A hierarchical nano to macro multiscale analysis of monotonic behavior of concrete columns made of CNT-reinforced cement composite

There is an increasing demand for the use of high performance concrete in buildings to reduce significant damage due to extreme loadings. Carbon nanotubes (CNT) with their superior properties are among new materials, which can be used in concrete members. A hierarchical multiscale approach is adopted in this research to obtain the monotonic behavior of CNT-reinforced concrete, noting that, to the best knowledge of the authors, no experimental results are available for its monotonic behavior. At the nano scale, the mechanical properties of carbon nanotubes (CNT) is derived by the molecular dynamics approach. Afterwards, a micromechanical finite element method is adopted at the micro scale to determine the stress-strain curve of CNT-reinforced cement. The whole structure of a concrete sample, including all its major phases, is simulated at the meso scale by the finite element method. Finally, at the macro scale, the monotonic behavior of a concrete column made of CNT-reinforced cement is studied. The results of simulations indicate that by increasing the volume fractions of CNTs, the energy absorption capacity, the curvature ductility and the ultimate moment capacity of the CNT-reinforced concrete columns increase significantly.