C3S Particles Research Articles

Clarifying the three stages of elasticity development during C3S hydration: Contributions of ion correlation forces and van der Waals interactions

The elasticity development of cement-based materials is primarily attributed to the hydration of C3S. Indeed, it is directly linked to the evolution of driving forces, encompassing both the ion correlation forces and van der Waals interactions. However, clarifying and distinguishing their respective contributions at each stage is really challenging. In this paper, the elasticity development of C3S-CaCO3 pastes can be divided into three stages according to the dominant driving force. The onset of the second stage occurs within the induction period, while the onset of the third stage marks the transition from the induction period to the acceleration period. During the first stage, the van der Waals interactions serve as the dominant driving force, with the role of ion correlation forces between C3S particles being secondary. Moving to the second stages, the strengthening of ion correlation forces between CSH particles become increasingly important in enhancing elasticity. In the third stage, the elasticity development stems from the combined contributions of van der Waals interactions and ion correlation forces between CSH particles. It is noted that the contribution of ion correlation forces significantly outweighs that of van der Waals interactions, with the latter being influenced by the increase in solid volume fraction.

Advancements in Heavy Metal Stabilization: A Comparative Study on Zinc Immobilization in Glass-Portland Cement Binders.

Recent literature has exhibited a growing interest in the utilization of ground glass powder (GP) as a supplementary cementitious material (SCM). Yet, the application of SCMs in stabilizing heavy metallic and metalloid elements remains underexplored. This research zeroes in on zinc stabilization using a binder amalgam of GP and ordinary Portland cement (OPC). This study juxtaposes the stability of zinc in a recomposed binder consisting of 30% GP and 70% OPC (denoted as 30GP-M) against a reference binder of 100% CEM I 52.5 N (labeled reference mortar, RM) across curing intervals of 1, 28, and 90 days. Remarkably, the findings indicate a heightened kinetic immobilization of Zn at 90 days in the presence of GP-surging up to 40% in contrast to RM. Advanced microstructural analyses delineate the stabilization locales for Zn, including on the periphery of hydrated C3S particles (Zn-C3S), within GP-reactive sites (Si*-O-Zn), and amid C-S-H gel structures, i.e., (C/Zn)-S-H. A matrix with 30% GP bolsters the hydration process of C3S vis-à-vis the RM matrix. Probing deeper, the microstructural characterization underscores GP's prowess in Zn immobilization, particularly at the interaction zone with the paste. In the Zn milieu, it was discerning a transmutation-some products born from the GP-Portlandite reaction morph into GP-calcium-zincate.

Preparation of functionalizable poly(propylene–styrene)/polyacrylonitrile millimeter‐scale particles with core‐shell morphology

AbstractCore‐Shell (CS) polymeric particles have attracted great interest due to their high mechanical, thermal, and chemical stability and their surface properties. In this study, functionalizable CS poly(propylene/styrene)/poly(acrylonitrile) (PP/PS/PAN) particles were prepared through heterogeneous polymerizations in a batch reactor. Commercial PP particles and PP/PS particles (prepared by seeded suspension polymerization of styrene (Sty) on PP spheres) were applied as core components of the final structure, while the shell was prepared through acrylonitrile dispersion polymerization. The degree of swelling of the core particles by Sty played an important role for the adhesion of the PAN shell, which for PP particles was 24 wt%, whereas for PP/PS hybrid particles it was 57 wt%. The particles (PP/PS and CS) were characterized through image analysis, revealing a uniform and smooth surface for PP/PS spheres and a uniform porous shell for CS particles. Particle size distributions, thermal degradation, chemical structures, degrees of crystallinity, and textural properties were also evaluated. The PAN shell adhered to the PP/PS particles without forming a copolymer, and the CS particles formed by a PP/PS core and PAN shell had sizes of 4.54 ± 1.24 mm, specific area of 2.70 m2g−1 and PAN content of 15.98 ± 0.82% (m/m) of total particles.

In vitro study of the embolic characteristics of imipenem/cilastatin particles

BackgroundImipenem/cilastatin (IPM/CS) has long been administered intravenously as a carbapenem antibiotic. However, since this agent is poorly soluble in liquid, occasional reports have described its use as a short-acting, temporary embolic agent. The purpose of this study was to elucidate the characteristics of IPM/CS particles, which are thought to have pain-relieving effects against osteoarthritis-related pain, as an embolic agent.MethodsThree aspects of IPM/CS as an embolic agent were evaluated in vitro: particle size; particle shape; and change in particle size over time. For particle size, the long diameter was measured.ResultsMean particle size (n=244) was 29.2±12.0 µm (range, 1–60 µm). Shape (n=109) was round in 18.35%, elliptical in 11.93%, and polygonal in 69.72%, showing that most particles were polygonal. In observations of changes in particle size over time (n=9), particles had decreased to 75% of their original size at 82±10.7 min, 50% at 89.3±9.14 min, 25% at 91.3±8.74 min, complete dissolved at 91.8±9.02 min. A rapid shrinkage in diameter was seen in the final period.ConclusionsIPM/CS particles are ultrafine and the majority display a polygonal shape. This substance shows ultra-short embolic activity. This study revealed the characteristics of a substance that demonstrates an embolic effect not found in existing embolic materials.

Hydration kinetics and mechanism of C3S with cellulose nanocrystals

Tricalcium silicate (C3S) is the primary ingredient in ordinary Portland cement (OPC). Understanding the hydration kinetics of C3S with cellulose nanocrystals (CNC) is the key to unveiling the intrinsic mechanism of CNC affecting OPC hydration. This study investigates the hydration interactions between C3S and CNC through extensive testing. Findings indicate that CNC incorporation can initially slow the hydration reaction and postpone the early-stage hydration of C3S. However, past the initial period (3 days in this study), CNC presence enhances the hydration pace and aids the hydration process, leading to an increase in the formation of calcium silicate hydrate (C–S–H) and calcium hydroxide (CH) without creating new phases. Further, the presence of CNC promotes the homogenous hydration of C3S, ensuring a homogenous distribution of hydration products. It also reduces the Ca/Si ratio in the C–S–H, without altering the C–S–H morphology. A correlation is made between heat flow and the thickness of hydration products enveloping C3S particles, confirming that CNC can intensify the inward water diffusion rate through C3S particles for the same hydration product thickness. Critically, it is found that the effect of CNC on C3S hydration is dependent on the water/C3S ratio. A low or moderate water/C3S ratio can promote C3S hydration but a very high water/C3S ratio diminishes the beneficial effects of CNC on C3S hydration. Finally, the study proposes a explanation for CNC's influence over the hydration of C3S with varying water/C3S ratios.

Interplay of unit-speed constraint and singular communication in the thermodynamic Cucker-Smale model.

We study collision avoidance resulting from unit-speed constraint and singular communication weight in a thermo-mechanical Cucker-Smale (TCS) flocking ensemble moving in a Euclidean space. The TCS model governs the flocking dynamics of the CS particles in the presence of a self-consistent temperature field. The issue of collision avoidance has been addressed in the realistic modeling of collective particle models, and it has been investigated in the CS and TCS models without unit-speed constraint. In this paper, we take one further step by examining how unit-speed constraint and singular communication weights can result in collision avoidance between particles. For this, we introduce a sufficient framework to ensure collision avoidance in terms of system parameters and initial data.

Investigation of dynamic contact between cold spray particles and substrate based on 2D SPH method

In cold spray, the study of the dynamic contact between the particle and the substrate in the high-velocity impact is essential during particle deposition. To entirely reveals the dynamic contact process, the SPH (Smoothed Particle Hydrodynamics) method is applied to virtual experiments to avoid the time-consuming and high costs in real experiments due to scale. In particular, an interface force model is proposed to completely describe the dynamic contact between the cold spray particles (CS particles) and substrate, which has the ability to eliminate the unphysical SPH particle penetration, rebounding phenomenon, and insufficient momentum transfer. The variation of the steady mean temperature of the CS particle surface with the initial velocity is analyzed and the critical velocity of particle deposition is successfully predicted. Furthermore, the effect of particle shapes on the deposition is discussed, which shows that the circular particles are more favourable to be deposited than the elliptical ones. The cold spray SPH model with the novel dynamic contact developed in this paper is in favor of understanding the mechanism of CS particles deposition and guiding the cold spray processes in a certain extent.

High Density Polyethylene/Calcium Silicate Hybrid Composite: Preparation, Characterization and <i>In-Vitro</i> Bioactivity

The high density polyethylene/calcium silicate (HDPE/CS) hybrid composites were prepared using a twin-screw extruder and shaped into test specimens using a compression molding machine. The CS loadings, limited to a total of 20 %vol, were incorporated in HDPE matrix. The morphological behavior, thermal behavior, mechanical properties and bioactivity of the composites were investigated and compared with the neat HDPE under identical conditions. It was found that poor dispersion of the CS particles was observed in the composites with high CS loadings because of only weak interaction between CS particles and HDPE. The percentage of HDPE crystallinity was insignificantly changed when adding CS particles in the HDPE/CS composites. The stiffness of the HDPE/CS hybrid composites was strongly improved and reached the maximum values of flexural and compressive moduli at 1190 MPa (35% greater than the neat HDPE) and 581 Ma (17% greater than the neat HDPE), respectively, with 15 % CS loading. The higher the CS loading, the greater the hardness of the HDPE/CS composites were seen. However, the flexural strength of the HDPE/CS composites (up to 15% CS loading) was not considerably altered. Moreover, both flexural and compressive properties were lowered with higher CS content (20%) due to the generated voids in the HDPE/CS composites. After soaking in simulated body fluid (SBF) at 36.5°C for 7–49 days, the HDPE/CS composites could induce the formation of ball-like HA aggregates covering on the composite surface, indicating its bioactivity. This research successfully prepared HDPE/CS hybrid composites with fast rate bioactivity and their modulus and strength values were within those for human trabecular bone. Therefore, the HDPE/CS hybrid composites had potentially used as bioactive materials for medical applications.

Complexes of Charged-Neutral Block Copolymers and Surfactants: Process-Dependent Features and Long-Term Stability of Their Aqueous Dispersions

Aqueous dispersions of charged-neutral block copolymers (poly(acrylamide)-b-poly(acrylate)) complexed with an oppositely charged surfactant (dodecyltrimethylammonium) have been prepared by different approaches: the simple mixing of two solutions (MS approach) containing the block copolymer and surfactant, with their respective simple counterions, and dispersion of a freeze-dried complex salt prepared in the absence of simple counterions (CS approach). The CS particles were investigated under different conditions: dispersion of a CS in salt-free water and dispersion of a CS in a dilute salt solution, the latter condition yielding dispersions with the same composition as the MS process. Additionally, aged dispersions (up to 6 months) and dispersed complexes of the polyacrylate homopolymer and dodecyltrimethylammonium surfactant were evaluated. By employing different characterization techniques, it was seen that dispersions prepared by the MS approach display nanometric spherical particles with disordered cores, and poor colloidal stability, partially caused by the absence of surface charge (ζ-potential close to zero). Oppositely, anisometric particles were formed in CS dispersions and were large enough to sustain micellar cubic cores. The CS particles presented long-time colloidal stability, partially due to a net negative surface charge, but the stability varied with the length of the neutral block composing the corona. Our results demonstrate that all dispersed particles are metastable structures, with physicochemical properties strongly dependent on the preparation procedure, thus making these particles suitable for fundamental studies and potential applications where accurate control of their properties, including size, shape, internal structure, and stability, is desired.

Physical, Thermal, and Chemical Properties of Fly Ash Cenospheres Obtained from Different Sources.

Cenospheres are hollow particles in fly ash, a by-product of coal burning, and are widely used as a reinforcement when developing low-density composites called syntactic foams. This study has investigated the physical, chemical, and thermal properties of cenospheres obtained from three different sources, designated as CS1, CS2, and CS3, for the development of syntactic foams. Cenospheres with particle sizes ranging from 40 to 500 μm were studied. Different particle distribution by size was observed, and the most uniform distribution of CS particles was in the case of CS2: above 74% with dimensions from 100 to 150 μm. The CS bulk had a similar density for all samples and amounted to around 0.4 g·cm-3, with a particle shell material density of 2.1 g·cm-3. Post-heat-treatment samples showed the development of a SiO2 phase in the cenospheres, which was not present in the as-received product. CS3 had the highest quantity of Si compared to the other two, showing the difference in source quality. Energy-dispersive X-ray spectrometry and a chemical analysis of the CS revealed that the main components of the studied CS were SiO2 and Al2O3. In the case of CS1 and CS2, the sum of these components was on average from 93 to 95%. In the case of CS3, the sum of SiO2 and Al2O3 did not exceed 86%, and Fe2O3 and K2O were present in appreciable quantities in CS3. Cenospheres CS1 and CS2 did not sinter during heat treatment up to 1200 °C, while sample CS3 was already subjected to sintering at 1100 °C because of the presence of a quartz phase, Fe2O3 and K2O. For the application of a metallic layer and subsequent consolidation via spark plasma sintering, CS2 can be deemed the most physically, thermally, and chemically suitable.

Direct observation of C3S particles greater than 10 μm during early hydration

Fast tomography, a non-destructive imaging technique, was used to study the spatial behavior of monoclinic tricalcium silicate (mC3S) from the first few seconds to one hour of hydration at a water to solids ratio of 0.43. The microstructure evolution of over 9,000 individual particles was directly observed and analyzed at 1 μm per pixel. These particles have an estimated diameter of 10 to 31 μm. These particles occupy ≈ 70 % of the total solids volume of the paste sample and so understanding the changes during hydration is important. The results show that these mC3S particles dissolve and contribute a significant amount of ions that likely participate in subsequent reactions. The dissolution of these particles occurs in localized regions with an observed depth of up to 6 µm. The findings show that these particles cannot be ignored in hydration reactions and these observations can provide further insights into the mechanism of the initial dissolution of hydration.

Direct observation of C3S particle dissolution using fast nano X-ray computed tomography

This paper uses a sequence of 3D images at a 50 nm pixel size to study the dissolution behavior of tricalcium silicate (C3S) particles with a water to solids ratio of 1.10 from 18 min to 7 h of hydration. 550 particles with dimensions ranging from 0.41 μm to 12 μm were directly observed. The results suggest that C3S particles have different dissolution rates with time; however, the dissolution rate seems to correlate well with the particle surface area and is independent of the particle size. These findings provide insights into the behavior of C3S materials and are an important step in understanding and modeling the dissolution of these materials.

Effect of citric-acid-modified chitosan (CAMC) on hydration kinetics of tricalcium silicate (C3S)

Studying the mechanism by which organic admixtures affect the hydration and dissolution of tricalcium silicate (C3S) reveals the effect of organic admixtures on ordinary Portland cement and enables target regulation of cement-based materials. In this study, the effects of citric-acid-modified chitosan (CAMC) on the hydration exotherm, hydration products, and microscopic morphology of C3S were investigated. The interface structures, ion adsorptions, and dissolution properties of CAMC and C3S were analyzed using a molecular dynamics simulation method. The results showed the presence of an attraction between the C3S surface and CAMC due to the existence of Op-Hw, Op-Cas, and Hp-Ow ion pairs. CAMC adsorbed most of the Ca ions released upon dissolution of C3S in the aqueous solution and the resulting pairs exhibited low solubilities. The Ca ions were located on the surfaces of C3S particles, preventing the dissolution of the particles and proving the interference effect of additives on the hydration of the cement silicate phase.

Towards the optimization of the Cs evaporation configuration for long pulse operation of negative ion sources

Negative ion sources for neutral beam injection rely on surface production of negative ions on a caesiated low work-function surface (plasma grid). To maintain the low work function in long pulses (one hour) and the desired source performance (extracted H-/D- ions and limited co-extracted electrons), Cs needs to be constantly delivered onto the plasma grid. The CsFlow3D code was applied to the RF driven negative ion source ELISE to simulate the evaporation and the plasma-assisted redistribution of Cs. The Cs flux stability is investigated for consecutive one hour plasma pulses and compared with experiments. The effect of different positions of the Cs oven for the case of ELISE equipped with two racetrack shaped RF drivers was investigated: a considerable increase of the Cs flux occurs when evaporating where the plasma is in contact with surfaces, as confirmed also by the back-tracking of the Cs particles reaching the PG. Additionally, an alternative evaporation method close to the plasma grid was designed with the help of CsFlow3D and tested in BATMAN Upgrade, with the aim of increasing the Cs flux onto the PG and achieve a better control of caesiation in long pulses.

Evolution of the particle size distribution of tricalcium silicate during hydration by synchrotron X-ray nano-tomography

The particle size distribution of tricalcium silicate (C3S) is essential for the modelling of early C3S hydration kinetics. In this study, this parameter is analysed during the main hydration period until the first 20 h by synchrotron near-field ptychographic (NF-PXCT) and holographic (HXCT) computed nano-tomography. Additionally, X-ray diffraction, 29Si NMR, thermal analysis, scanning electron microscopy, and inductively coupled plasma-optical emission spectroscopy were used to investigate the system evolution. The time-dependent pore solution composition is also provided to gain further information.HXCT and NF-PXCT show comparable values regarding the evolution of the C3S particle size distribution during hydration, indicating that C3S particles smaller than 1.3 μm are completely dissolved after 20 h of hydration. The results can be reasonably reproduced by numerical models if for all particle sizes a constant reacted rim thickness for each degree of hydration is assumed. Data on the aqueous phase composition are also provided.

Influence of Particle Internal Pores on Hydration Kinetics and Microstructure Development in Tricalcium Silicate Hydration

AbstractThe accurate reconstruction of the morphologic organization of reactants would be a crucial aspect in understanding tricalcium silicate (C3S) hydration. However, C3S particles are generally...

Emergent behaviors of a thermodynamic Cucker‐Smale flock with a time‐delay on a general digraph

We present emergent flocking dynamics of a thermodynamic Cucker‐Smale (TCS) flock on a general digraph with spanning trees under the effect of communication time‐delays. The TCS model describes a temporal evolution of mechanical and thermodynamic observables such as position, velocity and temperature of CS particles. In this paper, we study how variations in mechanical and thermodynamic variables can decay to zero along a time‐independent network with position dependent weights from initial state configuration. For this, we provide a sufficient framework for a mechanical and thermodynamical flocking in terms of initial configuration, network topology, and system parameters. We also present several numerical examples and compare them with analytical results.

Reinforcement of agricultural wastes liquefied polyols based polyurethane foams by agricultural wastes particles

AbstractFour kinds of agricultural wastes particles (XS: oilseed rape straw [OS], rice straw [RS], wheat straw [WS], and corn stover [CS]) were used to reinforce agricultural wastes liquefied polyol (P‐XS) based polyurethane (PU) foam. Different XS loading dosages (0% ~ 15%) are investigated to confirm suitable filler concentrations for modifying foams. RS particles show great promoting ability, OS particles reveal complex influence, while WS and CS particles display mild effect on foaming process. With 1% of OS, 6% of RS, 3% of WS, or 1% of CS incorporating in matrix materials, the reinforced foam could keep applicable density, reach better physical and mechanical property, display more uniform cellular structure, and show higher thermal stability with more excellent water absorption ability. Using of agricultural wastes as polymer filler is economical, simple, environmental, and wide applicable for biomass utilization and biopolymer preparation.

Effect of grain size on the physicomechanical properties

Abstract In this study, locally available waste coconut (Cocos nucifera) shells (CSs) were investigated as possible replacement for asbestos-based brake pads. The CS-based brake pad was tested for its physicomechanical properties and compared with a commercial brake pad used as control sample. The results showed that (a) an improved interfacial bonding between the CS particles and the binder as the grain size decreases; (b) the 90 μm grain size sample had better physicomechanical properties than the control sample in all tests except the thermal conductivity and stability tests; and (c) the hardness, compressive strength, and density of the CS-based brake pad decreased with increasing grain size, whereas the absorption properties increased with increasing grain size. The study showed that further reduction of the grain size below 90 μm and matrix impregnation with metals of good thermal conductivity could provide significant improvements to properties of the CS-based brake pad.

Simulations of diffusion-controlled and dissolution mechanisms with respect to the deceleration period of tricalcium silicate hydration

The macroscopic properties of concrete are largely determined by the deceleration period of cement hydration. Tricalcium silicate (C3S), a major component of Portland cement clinker, is usually utilized as a material model to investigate hydration controlling mechanisms. However, there still exist debates on the controlling mechanisms during different hydration periods. Lack of complete knowledge of hydration controlling mechanisms would lead to incorrect predictions about the macroscopic properties of cement or concrete. The diffusion-controlled and dissolution mechanisms are utilized to explain the occurrence of the deceleration period. However, in terms of the diffusion-controlled mechanism, the analysis on the occurrence of the deceleration period which is affected by the coupled effects of factors remains lacking. In addition, in terms of the dissolution mechanism, the effect of the evolution of the interfacial dissolution rate or reactive surface area on the occurrence of the deceleration period is still not clear. The purpose of this study was to analyze the above issues and to verify the two mechanisms through a simulation analysis. A new simulation model considering the diffusion-controlled and dissolution mechanisms was proposed. The obtained results indicated that: (1) The simulation considering the dissolution mechanism alone would lead to a higher degree of hydration under practical water to cement ratio during the deceleration period, compared with the experiment. (2) The anisotropic dissolution of C3S particles would transform into the isotropic dissolution when the hydration entered the deceleration period. (3) The initial fall in the hydration of C3S could be reproduced by the simulation model proposed in this study under the consideration of the dissolution mechanism. (4) If the deceleration period was caused by the dissolution mechanism, the dominant factor would be the decrease of the reactive surface area rather than the evolution of the interfacial dissolution rate. (5) The occurrence of the deceleration period should not be ascribed to the diffusion-controlled mechanism, because the time when this mechanism worked was later than the time when hydration rate started to decrease.