From risk study to field evidence: an unprecedented and isolated case of delayed ettringite formation in Brazil

Abstract

This paper describes the first ever reported case in Brazil where delayed ettringite formation (DEF) has been confirmed as the sole cause of deterioration in field concrete. Still under construction and less than 2 years old, numerous cracks were observed in the foundation structures of a building located in Recife, a city known for its history of alkali–aggregate reaction (AAR) cases. In addition to a field survey of cracks, microstructural analyses, tests for residual expansion and compressive strength, a review of the structural design, determination of sulfate content in the groundwater and simplified thermal analysis were carried out. The results confirmed that DEF was the sole cause of the damage present in cast-in-place concrete structures, with no evidence of AAR or any other deterioration process. This work corroborates previously published studies on the high risk of the occurrence of DEF in the region, demonstrating the urgent need for a preventive technical standard in the country, considering the chemical composition of cements and prior thermal analyses to adopt possible preventive measures to limit the maximum internal temperature of concrete.