Hydration Of Tricalcium Silicate Research Articles

Sulfonation of graphene and its effects on tricalcium silicate hydration

Sulfonate graphene nanosheet (SGN), as a new chemical admixture obtained by sulfonation of graphene, has been used to investigate the effects on tricalcium silicate (C3S – Conventional cement chemistry notation is often used in this article to specify the composition of solid phase, whereby C = CaO, S = SiO2, F = Fe2O3 and H = H2O) hydration. Results show that SGN can prolong the dissolution period and induction period during C3S hydration owing to its adsorption behavior. In situ X-ray diffraction analysis demonstrated that the crystal growth on 001 planes of Calcium hydroxide (CH) will be enforced by addition of SGN, which is probably by the following steps: 1) Ca2+ released by C3S more likely diffused to the surface of SGN prior to nucleation of CH; 2) the nanosheets provide a template for aligned growth of the CH especially on the 001 planes. Meanwhile, scanning electron microscope photos directly show that the growth of CH is layer by layer on the 001 plane when SGN was added. Hopefully, the mechanism of C3S hydration cooperating with SGN proposed in this paper can make a guidance for the application of SGN in cement based materials.

Effect of aluminum sulfate on the hydration of tricalcium silicate

In order to obtain a deep understanding of the hydration of sprayed concrete, C3S pastes with and without aluminum sulfate (AS) were comparatively investigated. The results showed that AS significantly accelerated the hydration of C3S and refined the pore structure of the hardened C3S paste, by reacting with the calcium ions to produce ettringite; this acted as nucleation seeds to induce the formation of CSH gel. Differing from CSH based nucleation seeds, the ettringite-based nucleation seeds were formed in bulk solution where was away from rather than inside the rich silicate layer, thereby inducing the formation of CSH gel in the interspace among C3S particles. Furthermore, the formation of ettringite consumed a large amount of calcium ions, which not only expedited the dissolution of C3S to release the calcium ions into solution, but also perturbed the crystallization of calcium hydroxide (CH), resulting in formation of amorphous CH.

Effect of graphene oxide (GO) on hydration of tricalcium silicate (C3S)

In this study, the interaction between the major phase of cement clinker, C3S, and GO was explored to investigate its effect on the microstructures of G3S/GO composites at different GO dosages in a range of 0–0.05 wt%. The compressive strength of C3S/GO composites was tested and their microstructural developments were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TG), nitrogen adsorption and 29Si solid-state nuclear magnetic resonance (NMR) techniques. The results show that the addition of GO can improve the compressive strength of C3S/GO paste up to 32.5% at 1 day. In addition, the incorporation of GO provided an increasing number of nucleation sites to form denser microstructure and refined the pore structure by reducing the total porosity and increasing the gel pores. In particular, the hydration degree was increased by approximately 20% at the age of 7 days when the GO dosage was in the range of 0.03–0.05 wt% as evidenced by TG and NMR results. The ratio of Q2/Q1 in C-S-H gel decreased slightly with the increased GO content, which was further corresponding to the decreased mean chain length of C-S-H gel. Therefore, the introduction of GO exerts a positive effect on the hydration of C3S, which provides essential supports to the hydration mechanism of GO in Portland cement matrix.

Mechanism of tricalcium silicate hydration in the presence of polycarboxylate polymers

The early-age hydration of cement is inhibited in the presence of comb-shaped polycarboxylate ether (PCE) polymer—a dispersant commonly added to control rheological properties of fresh cement paste. This study employs a series of microcalorimetry experiments and phase boundary nucleation and growth simulations to elucidate the effects of dosage and molecular architecture of PCE on hydration of tricalcium silicate (Ca3SiO5 or C3S in cement notation), the dominant phase in cement. Results show that PCE—regardless of its molecular architecture—suppresses early-age hydration of C3S. PCE-induced retardation becomes increasingly more pronounced as dosage of PCE in the paste increases. Such suppression of C3S hydration has been attributed to adsorption of PCE molecules on silicate surfaces, which inhibit topographical sites of C3S dissolution and C–S–H nucleation, and impede the post-nucleation growth of C–S–H. This study develops a correlation between molecular architecture of PCE and its ability to suppress C3S hydration through quantitative analyses of retardation effects induced by PCEs with different molecular architectures. The numerical equation, describing such correlation, offers a reliable, and, more importantly, a readily quantifiable indicator of PCE’s potential to suppress C3S hydration in relation to its dosage and molecular architecture. In the context of practical application of this study, the aforementioned numerical equation can be used to order and rank PCEs—of various molecular architectures—on the bases of their potentials to suppress C3S hydration, and to select ones that cause the optimum (i.e., user-desired) extent of hydration suppression.

Pore structure development during hydration of tricalcium silicate by X-ray nano-imaging in three dimensions

Tricalcium silicate (C3S) is the most important component among the four main clinker phases of Portland cement. Pure C3S is widely used as a simplified model system of cement in various researches. However, the spatial structure development of cement, even pure C3S during hydration at the nano-scale has been rarely directly reported. In this work, X-ray nano-computed tomography (X-ray Nano-CT), a non-destructive X-ray analytical method, was used to study the hydration of a pure C3S sample with a water/C3S mass ratio of 0.5. The three-dimensional (3D) structure of the hydrating C3S specimen was investigated to see the internal pore structure evolution within the hardened C3S paste. Investigation of the 3D structural development of the C3S specimen at different hydration times was performed to monitor the changes of pore shapes and sizes/volumes. It is found that volumes of the sealed pores generally grow larger, and the open pores become smaller while the volume and the external morphology of the whole hardened C3S paste remains almost the same during hydration.

Effect of triethanolamine hydrochloride on the performance of cement paste

Triethanolamine (C6H15NO3, TEA) is one of the known organic amine accelerators for the cement-based materials. Triethanolamine hydrochloride (C6H15NO3·HCl, TEA·HCl), part of whose molecular structure is the same as TEA, can also be regarded as chloride. Thus the water requirement for the normal consistency, setting time, strength, hydration heat liberation, calcium hydroxide (CH) and ettringite (AFt) contents in the hardened paste with TEA·HCl were analyzed and the effect of TEA·HCl on the performance of cement paste was studied to assess the feasibility of TEA·HCl used as an identical accelerator. The results indicate that moderate TEA·HCl decreases the water requirement for the normal consistency and this decline is related to the formation of the absorbed film on the cement particle. Zeta electric potential result also proves the appearance of the absorbed film. It also shortens the setting times and alters strengths. But the alterations of setting times and strengths depend on the TEA·HCl content. Heat liberation result implies that it delays the end time of the induction period and also postpones tricalcium silicate (3CaO·SiO2, C3S) hydration at early age, however moderate TEA·HCl increases the rate of C3S hydration in accelerated phase. Excessive TEA·HCl accelerates the AFt conversion to monosulfoaluminate (AFm) after several hours. The conversion product is the AFm with 14 H2O. TEA·HCl changes the total heat liberation, and these pastes with more TEA·HCl liberate more heat before about 12 h, but this case is reverse after about 12 h. X-ray powder diffraction (XRD) and differential thermal analysis (DTA) results conformably confirm that excessive TEA·HCl delays C3S hydration and decreases CH content in the hardened paste, but it increases the AFt content in the hardened paste. Hardened pastes with TEA·HCl provide the higher content of AFt than the control even at 28d. Heat liberation, CH and AFt contents are closely responsible for the results of the setting times and strengths. These results will provide a reference for the TEA·HCl application as an accelerator in the practice.

New insights into tricalcium silicate hydration in paste

AbstractThe knowledge of the aqueous phase composition during the hydration of tricalcium silicate (C3S) is a key issue for the understanding of cement hydration. A new in situ method of computing calcium ion concentration from the measurement of the electrical conductivity on paste was coupled to isothermal calorimetry and BET measurements to get new insights on the early hydration of C3S. Ion concentrations of the aqueous phase are mainly dependent on the degree of hydration and the water to C3S ratio. In the case of C3S paste, the calcium and silicon concentrations determined at low degrees of hydration can be related to the equilibrium curve of C‐S‐H having C/S = 1.27 and named C1.27SHy. It is expected that C1.27SHy thermodynamically controls the aqueous phase composition at this early stage. Indeed, the formation of C1.27SHy is quasi‐immediate when C3S is in contact with water inducing a very rapid increase of the specific surface area that remains constant during the induction period. At higher degrees of hydration, the aqueous phase composition departs from the C1.27SHy equilibrium curve. C1.27SHy appears to be a metastable C‐S‐H that could be related to an intermediate phase previously reported. The quasi‐immediate precipitation of C1.27SHy on C3S surface explains why calcium and silicon concentrations remain low during early hydration even though C3S is strongly undersaturated. This also agrees with the control of the end of the induction period by the nucleation and growth of more stable C‐S‐H.

Preparation of bio-inspired polydopamine coating on hydrated tricalcium silicate substrate to accelerate hydroxyapatite mineralization

A layer of polydopamine (PDA) was successfully deposited on hydrated tricalcium silicate (TCS) substrate via facile dip-coating of hydrated TCS disk in an aqueous solution of dopamine. The results showed that the continuous release of Ca(OH)2 from hydrated TCS substrate accelerated reaction of noncovalent self-assembly and covalent polymerization of dopamine and therefore a faster deposition of PDA coating on hydrated TCS substrate. Furthermore, amorphous calcium phosphate (ACP) that is the precursor phase of bone-like hydroxyapatite (HA) can rapidly precipitate on the surface of PDA-coated TCS within 5 min in simulated body fluid (SBF).

Nano-scale mechanical properties investigation of C-S-H from hydrated tri-calcium silicate by nano-indentation and molecular dynamics simulation

Calcium silicate hydrate (C-S-H) is the most important hydration product in cementitious material. Due to its complexity, the investigation on its mechanical properties is still in progress. In this study, synthesized C3S was utilized to produce relatively pure C-S-H gels with two different water/solid ratios. Then mechanical properties of the C-S-H were measured and characterized by nano-indentation and SEM/EDX/BSE. Two types of C-S-H with Ca/Si ratio around 1.8 were observed through statistical analysis of the indentation modulus (Er) and hardness (H). The looser one possessing lower Er around 25–30 GPa while the denser one possesses higher Er of 35.9 GPa. Both phases have higher stiffness than those of high density (HD) and low density (LD) phase obtained from cement pastes. Furthermore, molecular dynamics provides mechanical understanding of C-S-H gel at nano-scale. Based on the crystal structure of tobermorite 11 Å, 64 models with Ca/Si ratios from 1.3 to 2.0 were constructed for uniaxial tension test. The stiffness and cohesive strength of the C-S-H gel are greatly influenced by Ca/Si ratio, water content and nano-porosity. With increasing Ca/Si ratio from 1.3 to 2.0, long silicate chains were broken to shorter ones and more water molecules penetrated into defect regions. The destroyed silicate skeleton and the “hydrolytic weakening” effect resulted in the reduction of the mechanical properties of C-S-H gels. Concurrently considering the intrinsic porosity and chemical compositions, the appropriate micromechanical models are utilized to upscale the molecular properties to higher level.

Coherent diffraction study of calcite crystallization during the hydration of tricalcium silicate

The aim of this work is using Bragg coherent X-ray diffraction imaging (BCDI) to study the calcite crystallization during carbonation of hydrated tricalcium silicate (C3S). Portland cement is a very complex synthesized product whose 50–70% mass is composed of C3S, which is the most important phase to produce calcium silicate hydrates and calcium hydroxide. Hence, its hydration contributes greatly to the hydration of cement and later to the carbonation of cement products when it reacts with CO2, often from the air, to form calcium carbonates. BCDI has emerged in the last decade as a promising high-resolution lens-less imaging approach for characterization of various samples. It has made significant progress with the development of X-ray sources and phase-retrieval algorithms. BCDI allows for imaging the whole three-dimensional structure of micro- and sub-micro- crystalline materials and can show the strain distribution at the nanometer spatial resolution. Results show that calcite crystallization follows a through-solution reaction and the growth model of the calcite crystal can be explained by using “phase domain” theory. During carbonation, calcite crystals grow by increasing the number of phase domains within them while the domain size remains at about 200–300 nm.

Preparation of Ca/Al-Layered Double Hydroxide and the influence of their structure on early strength of cement

Ca/Al-Layered Double Hydroxide (Ca/Al-LDH), was a kind of important anionic clays with broad applications owing to its properties of exchangeable anion and adjustable particle size. In this study, Ca/Al-LDH had been successfully prepared by co-precipitation method, and it was found that the particle size, crystallinity and morphology of Ca/Al-LDH could be tuned via changing ethanol/water ratio of solution. More interestingly, with the increase of the Ca/Al-LDH’s dosage, the different crystal structure of Ca/Al-LDH had promoting effect on the development of the early strength of the cement slurries, however, the change trend of the strength growth rate of various kinds of cement slurries were quite different. Meanwhile, experimental results disclosed that the crystallinity and particle size of Ca/Al-LDH determined its interaction with cement hydration particles. That was likely to lead to a change in tricalcium silicate (C3S) and tricalcium aluminate (C3A) hydration process of accelerating or retarding under the different Ca/Al-LDH content, thus enabling the early strength development of slurry to exhibit different trends. And this finding could provide further interpretation for the effect of hydrotalcite-like materials on cement hydration process and offer a theoretical exploration for its practical application in the future.

Multiscale understanding of tricalcium silicate hydration reactions

Tricalcium silicate, the main constituent of Portland cement, hydrates to produce crystalline calcium hydroxide and calcium-silicate-hydrates (C-S-H) nanocrystalline gel. This hydration reaction is poorly understood at the nanoscale. The understanding of atomic arrangement in nanocrystalline phases is intrinsically complicated and this challenge is exacerbated by the presence of additional crystalline phase(s). Here, we use calorimetry and synchrotron X-ray powder diffraction to quantitatively follow tricalcium silicate hydration process: i) its dissolution, ii) portlandite crystallization and iii) C-S-H gel precipitation. Chiefly, synchrotron pair distribution function (PDF) allows to identify a defective clinotobermorite, Ca11Si9O28(OH)2.8.5H2O, as the nanocrystalline component of C-S-H. Furthermore, PDF analysis also indicates that C-S-H gel contains monolayer calcium hydroxide which is stretched as recently predicted by first principles calculations. These outcomes, plus additional laboratory characterization, yielded a multiscale picture for C-S-H nanocomposite gel which explains the observed densities and Ca/Si atomic ratios at the nano- and meso- scales.

A contribution to the characterization of the silicate-water interface – Part II: Atom Probe Tomography of tricalcium silicate

This work explores the possibility to investigate the nanoscale cement-water interface by means of atom-probe tomography (APT). For this purpose, the main compound of Ordinary Portland Cement, tricalcium silicate, and its hydration product calcium-silicate-hydrate have been analyzed by APT. Of special interest was the surface of anhydrous and hydrated tricalcium silicate. The results show, that a nanoscale characterization of tricalcium silicate with APT is possible by carefully controlling the various measurement parameters. Furthermore, our results indicate, that the conditions during focused ion beam sample preparation, especially the high vacuum and energy input, are potentially harmful to calcium-silicate-hydrate. Future developments in cryo sample preparation will greatly enhance the applicability of APT on cement and its hydration products.

Acidic and alkaline chemicals' influence on a tricalcium silicate-based dental biomaterial.

Bioactive hydraulic tricalcium silicate materials are commonly used in several dental procedures. Mineral Trioxide Aggregate (MTA) is one such material, which is used in a variety of clinical applications, the most recent of which is root canal sealing material, during which, the MTA potentially comes in contact with remnants of the chemical agents used for disinfecting root canals. The effects of commonly used root canal irrigating solutions on MTA have not been investigated in depth, thus far. The aim of this study was to determine the effect of five common chemical agents used in root canal preparation (sodium hypochlorite/NaOCl, ethylene diaminetetraacetic acid/EDTA, mixture of sodium hypochlorite and etidronic acid/NaOCl + EA, mixture of EDTA and Chlorhexidine/QMix, or saline) on a commercial tricalcium silicate (MTA Plus). Samples were analyzed using scanning electron microscopy with energy dispersive spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy and Inductively coupled plasma techniques to see effects of phases formed and calcium ion release. Specimens immersed in NaOCl and NaOCl + EA had strong peaks for calcium hydroxide, but materials exposed to EDTA and QMix had lesser XRD peaks for calcium hydroxide. The calcium hydroxide peak in the XRD indicates hydration of tricalcium silicate and formation of amorphous calcium silicate hydrate. Calcium released from samples immersed in EDTA and NaOCl was less than in NaOCl + EA and QMix solutions. Fewer calcium phosphate crystals and less calcium hydroxide were observed with the samples in NaOCl, EDTA and QMix, which could have an important impact as it negatively influences the bioactivity. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 377-387, 2019.

Molecular dynamics study on the Tri-calcium silicate hydration in sodium sulfate solution: Interface structure, dynamics and dissolution mechanism

The hydration and dissolution of tri-calcium silicate mineral is of great importance for guiding the material design. In order to understand the hydration mechanism of C3S mineral in sodium sulfate solution, molecular dynamics was employed to construct three interface models of C3S and Na2SO4 solution of 0 mol/L, 0.79 mol/L and 1.58 mol/L and the structure, dynamics and dissolution properties of the interfacial species were investigated. Due to hydrophilic nature of C3S surface, the water molecule in hydrate layer deeply tessellated on the vacancy surface region shows high intensity packing, ordered arrangement, enlargement of the dipolar moment value and orientation preference. With progressively increasing simulation time, the hydroxyl groups and calcium atoms in the high reactive surface gradually escape from the substrate bonding restriction and diffuse away to the solution region. Furthermore, both ions prefer to adsorbing on the surface of tri-calcium silicate mineral: the highly solvated surface calcium ions associate with the oxygen sites in the sulfate ions, forming the CaSO4 ionic pairs in the interfacial region; the sodium ions are attracted by the non-bridging oxygen in the silicate monomers, forming NaO connection. The surface adsorbed water molecules, sulfate and sodium ions, strongly associated with the calcium atoms and hydroxyl groups, form a ionic and hydrate layer, stabilizing the tri-calcium silicate surface and inhibiting the dissolution of ions in C3S. With increasing ions’ concentration, the sulfate and sodium ions in the solution are more probable to form cation-anion pairs and further accumulate to the ionic cluster.

Admixture compatibility in metakaolin–portland-limestone cement blends

Despite potential benefits including enhanced mechanical properties, reduced permeability, and decreased environmental impact, higher rates of metakaolin substitution for cement (> 10% MK by mass of cement) have been limited practically because of lower workability in such mixtures. When metakaolin is combined with portland-limestone cement (PLC), potential synergies further enhance hardened concrete performance and decrease environmental impact, but the greater surface area of PLCs suggests even greater challenges for workability in such blends. This study evaluates four water-reducing admixture chemistries-polycarboxylate ether (PCE), calcium lignosulfonate (LS), naphthalene formaldehyde condensate (PNS) and polymelamine sulfonate (PMS)—to assess their effectiveness in metakaolin-PLC combinations at up to 30% MK. At that upper bound, only PCE and PMS impart adequate workability within their recommended dosage limits. While PMS delays tricalcium silicate hydration and LS shows significant incompatibilities at higher MK contents, PCE has the least effect on hydration and can be used at a consistent dosage rate up to 30% MK.

A Critical Comparison of 3D Experiments and Simulations of Tricalcium Silicate Hydration.

Advances in nano-computed X-ray tomography (nCT), nano X-ray fluorescence spectrometry (nXRF), and high-performance computing have enabled the first direct comparison between observations of three-dimensional nanoscale microstructure evolution during cement hydration and computer simulations of the same microstructure using HydratiCA. nCT observations of a collection of triclinic tricalcium silicate (Ca3SiO5) particles reacting in a calcium hydroxide solution are reported and compared to simulations that duplicate, as nearly as possible, the thermal and chemical conditions of those experiments. Particular points of comparison are the time dependence of the solid phase volume fractions, spatial distributions, and morphologies. Comparisons made at 7 h of reaction indicate that the simulated and observed volumes of Ca3SiO5 consumed by hydration agree to within the measurement uncertainty. The location of simulated hydration product is qualitatively consistent with the observations, but the outer envelope of hydration product observed by nCT encloses more than twice the volume of hydration product in the simulations at the same time. Simultaneous nXRF measurements of the same observation volume imply calcium and silicon concentrations within the observed hydration product envelope that are consistent with Ca(OH)2 embedded in a sparse network of calcium silicate hydrate (C-S-H) that contains about 70 % occluded porosity in addition to the amount usually accounted as gel porosity. An anomalously large volume of Ca(OH)2 near the particles is observed both in the experiments and in the simulations, and can be explained as originating from the hydration of additional particles outside the field of view. Possible origins of the unusually large amount of observed occluded porosity are discussed.

Discussion of the paper “A new view on the kinetics of tricalcium silicate hydration,” by L. Nicoleau and A. Nonat, Cem. Concr. Res. 86 (2016) 1–11

In contradiction to the proposition of Nicoleau and Nonat, it is shown that the rate of hydration of anhydrous tricalcium silicate (C3S) cannot be controlled by the rate of dissolution of the anhydrous phase in typical C3S pastes except at extremely early ages. The strongest evidence for this is the observation that the hydration of C3S in pastes is strongly accelerated by the addition of afwillite seeds, to the extent that it hydrates almost completely by 7days. It is suggested that the hydration rate at later ages is primarily controlled by the porosity and permeability of the hydration products.

Rate-limiting reaction of C3S hydration - A reply to the discussion “A new view on the kinetics of tricalcium silicate hydration” by E. Gartner

In the case of coupled solids-solution reactions, any mean accelerating or decelerating one of the reaction, will also change the other reaction(s) in the same way, through the coupling mediated by the solution. The observation of any kinetic change by one of these means should not lead to too rapid conclusion on the limitation of kinetics and it must be done with great caution. Contrary to what Gartner mentioned, the acceleration of C3S hydration by the addition of calcium silicate hydrate seeds, is not a trivial evidence suggesting that hydration kinetics “has to be” limited by the C-S-H precipitation and that the C3S dissolution can be neglected. In our paper, efforts have been made to highlight again the importance of C3S dissolution, based on the Gartner's discussion points.

Development of a new calcium sulfoaluminate (synthetic ye'elimite) blended PII 52.5 cement

The aim of this paper is to examine the effect of a blending dose of calcium sulfoaluminate (synthetic ye'elimite, C4A3$) and gypsum on the hydration and hardening properties of a new ye'elimite (C4A3$) blended PII 52.5 cement. By using X-ray diffractometry, mercury intrusion porosimetry, thermogravimetry and scanning electron microscopy, it was revealed that the hydration of tricalcium silicate (C3S) is significantly retarded by the lack of gypsum; the renewed hydration of tricalcium aluminate (C3A) was retarded in cement pastes containing a high amount of C4A3$. The dosage of C4A3$ and the ratio of gypsum/C4A3$ both have a notable influence on the hydration heat, hydration products and the compressive strength and linear expansion. The cement paste containing 3% C4A3$ at gypsum/C4A3$ ratio of 2 exhibited the best performance, in terms of both high early and long-term compressive strength and acceptable linear expansion (0·04% on 300 d); the cement can therefore be adopted in industrial structures.