We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1–2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar.
In this research, multi-walled carbon nanotubes were used to delay the propagation and growth of cracks in cement mortar on the nanoscale. To improve the dispersion of multi-walled carbon nanotubes in the cement mix a polycarboxylate superplasticizer was used. The mechanical strength of multi-walled carbon nanotubes-cement nanocomposites mix containing 0.1–2% nanotubes by weight (wt) and 0.5% superplasticizer by (wt) was measured and compared with that of cement prepared without multi-walled carbon nanotubes. It was found that the tensile strength of the specimens increased about 70% up to 0.3%, multi-walled carbon nanotubes. With further increase in multi-walled carbon nanotubes, a decrease in tensile strength was observed. Field-emission scanning electron microscopy used to observe the fracture surface of specimens containing 0.3 wt% nanotubes indicated that the multi-walled carbon nanotubes were well dispersed and there were no agglomerates visible in the matrix. Field-emission scanning electron microscopy observation also revealed good bonding between the multi-walled carbon nanotubes and the surrounding cement matrix. In addition, X-ray diffraction data showed the multi-walled carbon nanotubes accelerated the dissolution and growth of the calcium silicate hydrate hydration products compared with the control cement mortar. Mercury intrusion porosimetry test results showed that chemical species could not penetrate the specimens containing 0.1 wt% and 0.3 wt% multi-walled carbon nanotubes as easy as other specimens. Thermogravimetric analysis results indicated that the cement hydration was enhanced in the presence of the multi-walled carbon nanotubes.
In this study the feasibility of using the artificial neural networks modeling in predicting the effect of MWCNT on amount of cement hydration products and improving the quality of cement hydration products microstructures of cement paste was investigated. To determine the amount of cement hydration products thermogravimetric analysis was used. Two critical parameters of TGA test are PHPloss and CHloss. In order to model the TGA test results, the ANN modeling was performed on these parameters separately. In this study, 60% of data are used for model calibration and the remaining 40% are used for model verification. Based on the highest efficiency coefficient and the lowest root mean square error, the best ANN model was chosen. The results of TGA test implied that the cement hydration is enhanced in the presence of the optimum percentage (0.3 wt%) of MWCNT. Moreover, since the efficiency coefficient of the modeling results of CH and PHP loss in both the calibration and verification stages was more than 0.96, it was concluded that the ANN could be used as an accurate tool for modeling the TGA results. Another finding of this study was that the ANN prediction in higher ages was more precise.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.