Assessment of Concrete Impairments over Time Triggered by DEF

Abstract

Expansive reactions such as delayed ettringite formation (DEF) can lead to mechanical and microstructural changes in concrete, resulting in considerable damage to the structures. DEF usually occurs in concrete that has reached a high temperature after being exposed to moisture. This paper presents the assessment of concretes with and without pozzolan in laboratory in order to monitor and evaluate expansions, as well as their main properties and characteristics over a period of 12 months, after undergoing DEF at a temperature of 85°C and with drying-wetting cycles. An increase in expansion caused by DEF was tracked through a series of microscopical observations, along with evaluations of concrete deterioration. Additional tools, such as the stiffness damage test (SDT) and deteriorated damage index (DRI), were also employed in the experiments. Furthermore, an overall approach to DEF was adopted, together with a performance appraisal based on data from the research program and a detailed analysis to quantify the extent of the damage to concretes and to estimate the different deterioration levels.