Mechanical and piezoresistive properties of self-sensing smart concretes reinforced by carbon nanotubes

Concrete structures such as bridges, towers, and roads are constantly prone to damage due to development of cracks, stresses, and other defects. The present study is focused on manufacturing of self-sensing smart concretes and investigates their mechanical and piezoresistive behavior for health monitoring of concrete structures. To this end, concrete is combined with multi-walled carbon nanotubes (MWNTs) to produce an internal electrical network. Using the high piezoresistive properties of the carbon nanotubes, the concrete is able to indicate the mechanical stresses. Carbon nanotubes are also capable of reinforcing concretes and increasing mechanical strength. To this end, the concrete nanocomposite was prepared in three general cases including cement paste and concretes of grade 400 and 350 for water-cement ratios of 0.45 and 0.6. Then, the effect of different weight percentages of carbon nanotubes on the electrical and mechanical properties of the nanocomposite was experimentally investigated. In the next stage, the piezoresistive property of concrete was investigated when subject to static and dynamic loads. The results indicate that concrete nanocomposites are sensitive to the amount of applied compressive stresses so that application of compressive stresses up to 6 MPa leads to changes of up to 8 percent in the electrical resistance of concrete in the case of using cement paste nanocomposite reinforced with 1 wt.% of carbon nanotubes.