DFT Study on the Effect of Water on the Carbonation of Portlandite

Funk, Andreas; Trettin, H. F. Reinhard

doi:10.1021/ie302972k

Cited by 18 publications

(15 citation statements)

References 33 publications

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“…As it was explained in literature, 39,40 carbonates are formed through different kind of processes. The first mechanism is the diffusion of CO 2 into the empty pores of the surface where it will react with water from the pore solution, forming carbonic acid.…”

Section: Resultsmentioning

confidence: 96%

Effect of polymer-coated silica particles in a Portland cement matrix via in-situ infrared spectroscopy

Hafshejani

Feng

Wohlgemuth

et al. 2020

Journal of Composite Materials

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It is often of great importance in engineering to know precisely the properties of a material used with regard to its strength, its plasticity or its brittleness, its elasticity, and some other properties. For this purpose, material samples are tested in a tensile test by clamping the sample with a known starting cross-section in a tensile testing machine and loading it with a tensile force F. The force is then graphically displayed over the length change ΔL caused. This curve is called the force-extension diagram. In this study, a new measurement method enables for the first time, depending on the applied uniaxial stress, an insight at the atomic level into various energy dissipation processes at cement-based materials with the help of infrared spectroscopy. The samples are modified by adding SiO2 particles, which are coated by a polymer (PEG-MDI-DMPA) of different PEG molecular weights. Results show that elongating and breakage of [Formula: see text] and [Formula: see text] bonds play an essential role in the strain energy dissipation. Compared to the pure cement, the modified samples are affected more by elongating and breakage of [Formula: see text] as the admixture can effectively reduce the energy barrier of the hydrolytic reaction. The incorporating of particles into the cement matrix induces new mechanisms for energy dissipation by stretching of [Formula: see text] bending vibrations. Stretching vibration of the [Formula: see text] group indicates that part of the energy is dissipated by breakage of hydrogen bonding between the carboxyl group and PEG chains. Besides, a higher value of the ultimate fracture force following an increase in the molecular weight of PEG shows stronger bonding between particles and the cement matrix. As the chain-length of PEG is increased, less energy is absorbed through the other processes (especially at a higher level of strain). Thus, there is a balance between the whole deformation (toughness) and the strength of samples with the increase of the PEG molecular weight.

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Section: Resultsmentioning

confidence: 96%

Effect of polymer-coated silica particles in a Portland cement matrix via in-situ infrared spectroscopy

Hafshejani

Feng

Wohlgemuth

et al. 2020

Journal of Composite Materials

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“…Formation of solid calcium carbonates results from the reaction of free Ca 2+ ions and CO 3 −2 carbonate ions. 38 The reaction is strongly influenced by the chemical potential of water in the environment. The adsorption of CO 2 on CaSiO 3 with a water monolayer completely changes its mechanism.…”

Section: ■ Resultsmentioning

confidence: 99%

Carbonation Competing Functionalization on Calcium-Silicate-Hydrates: Investigation of Four Promising Surface-Activation Techniques

Giraudo

Thissen

2016

ACS Sustainable Chem. Eng.

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In this study, ultrathin calcium-silicate-hydrate (C-S-H) phases on silicon wafers were prepared, which are partially terminated by calcium carbonates. First, a density functional theory (DFT) analysis was performed, to define the nature of the carbonates that are stable in the structure, concluding that two different kinds of them will be present on the surface. Then, by means of four different experimental handling techniques, the C-S-H phases were activated by disposing the carbonate termination: (1) UV-light (365 nm) radiation as a function of time, (2) direct heating between room temperature (RT) and 840 °C, (3) wet chemical treatment by an aqueous solution with a defined pH value as a function of time and (4) Ar/O2-plasma treatment. Fourier transform infrared (FTIR) spectroscopy was implemented to confirm that every method successfully reduced the carbonate termination of the ultrathin C-S-H phases. Interestingly, the effects of the diverse treatments on the C-S-H phases are very different. UV-light radiation eliminates partially carbonates from the C-S-H phases; but in contrast to the other treatments, the rate of this activation is very low. Temperatures up to 700 °C are necessary to remove the carbonates by direct heating. Remarkably, at these high temperatures, the remaining calcium-silicate (C-S) phases start to change their crystal structure, which was proved by means of X-ray diffraction (XRD). During wet chemical treatment, in addition to the carbonates removal, C-S-H phases were also affected, due to the low pH value (≤4) of the implemented solution. Finally, the most rapid activation at RT was provided by Ar/O2-plasma treatment, without drastic impacts on the C-S-H phases.

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“…This implies that fully hydroxylated surfaces suppress the formation of carbonate ions, hence, a higher reactivity barrier for CO 2 with the (001) surface in comparison to the (100) and (110) surfaces. Indeed, the probability of carbonation of the (001) surface in solid-state form has been reported to be very low under ambient conditions [28] and experimental results have indicated that almost no carbonation occurs in the absence of water [73,79].…”

Section: Structural and Dynamical Analysis Of Scco2 Within Portlandite Poresmentioning

confidence: 99%

“…Nevertheless, due to the complexity of the subsurface environmental conditions, it is difficult to experimentally disentangle various factors controlling the carbonation of wellbore cement. In this regard, atomistic computer simulation approaches have proven to be very useful because of their ability to provide atomic-scale quantitative information about the physical and chemical processes occurring during carbonation [26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

“…Portlandite is a hydrous mineral which is very reactive with CO 2 , making it a good model for understanding carbonation reaction mechanisms in cement and in other hydrous minerals with similar structure (e.g., Mg(OH) 2 ). The carbonation reaction mechanism of portlandite has been a subject of many recent studies using experimental [30][31][32][33][34][35][36][37][38] and atomistic simulation [28,39] techniques. It is proposed that carbonation of portlandite is based on either a solid-state mechanism [34,37,40] or via coupled dissolution-precipitation reaction mechanism in a water-rich environment [31].…”

Section: Introductionmentioning

confidence: 99%

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Carbonation Reaction Mechanisms of Portlandite Predicted from Enhanced Ab Initio Molecular Dynamics Simulations

Mutisya

2021

Minerals

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Geological carbon capture and sequestration (CCS) is a promising technology for curbing the global warming crisis by reduction of the overall carbon footprint. Degradation of cement wellbore casings due to carbonation reactions in the underground CO2 storage environment is one of the central issues in assessing the long-term success of the CCS operations. However, the complexity of hydrated cement coupled with extreme subsurface environmental conditions makes it difficult to understand the carbonation reaction mechanisms leading to the loss of well integrity. In this work, we use biased ab initio molecular dynamics (AIMD) simulations to explore the reactivity of supercritical CO2 with the basal and edge surfaces of a model hydrated cement phase—portlandite—in dry scCO2 and water-rich conditions. Our simulations show that in dry scCO2 conditions, the undercoordinated edge surfaces of portlandite experience a fast barrierless reaction with CO2, while the fully hydroxylated basal surfaces suppress the formation of carbonate ions, resulting in a higher reactivity barrier. We deduce that the rate-limiting step in scCO2 conditions is the formation of the surface carbonate barrier which controls the diffusion of CO2 through the layer. The presence of water hinders direct interaction of CO2 with portlandite as H2O molecules form well-structured surface layers. In the water-rich environment, CO2 undergoes a concerted reaction with H2O and surface hydroxyl groups to form bicarbonate complexes. We relate the variation of the free-energy barriers in the formation of the bicarbonate complexes to the structure of the water layer at the interface which is, in turn, dictated by the surface chemistry and the degree of nanoconfinement.

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DFT Study on the Effect of Water on the Carbonation of Portlandite

Cited by 18 publications

References 33 publications

Effect of polymer-coated silica particles in a Portland cement matrix via in-situ infrared spectroscopy

Effect of polymer-coated silica particles in a Portland cement matrix via in-situ infrared spectroscopy

Carbonation Competing Functionalization on Calcium-Silicate-Hydrates: Investigation of Four Promising Surface-Activation Techniques

Carbonation Reaction Mechanisms of Portlandite Predicted from Enhanced Ab Initio Molecular Dynamics Simulations

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