Multifunctional behavior of CNT- and CB-based composite beams

Abstract

The investigation was performed on the self-sensing behavior of reinforced geopolymer concrete beams produced at ambient curing. Prior to investigation, carbon nanotubes (CNT) and carbon black (CB) were used in small-scale geopolymer specimens at different ratios and the electrical properties of the composites were tailored in the favor of self-sensing functionality. After characterization of mechanical and electrical properties, 150 x 150 x 750 mm(3) (width x height x length) self-sensing reinforced geopolymer beams were produced with a span/effective depth ratio of 2.0. An experimental procedure was designed to obtain a mixed failure mode of shear and flexural. Engineering properties of large-scale beams were evaluated in terms of flexural strength, deflection capacities, initial stiffness and ductility ratios with the proposed design. Simultaneously, self-sensing assessments were performed continuously by the evaluation of relative factor in electrical resistivity of geopolymer beams at different loading levels. Microstructural and experimental results revealed that CNT-based beams significantly enhanced the load-carrying capacity and ductility that provided a high amount of energy dissipation capacity compared to CB-based beams. CNT-based beams exhibited 107.7%, 188.9%, 217% and 51% higher relative factor in electrical resistivity compared to CB-based beams at 25%, 50%, 75% and 100% of total applied load, respectively. Results indicate that applied load was continuously sensed by all geopolymer beams although CNT-based beams were more responsive to change of strain compared to CB-based beams at earlier stages of loading. (C) 2021 Elsevier Ltd. All rights reserved.