Evaluating the impact of curing temperature in delayed ettringite formation using electrochemical impedance spectroscopy

Abstract

Abstract Delayed ettringite formation (DEF) could be deleterious and reduce the serviceability of structures built with precast concrete elements subjected to a short-term heat curing regime. Over 3 decades of research many characterization techniques have been developed to study the impact of DEF in cementitious systems. This paper attempts to assess the physical alterations due to DEF in cementitious systems using electrochemical impedance spectroscopy (EIS). Mortar specimens were made with two different cements exposed to different curing regimes and prone to DEF attack. At later age of 500\xa0days after the significant expansion due to DEF, impedance arcs of mortar specimens were collected. Electrical resistivities owing to continuously connected pores and discontinuously connected pores were calculated with the impedance values. Electrical resistivities were compared with linear expansion and mass change of mortars. Results show a significant reduction in impedance with an increase in curing temperature due to physical damage and electrical resistivity was lowest for mortars with high DEF expansion. Precipitation of heterogenous DEF in confined microstructure capable of generating expansion further contributes to the lowering the electrical resistivity. This research shows EIS can be used to monitor the physical damage in the microstructure of the cementitious system to study deterioration mechanisms such as DEF.