Self-sensing capability of Engineered Cementitious Composites: Effects of aging and loading conditions

Self-sensing capability of 7-, 28-, 90- and 180-day-old Engineered Cementitious Composites (ECC) incorporated either with carbon fibers (CF/ECC-CF) at micro-scale or multi-walled carbon nanotubes (CNT/ECC-CNT) and carbon black (CB/ECC-CB) at nano-scale were investigated herein. Mechanical properties (compressive strength, splitting tensile strength/deformation, flexural strength/deformation) of different-age mixtures were evaluated. Control mixture (ECC-Control) without any carbon-based material was also produced and tested for comparison. Depending on the loading condition, equipment utilizing either direct current (DC) or alternating current (AC) was used for self-sensing assessments. Results showed that carbon-based materials generally improve the mechanical properties of ECC-Control specimens depending on the type of carbon-based materials, specimens' age and loading conditions. All specimens sensed different types of damage except 180-day-old ECC-Control specimens loaded under uniaxial compression and splitting tension due to abrupt increments in impedance results exceeding the limits of testing device which revealed the importance of presence of electrically-conductive materials for achieving enhanced self-sensing capability independent of aging, testing configuration/equipment, loading conditions and microcrack characteristics. CF is the best to improve self-sensing capability of ECC-Control specimens for all ages and loading conditions. Self-sensing performances of ECC-CNT and ECC-CB are comparable and utilization of nano-size carbon-based materials is suggested in cases where reversibility in self-sensing is needed. (C) 2019 Elsevier Ltd. All rights reserved.