derive a high number of important details on sulphate attack on hardened concrete, but are not able to forecast the performance of this material under field conditions. In order to obtain reliable information on the long term behaviour of concrete, a survey is presented that looks at sulphate and sulphide containing environments in a particular region in mid-Europe. Twenty concrete structures have been sampled and analyzed.The classical idea of sulphate attack considering the migration of sulphate ions from ground or river water into concrete with subsequent phase transformation and damage has not been confirmed. This kind of exposure was found to be rare and no serious deterioration has been observed in connection with it. However, concrete is liable to be destroyed when in contact with sulphide bearing environments or if intimately mixed with gypsum. Disintegration and serious expansion requiring immediate repair has been observed. Information on all investigated structures are presented in this article and in more detail in a separate report.

► Sulphate attack on concrete under field conditions has been investigated in this study.
► Twenty structures were sampled having an age between 1 and 47 years.
► Sulphate attack is rare under field conditions.
► Most damages were observed in connection with pyrite oxidation.