Elucidation of Calcite Structure of Calcium Carbonate Formation Based on Hydrated Cement Mixed with Graphene Oxide and Reduced Graphene Oxide

Yaseen, Sarah Abduljabbar; Yiseen, Ghadah Abdaljabar; Li, Zongjin

doi:10.1021/acsomega.9b00042

Cited by 87 publications

(83 citation statements)

References 60 publications

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“…Some carbonates could also be present, e.g., a single asymmetric stretching band observed between 1450 and 1400 cm −1 could be attributed to MgCO 3 . After 95 days of hydration, there were two major differences between cement and CWA in the hydrated samples ( Figure 9 b); the broad band at about 3400 cm −1 corresponding to the O−H stretching vibrations (v1 and v3) in the water molecules was much more pronounced in CWA than in cement, confirming that CWA retains water [ 46 ]. The band in the range 1420–1480 cm −1 is attributed to CO 3 2− /HCO 3 − [ 45 ], confirming the formation of more carbonates in CWA.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Crystalline Waterproofing Admixtures on the Self-Healing and Permeability of Concrete

et al. 2021

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This paper investigates the effectiveness of a specific crystalline waterproofing admixture (CWA) in concrete as a function of a water–binder ratio. Four concrete mixes with and without CWA were prepared; two of them with a water–binder ratio of 0.45 and two of them with a water–binder ratio of 0.55. Water permeability and compressive strength were tested on hardened concrete specimens and self-healing of cracks over time was observed. Cement paste and CWA paste were prepared to clarify the results obtained on the concrete specimens. SEM and EDS and XRD and FTIR were performed on the hardened pastes to explain the mechanism of CWA working. The results show that the addition of CWA had no significant effect on the compressive strength of the concrete, but reduced the water penetration depth in the concrete, and the reduction was more effective for mixes with lower water–binder ratio. Regarding the self-healing effect, it can be concluded that the addition of CWA improves the crack healing in concrete, but the efficiency of self-healing is highly dependent on the initial crack width. The mechanisms involved in the reduction of water penetration depth and crack healing in concrete can be explained by different mechanisms; one is creation of the CSH gel from unreacted clinker grains, then formation carbonate, and additional mechanism is gel formation (highly expansive Mg-rich hydro-carbonate) from magnesium based additives. The presence of sodium silicate, which would transform into carbonate/bicarbonate, also cannot be excluded.

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Section: Resultsmentioning

confidence: 99%

The Effect of Crystalline Waterproofing Admixtures on the Self-Healing and Permeability of Concrete

et al. 2021

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“…This is expected since the reaction of some of the CH with fly ash could have been accelerated by the drying regime adopted to reduce sw. Some of the crystalline species were identified as CH particles and some as precipitated calcium carbonate [36][37][38], as was noticed from EDX spot analysis. As can be noticed from these figures, for both the Class C and Class F fly ash blends, local accumulation of crystalline morphologies is seen.…”

Section: Mixtures Processed Through Consolidation and Extrusionmentioning

confidence: 67%

Carbonation Processing and Characterization of Fly Ash-Portlandite Blends as Cement-Free Binding Agents

Neithalath

2021

CTCSE

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Carbonation of fly ash mortars augmented with portlandite (CH) under ambient conditions to produce cement-free binding agents that sequester CO 2 is discussed. Fly ash-CH blends are proportioned to produce shape-stable mixtures that can be conventionally cast or extruded. The strength and CO2 uptake are noted to strongly depend on specimen saturation. High-Ca fly ash blended with 10% CH (by mass) results in a 7-day compressive strength of more than 35 MPa when carbonated, which is ~40% higher than that of the conventionally cured mixture, and a CO 2 uptake of ~8% by mass of the binder. Low-Ca fly ash blended with 30% CH results in 15 MPa strength, which is 3 times higher than that of the conventionally cured mixture, and a CO 2 uptake of ~16% by mass of the binder. The proportion of initial voids that remain after carbonation or conventional curing, which scales well with compressive strength, is shown to be a convenient measure to quantify the relative efficiency of carbonation. Thermal analysis, electron micrographs and X-ray maps, and FTIR spectroscopy confirm the carbonation efficiency of the mixtures. The beneficial effects of low w/p and particle packing in extrudable mixtures towards providing increased strengths and CO2 uptake are also brought out. Overall, this study establishes the applicability (in terms of strength) of portlandite-enriched fly ashes to form binding agents with significantly lower CO 2 footprint for several construction applications.

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“…These strongest absorption bands are located at 3440.8, 1636, 1471, 1426.9, 980.6, 879.3, 667.7, and 458.3 cm –1 , respectively. In the spectrum of the control, the sharp peak at 3640 cm –1 was assigned to Ca(OH) 2 , which formed during the cement hydration reaction [ 76 ]. However, this sharp peak did not appear in the other spectra, indicating that the cement hydration reaction was inhibited or that the CH was consumed [ 77 ].…”

Section: Resultsmentioning

confidence: 99%

Using Fumed Silica to Develop Thermal Insulation Cement for Medium–Low Temperature Geothermal Wells

et al. 2022

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During geothermal energy development, the bottom high-temperature fluid continuously exchanges heat with the upper low-temperature wellbore and the stratum during its rising process. Thermal insulation cement (TIC) can increase the outlet temperature, thus effectively reducing the heat loss of the geothermal fluid and improving energy efficiency. In this study, vitrified microbubbles (VMB) were screened out by conducting an orthogonal test of compressive strength (CS) and thermal conductivity (TC) on three inorganic thermal insulation materials (VMB, expanded perlite (EP), and fly-ash cenosphere (FAC)). Fumed silica (FS) was introduced into the cement with VMBs, as its significant decreasing effect on the TC. Moreover, a cement reinforcing agent (RA) and calcium hydroxide [CH] were added to further improve the CS of TIC at 90 °C. The fresh properties, CS, TC, hydration products, pore-size distribution, and the microstructure of the cement were investigated. As a result, a TIC with a TC of 0.1905 W/(m·K) and CS of 5.85 MPa was developed. The main conclusions are as follows: (1) Increasing the mass fraction of the thermal insulation material (TIM) is an effective method to reduce TC. (2) The CH content was reduced, but the C–S–H gel increased as FS content increased due to the pozzolanic reaction of the FS. (3) As the C–S–H gel is the main product of both the hydration and pozzolanic reactions, the matrix of the cement containing 60% FS and VMBs was mainly composed of gel. (4) The 10% RA improved the cement fluidity and increased the CS of TIC from 3.5 MPa to 5.85 MPa by promoting hydration.

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Elucidation of Calcite Structure of Calcium Carbonate Formation Based on Hydrated Cement Mixed with Graphene Oxide and Reduced Graphene Oxide

Cited by 87 publications

References 60 publications

The Effect of Crystalline Waterproofing Admixtures on the Self-Healing and Permeability of Concrete

The Effect of Crystalline Waterproofing Admixtures on the Self-Healing and Permeability of Concrete

Carbonation Processing and Characterization of Fly Ash-Portlandite Blends as Cement-Free Binding Agents

Using Fumed Silica to Develop Thermal Insulation Cement for Medium–Low Temperature Geothermal Wells

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