Hydration Kinetics Of Tricalcium Silicate Research Articles

Anti-washout tricalcium silicate cements modified by konjac glucomannan/calcium formate complex for endodontic applications

Although tricalcium silicate (TCS)-based cement showed a great clinical success as the dental filling material, a big challenge encountered by TCS is its poor anti-washout property. Thus, the purpose of this study is to develop a novel TCS-based cement with excellent anti-washout ability by incorporation of konjac glucomannan (KGM)/calcium formate (CF) complex. The self-setting characteristics, anti-washout ability, setting time, compressive strength, porosity, injectability and flowability of the cements were investigated. Furthermore, antibacterial property and cell cytocompatibility of TCS/CF were also assessed. The results showed that KGM could enhance the washout resistance of TCS pastes while it hindered hydration reaction. CF can further increase the anti-washout ability of TCS cement and shorten its setting time from 420 to 174 min because of the accelerating effect of CF on hydration kinetics of TCS. Compared with TCS pastes, TCS cement containing CF showed an increased compressive strength while the addition of CF decreased the injectability of pastes without an obvious effect on flowability. The antibacterial activity of TCS/CF against S. aureus increased with the amount of CF. Moreover, TCS/CF had good cell cytocompatibility. Our results suggested that incorporation of KGM/CF is a superior strategy to enhance the anti-washout ability of TCS-based dental cements, which have the potential use for endodontic applications.

Hydration kinetics and microstructure evolution of NaCl-mixed tricalcium silicate pastes

The hydration kinetics of tricalcium silicate (C3S) pastes mixed with different concentrations of NaCl solutions were investigated by performing isothermal calorimetry tests. At the same time, the Boundary Nucleation and Growth (BNG) model was used to analyze the calorimetry data. The model fitted well with the calorimetric results. C3S pastes mixed with NaCl solutions followed a similar reaction path to those prepared with DI water, with an accelerated reaction rate as the NaCl concentration increased. The specific parameters, such as the induction and acceleration durations, were quantified, and the relationship was established. The BNG modelling results indicated that the increasing NaCl concentration significantly increased the nucleation rate of the hydration products while decreasing their growth rate slightly. That was supported by the SEM and STEM observations. The presence of NaCl modified the morphology of the early-age calcium silicate hydrates (C-S-H) to relatively shorter and thinner fibres, which had a more compact microstructure and higher micromechanical properties than those in pure C3S pastes.

Granulometric effect of silica nanoparticles on hydration kinetics and microstructure of cement based materials

Effect of particle size of two types of silica nanoparticles (SNPs) on hydration kinetics of tricalcium silicate (C3S) and Portland cement was investigated. Two different types of SNPs were used in the present study, first one is the synthesized by sol-gel method (SNPs-sg) having particle size 30–70 nm, while the second one is the synthesized by Flame Spray Pyrolysis method (SNPs-fsp) having particle size <10 nm. The dosages of SNPs used in this study varied from 1–10% and water/binder ratio used for the hydration was 0.4. Rietveld analysis of XRD results show that at 4 h of hydration, the unhydrated content in control samples at 4 h hydration was ∼88% and in presence 1% SNPs-sg, it was ∼75%, however, in presence of SNPs-fsp, the content of unhydrated C3S was ∼60%. Further, FTIR results reveal that in case of control samples at 1 h of hydration, the characteristic peaks of C3S at 850 cm−1 and 940 cm−1 are present, while, with 1% SNPs-sg addition, reduction in the intensity C3S peaks were observed showing acceleration in dissolution rate and a broader peak is observed at ∼1110 cm−1 with 1% SNPs-fsp samples indicating the starting of polymerization in silicate chain of C-S-H gel.

Influence of size‐classified and slightly soluble mineral additives on hydration of tricalcium silicate

AbstractEarly‐age hydration of cement is enhanced by slightly soluble mineral additives (ie, fillers, such as quartz and limestone). However, few studies have attempted to systematically compare the effects of different fillers on cementitious hydration rates, and none have quantified such effects using fillers with comparable, size‐classified particle size distributions (PSDs). This study examines the influence of size‐classified fillers [ie, limestone (CaCO3), quartz (SiO2), corundum (Al2O3), and rutile (TiO2)] on early‐age hydration kinetics of tricalcium silicate (C3S) using a combination of experimental methods, while also employing a modified phase boundary and nucleation and growth model. In prior studies, wherein fillers with broad PSDs were used, it has been reported that between quartz and limestone, the latter is a superior filler due to its ability to partake in anion‐exchange reactions with C‐S‐H. Contrary to prior investigations, this study shows that when size‐classified and area matched fillers are used—which, essentially, eliminate degrees of freedom associated with surface area and agglomeration of filler particulates—the filler effect of quartz is broadly similar to that of limestone as well as rutile. Results also show that unlike quartz, limestone, and rutile—which enhance C3S hydration kinetics—corundum suppresses hydration of C3S during the first several hours after mixing. Such deceleration in C3S hydration kinetics is attributed to the adsorption of aluminate anions—released from corundum's dissolution—onto anhydrous particulates’ surfaces, which impedes both the dissolution of C3S and heterogeneous nucleation of C‐S‐H.

Hydration kinetics of tricalcium silicate with the presence of portlandite and calcium silicate hydrate

This work was designed to investigate the hydration kinetics of C3S with portlandite and calcium silicate hydrate (C-S-H). The hydration heat, T2 relaxation time and XRD of hydration products were determined to evaluate the hydration performance. C-S-H and CH present distinct influence on the early hydration of C3S. C-S-H facilitates early hydration of C3S, reduces the induction period and increases the hydration rate at 10 or 20 °C, but CH prolongs the induction period. Up to 30 and 40 °C, the induction period is not affected by C-S-H or CH. The catalytic effect was evaluated by activation energy. C-S-H has the catalytic effect on nucleation of hydration products but CH exploits the opposite effect. CH presents a positive effect on the structure development of hydration products to gain a denser skeleton before 10 h. Moreover, the Ca/Si ratio of hydration products is altered for the presents of CH and C-S-H.

Effect of particle size distribution of metakaolin on hydration kinetics of tricalcium silicate

AbstractThe focus of this study is to elucidate the role of particle size distribution (PSD) of metakaolin (MK) on hydration kinetics of tricalcium silicate (C3S–T1) pastes. Investigations were carried out utilizing both physical experiments and phase boundary nucleation and growth (pBNG) simulations. [C3S + MK] pastes, prepared using 8%mass or 30%mass MK, were investigated. Three different PSDs of MK were used: fine MK, with particulate sizes &lt;20 µm; intermediate MK, with particulate sizes between 20 and 32 µm; and coarse MK, with particulate sizes &gt;32 µm. Results show that the correlation between specific surface area (SSA) of MK's particulates and the consequent alteration in hydration behavior of C3S in first 72 hours is nonlinear and nonmonotonic. At low replacement of C3S (ie, at 8% mass), fine MK, and, to some extent, coarse MK act as fillers, and facilitate additional nucleation and growth of calcium silicate hydrate (C–S–H). When C3S replacement increases to 30% mass, the filler effects of both fine and coarse MK are reversed, leading to suppression of C–S–H nucleation and growth. Such reversal of filler effect is also observed in the case of intermediate MK; but unlike the other PSDs, the intermediate MK shows reversal at both low and high replacement levels. This is due to the ability of intermediate MK to dissolve rapidly—with faster kinetics compared to both coarse and fine MK—which results in faster release of aluminate [Al(OH)4−] ions in the solution. The aluminate ions adsorb onto C3S and MK particulates and suppress C3S hydration by blocking C3S dissolution sites and C–S–H nucleation sites on the substrates’ surfaces and suppressing the post‐nucleation growth of C–S–H. Overall, the results suggest that grinding‐based enhancement in SSA of MK particulates does not necessarily enhance early‐age hydration of C3S.

Formation of C–S–H nuclei using silica nanoparticles during early age hydration of cementitious system

This study is focused on the formation of calcium silicate hydrate (C–S–H) seeds during the pre-induction and induction period of hydration in the presence of silica nanoparticles (SNPs). In addition to this, the effect of the formed C–S–H seeds on the hydration kinetics of tricalcium silicate (C3S) is also well investigated and elucidated. From the X-ray diffractometer results, it is observed that the optimum dosage of SNPs for the formation of C–S–H seeds within 60 min of hydration is 3% and the incorporation of SNPs in C3S phase also results in the delayed formation of crystalline calcium hydroxide nuclei. From the isothermal calorimetry and thermogravimetric analyzer results, it is observed that the presence of SNPs results in the shortening of the induction period of C3S hydration. From the Fourier-transform infrared spectroscopy and field emission scanning electron microscope results, it is observed that the presence of SNPs results in the accelerated early hydration rate of C3S and polymerization in the silicate chain. These results reveal that significant acceleration in C3S hydration occurred after the formation of C–S–H seeds.

Effect of the densification of C–S–H on hydration kinetics of tricalcium silicate

AbstractEffect of water to cement (w/c) ratio and temperature profiles on the densification of C–S–H (calcium silicate hydrate gel) and hydration kinetics of triclinic tricalcium silicate (C3S) is studied beyond the first day of hydration. Calorimetry and quantitative X‐ray diffraction/Rietveld analysis show that degree of hydration is unaffected by w/c up to 7 days and marginally thereafter. Coupling the degree of hydration with the portlandite content measured from thermal analysis indicate that C/S ratio of C–S–H decreases with increasing w/c. There is a clear increase in the portlandite content with increasing w/c, even though the degree of hydration is unchanged, due to the variations in C/S ratio of C–S–H. On the other hand, when C3S is initially cured at a lower temperature (20°C) and then at a higher temperature (40°C), there is a significant increase in the reactivity even until 28 days and vice versa. These experimental results were explained using the densified volumetric growth hypothesis, which assumes that hydration kinetics are dependent on the internal surface area of C–S–H.

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.

Influence of aluminates on the hydration kinetics of tricalcium silicate

We used a combination of experimental and modelling techniques to study the effect of NaAlO2 on C3S hydration. pH sensitive inhibition of C3S hydration occurred at an early age of reaction, but was followed by an increased amount of hydrates formed later. Most results suggest that aluminates hinder C3S dissolution. It is hypothesised that this takes place in active dissolution areas, present with a higher density on finer particles. Annealing reduces their number and increases retardation for a given dosage of aluminates. The view that aluminates act by hindering dissolution is supported by molecular dynamics (MD) simulations. They establish that aluminates can adsorb on the hydroxylated C3S mainly through strong ionic interactions between aluminate and calcium ions on the surface of silicate. Upon progress of hydration and at higher pH values, the binding strength of aluminates to the hydroxylated C3S decreases so that its passivating effect, and retardation, are reduced.

An Ideal Solid Solution Model for C-S-H.

A model for an ideal solid solution, developed by Nourtier-Mazauric et al. [Oil & Gas Sci. Tech. Rev. IFP, 60 [2] (2005) 401], is applied to calcium-silicate-hydrate (C-S-H). Fitting the model to solubility data reported in the literature for C-S-H yields reasonable values for the compositions of the end-members of the solid solution and for their equilibrium constants. This model will be useful in models of hydration kinetics of tricalcium silicate because it is easier to implement than other solid solution models, it clearly identifies the driving force for growth of the most favorable C-S-H composition, and it still allows the model to accurately capture variations in C-S-H composition as the aqueous solution changes significantly at early hydration times.

A new view on the kinetics of tricalcium silicate hydration

C3S hydration is an interesting example of chemical coupling between C3S dissolution, C–S–H and portlandite precipitation. It occurs because Ca2+, OH− and silicate ions are present in C3S, in both hydration products and in the surrounding solution. Various experimental data sets reveal that the undersaturation with respect to C3S always increases when C3S hydration enters into the deceleratory phase, leading to the conclusion that C3S dissolution is at the origin of this deceleration, not C–S–H growth. In addition, as soon as portlandite precipitates, the dissolution limits the hydration already in the acceleratory hydration step. The evolution of the undersaturation cannot account for the hydration peak. Rather, it results from an extension and subsequently a decrease of the C3S reactive surface area. The formation and coalescence of dissolution etch-pits can provide a reasonable explanation for the C3S hydration kinetics.

Time dependent driving forces and the kinetics of tricalcium silicate hydration

Simulations of tricalcium silicate (C3S) hydration using a kinetic cellular automaton program, HydratiCA, indicate that the net rate depends both on C3S dissolution and on hydration product growth. Neither process can be considered the sole rate-controlling step because the solution remains significantly undersaturated with respect to C3S yet significantly supersaturated with respect to calcium silicate hydrate (C–S–H). The reaction rate peak is attributed to increasing coverage of C3S by C–S–H, which reduces both the dissolution rate and the supersaturation of C–S–H. This supersaturation dependence is included in a generalized boundary nucleation and growth model to describe the kinetics without requiring significant impingement of products on separate cement grains. The latter point explains the observation that paste hydration rates are insensitive to water/cement ratio. The simulations indicate that the product layer on C3S remains permeable; no transition to diffusion control is indicated, even long after the rate peak.

A Reaction Zone Hypothesis for the Effects of Particle Size and Water‐to‐Cement Ratio on the Early Hydration Kinetics of C3S

The hydration kinetics of tricalcium silicate (C3S) has been the subject of much study, yet the experimentally observed effects of the water‐to‐cement (w/c) ratio and particle size distribution have been difficult to explain with models. Here, we propose a simple hypothesis that provides an explanation of the lack of any significant effect of w/c on the kinetics and for the strong effect of the particle size distribution on the amount of early hydration associated with the main hydration peak. The hypothesis is that during the early hydration period the calcium–silicate–hydrate product forms only in a reaction zone close to the surface of the C3S particles. To test the hypothesis, a new microstructure‐based kinetics (MBK) model has been developed. The MBK model treats the C3S particle size distribution in a statistical way to save computation time and treats the early hydration as essentially a boundary nucleation and growth process. The MBK model is used to fit kinetic data from two published studies for C3S with different size distributions, one for alite (impure C3S) pastes and one for stirred C3S suspensions. The model is able to fit all the data sets with parameters that show no significant trend with particle size, providing support for the reaction zone hypothesis.

Influence of acrylic superplasticizer and cellulose-ether on the kinetics of tricalcium silicate hydration reaction

This paper reports on the analysis of the hydration kinetics of a tricalcium silicate paste cured in presence of polymers industrially used in the extrusion process of mortars. In particular, we investigated the effect of a rheology-modifying additive (a methyl hydroxy ethyl cellulose) and a superplasticizer (a polyacrylic polymer). These polymers have been added to tricalcium silicate paste, both separately and together, to understand their distinct influence on the tricalcium silicate hydration and their possible synergies. The kinetic curves have been monitored from 10 to 40°C by means of Differential Scanning Calorimetry and fitted using the generalized Boundary Nucleation and Growth Model combined to a diffusion-limited model, to extract: induction times, reaction rates, activation energies and diffusion coefficients. As a main result, this paper contributes to the advancement of the knowledge in the field of the extrusion process of cementitious materials, providing a thermodynamic support to the empirical evaluations of the additives performances.

The effect of water-to-cement ratio on the hydration kinetics of tricalcium silicate cements: Testing the two-step hydration hypothesis

Recent efforts to model tricalcium silicate based cements assume a two-step hydration mechanism where, in the first step, the empty space between cement particles rapidly fills with a low density calcium silicate hydrate (C-S-H) and in the second step, the thus formed C-S-H densifies slowly. This gives rise to models that nicely mimic the shape of experimentally observed hydration calorimetry curves and explains the transition between Stage 3 (acceleration) and Stage 4 (decreasing rate) hydration as well as post Stage 4 continued slow reaction. If this mechanism is correct, however, one would expect that the amount of heat energy released should increase with available space between particles, i.e. with water-to-cement ratio. A series of experiments, wherein the water-to-cement ratio was systematically varied showed little or no increase in total heat released when the water-to-cement ratio was doubled or tripled suggesting that the two-step mechanism may need revision.

Hydration kinetics of tricalcium silicate by calorimetric methods

The kinetics of the cement hydration reaction is a relevant issue in the cement research field, particularly in the presence of additional inorganic and organic components that consistently increase the complexity of the cement paste. In the present study, the hydration reaction of pure tricalcium silicate has been monitored by different calorimetric approaches: the conventional Isothermal Conduction Calorimetry (IC) and a novel Differential Scanning Calorimetry (DSC) protocol. The measured hydration curves have been modeled by using the Boundary Nucleation and Growth Model (BNGM) to extract thermodynamic parameters of the early stages of the hydration reaction. IC and DSC methods provide similar results in terms of rate constants, linear growth, and nucleation rates even though the IC accesses the total evolved heat while DSC discloses the fraction of unreacted water. The validation of the DSC approach as a reliable analytical method to the study of cement hydration kinetic is of particular importance because it allows following very long hydration processes, such as those of pastes containing organic retarders or superplasticizers. The thermodynamic and kinetic parameters for the tricalcium silicate setting has been also evaluated and discussed as a function of the surface area of the powder.

New Insights Into the Effect of Calcium Hydroxide Precipitation on the Kinetics of Tricalcium Silicate Hydration

After decades of research, there still is no universal agreement on the basic mechanisms that are responsible for the induction period (Stage 2) in cement hydration at early times. This paper surveys several theories and critical experimental data on early‐age hydration kinetics of tricalcium silicate, the most abundant phase in Portland cement clinker. Using HydratiCA, a kinetic cellular automaton model of cement hydration and microstructure development, we investigate two of the leading hypotheses on the mechanism of slow hydration in Stage 2, and see for each one the implications of suppressing the growth of calcium hydroxide formation. Each hypothesized mechanism leads to quite different kinetic behavior when calcium hydroxide is suppressed, a result which indicates a line of future experimental inquiry that could decisively determine the Stage 2 mechanism. Furthermore, the simulations demonstrate how the early theory of calcium hydroxide triggering might be reconciled to the more modern theoretical models and to the experimental data.

Influence of TiO2 Nanoparticles on Early C3S Hydration

The effect of nanoanatase titanium dioxide (TiO2) powder on early‐age hydration kinetics of tricalcium silicate (C3S) was investigated. Isothermal calorimetry was performed on C3S pastes with 0%, 5%, 10%, and 15% of TiO2 addition by weight, and two mathematical models—the Avrami (or JMAK) model and the boundary nucleation model (BN model)—were fitted to the data. For all of the mixes, the addition of TiO2 increased the peak reaction rate, and increased the degree of hydration at 12 and 24 h. The rate of hydration of 10% and 15% TiO2 pastes were accelerated, while the 5% TiO2 paste was delayed, lengthening the induction period as compared with the control paste. The model fits demonstrate that the BN model captures the kinetics of the reaction better, particularly in the deceleration period, than the Avrami model. This is related to the ratio of rate parameters (kB/kG) of the BN model, that the increasing ratio gives a more unsymmetrical shape of a rate curve. The increase in kB/kG with TiO2 addition at 5%, 10%, and 15% suggests that hydration product is formed on or near the surfaces of TiO2 particles, as well as on the C3S surface. These results demonstrate that the addition of TiO2 nanoparticles accelerates the early hydration by providing additional nucleation sites, forming the foundation for future optimization of photocatalytic and other nanoparticle‐containing cements.