The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious composites

Model of the Mechanical Behavior of Cementitious Matrices Reinforced with Nanomaterials

“…Its initial values are estimated at ] = 1/3 and remain approximately constant in tension tests up to the limit point. Its effective value rises to ] = 0.5 near the limit points in compression regardless of the boundary condition, consistent with experimental results from previous studies on confined plain concrete [9][10][11]. It is therefore concluded that using ] = 0.5 as the criterion of compressive failure complies with the experimental evidence.…”

“…In all cases, however, the postlimit behavior was significantly improved, marked again by smaller values of apparent secant ] as compared to the unreinforced counterpart. This behavior is the same as that of FRC under unconfined compression [1] and is very similar to that of confined conventional concrete [9,11]; a mechanisticbased interpretation of the effective confinement provided by CNT fibers in the gel has been derived and corroborated with experimental results in [5]. Generally, better overall convergence and stability of deformation were observed.…”

“…Comparison of results at these levels of reinforcement with results from plain paste samples indicates the following effects (Figures 4(a) and 4(b)). (a) When using unrealistically high CNT content (a theoretical limit), the peak load-bearing capacity is effectively doubled, presenting the behavior of passively confined concrete (Figure 4(b)); note that past work has illustrated the role of CNT or CNF reinforcement as effective internal confinement [5,11]. This is quantified not only by the increased compressive strength of the composite, but also by the reduced dilation rate (apparent values of the secant Poisson ratio, ]).…”

“…Journal of Engineering a significant confining effect occurring in the microstructure of the matrix and effectively increasing the apparent material stiffness [1,4,5,11].…”

Effect of Adding Carbon Nanotubes on Corrosion Rates and Steel-Concrete Bond

“…The interface or CNTs with C-S-H is achieved by the large number of atoms present at the nanotube surface. CNTs have high flexibility, and its microstructure shape as tubes is capable of bending in circles and forming bridges crossing the micro and Nano-cracks developed in the cement composites, which in turn, increases the strength of the cement composites 26 . CNTs can be widely distributed in the concrete paste, and as a Nano material, its interaction with the paste is more intense than that of the larger fibers.…”