Piezoresistive characteristics of CNT/Carbonyl iron powder-embedded cementitious composites

Abstract

In this dissertation proposed the applicability of cementitious composites composed of carbon nanotube (CNT) and carbonyl iron powder (CIP) for structure health monitoring (SHM). A polycarboxylate-based superplasticizer and silica fume were used to effectively disperse the CNT and CIP in cement pastes. The dispersion of conductive material in the cement pastes was evaluated through electrical resistance measurement, zeta-potential test, and precipitation test. The piezoresistive sensing characteristics of cementitious composites under cyclic loading conditions were explored. The effect of CIP incorporation on the electrical resistance change, time-based peak shifts, repeatability as expressed as R2 and the durability of the composites were evaluated. The results indicated that the incorporation of CIP improved the electrical conductivity of the composite with a high CNT content, and improved the piezoresistive characteristics under cyclic loadings. In addition, the piezoresistive characteristics of cementitious composites according to the loading conditions were analyzed. The piezoresistive characteristics of the composites were different according to the speed, acceleration and magnitude of the applied load. Furthermore, crack detection test with real-time monitoring under constant compressive loadings was conducted. The effects of various temperature conditions on the piezoresistive characteristics of cementitious composites were studied. Changes in piezoresistive characteristics of the composites exposed to high temperature and the composites subjected to freeze-thaw cycles were analyzed. In addition, a real-time electrical resistance change experiment according to temperature change was also performed.