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Unit cell of tricalcium aluminate (cubic, space group Pa3 ¯, ref. 48). The lattice constant is 1.5263 nm and distinct atom types are labeled. Viewed from the c axis onto the ab plane.
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Tricalcium aluminate (C3A) is a major phase of Portland cement clinker and some dental root filling cements. An accurate all-atom force field is introduced to examine structural, surface, and hydration properties as well as organic interfaces to overcome challenges using current laboratory instrumentation. Molecular dynamics simulation demonstrates...
Citations
... Compared with other force fields such as ClayFF, it is more efficient for large systems due to the lower computational cost [48][49][50] IFF It yields the consistency of inorganic and organic thermodynamics and is used in the simulation of the inorganicorganic interface. It is applicable for all kinds of elements and does not depend on quantum mechanical calculations of atomic charges [51][52][53] CVFF It is a generalized valence force field that has been parameterized for water, various functional groups, and some inorganic materials, including silica [25,54,55] Cement-FF All cementitious materials can be modeled with this force field. Potentials developed for similar atomic species systems are combined and adjusted in the model [56] Dreiding This is a strictly diagonal force field possessing cosine-Fourier expansion torsion and harmonic valence terms. ...
Concrete is the most popular construction material in infrastructure projects due to its numerous natural advantages. Nevertheless, concrete constructions frequently suffer from low tensile strength and poor durability performance which are always urgent tasks to be solved. The concrete reinforced by various nanomaterials, especially graphene and its associated nanostructures (GANS), shows excellent chemical and physical properties for engineering applications. The influence of GANS on cement composites is a multiscale behavior from the nanoscale to the macroscale, which requires a number of efforts to reveal via numerical and experimental approaches. To meet this need, this study provides a comprehensive overview of the numerical modeling for GANS reinforced concrete in various scales. The background and importance of the topic are addressed in this study, along with the review of its methodologies, findings, and applications. Moreover, the study critically summarizes the performance of GANS reinforced concrete, including its mechanical behavior, transport phenomena, and failure mechanism. Additionally, the primary challenges and future prospects in the research field are also discussed. By presenting an extensive overview, this review offers valuable insights for researchers and practitioners interested in numerical simulation to advance concrete science and engineering.
... Subsequent force-field classical molecular dynamics (MD) simulations partially addressed this limitation and revealed that the non-bridging O atoms in the six-member rings of AlO 4 tetrahedra are more prone to protonation than the bridging O sites. Consequently, the surrounded Ca ions can readily accommodate the hydroxide ions (OH -) induced by water dissociation, leading to the formation of calcium hydroxide (CH) 27 . Nevertheless, these non-reactive classical MD simulations appear insufficient to capture the bond breakage and formation involved in the initial dissolution process of C 3 A, along with the corresponding free energy landscapes. ...
... These results can be supplemented by classical MD simulations on the RDF of C 3 A/water interface model, where a low Al-O w coordination at 1.90 Å with number of 0.23 per/Al atom is observed in the large simulation box with long simulation time (Supplementary Note 4 and Supplementary Fig. 3). This bond length slightly deviates from the equilibrium bond length determined by experiments and simulations 24,27,40 , indicating the weak interactions between Al and O w . To further clearly interpret this, the number densities of H w and O w in the interface region were projected to C 3 A surface (Fig. 1f, g). ...
... This limited proton hopping is yet attributed to the highly nucleophilic nature of the O t ions, particularly the O nb ions, which form strong bonds with H w ions and consequently restrict proton transfers. This behavior is similar with what has been observed on ionic oxygen ions on C 3 S surfaces 24,27,43 . ...
Portland cement (PC) is ubiquitously used in construction for centuries, yet the elucidation of its early-age hydration remains a challenge. Understanding the initial hydration progress of tricalcium aluminate (C3A) at molecular scale is thus crucial for tackling this challenge as it exhibits a proclivity for early-stage hydration and plays a pivotal role in structural build-up of cement colloids. Herein, we implement a series of ab-initio calculations to probe the intricate molecular interactions of C3A during its initial hydration process. The C3A surface exhibits remarkable chemical activity in promoting water dissociation, which in turn facilitates the gradual desorption of Ca ions through a metal-proton exchange reaction. The dissolution pathways and free energies of these Ca ions follow the ligand-exchange mechanism with multiple sequential reactions to form the ultimate products where Ca ions adopt fivefold or sixfold coordination. Finally, these Ca complexes reprecipitate on the remaining Al-rich layer through the interface-coupled dissolution-reprecipitation mechanism, demonstrating dynamically stable inner-sphere adsorption states. The above results are helpful in unmasking the early-age hydration of PC and advancing the rational design of cement-based materials through the bottom-up approach.
... A PCFF-based energy expression has been shown in Eq. (2) which demonstrates higher order harmonic terms representing vibration due to internal degree of freedoms and nonbonded inter-molecular interactions are expressed with the sum of vdW and coulomb terms. This force field has been effectively used in demonstrating mechanical and thermal properties of cement paste constituents [19,26,[34][35][36][37]. ...
Energy storage provides a greener path of efficient energy utilization. Recent trends of research suggest concrete as a potential thermal energy storage (TES) material. Its cheap commercial availability makes it one of the most deserving candidates. Cement paste is the key glue of concrete, hence performance of its major components in thermal conduction seeks thorough scientific study. Portlandite or calcium hydroxide is the second major component of cement paste, microscopically visible at a scale length of <10 − 4 m. Molecular dynamics (MD) simulation has been utilized to investigate the thermal transport mechanism of portlandite at an atomistic scale. The thermal conductivity of this component has been computed using three major force fields which are compared with the experimental outcome using modulated differential scanning calorimetry (MDSC). It has been observed that the simulation outcomes are in order with the experimental value but the results are sensitive to the choice of force fields. Excitation of molecules during thermal transport is predominantly governed by lower-frequency molecular vibration indicating the existence of Boson Peaks. This manuscript presents the full thermal conductivity tensor of portlandite along with the possible mechanism associated with thermal transport.
... The results of the semi-quantitative analysis of the OPC specimen are shown in Figure 1. The results of the mineralogical composition of OPC show that the main mineral phases are alite (C3S, 64.3 wt.%), belite (C2S, 10.1 wt.%), tricalcium aluminate (C3A, 2.5 wt.%) and tetracalcium aluminoferrite (C4AF, 16.0 wt.%) [24][25][26][27]. ...
... The results of the chemical analysis of GGBFS are presented in Table 2 and show that the sum of the oxides (CaO + MgO + SiO2) is 83.38% (Table 2), i.e., more than 2/3, while the ratio of The results of the semi-quantitative analysis of the OPC specimen are shown in Figure 1. The results of the mineralogical composition of OPC show that the main mineral phases are alite (C 3 S, 64.3 wt.%), belite (C 2 S, 10.1 wt.%), tricalcium aluminate (C 3 A, 2.5 wt.%) and tetracalcium aluminoferrite (C 4 AF, 16.0 wt.%) [24][25][26][27]. ...
Granulated blast furnace slag (GBFS) is a byproduct of the iron production process. The objective of this study is to determine the effects of ground granulated blast furnace slag (GGBFS), used as a replacement admixture (0-40 wt.%) for ordinary Portland cement (OPC), on the setting time, the heat of hydration, and the mechanical properties of cement mortar. The influence of GGBFS as a replacement additive on the setting time shows that it has an accelerating effect on cement hydration. Calorimetric measurements were performed on the cement paste system to determine the effects of GGBFS on the hydration of OPC. Calorimetric measurements carried out show that the replacement of GGBFS in an amount up to 40 wt.% reduces the total heat of hydration by up to 26.36% compared to the reference specimen. The kinetic analysis performed on the calorimetric data confirms the role of GGBFS as an accelerator by shortening the time during which the process of nucleation and growth (NG), as the most active part of hydration, is reduced up to 2.5 h. The value of the Avrami-Erofee constant indicates polydispersity and heterogeneous crystallization. Mechanical tests of cement mortars were performed after 3, 7, 14, 28, 70, and 90 days of hydration and showed that replacement addition of GGBFS slightly reduced the mechanical properties in the early phase of hydration, while in the later phase of hydration it contributed to an increase in the mechanical properties.
... Despite the intriguing findings, one should be aware that excluding solvation and surface complexation in an aqueous environment could cause uncertainties in the results, thereby compromising their practical applicability. 50,51 Sutton et al. 171 ranked the interactions of 20 bis-phosphinate ligands toward calcite (104) and Ce-bastnasite (100) surfaces using a combination of DFT and MD calculations. Covalent bonds were revealed for four ligand-surface configurations, namely, bidentate, repeated monodentate, staggered monodentate, and neighboring monodentate. ...
Froth flotation is the most versatile process in mineral beneficiation, extensively used to concentrate a wide range of minerals. This process comprises mixtures of more or less liberated minerals, water, air, and various chemical reagents, involving a series of intermingled multiphase physical and chemical phenomena in the aqueous environment. Today's main challenge facing the froth flotation process is to gain atomic-level insights into the properties of its inherent phenomena governing the process performance. While it is often challenging to determine these phenomena via trial-and-error experimentations, molecular modeling approaches not only elicit a deeper understanding of froth flotation but can also assist experimental studies in saving time and budget. Thanks to the rapid development of computer science and advances in high-performance computing (HPC) infrastructures, theoretical/computational chemistry has now matured enough to successfully and gainfully apply to tackle the challenges of complex systems. In mineral processing, however, advanced applications of computational chemistry are increasingly gaining ground and demonstrating merit in addressing these challenges. Accordingly, this contribution aims to encourage mineral scientists, especially those interested in rational reagent design, to become familiarized with the necessary concepts of molecular modeling and to apply similar strategies when studying and tailoring properties at the molecular level. This review also strives to deliver the state-of-the-art integration and application of molecular modeling in froth flotation studies to assist either active researchers in this field to disclose new directions for future research or newcomers to the field to initiate innovative works.
... The incorporation of Na, but to some extent also K, alters the crystal structure slightly and stepwise to lower symmetries [3,[5][6][7][8][9]. This basic understanding of the crystallography of Ca 3 Al 2 O 6 was substantially refined and extended to its mechanical behaviour in the last years [10][11][12][13]. Industrial Portland cement clinkers contain commonly a cubic and/or an orthorhombic polymorph of Ca 3 Al 2 O 6 [14][15][16], depending on the Na 2 O equivalent and the sulfur/ alkali ratio of the clinkers. ...
... The last commonly reported reaction product is hydrogarnet (Ca 3 Al 2 (OH) 12 ) [51,[57][58][59][62][63][64][65][70][71][72]. When Ca 3 Al 2 O 6 reacts with a stoichiometric amount of water, hydrogarnet is considered the only reaction product in equilibrium; OH-AFm and C 2 AH 8 are only intermediates [35] (Fig. 4). ...
Experiments, simulations and derived theories for the hydration of tricalcium aluminate in Portland cement-related systems are summarized and further conclusions are drawn. Highly reactive calcium sulfates lead to an earlier sulfate depletion, possibly due to their faster dissolution and consequently enhanced sulfate consumption by forming more ettringite instead of AFm. Sodium in solid solution decreases the crystal symmetry of tricalcium aluminate and is released over-proportionally during dissolution. When reacting only with water, sodium in solid solution and in the pore solution decreases the dissolution. At lower humidity, hydration starts with a delay, and the minimum humidity that allows a reaction depends on the overall composition of the system. Organic admixtures may interfere with the balance between aluminate phases and calcium sulfates thus disturbing the silicate reaction. The retardations of aluminate phases by sulfate and silicate phases by aluminate are likely due to surface sorption of ions suppressing the dissolution.
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... The maxima near 897, 863, 817, 786, 740 and 705 cm −1 represent AlO 4 tetrahedral groups (stretching vibrations of Al-O bonds in aluminate rings), and those close to 520, 510, 460 and 414 cm −1 indicate AlO 6 octahedral groups. The Ca-O bands appear at lower frequencies (412 cm −1 ) [18,22]. The experiments on the structure of aluminate rings in tricalcium aluminate according to X-ray data show that Al 6 O 18 rings consist of six AlO 4 tetrahedra connected by bridging O atoms [23]. ...
This paper presents a study related to the biological degradation of a tricalcium aluminate (C3A) phase treated with reactive media from the agricultural industry. During one month of setting and hardening, synthetic C3A was subjected to corrosion in corn silage, pig slurry and chicken manure. The hardening process of the C3A phase in water was used as a reference sample. The phase composition and microstructure of the hydrating tricalcium aluminate slurries were characterised by X-ray diffraction (XRD), thermal analysis (DTA/TG/DTG/EGA), scanning microscopy (SEM, EDS) and infrared spectroscopy (FT-IR). In the samples studied, it was observed that the qualitative and quantitative phase composition of the synthetic tricalcium aluminate preparations changed depending on the corrosion exposure conditions. The main crystalline phases formed by the hydration of the examined samples in water as well as in corrosive media were the catoite (Ca3Al2(OH)12) and hydrocalumite (Ca2Al(OH)7·3H2O) phases. Detailed analysis showed the occurrence of secondary crystallisation in hydrating samples and the phases were mainly calcium carbonates (CaCO3) with different crystallite sizes. In the phase composition of the C3A pastes, varying amounts of aluminium hydroxides (Al(OH)3) were also present. The crystalline phases formed as a result of secondary crystallisation represented biological corrosion products, probably resulting from the reaction of hydrates with secondary products resulting from the metabolic processes of anaerobic bacterial respiration (from living matter) associated with the presence of bacteria in the reaction medium. The results obtained contribute towards the development of fast-acting and bio-corrosion-resistant special cements for use in bioenergetics.
... In tricalcium aluminate (Ca 3 Al 2 O 6 , C 3 A), four chemically distinct atomic types of calcium, aluminum, apical oxygen, and epoxide can be identified. Mishra et al. thoroughly validated its atomic force field and used it to simulate the adsorption process [25]. Therefore, in this paper, tricalcium aluminate was chosen as a simulation object to investigate the microscopic transport mechanism of activators in self-heating food packaging. ...
The aluminum-based flameless ration heaters (FRHs) in self-heating food packaging are the heating elements, while water is the activator. Inevitable inadequate reactions can lead to reduced heating capacity and material waste. The transport behavior of activators (water and ions) in the main components of FRHs was investigated with molecular dynamics to study the mechanism of low exothermic efficiency. This paper transported a mixed solution composed of calcium ions, sodium ions, chloride ions, and water in the nanopores with three pore sizes 1.0, 1.5, and 2.5 nm. Results demonstrate that the formation of hydrogen bonds at the surface of tricalcium aluminate (C3A) with water can slow the movement of water molecules. Sodium, calcium ions, and oxygen atoms on the surface of C3A combine competitively through surface chemical bonding, forming Ca-O and Na-O bonds. In addition, as the pore size becomes smaller, the hindering effect of the nano-pore channel becomes stronger. Calcium ions and chloride ions form ion pairs through ionic bonding, which can continuously aggregate to hinder the transport of water molecules and ions. This work provides a basis for understanding the study of the transport and adsorption behavior of liquids in C3A pores and provides a viable idea for subsequent experimental studies.
... [63]. The absorption peaks observed in the frequency range 920-800 cm −1 and below 500 cm −1 can be attributed to AlO 4 tetrahedral and AlO 6 octahedral groups of tricalcium aluminate (3CaO Al 2 O 3 or C 3 A) [64,65]. On the other hand, the absorption maximum near 650 cm −1 could be assigned to oxidized iron carbide phases, whereas the broad absorption is around at 3450 cm −1 and the weak band at 1630 cm −1 , due to vibrations of adsorbed water molecules on KBr or the sample. ...
Carbon-red mud foam/paraffin hybrid materials were prepared and studied for their thermal energy storage and electromagnetic interference (EMI) shielding properties. The host matrices were prepared utilizing the polymeric foam replication method, with a polyurethane sponge as a template, resin as a carbon source, and red mud as a filler. The paraffins, n-octadecane (OD) and the commercial RT18HC, were used as organic encapsulant phase change materials (PCMs) into the open pore structure of the foams. The foams’ morphological and structural study revealed a highly porous structure (bulk density, apparent porosity P > 65%), which exhibits elliptical and spherical pores, sized from 50 up to 500 μm, and cell walls composed of partially graphitized carbon and various oxide phases. The hybrid foams showed a remarkable encapsulation efficiency as shape stabilizers for paraffins: 48.8% (OD), 37.8% (RT18HC), while their melting enthalpies (ΔHm) were found to be 126.9 J/g and 115.5 J/g, respectively. The investigated hybrids showed efficient electromagnetic shielding performance in frequency range of 3.5–9.0 GHz reaching the entry-level value of ~20 dB required for commercial applications, when filled with PCMs. Their excellent thermal and EMI shielding performance places the as-prepared samples as promising candidates for use in thermal management and EMI shielding of electronic devices as well.
... This momentum is gaining pace in the field of cement and concrete research. To date, the vast majority of computational works in this field has been concerned with C-S-H, silica, clay, and other cement phases [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]. ...
... One of the main difficulties is to combine the organic and inorganic force fields to define cross interactions. Among the force fields developed for cement systems, the INTERFACE force field (IFF) is at the forefront in simulating organicinorganic and aqueous-inorganic interfaces [51,52,58,68] and is compatible with most of the force fields used for organic materials. For the simulation of heterogeneous materials, such as mineral-organic interactions in high accuracy and computational speed, it is helpful when the models capture chemical bonding, structures, energy differences such as surface energies, contact angles, surface chemistry, and bulk properties using interpretable parameters and a common energy expression, which IFF provides for as described in the previously mentioned references. ...
Chemical admixtures are an essential ingredient of modern concrete mix, but many of their molecular scale working mechanisms remain poorly described. In this respect, recent advances in computational methods, provide a unique opportunity to gain the needed molecular level insights into the mechanism of action of chemical admixtures in cementitious systems. Such studies are slowly increasing in number and this paper proposes a review on approaches that deal with molecular simulations of chemical admixtures. The key properties studied so far are mainly adsorption behaviors and conformations of monomers, oligomers and polymers (molecular weight ~ 10,000 g/mol). Our aim is to identify opportunities, challenges and give perspectives on the future of molecular modeling of chemical admixture-cement interactions.
