Electrochemical Characterization and Inhibiting Mechanism on Calcium Leaching of Graphene Oxide Reinforced Cement Composites

Long, Wu-Jian; Ye, Tao–Hua; Li, Lixiao; Feng, Gan-Lin

doi:10.3390/nano9020288

Cited by 19 publications

(6 citation statements)

References 48 publications

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“…According to Zhou et al [ 23 ], the integrity of the complex liquid is proportional to the viscosity. Thirdly, 2D nanomaterials can absorb a large amount of water inside their interlayers due to an excellent specific surface area [ 33 ], leading to the reduction of the content of the lubricant among the particles.…”

Section: Resultsmentioning

confidence: 99%

“…As for all samples, the impedance diagram consists of a semicircle and a line, representing a resistive behavior at low frequencies and a capacitive behavior at high frequencies [ 42 ]. Moreover, the impedance of the geopolymer pastes is generally higher than that of the OPC pastes [ 33 ]. It can be clearly seen from Figure 13 a that the diameter of the semicircle of rG1 and rG2 increased gradually compared to R0, revealing that rGO nanosheets can improve the impedance of AASC.…”

Section: Resultsmentioning

confidence: 99%

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Investigation of Graphene Derivatives on Electrical Properties of Alkali Activated Slag Composites

et al. 2021

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Reduced graphene oxide (rGO) has been widely used to modify the mechanical performance of alkali activated slag composites (AASC); however, the mechanism is still unclear and the electrical properties of rGO reinforced AASC are unknown. Here, the rheological, mechanical, and electrical properties of the AASC containing rGO nanosheets (0, 0.1, 0.2, and 0.3 wt.%) are investigated. Results showed that rGO nanosheets addition can significantly improve the yield stress, plastic viscosity, thixotropy, and compressive strength of the AASC. The addition of 0.3 wt.% rGO nanosheets increased the stress, viscosity, thixotropy, and strength by 186.77 times, 3.68 times, 15.15 times, and 21.02%, respectively. As for electrical properties, the impedance of the AASC increased when the rGO content was less than 0.2 wt.% but decreased with the increasing dosage. In contrast, the dielectric constant and electrical conductivity of the AASC containing rGO nanosheets decreased and then increased, which can be attributed to the abundant interlayer water and the increasing structural defects as the storage sites for charge carriers, respectively. In addition, the effect of graphene oxide (GO) on the AASC is also studied and the results indicated that the agglomeration of GO nanosheets largely inhibited the application of it in the AASC, even with a small dosage.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Investigation of Graphene Derivatives on Electrical Properties of Alkali Activated Slag Composites

et al. 2021

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“…Besides, the sheet edges of GO get scrolled up during the reduction process, as shown in Figure 3B (Yan et al, 2015). The intercalation of oxygen-containing groups indicates successful reduction process (Long et al, 2019b). The wrinkled and folded rGO has a higher surface area that can promote better interfacial adhesion with the geopolymer matrix (Kim et al, 2010;Liu et al, 2015).…”

Section: Graphene Reinforced Geopolymer Nanocompositesmentioning

confidence: 99%

Mechanical Strength of Graphene Reinforced Geopolymer Nanocomposites: A Review

Tay

Mazlan

2021

Front. Mater.

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The emergence of high-strength graphene marks a new milestone in the material science field. With only a small percentage inclusion into the matrix system, this organic nanoparticle could tremendously improve the strength in vast arrays of composites. At the same time, there is a growing interest in using the low-cost, lightweight, and high early strength geopolymer as the new binder for concrete. Compared to the traditional Ordinary Portland Cement (OPC), geopolymer emits 80% less CO2 during its production while exerting similar strength. Thus, the geopolymer has the potential to commercialize as new and green concrete. Geopolymer is a mixture of aluminosilicate powders and alkaline solutions. When incorporated with nano-sized graphene, the material forms a composite known as Graphene Reinforced Geopolymer Nanocomposite (GRGN). The addition of graphene enhances the strength of geopolymer, which can further improve its competitiveness. However, this depends on several factors, including the types of graphene, the surface modification of graphene, and the concentration of alkaline solutions. Generally, the presence of graphene alters the porous structure of geopolymer into a substantially filled porous structure, thus increasing compressive strength and flexural strength. On the other hand, Graphene Oxide (GO) undergoes a chemical reduction in the alkaline solution, producing epoxy functional groups. The chemical treatment results in two conditions which are weak interaction between graphene and geopolymer matrix, and better graphene dispersibility in geopolymer matrix. This review also highlights the analytical modelling aspect of GRGN. The dissolution of Si(OH)4 and Al(OH)4- from the aluminosilicate source was consistent with experimental work and analytical modeling, while the dissolution of Si–OH on the surface-modified graphene indicated otherwise. Therefore, this paper will provide an insightful review of the GRGN mechanical properties.

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“…As shown in Figure 4a,c,e, the structural defects in rGO nanosheets increase with elevated temperatures, which is in line with the Raman results. According to Long et al [25,26], the wrinkled and folded areas on the GO surface derive from the intercalation of the abundant oxygen-containing groups. Thus, the number of oxygen-containing groups on rGO nanosheet decreases with elevated temperatures due to alkali reduction, as shown in Figure 4b,d,f.…”

Section: Characterization Of Rgo Nanosheetsmentioning

confidence: 99%

“…Due to the similar characteristics of rGO and GO nanosheets [11], the assumptions proposed for the hydration process of GO-reinforced cement may also be used to explain that of rGO-reinforced geopolymers. First, graphene-based nanosheets are excellent water-sorbents owing to the super-high specified surface area [25]. Therefore, the addition of rGO nanosheets can relatively increase the concentration of OH − ions produced from the decomposition of alkali activators.…”

Section: Hydration Processmentioning

confidence: 99%

Reinforcing Mechanism of Reduced Graphene Oxide on Flexural Strength of Geopolymers: A Synergetic Analysis of Hydration and Chemical Composition

Long

Luo

et al. 2019

Nanomaterials

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With the development of nanotechnology, reduced graphene oxide (rGO) has been used to improve the flexural strength of geopolymers. However, the reinforcing mechanism of rGO nanosheets on the flexural strength of geopolymers remains unclear. Here, this reinforcing mechanism was investigated from the perspectives of hydration and chemical composition. The effect of the reduction degree on rGO-reinforced geopolymers was also studied using isothermal calorimetry (IC), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) tests. Results show that the hydration degree and flexural strength of geopolymers effectively increase due to rGO addition. After alkali reduction at a temperature of 60 °C, rGO nanosheets have maximum reinforcement on the flexural strength of geopolymers with an increment of 51.2%. It is attributed to the promotion of slag hydration, as well as the simultaneous formation of calcium silicate hydrate with low Ca/Si ratio (C-S-H(I)) and calcium aluminosilicate hydrate (C-A-S-H) phases due to the inhibiting effect of rGO nanosheets on Al substitution on the end-of-chain silicates of C-S-H and C-A-S-H gels. In addition, different reduction degrees have almost no effect on the chemical composition of rGO-reinforced geopolymers, while excessive reduction impairs the improving effect of rGO nanosheets on the hydration process and flexural strength of geopolymers due to significant structural defects.

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Electrochemical Characterization and Inhibiting Mechanism on Calcium Leaching of Graphene Oxide Reinforced Cement Composites

Cited by 19 publications

References 48 publications

Investigation of Graphene Derivatives on Electrical Properties of Alkali Activated Slag Composites

Investigation of Graphene Derivatives on Electrical Properties of Alkali Activated Slag Composites

Mechanical Strength of Graphene Reinforced Geopolymer Nanocomposites: A Review

Reinforcing Mechanism of Reduced Graphene Oxide on Flexural Strength of Geopolymers: A Synergetic Analysis of Hydration and Chemical Composition

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