Hydration Of Tricalcium Silicate Research Articles

Effect of Alkalis on Tricalcium Silicate Hydration with and without Incorporating Metakaolin

Effect of Alkalis on Tricalcium Silicate Hydration with and without Incorporating Metakaolin

Mineral dissolution mechanism of alite polymorphs from ReaxFF molecular dynamics and 29Si NMR investigations

The hydration of tricalcium silicate (C3S, C = CaO, S = SiO2) played a critical role in the mechanical property improvement in cement-based cementitious materials. In this study, we investigated the hydration mechanism of M3- and T1-C3S polymorphs using molecular dynamics simulation with the ReaxFF force field. Six surfaces were selected by their low-index surface energy and surface areas of the Wulff structure to study their hydration process, including M3-C3S (100), (001) and (111) surfaces, as well as T1-C3S (001), (010) and (111) surfaces. Bonding formation kinetics and radial distribution functions were analyzed. Results show that water dissociation degrees on the studied surfaces were comparable, independent of the crystal polymorphs. The final bond formation percent of Ca-OwH and Os/Oi-H on all the surfaces exhibited little difference. However, we observed the formation of pentacoordinate silicon atoms with a [SiO5]6- trigonal bipyramid structure, occurring earlier in M3-C3S than in T1-C3S. Furthermore, the M3-C3S exhibited a higher abundance of pentacoordinate silicon atoms compared to the T1 crystal, suggesting greater reactivity of M3-C3S. This study provided valuable insights into enhancing the quality of cement clinker and activating other silicate minerals in supplementary cementitious materials.

Exploring macroscopic and microscopic impacts of alcohol amine modified with water-reducing agent on cementitious material and its application

In order to meet function requirements of slope protection and ecology for grass-planting concrete with a random porous structure, this study proposes two typical alcohol amines, namely, water-reducing agent modified triethanolamine (TEA) and diethanol monoisopropanolamine (DEIPA), as admixtures for the production of grass-planting concrete. The crystal structures, elemental ratios, and hydration products of cementitious materials with modified alcohol amines were investigated to explore their mechanism of action, reinforcement, and appropriate dosage. The compressive strength of cementitious materials and the spread of mortar made from modified alcohol amines were investigated to evaluate their impact on the compressive strength and workability of grass-planting concrete. The results show that modified TEA can more uniformly reduce the calcium-silicon ratio of the hydration products, leading to enhanced crystallization and densification at a dosage of 0.08%. At a dosage of 0.16%, modified DEIPA can effectively promote the hydration of tricalcium silicate and the secondary hydration of generated calcium hydroxide. The reduction in calcium hydroxide content resulted in an increase in strength. Both these amines enhance the bonding ability of cementitious materials. The spread of the modified cementitious materials is further improved, and suitable cementitious materials with a low water-cement ratio can be obtained for making grass-planting concrete to create uniformly wrapping coarse aggregates with the cementitious material. Modified TEA and modified DEIPA significantly increased the 28-day compressive strength of cementitious material by more than 104%, and the improvement effect of modified DEIPA was significantly better than that of modified TEA. The modified alcohol amines show great potential for practical application in production.

Influence of iron doped TiO2 nanotubes on the hydration of tricalcium silicate

AbstractEnvironmental pollution is one of biggest challenges facing the world. The promising technology to control this problem is utilization of semiconductor materials as photocatalyst. It is well known that normal TiO2 showing photocatalytic activity in the UV light, so to decrease the band gap and shifting into visible light, titanium dioxide nanotubes was doped with Fe3+ ions. The influence of fabricated Fe‐doped TiO2 nanotubes (Fe/TiNTs) on the hydration of tricalcium silicate (C3S) have been studied. Addition of 1.0 wt%, 2.0 wt% and 3.0 wt% of Fe/TiNTs into C3S system significantly accelerated the course of hydration. Study on the hydration products after 8h, 1d and 7d improved the degree of hydration. The enhancing of compressive strength of hydrated C3S after 7d, 14d and 28d was observed comparing to the normal TiO2 nanotubes (TiNTs). Also treating both Fe/TiNTs and TiNTs with supersaturated Ca(OH)2 solution revealed a strong interaction between Ca2+‐ ions and nanotubes particularly in the presence of iron (Fe/TiNTs). The specific surface area of hydration products in the presence of Fe/TiNTs was increased. In this study, isothermal calorimetry was utilized for the course of hydration, x‐ ray powder diffraction (XRD) for the phase composition in combination with simultaneous thermal analysis (STA) and gas adsorption (GA) for measuring specific surface area of nanotubes and hydration products.

Development of CO2-integrated 3D printing concrete

3D printing concrete (3DPC) technology is a promising technique for construction due to its advantages such as no formwork is needed, fast production, automation, and high architectural freedom. However, the layer-by-layer extrusion method has stricter requirements on the rheological properties of concrete. One of challenges of this technology is how to improve the rheological properties of concrete to satisfy the conflicting requirements during pumping and after extrusion. This study proposed to use CO2 as accelerator and rheology modifier by injecting CO2 during secondary mixing to improve the rheological and mechanical properties of 3DPC. The influences of the secondary CO2 mixing on the properties of poured concrete and 3DPC were investigated. After using the secondary CO2 mixing, the setting time and workability of concrete were reduced, which contributed to the significantly improved buildability of 3DPC. This was because CO2 accelerated the hydration of tricalcium aluminate (C3A) and tricalcium silicate (C3S) during the secondary mixing. After that, they were continuously accelerated by the calcium carbonate formed during CO2 mixing. Also, the compressive strength of poured concrete was enhanced by the secondary CO2 mixing because it reduced the volume of larger pores (>200 nm) and promoted the formation of calcium silicate hydrates (C-S-H), which simultaneously slightly increased the drying shrinkage. In addition, after using the secondary CO2 mixing, the compressive strength and interlayer bond strength of 3DPC was enhanced.

Increasing the Hydration Activity of Tricalcium Silicate by Adding Microdispersed Ettringite as a Nucleating Agent.

Tricalcium silicate (C3S) as a binder material has a decisive influence on the processes of hardening and strength gain of cements and concretes. One of the promising directions is the introduction of dispersed additives into cement mixtures, which allow micro-level control of the composition of hydration products and change the dynamics of the structure formation of cement stone. In this paper, the effect of a microdisperse ettringite additive on the kinetics of the hydration and hardening process of tricalcium silicate was studied. It was shown that ettringite crystals selectively adsorb Ca2+ and OH- ions from a saturated solution of calcium hydroxide, which contributes to the formation of hydrosilicate nuclei on their surface during cement hydration. Hydration of C3S in the presence of ettringite proceeds more intensively; the addition of ettringite contributes to an increase in the content of calcium hydrosilicates in hydration products at the initial stage of the process. Addition of 10 wt.% ettringite to C3S reduces the induction period of the beginning of the main phase of heat release by around two times and increases the amount of heat released on the 1st day of hydration by 15% compared to the control sample. According to electron microscopy data, it was found that during the first hours of hydration of modified C3S, a significant number of nuclei of fibrous particles of calcium hydrosilicates with sizes of 0.2-2 microns were formed on the surface of ettringite crystals. According to the results of kinetic modeling of the setting process of cement pastes using the Avrami-Erofeyev model, it was shown that in the presence of the addition of microcrystals of ettringite, the setting rate is characterized by a slowdown in nucleation, whereas for a sample without an additive, this process proceeds with an acceleration of the formation of solid-phase nuclei. Based on the comparison of kinetic results and mechanical measurements, it is concluded that needle crystals of ettringite during C3S hydration and cement stone hardening are preformed centers for the growth of hydrosilicate nuclei, and they also act as a reinforcing filler, increasing the bending strength of modified samples. The results of the work can be used in practice in the development of methods for controlling the processes of hydration and hardening of cements, as well as for controllable structure formation of cement stone which is important in particular for 3D printing of building products and constructions.

Multiscale deterioration of recycled aggregate gel network via solar irradiation: Reaction molecular dynamics and experiments

Nowadays, the efficient recycling of construction waste and the sustainability of recycled concrete have faced challenges due to the reduced performance of recycled aggregate (RA). One significant factor impacting the performance of RA is solar irradiation, which occurs throughout the entire service life of a construction project. However, the analysis of the effect of solar irradiation on hardened cement paste has not been fully addressed. This research presents a comprehensive investigation of the multi-scale deterioration of RA caused by solar irradiation. The dynamic evolution of the atomic and chemical structure of synthetic Calcium Silicate Hydrate (C-S-H) gel, the morphological changes in tricalcium silicate (C3S) hydration products, and the alteration of pore structure in the cement paste are unveiled through the combination of reactive molecular simulation and experimental approaches. The results indicate that solar irradiation disrupts the structure of C-S-H, leading to the migration of water molecules from the interlayer spaces of C-S-H to the pore spaces. This prompts the formation of a new, denser gel. However, as a consequence, more capillary pores are formed within the cement paste. The research outcomes provide a bottom-up, multi-scale insight into the reduced performance of RA under solar irradiation. Furthermore, the transmission mechanism of deterioration information at various scales is established, facilitating comprehension of the correlation between gel characteristics and macro-performance. This research paves the way for strategies to ameliorate the sustainability of recycled concrete, addressing the challenges associated with solar irradiation and enhancing the overall performance of recycled aggregate in concrete applications.

Effect of Iron-Doped TiO2 Nanotubes on the Hydration of Tricalcium Silicate

Environmental pollution is one of the most serious and global problems for humans. Photocatalysis is a promising technology to control environmental pollution via the utilization of semiconductor materials as a photocatalyst. In this study, iron-doped TiO2 nanotubes (Fe/TiNTs) with an increased photocatalytic effect at longer wavelengths compared to undoped TiNTs were used, and the effect on the early hydration and mechanical properties of the main clinker phase tricalcium silicate (C3S) was investigated for the first time. Prior to the incorporation of nanotubes into C3S, it was treated with a supersaturated Ca(OH)2 solution. The addition of 1 and 2 wt.% of Fe/TiNTs into the C3S system significantly accelerated the course of hydration. The degree of hydration for the hydration products after 8 h, 1 d and 7 d have improved. The enhancement of compressive strength after 7 d, 14 d and 28 d were observed compared to normal TiO2 nanotubes (TiNTs). Treating Fe/TiNTs with a supersaturated Ca(OH)2 solution revealed a stronger interaction between Ca2+-ions and nanotubes. Fe/TNTs were synthesized via a modified hydrothermal process. The study shows that Fe/TiNTs can be used as a nanomaterial in cement-based building materials due to their enhanced interaction with the system.

Effect of Sodium Gluconate on Properties and Microstructure of Ultra-High-Performance Concrete (UHPC).

The properties of concrete can be significantly affected by sodium gluconate (SG) at very small dosages. In this paper, the effects of SG on the fluidity, setting time, heat of hydration, and strength of ultra-high-performance concrete (UHPC) were studied. The results show that (1) in the plastic stage, SG inhibited the formation of early ettringite (AFt) and delayed the hydration of tricalcium silicate (C3S) and dicalcium silicate (C2S). SG increased the initial fluidity of UHPC without decreasing within 1 h. When the SG dosage was ≥0.06%, the slumps at 30 min and 60 min increased slightly. (2) In the setting hardening stage, the addition of SG inhibited the formation of calcium hydroxide (CH), which significantly extended the setting time of UHPC. When the dosage of SG was 0.15%, the initial and final setting times were 5.0 times and 4.5 times that of the blank group, respectively. SG had no obvious effect on the hydration rate of cement in the accelerated period, but the peak hydration temperature of UHPC was increased when the SG dosage was 0.03~0.12%. (3) In the strength development stage, the 1 d and 3 d strength of UHPC decreased significantly with the increase in the SG dosage. However, SG could promote the formation of AFt at the pores and aggregate interface in the later stage, reduce the porosity of cementite, and improve the compressive strength of UHPC in 28 d, 60 d, and 90 d. When the SG dosage was 0.12%, the 90d strength increased by 13%.

Revisiting the strengthening mechanisms of graphene oxide reinforced cement: Effects of dispersion states

When GO suspension is mixed with cement, different GO dispersion states exist, including well-dispersed state (WDS), grain-adsorbed state (GAS), and self-agglomerated state (SAS). Although the seeding effect mechanism of GO in WDS is well accepted, how GO in GAS and SAS impacts hydration is still an open question. In this study, we selectively studied the effects of GAS and SAS on tricalcium silicate (C3S) hydration. The results revealed that GO in GAS limits the accessibility of reactant for hydration at early age, without notably affecting the subsequent hydration. Instead, GO in SAS strongly absorbs calcium ions from pore solution to significantly decrease its over-saturation degree, which results in more tightly compacted hydrates formed on C3S surface and thus inhibits hydration. These results lead to an improved understanding of GO in cement hydration, and help us unlock the potential of GO in cementitious materials.

The impact of metakaolin on the hydration of tricalcium silicate: effect of C-A-S-H precipitation

Introduction:Metakaolin (MK) is used as supplementary cementitious material to reduce the CO2footprint of Portland cements. However, the early hydration of Portland cement (OPC) is often retarded due to its use. The present work investigates the mechanisms of this retardation. Focus is laid on the interaction of MK with the main clinker phase C3S (Ca3SiO5, pure form of alite) that is known to govern the kinetics of early hydration of OPC.Methods:Hydration reactions of MK and C3S were analysed by optical emission spectroscopy, electron microscopy, thermal analysis, X-ray diffraction and reaction calorimetry.Results:Results on MK showed that compared to sodium ions the presence of calcium ions reduced the maximum amounts of silicate and aluminate ions released into solution by MK. For MK + C3S mixtures, C-A-S-H was formed at the surfaces of both C3S and MK within minutes with a composition of (CaO)1.3(SiO2)0.8(Al2O3)0.2(H2O)2.7. The solubility constant of (CaO)1.3(SiO2)0.8(Al2O3)0.2(H2O)2.7was determined.Discussion:C-A-S-H appeared to be an unsuitable substrate for C-S-H nucleation. Therefore, its formation during early hydration is expected to play an important role in the retardation of C3S hydration. Indeed, when C-A-S-H seeds are formed, less C-S-H seeds are formed leading to lengthen the duration of the induction period. The presence of sulfate ions reduces the amount of C-A-S-H seeds as most aluminate ions are consumed to form ettringite. Consequently, sulfate ions induce an increase of the hydration kinetics such as observed in MK + C3S mixtures.

Influence of light radiation on performance-structure of tricalcium silicate (C3S) hydration products

In this work, high-power Xenon radiation is used to simulate real sunlight radiation and calcium silicate hydrate is prepared by hydration of tricalcium silicate (C3S) with two water-to-solids (w/s) ratios of 0.5 and 10. The absorbance, compositions, silicate chain structure, pore structure and micromorphology of C3S hydration products (C3S-H) after exposure to Xenon radiation were determined using XRD, TG, FITR, 29Si solid-stated NMR, BET and SEM. First of all, fibrous and needle-like calcium silicate hydrate is observed in C3S-H/10 while flaky and honeycomb-like shape is observed in C3S-H/0.5. Although there are remarkable differences in the micromorphology of calcium silicate hydrate in C3S-H with different w/s ratios, Xenon radiation reduces the amount of bound water, increases the polymerization of silicate chain and refines the nanopore structure of calcium silicate hydrate. The underlying mechanism for the re-organization of chemical structure is attributed to improved polymerization of silicate chains. In addition, the refinement on the nanopore structure is due to the coupling actions of shrinking and polymerization of calcium silicate hydrate sheets. The findings could provide basic knowledge regarding the durability of cement-based materials serviced in atmospheric environments especially with strong solar radiation.

The nucleation of C-S-H via prenucleation clusters.

The nucleation and growth of calcium-silicate-hydrate (C-S-H) is of fundamental importance for the strength development and durability of the concrete. However, the nucleation process of C-S-H is still not fully understood. The present work investigates how C-S-H nucleates by analyzing the aqueous phase of hydrating tricalcium silicate (C3S) by applying inductively coupled plasma-optical emission spectroscopy as well as analytical ultracentrifugation. The results show that the C-S-H formation follows non-classical nucleation pathways associated with the formation of prenucleation clusters (PNCs) of two types. Those PNCs are detected with high accuracy and reproducibility and are two species of the 10 in total, from which the ions (with associated water molecules) are the majority of the species. The evaluation of the density and molar mass of the species shows that the PNCs are much larger than ions, but the nucleation of C-S-H starts with the formation of liquid precursor C-S-H (droplets) with low density and high water content. The growth of these C-S-H droplets is associated with a release of water molecules and a reduction in size. The study gives experimental data on the size, density, molecular mass, and shape and outlines possible aggregation processes of the detected species.

Understanding the role of C–S–H seed/PCE nanocomposites, triethanolamine, sodium nitrate and PCE on hydration and performance at early age

Compared to thermal curing, the application of C–S–H/PCE nanocomposites (CPNs) and triethanolamine (TEOA) compound admixture is a green and highly efficient hydration acceleration strategy. Commercial CPNs usually contain polycarboxylate (PCE) and residual sodium nitrate (NN). It is still uncertain whether their presence has some influence on the hydration of cement with this admixture. The experimental results show that TEOA-NN promotes hydration, and then the setting times are shortened and the early compressive strength is increased; it advances the start of the acceleration period, slightly increases tricalcium silicate (C3S) hydration, or further improves tricalcium aluminate (C3A) hydration. TEOA-PCE significantly retards C3S and C3A hydration at 1 d. In contrast, TEOA-CPNs exhibit excellent mechanical properties and hydration heat owing to its strong promotion of the hydration of C3S and C3A. These results can provide guidance for the formulated design of CPNs-based admixtures.

Lead retardation on cement hydration: Inhibition and re-acceleration of clinker dissolution

Lead-bearing solid wastes strongly retard the hydration of Portland cement. In this work, the effect of Pb(NO3)2 and PbCl2 on the hydration of Portland cement and tricalcium silicate (C3S) was investigated. The results show that both Pb(NO3)2 and PbCl2 prominently delay the end of the dormant period, the setting time of cement paste, and decrease compressive strength especially at lead dosages of 1%. Conductivity, pH, and elemental concentration in C3S suspension underlined a strong effect of lead on C3S reaction kinetics. XRD and SEM-EDS measurements indicated the formation of lead silicates and chloride (hydr)oxides. Alite dissolution is probably retarded by the formation of surface complexes between Pb(II) with silanol groups on clinker surface. The increase of pH and precipitation of less soluble Pb-hydrates lowers Pb concentrations and the inhibition induced by Pb(II).

Interface Microstructure–Based Mechanical Property Evaluation of C-S-H

The grain–grain interface of cement, which is composed of the complex needle-shaped microstructure of calcium silicate hydrate (C-S-H), is crucial in the development of the mechanical properties of cementitious composites. These C-S-H needles grow radially outward from the grain surface. This work proposes a combined experimental and modeling approach to incorporate the finer details of these needle geometries and the distribution of mechanical properties in an interface-based multiscale mechanical model for hydrating tricalcium silicate (C3S). At micrometer and sub-micrometer length scales (<5 μm), electron microscopy images revealed that the geometrical nature of these needles at the grain interface varies with days of hydration. The mechanical properties of C-S-H at the nanoscale were observed to be higher at the inner core and reduced toward the outer product. The model developed can incorporate the details of these needle microstructures and their mechanical properties at the microscale and can predict the bulk properties of hydrated C3S at higher scales.

The effect of irrigating solutions on the hydration of tricalcium silicate cements: an in vitrostudy

Background:Calcium silicate cements are hydraulic cements, routinely used for perforation repairs. During such repairs, these cements are invariably exposed to irrigating solutions.Aim:This study aimed to understand the effect of irrigating solutions on the hydration of calcium silicate cements. Materials and Methods:Sixty extracted teeth were taken and horizontal sections of 2mm were obtained. These samples were randomly divided into two groups viz. Biodentine and BioMTA Plus groups later these cements were condensed into the canal spaces and allowed to set until their setting time. These samples were further subdivided and allowed to encounter three irrigating solutions viz. Normal saline, 17% EDTA, and 2% Chlorhexidine for 5 minutes. These were allowed to mature in an incubatorfor seven days and subjected to Scanning Electron Microscopy and Energy Dispersive X-ray analysis.Results: The SEM analysis of the Biodentine/control group displayed a petal-like appearance, with a Ca/Si ratio of 2. Whereas, the Biodentine/Normal saline,Biodentine/17% EDTA and Biodentine/2% Chlorhexidine group displayed crumbled paper-like appearance. The Ca/Si ratios for the Biodentine/Normal saline, Biodentine/17% EDTA and Biodentine/2% Chlorhexidine were 2.72, 1.6, and 4.21,respectively. In the BioMTA Plus group, all the SEM analyses displayed round crystalline structures in all groups. The Ca/Si ratio of BioMTA Plus/Control,BioMTA Plus/17% EDTA and BioMTA Plus/2% Chlorhexidine were25.5, 17.42, 24.1, and 39.4, respectively.Conclusion:The study concluded that the irrigating solutions did not affect the hydration mechanism of Biodentine and BioMTA Plus despite the variations in the Ca/Si ratios and surface morphology.

Mechanisms of hydration heat inhibitors on the early heat release process of cement

We evaluated the effects of hydration heat inhibitors on the early hydration heat release process of cement and its main mineral components. We used a microcalorimetric method to determine the effects of various proportions and properties of hydration heat inhibitors on the hydration of portland cement, tricalcium silicate, and tricalcium aluminate: concentration (C) = 40% m/m hydroxydiphosphonic acid (HEDP) (1-hydroxyethylidene-1,1-diphosphonic acid) and C = 40% m/m diethylene triamine pentonyphosphonic acid (DTPMPA) (diethylenetriaminepentamethylene phosphonic acid). We also analyzed and tested the heat release rate and cumulative heat release during the hydration of cement and its main mineral components. The hydration heat inhibitors decreased the heat release rate of cementitious materials by means of adsorption, chelation, precipitation, complex formation, and control of calcium hydroxide crystals. Among these materials, the hydration heat inhibitor had the most substantial effect on the composition of tricalcium silicate clinker, reducing the peak temperature at the initial stage of hydration and delaying its occurrence time. These results are pertinent to controlling and selecting the early hydrothermal release process of cement systems.

Densifying hydration products of alite by a bio-inspired admixture

A bio-inspired, plant-derived polyphenol, tannic acid (TA) was identified as a renewable admixture to improve the compressive strength of concretes. Aiming to understand the underlying mechanism responsible for this strength improvement, this study examines how TA mediates the hydration of tricalcium silicate (alite). Experimental study shows that TA can form complex with calcium ions through chelating, retarding the hydration of the alite and changing of the hydration products. Particularly, X-ray diffraction analysis shows that TA makes calcium hydroxide preferentially grow on the [001] face. Fourier-transform infrared spectroscopy and 29Si MAS NMR results reveal that the mean chain length of calcium silicate hydrate (CSH) is reduced by TA. More importantly, mercury intrusion porosimetry testing reveals that pores with size near 30 nm was almost eliminated by adding TA, leading to higher elastic modulus of the produced CSH and higher compressive strength of the produced concrete.

Hydration of blended cement with high-volume slag and nano-silica

Utilization of nano-silica is an effective method to improve the early properties of blended cement containing high-volume slag. In current work, the hydration of blended cement with high-volume slag (40 wt%, 60 wt% and 80 wt%) and nano-silica has been investigated by testing setting time, heat of hydration, compressive strength, hydration products and pore structure. The results illustrate that nano-silica can improve the hydration of slag and cement (including tricalcium silicate (C3S) hydration and transition from ettringite to monosulfate) before 3 d. The increased slag content affects the promotion of nano-silica on cement hydration. Besides, nano-silica inhibits the hydration of cement after 3 d. Furthermore, nano-silica can improve the content of chemically bound water and reduce Ca(OH)2 content. Combined use of appropriate content slag and nano-silica can better optimize the pore structure of hardened pastes, including pore size and cumulative porosity. Ultimately, nano-silica enhances the compressive strength of hardened paste, but the improvement effect of nano-silica gradually weakens with the increase of slag content and the extension of curing time. This paper can provide a theoretical basis for nano-silica modified cement with high-volume slag, and help to improve the early performance of cement with high-volume slag.