Unexpected Chemical Activity of a Mineral Surface: The Role of Crystal Water in Tobermorite

Izadifar, Mohammadreza; Natzeck, Carsten; Emmerich, Katja; Weidler, Peter G.; Gohari, Soheil; Burvill, Colin; Thissen, Peter

doi:10.1021/acs.jpcc.1c10151

Cited by 15 publications

(10 citation statements)

References 41 publications

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“…In recent years, molecular dynamics simulation has been used to study the basic structure and mechanical properties of C-S-H at the nanoscale. Hou et al [ 15 ] found that with an increasing C/S ratio, the silicate chain length gradually decreases, and more defective silicate chains appear, which could weaken the mechanical performance of C-S-H. Izadifar et al [ 16 , 17 ] studied the correlation between the composition and mechanical properties of C-S-H and the role of interlayer water by infrared spectroscopy and density functional theory (DFT). Abdolhosseini et al [ 18 ] proposed a combinatorial method for optimizing the properties of cement hydrates.…”

Section: Introductionmentioning

confidence: 99%

Effect of Different Initial CaO/SiO2 Molar Ratios and Curing Times on the Preparation and Formation Mechanism of Calcium Silicate Hydrate

Liao

et al. 2023

Materials

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To better understand the pozzolanic activity in fly ash used as a supplementary cementitious material in cement or concrete, calcium silicate hydrate (C-S-H) has been synthesized by adding silica fume to a supersaturated calcium hydroxide solution prepared by mixing calcium oxide and ultrapure water. Thermogravimetric analysis results have revealed the variation in the weight loss due to C-S-H in the samples and the conversion ratio of calcium oxide (the μCaO value), which represents the proportion of calcium oxide in the initial reaction mixture used to produce C-S-H, with curing time. The weight loss due to C-S-H and the μCaO value were both maximized (13.5% and 90.4%, respectively) when the initial C/S molar ratio was 1.0 and the curing time was 90 d. X-ray diffraction (XRD) analysis has indicated that C-S-H in the samples after curing for 7 d had the composition Ca1.5SiO3.5·xH2O. 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) analysis has revealed that the degree of polymerization of C-S-H increased with an increase in curing time for samples with an initial C/S molar ratio of 1.0. The ratio of internal to terminal tetrahedra (Q2/Q1) increased from 2.29 to 4.28 with the increase in curing time from 7 d to 90 d. At curing times ≥ 28 d, a leaf-like C-S-H structure was observed by scanning electron microscopy (SEM). An ectopic nucleation–polymerization reaction process is proposed for the formation mechanism of C-S-H.

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Section: Introductionmentioning

confidence: 99%

Effect of Different Initial CaO/SiO2 Molar Ratios and Curing Times on the Preparation and Formation Mechanism of Calcium Silicate Hydrate

Liao

et al. 2023

Materials

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“…The intercalation efficiency ( E i ) is proposed in order to compare the d 001 intensities of the original kaolinite spacing ( I KOS ) with that of the intercalated kaolinite spacing ( I KC ), as per the Equation (1) [ 21 ]:

As seen in Figure 2 , it is apparent that the peak intensity corresponding to the (001) crystal plane of the DMSO–kaolinite complex is higher than that of the FA–kaolinite complex. Further, the intensity of the characteristic peak at the (002) crystal plane of the DMSO–kaolinite complex is lower when compared to that of the FA–kaolinite complex [ 30 ].…”

Section: Resultsmentioning

confidence: 99%

“…The powder samples of the tests were dried and mixed with KBr for tablet processing. The conditions of the infrared test ranged from 400 cm −1 to 4000 cm −1 , the test resolution was 4cm −1 and each test was scanned 64 times [ 21 ]. Scanning electron microscopy (SEM) morphologies of the gold-coated powder samples were performed using the device of NOVA NANO SEM 430 with a field emission gun, a magnification of 30× up to 300,000 and the resolution for Gun.…”

Section: Methodsmentioning

confidence: 99%

Effects of Typical Solvents on the Structural Integrity and Properties of Activated Kaolinite by Wet Ball Milling

Luo

Chen

et al. 2022

Nanomaterials

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The influence of organic solvents on the structural integrity and properties of activated kaolinite were compared and analyzed via characterization techniques and molecular dynamics (MD) simulation. The results revealed that the organic intercalators can be easily inserted into the interlayer spaces of activated kaolinite within a short time of the wet ball milling. The DMSO intercalated kaolinites maintained structural integrity due to the high intercalation rate and the excellent buffering effect against the crushing force of milling during the delamination/exfoliation process. The delaminated layers of the DMSO–kaolinite complex exhibited a high specific surface area of 99.12 m2/g and a low average thickness of 35.21 nm. The calculated elastic properties of the organo-kaolinite complex manifested the intercalation of DMSO into a kaolinite interlayer, which could improve the compressibility and structural integrity of kaolinite nanosheets. The DMSO–kaolinite complex was easier to peel off when compared to the other organic intercalators due to its more intercalated molecules.

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“…The density functional theory (DFT) calculations [ 28 ] were carried out employing the Vienna ab initio simulation package (VASP) [ 29 , 30 , 31 , 32 , 33 , 34 , 35 ] with the projected-augmented wave (PAW) method [ 36 , 37 ] and pseudopotential were used to define electron-ion interaction. A well-converged plane-wave cutoff energy of 400 eV was employed for the structural relaxations.…”

Section: Materials and Computational Approachmentioning

confidence: 99%

Silicate Dissolution Mechanism from Metakaolinite Using Density Functional Theory

2023

Self Cite

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Metakaolin (MK) is a high-quality, reactive nanomaterial that holds promising potential for large-scale use in improving the sustainability of cement and concrete production. It can replace cement due to its pozzolanic reaction with calcium hydroxide and water to form cementitious compounds. Therefore, understanding the dissolution mechanism is crucial to fully comprehending its pozzolanic reactivity. In this study, we present an approach for computing the activation energies required for the dissolution of metakaolin (MK) silicate units at far-from-equilibrium conditions using the improved dimer method (IDM) and the transition-state theory (TST) within density functional theory (DFT). Four different models were prepared to calculate the activation energies required for breaking oxo-bridging bonds between silicate or aluminate units. Our results showed that the activation energy for breaking the oxo-bridging bond to a silicate neighbor is higher than that to an aluminate neighbor due to the ionic interaction. However, for complete silicate tetrahedra dissolution, a higher activation energy is required for breaking the oxo-bridging bond to the aluminate neighbor compared to the silicate neighbor. The findings provide methodology for missing input data to predict the mesoscopic dissolution rate, e.g., by the atomistic kinetic Monte Carlo (KMC) upscaling approach.

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Unexpected Chemical Activity of a Mineral Surface: The Role of Crystal Water in Tobermorite

Cited by 15 publications

References 41 publications

Effect of Different Initial CaO/SiO2 Molar Ratios and Curing Times on the Preparation and Formation Mechanism of Calcium Silicate Hydrate

Effect of Different Initial CaO/SiO2 Molar Ratios and Curing Times on the Preparation and Formation Mechanism of Calcium Silicate Hydrate

Effects of Typical Solvents on the Structural Integrity and Properties of Activated Kaolinite by Wet Ball Milling

Silicate Dissolution Mechanism from Metakaolinite Using Density Functional Theory

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