Chain Length Research Articles

Natural and anthropogenic forcing of ecological and environmental changes at Lake Qilu, SW China, since the last deglaciation

The ecological evolution of lakes and their watersheds and the driving mechanisms are a key topic in paleoenvironmental research. However, the relative impacts of human activities and climate change on lake ecosystems since the last deglaciation remain unclear. We conducted a high-resolution study of the chain length distribution and concentration of n-alkanes in a sediment core from Lake Qilu in SW China, to reveal the ecological changes and their controlling factors since 14.6 cal kyr BP. Based on studies of modern samples, short-chain, medium-chain, and long-chain n-alkanes are associated with bacteria/algae, aquatic plants, and terrestrial plants, respectively. Combining the ACL17–33, Paq, and Σn-alkane indices, we found that both aquatic and terrestrial plants proliferated at Lake Qilu from 14.6 to 6 cal kyr BP, which was associated with a relatively warm and wet climate and dynamic strong winds. During the interval from 6 to 2 cal kyr BP, aquatic plants flourished, accompanied by a rapid surge in the regional productivity, primarily due to human activities. After 2 cal kyr BP, anthropogenic eutrophication was the primary cause of the increase in bacteria and algae populations. These results suggest that, before 6 cal kyr BP, climatic factors dominated the n-alkanes distribution; whereas after 6 cal kyr BP, human activities became the primary factor controlling the n-alkanes and ecological changes in Lake Qilu.

Uncovering the mechanism controlling strength and microstructural evolution of belite-rich cement-based materials at different temperatures

The effect of temperature on the properties of belite-rich cement-based (BRC) materials is different from that on Portland cement (PC). This study provides a comprehensive understanding of the mechanisms controlling strength and microstructural evolution at different temperatures, especially C-S-H characteristics, of BRC materials. Phase assemblage, pore structure, and microscopic morphology of BRC paste, as well as phase composition and structure, chemically bound water, and bulk density of C-S-H were investigated using X-ray diffraction (XRD), thermogravimetric analysis (TGA), 1H and 29Si nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The strength of BRC mortar increased with temperature is because of the higher hydration degree of β-C2S, lower porosity (except for 60 °C), and increased main chain length (MCL) of C-S-H. Hydration degrees of 28-d β-C2S and C3S increased by 202.5% and 16.3%, respectively, while MCL increased by 39.4% from 5 to 60 °C. The higher temperature sensitivity of β-C2S is due to its activation energy being 12.4% greater than that of C3S in BRC paste. Additionally, gel porosity decreased with temperature due to decreased bound water content and increased 16.7% bulk density of C-S-H from 5 to 60 °C. Finally, the CaO/SiO2 was inversely proportional to MCL and bulk density, but positively to H2O/SiO2. The findings deepen the mechanistic understandings of the hydration kinetics and microstructural evolution for temperature-affected BRC material.

Valorization of levulinic acid by esterification with 1-octanol using a novel biocatalyst derived from Araujia sericifera

Levulinic acid, which can be obtained from biomass, has sparked great interest as a biologically-based chemical building block with wide versatility and potential. Its esterification with alcohols of different chain lengths is a promising valorization process for obtaining esters with various applications in the areas of biofuels/biolubricants, food and cosmetics, among others. In this work, the enzymatic esterification of levulinic acid and 1-octanol using a biocatalyst derived from Araujia sericifera latex was studied in systems with and without solvent. The influence of the molar ratio between alcohol and acid (ranging from 2:1–1:9), the biocatalyst loading (between 7.5 % and 17.5 % relative to the acid), the volume of n-heptane used as reaction solvent (from 0 to 4 ml), and the reaction time (6 hours) were investigated. The activity and stability of the biocatalyst in successive uses were also analyzed. A conversion of 49 % was achieved when the reaction was carried out in a solvent-free system, using an alcohol/acid molar ratio of 1:7 and after 5 h of reaction. On the other hand, the conversion was 65.1 % when the reaction was conducted in a system containing 1 ml of n-heptane as solvent, an alcohol/acid molar ratio of 1:8, and 5 h of reaction. In both cases, a temperature as low as 30 °C and an agitation speed of 300 RPM were used.

Enhancing emulsion stability and adsorption of Pickering emulsions using alkylated cellulose nanofibers

Cellulose nanofibers (CNFs) extracted from plant cell walls form a three-dimensional network in water and stabilize the dispersion of droplets, which are used as emulsion stabilizers. In this study, four types of alkyl-grafted CNFs (ACNFs) with different lengths of dialkyl chains (diC4, diC6, diC8, and diC10) were synthesized by the surface modification of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized CNF (TOCNF) to improve the stability of oil-in-water Pickering emulsions (PEs). The ACNF-stabilized emulsions with a 20/80 ratio of oil/water were prepared using two different oils (olive oil and eucalyptus oil) and the ACNF 1.0 % dispersion, and the changes over time were investigated at approximately 25 °C. Compared to TOCNF, the ACNFs provided more stable olive oil-PE (o-PE) and eucalyptus oil-PE (e-PE) although the stabilization behaviors of o-PE and e-PE differed. Olive oil, which contained rich long-chain fatty acids, was more likely to interact with the ACNFs, thereby promoting the interfacial adsorption of oil droplets. On the other hand, eucalyptus oil is mainly composed of 1,8-cineole and does not have alkyl chains, so the interaction with the ACNFs was weak and therefore, sufficient interfacial adsorption could not be obtained. The results of the particle size distribution and viscosity measurements also showed that the ACNFs contributed significantly to the stabilization of o-PE. Based on the overall experimental results, it was determined that the diC6-ACNF gave the most significant stability improvement. Therefore, we designed an alkylated CNF that mimics diC6-ACNF for MD simulations. MD simulations showed that hydrophobic modification created a hydrophobic interaction between the alkyl chain and dodecane molecules as the oil, leading to the enhancing adsorption of ACNF at the oil droplet interfaces.

Constructing potential energy surface for carbon-chain containing systems using the radial angular network with gradual expansion method.

Investigating molecular excitation induced by collisions requires the prior determination of accurate analytical potential energy surfaces for the colliding partners. For carbon-chain molecules, such as cyanopolyynes, this has been a longstanding challenge, resulting in the absence of rate coefficients for HC5N, HC7N, HC9N, and others, induced by collisions with He. To overcome this bottleneck, we introduce a new approach: the Radial Angular Network with Gradual Expansion (RANGE). This method jointly connects the construction of abinitio interaction potentials with the determination of their analytical forms. We use the HC3N-He molecular complex as a reference to assess the reliability of our method, given that its analytical potential has been derived using various methods. Additionally, we apply the RANGE approach to construct the analytical representation of the interaction potential for HC5N-He and HC7N-He. The analysis of the analytical potentials reveals three systematic trends: (i) the anisotropy increases with the length of the carbon chain, (ii) the number of local minima correlates with the number of carbon atoms, and (iii) the shallowest local minimum is consistently located at ∼30 cm-1 below the dissociation limit of the complex. Using the time-independent quantum mechanical close-coupling formalism, we briefly estimate the propensity rules governing the excitation of HC3N, HC5N, and HC7N induced by collisions with He. Consequently, the three collisional systems exhibit the same propensity rule, favoring Δj = 2 transitions.

Comprehensive Analysis of Input Shaping Techniques for a Chain Suspended from an Overhead Crane

Abstract This work investigates the use of input shaping techniques for controlling oscillations in a chain suspended from an overhead crane, aiming to enhance crane operations without sacrificing speed or safety. The study focuses on two specific input shaping strategies: step-input and polynomial-input shapers. The step-input shaper applies discrete changes at determined intervals, whereas the polynomial-input shaper utilizes a continuous function to adjust the crane's input throughout its operation. Numerical simulations assess the effectiveness of these techniques in reducing oscillations across various vibration modes of the chain and examine their impact on overall system performance metrics such as maneuver time, kinetic energy, robustness, and operational smoothness. Results from comprehensive simulations indicate that both input shapers significantly eliminated residual vibrations found in time-reduced inputs. The polynomial-input shaper demonstrated enhanced performance in decreasing the residual kinetic energy, and it promoted smoother operation and better adaptability to variations in chain length.

Remediation of per- and polyfluoroalkyl substances (PFAS) contaminated soil via soil washing with various water-organic solvents

The feasibility of soil washing for remediating PFAS-contaminated clay soil using various water-organic solvents was systematically investigated based on the combination of batch and column tests. Batch tests using 22 types of solvents highlighted that 0 % (water) and 5 % solvents could effectively extract PFCAs (≤ C9), while long-chain PFCAs (≥ C10) and PFSAs required 80 % solvents for optimal extraction, with efficiency in the order of EtOH ≤ MeOH < Acetonitrile (ACN), suggesting a strong correlation with carbon chain lengths and functional head groups. Column tests with six selected washing solutions indicated rapid desorption of PFOA and PFOS initially, peaking at liquid-to-solid (L/S) ratios of 3–4 for 0 % and 5 % solutions, and at an L/S ratio of 1 for 80 % solutions. To remediate 1 kg-dry soil to meet the legislatively permissible levels for groundwater in Japan (PFOA + PFOS < 50 ng/L), 11 L of 0 % solution (water) or 5 L of 80 % ACN are required for washing out PFOA, while 62 L of 0 % solution (water) or 53 L of 80 % ACN for PFOS. Future research should address the treatment of PFAS-rich wastewater generated from washing PFAS-contaminated soils and the impacts of washing solutions on soil.

Understanding the effect of alkyl chain on extraction of Np4+ and Pu4+ with hexaalkyl nitrilotriacetamides into an ionic liquid vis-à-vis a molecular solvent

Extraction of actinides using exotic ligands in room temperature ionic liquids is one of the most preferred areas of research these days. Though the amides are well studied for the extraction of actinides from nitric acid feeds, multiple amides (such as tripodal amides) are of recent origin, and reports on solvent extraction with these ligands in room temperature ionic liquids are very rare. In this work, the extraction of Np4+ and Pu4+ was studied with a series of N,N,N′,N′,N″,N″-hexaalkyl nitrilotriacetamides (NTAamides) in an ionic liquid with an objective to understand the effect of the alkyl chains length on their extraction ability. Bumim⋅Tf2N was chosen as ionic liquid due to its favourable viscosity for distribution studies. The extraction of tetravalent actinides Np4+ and Pu4+ increased linearly with increasing the alkyl chain of the NTAamides from n-butyl via n-hexyl to n-octyl. The extraction pattern was surprisingly opposite to the most observed extraction patterns in an ionic liquid, where the extraction generally decreases sharply upon increasing the feed acidity. The extracted species were ascertained as M(NO3)5⋅L (LH), where M = Np4+ or Pu4+, for each ligand. Consequent to the formation of an entirely divergent extracted complex, the extraction pattern is completely different than that expected in an ionic liquid.

Critical Evaluation and Meta-Analysis of Ecotoxicological Data on Per- and Polyfluoroalkyl Substances (PFAS) in Freshwater Species.

Despite the increasing concern regarding the ecological risks posed by per- and polyfluoroalkyl substances (PFAS), a lack of comprehensive understanding of their actual ecotoxicity remains. Through a meticulous examination of 91 peer-reviewed studies investigating effects at a population level and constructing probabilistic species sensitivity distributions (PSSDs), we present a state-of-the-science hazard assessment of PFAS in freshwater species. Using data subsets containing suboptimal data led to an overestimation of the predicted no-effect concentrations (PNECs) of PFAS. We report PNECs of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonates (PFSAs) in freshwater to be 4.8-2000 μg/L and 0.4-8.9 μg/L, respectively, derived from high-quality data. Statistical analyses revealed that both functional groups and carbon chain length significantly influenced (p < 0.05) the variations in toxicity observed among different PFAS. This study underscores the importance of obtaining high-quality PFAS ecotoxicity data to comprehend associated hazards. The PNECs of PFAS derived in this study are higher compared to those of micro/nanoplastics and persistent organic pollutants. Our research offers valuable insights into prioritizing the regulation of more toxic PFAS.

Differentiated adsorption of acetaminophen and diclofenac via alkyl chain-modified quaternized SBA-15: Insights from molecular simulation

The increasing presence of pharmaceuticals and personal care products (PPCPs) in aquatic systems pose significant environmental concerns. This study addresses this issue by synthesizing quaternized mesoporous SBA-15 (QSBA) with varied alkyl chain lengths of C1QSBA, C8QSBA, and C18QSBA. QSBA utilizes dual mechanisms: hydrophobic interactions via the alkyl chain and electrostatic attraction/ion exchange via the ammonium group. Diclofenac (DCF) and acetaminophen (ACT) were selected as target PPCPs due to their contrasting dissociation properties and hydrophobicity, which are the main characteristics of PPCPs. The adsorption of DCF and ACT revealed that longer alkyl chains enhanced the adsorption capacity of ACT through hydrophobic interactions, whereas dissociated DCF (DCF–) adsorption was superior owing to its high hydrophobicity (log Kow = 4.5) and electrostatic attraction. pH levels between 6 and 8 resulted in a high affinity for DCF–. Notably, among the three alkyl chains, only C18QSBA exhibited the most effective adsorption for DCF–. These PPCPs adsorption trends were confirmed through molecular simulations of adsorption under conditions in which competing ions coexisted. The molecular simulations show that while DCF– has lower adsorption energy than Cl−, OH−, and H3O+ ions in QSBA, enhancing its adsorption under various pH conditions. Conversely, ACT exhibits a higher adsorption energy, which reduces its adsorption efficiency. This suggests the potential application of QSBA with long alkyl chains in the treatment of highly hydrophobic and negatively charged PPCPs. Furthermore, this study emphasizes the importance of simulating adsorption under competing ion conditions.

Transport of a comb-like polymer across a nanochannel subject to a pulling force.

We investigate the dynamics of comb-like polymer translocation through a nanochannel using three-dimensional Langevin dynamics simulations based on a coarse-grained chain model. A comprehensive set of simulations are performed to examine the effects of system parameters such as the grafting densityρof the side chains, the polymer chain length, the nanochannel dimensions, and the magnitude of the pulling force on the translocation dynamics. For a given polymer chain length, keeping the backbone length is constant while varyingρ, we have found that the dependence of the mean translocation time⟨τ⟩onρis non-monotonic, with a maximum translocation time for a specificρat which the translocation is the slowest. The simulation results also show that⟨τ⟩is not significantly affected by the channel width above a certain radius, while the comb-like polymer translocation is hindered by a narrower channel due to increased interactions between the chain monomers and the channel. In addition,⟨τ⟩increases linearly with the nanochannel length. A linear scaling relationship between the mean translocation time⟨τ⟩and the chain lengthNof polymer is obtained,⟨τ⟩∼N. Similarly, the dependence of⟨τ⟩on the backbone chain sizeNbbhas a quasi-linear dependence,⟨τ⟩∼Nbb. On the other hand, the translocation velocityvfollows a power-law relationship with the polymer chain lengthNasv∼N-1. The mean translocation time also shows an inverse linear relationship with the magnitude of the pulling forceF,⟨τ⟩∼F-1. The power-law relationships discovered in this study contribute to the fundamental understanding of the comb polymer translocation dynamics and to establishing a framework for further investigations in this field.

Influence of solid residence time on the phosphorus adsorption of extracellular polymer substances

Influence of solid residence time (SRT) on phosphorus (P) adsorption of extracellular polymer substances (EPS) was investigated from the perspectives of the contents, compositions and properties of loosely bound and tightly bound extracellular polymers (i.e., LB-EPS and TB-EPS) and microbial community structure. The TP contents of EPS were 59.6±6.0 - 87.4±4.4 mg·g-1 VSS and 63.7% - 68.1% of those of sludge, which was still underestimated due to the residual TB-EPS protecting cell membrane integrity. The influences of SRT on the yield and compositions of TB-EPS were obviously greater than those of LB-EPS. Compared with the SRTs of 12 d and 18 d, the significant P storage enhancement of biological P removal (BPR) sludge with the SRT of 25 d was related with the increases of TB-EPS yield, polyP content and average chain length in TB-EPS. The P adsorption property of TB-EPS was slightly increased through increasing SRT, while the K, Mg and Ca adsorption properties were markedly reduced. Increasing extracellular P content could kept good BPR efficiency at longer SRTs, but the loss risk of phosphorus accumulating organism dominance was increased. Additionally, adding Mg and Ca salts might improve extracellular P adsorption at longer SRTs.

Phenotypic Analysis and Gene Cloning of Rice Floury Endosperm Mutant wcr (White-Core Rice).

The composition and distribution of storage substances in rice endosperm directly affect grain quality. A floury endosperm mutant, wcr (white-core rice), was identified, exhibiting a loose arrangement of starch granules with a floury opaque appearance in the inner layer of mature grains, resulting in reduced grain weight. The total starch and amylose content remained unchanged, but the levels of the four component proteins in the mutant brown rice significantly decreased. Additionally, the milled rice (inner endosperm) showed a significant decrease in total starch and amylose content, accompanied by a nearly threefold increase in albumin content. The swelling capacity of mutant starch was reduced, and its chain length distribution was altered. The target gene was mapped on chromosome 5 within a 65 kb region. A frameshift mutation occurred due to an insertion of an extra C base in the second exon of the cyOsPPDKB gene, which encodes pyruvate phosphate dikinase. Expression analysis revealed that wcr not only affected genes involved in starch metabolism but also downregulated expression levels of genes associated with storage protein synthesis. Overall, wcr plays a crucial role as a regulator factor influencing protein synthesis and starch metabolism in rice grains.

Elucidating maternal provisioning for bivalve larvae under ocean acidity extreme events

Ocean acidity extreme (OAX) events, triggered by climate change and anthropogenic activities, are projected to become more intense and frequent in coastal ecosystems, devastating marine bivalves and ecosystems they support. Maternal effects adaptively modulate offspring performance in response to climatic stressors, but whether and to what extent they can confer offspring resistance to OAX remain largely unknown. Here, we investigated impacts of OAX on the parental and larval lipidomes of Manila clams (Ruditapes philippinarum) to add further insights into the energetic nature of maternal effects. A total of 177 significantly down-regulated lipid components (categorized into glycerolipids mainly) were shown in OAX-stressed adults compared with those reared under ambient conditions, and following parental conditioning, larvae also exhibited a further decreasing down-regulation of the glycerolipid components. Triacylglycerols were identified as the predominant composition of glycerolipids and the primary sources of energy for gonadal maturation and larvae development. Yet, larvae spawn from adults exposed to OAX had significantly lower contents of triacylglycerols than those without a prior history of parental conditioning, with the carbon chain length and unsaturation degree of the triacylglycerol components being significantly affected. The latter was also in line with significant increases in the production of triacylglycerol byproducts (diacylglycerols). Overall, our findings suggest that when OAX prevailed during reproductive seasons of Manila clams, maternal effects could be maladaptive by depressing the energetic deposition of larvae, and may not be a potential adaptive modulator of marine bivalves to cope with unprecedented environmental change.

Synthesis and Mechanism of a Green Scale and Corrosion Inhibitor.

A new green water treatment agent, a poly(aspartic acid)-modified polymer (PASP/5-AVA), was synthesized using polysuccinimide and 5-aminovaleric acid (5-AVA) in a hybrid system. The structure was characterized, and the scale and corrosion inhibition performance were carried out with standard static scale inhibition and electrochemical methods, respectively. The mechanism was explored using XRD, XPS, SEM, and quantum chemistry calculations. The results indicated that PASP/5-AVA exhibited better scale and corrosion inhibition performance than PASP and maintained efficacy and thermal stability of the scale inhibition effect for a long time. Mechanistic studies indicated that PASP/5-AVA interferes with the normal generation of CaCO3 and CaSO4 scales through lattice distortion and dispersion, respectively; the combined effect of an alkaline environment and terminal electron-withdrawing -COOH groups can induce the stable C- ionic state formation in -CH2- of the extended side chain, thus enhancing its chelating ability for Ca2+ ions. At the same time, the extension of the side chain length also enhances the adsorption ability of the agent on the metal surface, forming a thick film and delaying the corrosion of the metal surface. This study provides the necessary theoretical reference for the design of green scale and corrosion agents.

Electrolytes from Alkoxyalkyl-substituted Imidazolium ionic liquids. Synthesis, characterization, properties and cell performance in LiFePO4 half-cells

Electrolytes based on lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt and alkoxyalkyl-substituted imidazolium ionic liquids (ILs) have been studied. We have synthesized three different 1-alkoxyalkyl-3-methylimidazolium TFSI salts with different chain lengths (from 4 to 10 atoms) and with one to three oxygen atoms at position 1- of the imidazole ring. Both the neat ILs as well as the cognate lithium doped electrolytes have been structurally and physicochemically characterized and electrochemically evaluated.Thermal analyses indicate that the glass transition temperature of the electrolytes is displaced to higher temperatures than those of the corresponding neat ILs, being also higher (more positive) upon increasing the number of oxyethylene units. On the other hand, all 1 M LiTFSI doped synthesized electrolytes are thermally stable up to 300 °C.Raman spectroscopy results indicate that the fraction of TFSI anions coordinated to lithium ion decreases on increasing the number of alkoxy units. This finding implies that there is more “free” lithium ion available to link to the ethereal oxygen of the side chain of the imidazolium ring system. This fact influences the ionic conductivity of the neat ILs and their cognate electrolytes.The electrochemical properties —namely high room temperature conductivities as well as wide electrochemical stability windows— indicate that these materials are promising electrolytes for lithium-ion batteries (LIBs). Lithium half-cells using LiFePO4 (LFP) olivine have been assembled in order to assess the electrochemical performance by means of both cyclic voltammetry and galvanostatic charge/discharge tests. Overall, we have found that the electrochemical performance of these cells is better than that reported 1 M LiTFSI [Pyr14][TFSI], a common electrolyte in LIBs. The generated half-cell from the 1-alkoxyalkyl-3-methylimidazolium TFSI salts possess a high capacity up to 145 mAh∙g−1 at a current of 2C.The results reported herein show a striking relationship between structure and properties.

Discrete Cyclic Polymers with Uniform Chain Length

Discrete Cyclic Polymers with Uniform Chain Length

Atypical sphingosine-1-phosphate metabolites—biological implications of alkyl chain length

AbstractSphingosine-1-phosphate (S1P) is a bioactive lipid signaling molecule with pleiotropic implications by both auto- and paracrine signaling. Signaling occurs by engaging five G protein-coupled receptors (S1P1-5) or intracellular pathways. While the extensively studied S1P with a chain length of 18 carbon atoms (d18:1 S1P) affects lymphocyte trafficking, immune cell survival and inflammatory responses, the biological implication of atypical S1Ps such as d16:1 or d20:1 remains elusive. As S1P lipids have far-reaching implications in health and disease states in mammalian organisms, the previous contrasting results may be attributed to differences in S1P’s alkyl chain length. Current research is beginning to appreciate these less abundant atypical S1P moieties. This review provides an up-to-date foundation of recent findings on the biological implications of atypical S1P chain lengths and offers a perspective on future research endeavors on S1P alkyl chain length–influenced signaling and its implications for drug discovery.

A theoretical exploration of monomer activation mechanisms in bis-lithium N[sbnd]heterocyclic carbenes complexes for enhanced understanding of charge distribution in ring-opening polymerization of ε-caprolactone

A comprehensive examination was conducted on the ring-opening polymerization (ROP) mechanism of ε-caprolactone (ε-CL) employing bis-lithium N-heterocyclic carbene complexes (bisLiNHCs) in a theoretical framework. The modeled reactions were carried out utilizing density functional theory at B3LYP level. An activated-monomer mechanism was observed, characterized by occurrence of two distinct transition states. Initiating with activation of ε-CL via two lithium atoms from bisLiNHCs catalysts, the ensuing step involved nucleophilic addition of carbonyl group stemming from the lithium benzoxide (LiBnO) initiator. The ring opening ε-CL was accomplished via classical cleavage of acyl-oxygen bond. The determination of reaction barrier heights for ε-caprolactone with bisLiNHCs catalysts involved the examination of potential energy profiles. The computed energy profiles revealed exothermic characteristics for each ROP reaction, with the identification of a rate-determining step occurring at the second transition state, which entailed cleavage of acyl-oxygen bond from monomer. Furthermore, through comparisons catalytic capabilities of bisLiNHCs derivatives and energy barrier heights, it was observed that the length and flexibility of linker chain as well as steric effects from substituent groups, significantly influenced the geometric configuration. These specific variations induce alterations in both distance and angular orientation, which are pivotal aspects influencing the chelation dynamics between lithium and oxygen atoms.

Molecular dynamics study on structural characteristics of amorphous C‐S‐H with different Ca/Si ratios

AbstractAs the major hydration product of cement, hydrated calcium silicate (C‐S‐H) governs the overall performance of cement‐based materials. The molar ratio of CaO to SiO2 (Ca/Si ratio) significantly affects the structure and properties of C‐S‐H. This study analyzed the effect of Ca/Si ratios (0.83–2.0) on the structural morphology evolution, bond lengths and angles, polymerization process, and nanoporosity of amorphous C‐S‐H, with the help of the ReaxFF force field. The results showed that the reacted C‐S‐H tend to form a fibrous network‐like morphology at low Ca/Si ratios, while the silicate chains are prone to accumulating at high Ca/Si ratios, forming a dense granular ovoid structure. Meanwhile, the Ca/Si ratio has no effect on the bond lengths and angles. In addition, the Ca2+ ions can interrupt the silicate chains during hydration, which leads to a decrease in the average silicate chain length with increasing Ca/Si ratio. The porosity of C‐S‐H decreases from 59.3% to 54.3% when the Ca/Si ratio increases from 0.83 to 2.0. It can be deduced from these findings that the increase in the Ca/Si ratio decreases the compressive strength of cement‐based materials but increases their durability.