Microstructure development and mechanism of hardened cement paste incorporating graphene oxide during carbonation

Long, Wu-Jian; Gu, Yu-cun; Xing, Feng; Khayat, Kamal H.

doi:10.1016/j.cemconcomp.2018.08.016

Cited by 91 publications

(30 citation statements)

References 60 publications

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“…In hydrated cement based materials, carbonation occurs when they are exposed to atmospheric CO 2 or dissolved CO 2 in water in form of carbonic acid [32]. The CH and CSH are the major phases attacked by CO 2 during carbonation as shown in (7) and (8), respectively [33];…”

Section: Carbonation Processmentioning

confidence: 99%

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Review of Carbonation Resistance in Hydrated Cement Based Materials

Marangu

Thiong’o

Wachira

2019

Journal of Chemistry

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Blended cements are preferred to Ordinary Portland Cement (OPC) in construction industry due to costs and technological and environmental benefits associated with them. Prevalence of significant quantities of carbon dioxide (CO2) in the atmosphere due to increased industrial emission is deleterious to hydrated cement materials due to carbonation. Recent research has shown that blended cements are more susceptible to degradation due to carbonation than OPC. The ingress of CO2 within the porous mortar matrix is a diffusion controlled process. Subsequent chemical reaction between CO2 and cement hydration products (mostly calcium hydroxide [CH] and calcium silicate hydrate [CSH]) results in degradation of cement based materials. CH offers the buffering capacity against carbonation in hydrated cements. Partial substitution of OPC with pozzolanic materials however decreases the amount of CH in hydrated blended cements. Therefore, low amounts of CH in hydrated blended cements make them more susceptible to degradation as a result of carbonation compared to OPC. The magnitude of carbonation affects the service life of cement based structures significantly. It is therefore apparent that sufficient attention is given to carbonation process in order to ensure resilient cementitious structures. In this paper, an indepth review of the recent advances on carbonation process, factors affecting carbonation resistance, and the effects of carbonation on hardened cement materials have been discussed. In conclusion, carbonation process is influenced by internal and external factors, and it has also been found to have both beneficial and deleterious effects on hardened cement matrix.

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Section: Carbonation Processmentioning

confidence: 99%

“…Equation 7represents moderate carbonation occurring on the surface layer of cement based materials leading to the formation of CaCO 3 [33]. The CaCO 3 formed is deposited on the pore network in the hydrated cement matrix resulting in pore refinement of the carbonated layer.…”

Section: Carbonation Processmentioning

confidence: 99%

Review of Carbonation Resistance in Hydrated Cement Based Materials

Marangu

Thiong’o

Wachira

2019

Journal of Chemistry

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“…The images reveal wrinkles on GO. The rGO, however, has fewer wrinkles due to the reduction of oxygen-containing functional groups [65]. In this study, the concentration of rGO solution was fixed at 5.0 g/L.…”

Section: Raw Materialsmentioning

confidence: 99%

Structural Applications of Thermal Insulation Alkali Activated Materials with Reduced Graphene Oxide

Long¹,

Lin²,

Tan³

et al. 2020

Materials

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Development of low thermal conductivity and high strength building materials is an emerging strategy to solve the heavy energy consumption of buildings. This study develops sustainable alkali activated materials (AAMs) for structural members from waste expanded polystyrene (EPS) beads and reduced graphene oxide (rGO) to simultaneously meet the thermal insulation and mechanical requirements of building energy conservation. It was found that the thermal conductivity of AAMs with 80 vol.% EPS and 0.04 wt.% rGO (E8–G4) decreased by 74% compared to the AAMs without EPS and rGO (E0). The 28-day compressive and flexural strengths of E8–G4 increased by 29.8% and 26.5% with the addition of 80 vol.% EPS and 0.04 wt.% rGO, compared to the sample with 80 vol.% EPS without rGO (E8). In terms of compressive strength, thermal conductivity, and cost, the efficiency index of E8–G4 was higher than those of other materials. A building model made from AAMs was designed using building information modeling (BIM) tools to simulate energy consumption, and 31.78% of total energy consumption (including heating and cooling) was saved in the building operation period in Harbin City, China. Hence, AAMs made of waste EPS beads and rGO can realize the structural and functional integrated application in the future.

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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%

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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Microstructure development and mechanism of hardened cement paste incorporating graphene oxide during carbonation

Cited by 91 publications

References 60 publications

Review of Carbonation Resistance in Hydrated Cement Based Materials

Review of Carbonation Resistance in Hydrated Cement Based Materials

Structural Applications of Thermal Insulation Alkali Activated Materials with Reduced Graphene Oxide

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

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