Nano-carbon cement based sensors for smart structures

The purpose of Structural health monitoring (SHM) is to monitor the in-situ behaviour of a structure, assess its performance, detect damage, and determine the condition of the structure. The object of this research is to analyse one type of sensor for SHM. More specifically, the piezoristive property of nano-carbon reinforced cement based sensor is examined. The nano-additives, carbon nanotube (CNT) and carbon nanofiber (CNF), in a cement mixture produce a piezoresistive material that can reveal a variation of strain with the variation of its electrical resistivity. This study aims to assess the various mixtures to produce the best sensor as a replacement of conventional strain sensor. The sensing abilities of different cement based mixtures are assessed as cylindrical specimens are put through cyclic load tests. Different variables affecting the sensor effectiveness are examined such as the effect of nano-additives and aggregate content. Standard compressive tests are also conducted to assess the nano-additive effect on the material structural integrity. Two different type of carbon fibre, the carbon nano-fiber (CNF) and the carbon nanotube (CNT) were examined in two different matrixes: one with the cement paste and the other with cement mortar. The first sets of experiments with cement paste served to validate previous studies on the subject and helped established the process for the 2^nd sets of experiments on cement mortar sensor. Results of the two sets of experiments are assessed and presented to highlight their sensing abilities.