Comprehending the occupying preference of manganese substitution in crystalline cement clinker phases: A theoretical study

Tao, Yong; Zhang, Wenqin; Shang, Dechen; Xia, Zhongsheng; Li, Neng; Ching, W. Y.; Wang, Fazhou; Hu, Shuguang

doi:10.1016/j.cemconres.2018.04.003

Cited by 63 publications

(43 citation statements)

References 51 publications

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“…Ca 2 Fe 2-x Al x O 5 is chosen here not only because it is the prototype of brownmillerite reported as early as 1928, 27 but also because it is one of the four main clinker phases of Portland cement, known as ferrite. [28][29][30] Especially in the high ferrite cement (HFC), the Ca 2 Fe 2-x Al x O 5 phase primarily accounts for the outstanding sulfate resistance. Like other brownmillerites, the special physical and chemical properties of Ca 2 Fe 2-x Al x O 5 are owing to its anoxic perovskite structure.…”

Section: Introductionmentioning

confidence: 99%

Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Tao

Zhang

et al. 2019

J Am Ceram Soc

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Brownmillerite‐type oxides are a large family of structural and functional materials that are of great concern. In this study, the occupancy mechanism of Fe and Al ions in brownmillerite Ca2FeAlO5 is revealed and the specific configuration of Ca2FeAlO5 is proposed for the first time. Through the energy analysis of a series of conjectured models based on well‐defined ab initio calculations, we find that the distribution of Al and Fe in Ca2FeAlO5 follows the “homogeneous layer principle”, namely, Al and Fe tend to form homogeneous octahedral layers or tetrahedral chains rather than mixed layers or chains of two elements along the b axis. The theoretical Ca2FeAlO5 structure with specific atomic occupancy is proposed based on energy analysis and previous experiments, which is of fundamental significance for further study of its physical and chemical properties. Moreover, the influence of entropy increment on the stability of Ca2FeAlO5 crystal is clarified, which paves the way to investigate the structures and properties of Ca2FeAlO5 and other brownmillerite members.

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Section: Introductionmentioning

confidence: 99%

Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Tao

Zhang

et al. 2019

J Am Ceram Soc

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“…The local charge density distribution of the energy band edges (VBM and CBM) qualitatively visualized the reactive sites of the pure γ-Ca 2 SiO 4 crystal, while the binding strength of ions in the system can be quantitatively estimated by the bond length (BL)-bond order (BO) analysis (Figure 3). The BO is obtained by calculating the degree of overlap of the electron cloud between two bonding atoms, which directly reflects the strength of the bond: the larger the BO, the stronger the bond (Dharmawardhana et al, 2013;Tao et al, 2018b). Therefore, the BO quantifies the difficulty of extracting ions from the crystal, which is related to the carbonation reactivity.…”

Section: Electronic Structures Of Pristine γ-Ca 2 Siomentioning

confidence: 99%

Screening Out Reactivity-Promoting Candidates for γ-Ca2SiO4 Carbonation by First-Principles Calculations

Tao

Zhang

et al. 2020

Front. Mater.

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γ-Ca 2 SiO 4 as a promising carbonation-activated cementitious material features an attractive capacity of carbon sequestration. Improving the carbonation reactivity of γ-Ca 2 SiO 4 is of great significance for its practical application. In this paper, first-principles calculations are performed to single out the potential candidates for carbonation activation from a series of dopants. Electronic structure analyses reveal that the carbonation reactivity is related to the reactive site distribution and the binding strength of γ-Ca 2 SiO 4 crystal. Ba, P, and F elements are found to decrease the overall binding strength of γ-Ca 2 SiO 4 crystal, which benefits the dissolution of ions from the crystal to take part in the carbonation reactions. The theoretical conjectures are validated by designed and previous experiments, which confirms the first-principles-based method to effectively guide our experimental investigation.

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“…In general it is perceived that the nanomaterials occupy the pores in the hydrated cement paste and therefore act as binders between the grains [3,4]. There are, however, studies to suggest that the nanoparticles (particularly 3d metals) might occupy interstitial positions in the crystal structure of clinker [5,6] and thus accelerate the hydration process. Since most of the composites present in the hydrated cement are based on calcium and silicon, changing the ratio between two ions has significant effect on the physical properties of the cement composite [7].…”

Section: Introductionmentioning

confidence: 99%

Role of electrostatic potential energy in carbon nanotube augmented cement paste matrix

Azeem

Saleem

2020

Construction and Building Materials

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The empirical data in conjunction with the quantum mechanical calculations show that the strength enhancement in the cement-carbon nanotubes (CNTs) composites is the courtesy of electrostatic potential energy. This is contrary to the general belief that the CNTs form bridges between the adjacent grains to slow down the breaking process. The yield point for the cement paste is improved up to 25% when prepared with 0.2 % by weight of various types of CNTs. A significant strength enhancement is observed with carboxyl functionalized (COOH) CNTs compared to other types. Further, an increase in the concentration of CNTs up to 0.4 wt% has a negative effect on the strength of the matrix. The electrostatic potential energy is mapped by using density functional theory (DFT) with ωB97X-D functional. At lower concentration of CNTs, ion-dipole interaction in the cement paste and the CNTs creates a very strong long range intermolecular force. Due to the increased entropy resulting from the exothermic hydration process, these forces augment the strength of the cement paste.

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Comprehending the occupying preference of manganese substitution in crystalline cement clinker phases: A theoretical study

Cited by 63 publications

References 51 publications

Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Screening Out Reactivity-Promoting Candidates for γ-Ca2SiO4 Carbonation by First-Principles Calculations

Role of electrostatic potential energy in carbon nanotube augmented cement paste matrix

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Comprehending the occupying preference of manganese substitution in crystalline cement clinker phases: A theoretical study

Cited by 63 publications

References 51 publications

Atomic occupancy mechanism in brownmillerite Ca2FeAlO5 from a thermodynamic perspective

Atomic occupancy mechanism in brownmillerite Ca2FeAlO5 from a thermodynamic perspective

Screening Out Reactivity-Promoting Candidates for γ-Ca2SiO4 Carbonation by First-Principles Calculations

Role of electrostatic potential energy in carbon nanotube augmented cement paste matrix

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Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective