Polymorphism of tricalcium silicate, the major compound of Portland cement clinker

Dunstetter, F.; Noirfontaine, Marie‐Noëlle de; Courtial, Mireille

doi:10.1016/j.cemconres.2004.12.003

Cited by 126 publications

(80 citation statements)

References 24 publications

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“…These species facilitate proton transfer between bridging oxygen atoms within the rigid 3D network in silicate glasses. 40 In contrast, tricalcium silicate is more flexible because of the lack of a 3D covalent bond network, 39,41 which makes unnecessary the formation of hydronium ions. Protons can therefore penetrate into the crystal, hopping from one oxygen to another, as reported for proton transfer in perovskites.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Insight on Tricalcium Silicate Hydration and Dissolution Mechanism from Molecular Simulations

Manzano

Durgun

López‐Arbeloa

et al. 2015

ACS Appl. Mater. Interfaces

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Hydration of mineral surfaces, a critical process for many technological applications, encompasses multiple coupled chemical reactions and topological changes, challenging both experimental characterization and computational modeling. In this work, we used reactive force field simulations to understand the surface properties, hydration, and dissolution of a model mineral, tricalcium silicate. We show that the computed static quantities, i.e., surface energies and water adsorption energies, do not provide useful insight into predict mineral hydration because they do not account for major structural changes at the interface when dynamic effects are included. Upon hydration, hydrogen atoms from dissociated water molecules penetrate into the crystal, forming a disordered calcium silicate hydrate layer that is similar for most of the surfaces despite wide-ranging static properties. Furthermore, the dynamic picture of hydration reveals the hidden role of surface topology, which can lead to unexpected water tessellation that stabilizes the surface against dissolution. KEYWORDS: dissolution, hydration, molecular dynamics, surface properties, water adsorption, calcium silicate ■ INTRODUCTIONThe hydration and dissolution of minerals is of crucial importance for a broad range of natural and synthetic phenomena: from the stability of minerals and rocks in watersheds and aquifers, 1 to hydrogen production and other heterogeneous catalytic reactions, 2,3 to the production, utilization, and ultimate degradation of building materials, 4 and to the durability of biomaterials, 5 to name only a few examples. The key properties at play during dissolution are controlled by interfacial reactions between water molecules and the solid surfaces, which can be probed experimentally via techniques such as AFM, vertical scanning interferometry (VSI), and the study of isotope exchange or solute fluxes to provide general information regarding the reaction rates or qualitative information about the formation of steps, pitches, and so on. 6 However, in many applications, much more control over the hydration and dissolution is desired, such as the ability to moderate the rate 7 or preferentially favor the dissolution of one crystal facet over other.8 To achieve such control, a deeper understanding of the molecular mechanisms governing hydration and dissolution is necessary.In this work, we use atomic-scale simulations to study the hydration of a calcium orthosilicate. We take a multistep approach, which is critical to piece together the relevant physical processes underlying hydration and dissolution. First, we analyze the surface energies and water molecule adsorption, extending beyond traditional approaches in order to obtain a more accurate picture of these properties. Next, we compare these surface properties with the results obtained from simulating a realistic hydration process over a period of 2 ns. We discuss the differences between the static and dynamic pictures and show that topological changes render the properties of the f...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Insight on Tricalcium Silicate Hydration and Dissolution Mechanism from Molecular Simulations

Manzano

Durgun

López‐Arbeloa

et al. 2015

ACS Appl. Mater. Interfaces

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“…Calcium silicates can exhibit different polymorphs depending on the temperature and/or impurities present. 11,26,27 In this study, we focus on the M-C 3 S and β-C 2 S surfaces as they are the most frequently observed polymorphs in many applications. We started with the relaxed bulk structures, 28,29 which are shown in Figure 1.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

The Characterization, Stability, and Reactivity of Synthetic Calcium Silicate Surfaces from First Principles

et al. 2014

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Calcium silicate compounds belong to a complicated class of silicates. Among their many industrial applications, calcium silicates are heavily used as a building material as they constitute the main ingredient in today's cement clinker. We report here an extensive surface analysis of synthetic calcium silicate phases (tricalcium silicate, C 3 S, and dicalcium silicate, C 2 S) using first-principles computational methods. We calculate surface energies (γ) for all lower-index orientations and determine the most stable surfaces as well as the equilibrium Wulff structures. We analyze the variation of γ with surface coordination number and find an interesting and unexpected trend where loss of coordination of ionic Ca and O atoms can lower γ. The stability of surface orientations is examined as a function of oxygen partial pressure. Finally, we compute the energy required to remove Ca from different surfaces and find that it is inversely proportional to γ, supporting the energetic preference of extracting atoms from higher energy surfaces. Knowledge of the atomic structure and properties of calcium silicate surfaces is important for understanding and controlling the hydration of such systems. ■ INTRODUCTIONCalcium silicate represents an interesting and complicated class of silicates, abundant in the earth's crust and important components of many minerals. These compounds have a number of uses in industry, the most important of which are in building materials, such as cement, 1,2 glass, 3 paint, and refractories, 4 although a wide range of other applications include light-emitting diodes, 5 pharmaceutical products, drug delivery, 6,7 and as a self-setting material for synthetic bone/ dental recovery and regeneration. 8−10 Especially in cement production, the compound is usually prepared synthetically in the form of tricalcium silicate (Ca 3 SiO 5 , C 3 S) and dicalcium silicate (Ca 2 SiO 4 , C 2 S) and constitutes the majority of (more than 75%) today's cement clinker together with other minerals.11,12 The annual production of calcium silicates in the form of clinker exceeding 3 billion tons leaves a huge environmental footprint due to the emission of more than 6% of anthropogenic CO 2 , 13 and thus, new strategies are sought to lower the intense energy requirements involved.14,15 C 2 S, which requires substantially lower manufacturing temperatures, reacts much more slowly with water than C 3 S, rendering it less useful. To date, we have little understanding of why certain phases of calcium silicate react differently than others, and even less of a clear picture of how to modify or control the hydration. Since the surface of these materials is the key interface where chemical reactions begin, knowledge of the atomic structure and properties of calcium silicate surfaces is important for understanding and predicting the hydration of such systems. 16In this work, we employ first-principles calculations to study and modify the structure and energetics of C 3 S and C 2 S surfaces. The surface energy (γ) is obt...

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“…3 that oxygen atoms are present in two different coordination environments. Among the 45 atomic sites, nine are present in special coordination environment such as O(5), O(6) and O (9). They are octahedrally coordinated by 6 calcium ions.…”

Section: Introductionmentioning

confidence: 99%

“…Only three polymorphic structures (R, M3 and T1) of C 3 S have been determined by synthesizing single crystals [2][3][4][5]. In order to perform accurate Rietveld quantitative phase analysis (QXRD), several studies in the last decade have focused on the crystal structure of alite [6][7][8][9][10]. Various models are available for T1, T2, T3, M1, M3 and R polymorphs, however, there is still no structural model for the M2 polymorph.…”

Section: Introductionmentioning

confidence: 99%

Research review of cement clinker chemistry

Ludwig

Zhang

2015

Cement and Concrete Research

245

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Polymorphism of tricalcium silicate, the major compound of Portland cement clinker

Cited by 126 publications

References 24 publications

Insight on Tricalcium Silicate Hydration and Dissolution Mechanism from Molecular Simulations

Insight on Tricalcium Silicate Hydration and Dissolution Mechanism from Molecular Simulations

The Characterization, Stability, and Reactivity of Synthetic Calcium Silicate Surfaces from First Principles

Research review of cement clinker chemistry

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