دانلود رایگان مقاله خواص مکانیکی و تعدیل مواد مرکب سیمانی تقویت شده CNT

Abstract

The mechanical and damping properties of CNT-reinforced cementitious composite structures were experimentally examined. In the experiments, an aromatic modified polyethylene glycol ether named TNWDIS and polyvinylpyrrolidone (PVP) were used to disperse CNTs, which were ultra-effective and compatible with cement hydrates. The growth of cement hydrates on the CNT surface was observed by Scanning Electron Microscopy (SEM) and identified by Energy Dispersive Spectrometry (EDS). X-ray Powder Diffraction (XRD) analysis suggested that the mechanism by which the CNTs and cement hydrates were combined was a physical process. The compressive and flexural strengths of CNT/cement composites were improved by 17.3 and 16.3%, respectively, through the addition of 0.1 wt.% CNTs dispersed by PVP, while the addition of CNTs dispersed by TNWDIS led to a very limited improvement in strength. In addition, the loss factor of CNT/cement matrix was measured, and 0.1 wt.% CNTs dispersed by TNWDIS improved the loss factor by 25.9%, which is nearly twice greater than the improvement caused by 0.1 wt.% CNTs dispersed by PVP.

4. Conclusions

The article presents the results of the mechanical and damping properties of CNT-reinforced cementitious composites at different concentrations of CNTs (0, 0.05, and 0.10 wt.%) using two dispersing surfactants. The conclusions of these investigations are summarized as follows: (1) The two proposed methods (TNWDIS and PVP) of dispersing CNTs in aqueous solution are both effective and have the same dispersion ability. Neither surfactant causes a change in the hydration process. CNTs were well distributed in the cementitious composites according to the SEM analysis. (2) The mechanical properties of CNT-reinforced cementitious composites increased with increasing CNT content. CNTs dispersed by PVP are more beneficial for enhancing the mechanical properties of cement paste than those dispersed by TNWDIS, indicating the better bonding strength between the CNTs and the matrix. (3) The results of EDS and XRD analysis suggest that hydroxylated CNTs combine with hydrates via a physical interaction, which provides the potential for increasing the damping behavior of CNT-reinforced composites. (4) The DMA tests proved the ameliorating effects of CNTs on the damping performance of the composites. The loss factor of the composites exhibited an obvious increase with CNT content. The enhancement of the damping behavior is mainly due to the generation of multi-phase boundaries and multiform interfaces. (5) The increase in the loss factor was more pronounced in CNTreinforced cementitious composites dispersed by TNWDIS than in those dispersed by PVP, indicating the greater interface friction and slippage due to weaker bonding in the former.