Decrease In Elastic Modulus Research Articles

Application of recycled concrete aggregates in continuous-graded cement stabilized macadam

This study investigates the potential of using recycled concrete aggregate (RCA) derived from construction and demolition waste as a replacement for natural aggregate in cement-stabilized macadam (CSM). Various substitution rates of RCA, ranging from 0 % to 100 %, were examined with a focus on mechanical properties and durability, including unconfined compressive strength (UCS), indirect tensile strength (ITS), compressive elastic modulus, drying shrinkage, frost resistance, scour resistance, and water damage resistance. Nanoindentation was used to analyze the interfacial transition zones (ITZs) within the CSM. The results show that with a fixed cement content, the UCS, ITS, and compressive elastic modulus decrease as the RCA content increases. Higher RCA content also leads to reduced drying shrinkage, frost resistance, scour resistance, and water damage resistance. Nanoindentation revealed that ITZ1 and ITZ2 have similar thicknesses (∼50 μm), while ITZ3 is about 80 μm thick, highlighting the intricate physical composition of ITZs, including pores, low-density C-S-H, high-density C-S-H, and Ca(OH)2. These findings provide critical insights for optimizing sustainable CSM design using RCA, thereby promoting environmental sustainability in road construction.

The Mechanical Properties of Orthodontic Aligners of Clear Aligner After Intraoral Use in Different Time Periods.

Although the technique of orthodontic aligners has risen in popularity, their mechanical properties have not been thoroughly investigated. The aim of this study was to evaluate the mechanical properties of the orthodontic aligners Clear Aligner after intraoral use for 7, 10 and 14 days, and to compare them with as-received aligners (0 days). It was also sought to examine the properties of the unprocessed raw material (polyethylene glycol terephthalate) used to manufacture these aligners. Thirty-two aligners by four patients were evaluated and studied at 0, 7, 10, 14 days of use. Each aligner was divided into three segments (two posterior and one anterior), which resulted in 96 samples. Also, 16 samples of unprocessed material were studied. For all samples, elastic modulus, ultimate tensile stress (UTS) and yield stress were calculated by conducting tensile testing. Additionally, material hardness was tested. The two-tailed Mann-Whitney test was performed, having set the level of significance at p = 0.05. Analysis of the measurements indicated a statistically significant decrease in elastic modulus between days 0 and 14 of use, of UTS between days 0 and 7, 7 and 10, and of yield stress between days 0 and 7. For hardness, in every period, posterior segments demonstrated significantly higher values than anterior segments. All properties of the unprocessed material were statistically significantly higher than the processed samples. The unprocessed material presented significant differences in every property tested in comparison to the processed aligners. The processed material showed further deterioration over time during use. The present study provides evidence that thermoforming and ageing affect the mechanical properties of the aligners.

Ensemble machine learning models for compressive strength and elastic modulus of recycled brick aggregate concrete

This study delivers an in-depth analysis of predicting the compressive strength and elastic modulus of recycled brick aggregate concrete (RBAC). It assembles an extensive database of 633 compression test results and develops five ensemble learning models—random forest (RF), gradient boosting regression trees (GBRT), extreme gradient boosting (XGB), light gradient boosting machine (LGBM) and stacking (St). These models are evaluated against existing empirical formulas with respect to their effectiveness. The findings reveal that machine learning (ML) models outperform existing formulas: for compressive strength prediction, traditional models achieve a maximum determination coefficient R² of 0.38, whereas ML models attain an R² range of 0.91–0.94. For elastic modulus, the highest R² values are 0.44 for traditional models and 0.97 for ML models. Notably, the LGBM and St models excel in predicting compressive strength and elastic modulus, respectively. The study also identifies critical parameters influencing RBAC’s compressive behavior and highlights their impact trends. Remarkably, while the mass-weighted water absorption of coarse aggregates and the replacement ratio of recycled brick aggregates (RBAs) have less impact on compressive strength compared to the effective water-to-cement ratio, they become more influential for elastic modulus. Additionally, the decrease in elastic modulus due to higher RBA replacement ratios or increased mass-weighted water absorption of coarse aggregates exceeds the corresponding reduction in compressive strength. This research not only deepens the understanding of RBAC’s mechanical properties but also provides valuable predictive tools for civil engineering applications.

The Influence and Mechanism of Polyvinyl Alcohol Fiber on the Mechanical Properties and Durability of High-Performance Shotcrete

This study investigates the impact of polyvinyl alcohol (PVA) fibers on the mechanical properties and durability of high-performance shotcrete (HPS). Results demonstrate that PVA fibers have a dual impact on the performance of HPS. Positively, PVA fibers enhance the tensile strength and toughness of shotcrete due to their intrinsic high tensile strength and fiber-bridging effect, which significantly improves the material’s splitting tensile strength, deformation resistance, and toughness, and the splitting tensile strength and peak strain have been found to be increased by up to 30.77% and 31.51%, respectively. On the other hand, the random distribution and potential agglomeration of PVA fibers within the HPS matrix can lead to increased air-void formations. This phenomenon raises the volume content of large bubbles and increases the average bubble area and diameter, thereby elevating the pore volume fraction within the 500–1200 μm and >1200 μm ranges. Therefore, these microstructural changes reduce the compactness of the HPS matrix, resulting in a decrease in compressive strength and elastic modulus. The compressive strength exhibited a reduction ranging from 10.44% to 15.11%, while the elastic modulus showed a decrease of between 8.09% and 12.67%. Overall, the PVA-HPS mixtures with different mix proportions demonstrated excellent frost resistance, chloride ion penetration resistance, and carbonation resistance. The electrical charge passed ranged from 133 to 370 C, and the carbonation depth varied between 2.04 and 6.12 mm. Although the incorporation of PVA fibers reduced the permeability and carbonation resistance of shotcrete, it significantly mitigated the loss of tensile strength during freeze–thaw cycles. The findings offer insights into optimizing the use of PVA fibers in HPS applications, balancing enhancements in tensile properties with potential impacts on compressive performance.

Factors Influencing Measurement of Dynamic Elastic Modulus from Disk-Shaped Concrete Specimen

The decrease in dynamic elastic modulus is a primary indicator of quantitative damage in concrete. To quantitatively assess depth-by-depth damage within a concrete structure, cylindrical specimens obtained through coring can be cut into disk specimens to measure the dynamic elastic modulus of concrete at each depth. To minimize external damage during coring, it is essential to extract cylinders with the smallest possible diameter. In addition, for higher resolution in depth-based damage assessment, creating disk specimens with the smallest possible thickness is necessary. However, there is no information available in the literature on experimental limitation of smallest possible diameter and thickness for dynamic elastic modulus of disk-shaped specimens. This study evaluated whether the dynamic modulus measured from various sizes of concrete disk specimens provided sufficient reliability compared to reference values obtained from cylinders. Moreover, the study examined how the presence of coarse aggregate and variation in the water–cement ratio significantly influenced the dynamic modulus measurement. In addition, test results from impulse excitation technique (IET) and impact resonance (IR) were compared to find a more reliable test method for dynamic elastic modulus of disk specimen. The experimental findings revealed that as the thickness-to-radius ratio of the disk specimens decreased, measured data variation increased. Mortar specimens without coarse aggregates showed less variability compared to concrete specimens, and the variation in dynamic modulus measured by IR was lower than that measured by IET.

Contact fatigue property of diamond-like carbon films with different structure in cyclic impact conditions

Repeated contact with high loads can cause damage to the surface of the DLC films and thus affect their fatigue strength. This study systematically investigates the contact fatigue damage of the DLC films with different carbon structures (a-C, a-C:H, and ta-C) by macro-scale cyclic impact tests with alternating loads. The results reveal that the a-C film possesses significantly superior contact fatigue property compared to the a-C:H and ta-C films under high load. The graphitization transformation of the a-C and a-C:H films lead to a decrease in hardness and elastic modulus. The work-hardening of the ta-C films results in an increase in hardness and elastic modulus. The findings indicate that under cyclic load impact conditions, films need a combination of load support and fatigue resistance to achieve optimum lifetime, and solely increasing film hardness could be accompanied by brittle fracture and higher wear.

Deposition of cellulose acetate coatings on titanium substrates by electrospraying for biomedical applications

Functional coatings have gained interest in the field of metal implants, as they reduce the complications associated with mechanical parameters and promote its integration. Among the other coating production methods electrospraying remains very little researched for this application despite its advantages. This study investigates the feasibility of the electrospraying method for the production of coatings with extended mechanical properties. Six biocompatible cellulose acetate coatings from solutions of (6–16) wt% were fabricated on titanium substrates using electrospraying. The layer thickness varied between the samples from 1.8 to 16.4 μm, while the roughness varied between the samples from 1 to 2 μm. Bending tests showed that the maximum elongation of the coatings between the samples gradually decreased from 40.00 % to 13.33 %. Stretching of detached films revealed decrease in tensile strength and elastic modulus from 58 to 30 MPa and from 2082 MPa to 978 MPa, respectively. Pull-off tests showed coatings adhesion strength of 0.8–1.4 MPa after sandblasting. Investigation of chemical composition and structure of the coatings using X-ray photoelectron spectroscopy, Fourier-transformed infrared and Raman spectroscopy showed results typical of cellulose acetate materials and confirmed that no structural changes took place during electrospraying. X-ray diffraction analysis revealed that the coatings obtained are amorphous. The coatings produced by the fast and cost-effective electrospraying process have competitive overall properties, while the coatings prepared from 10 and 12 wt% solutions are most suitable for use on titanium surfaces due to their mechanical properties and uniformity.

Mechanical properties and damage constitutive relationship of microwave irradiation of granite under uniaxial compression

Microwaves have great potential to increase the efficiency of hard rock breakage during mechanical excavation in engineering. This study conducted uniaxial compression tests on granite specimens after microwave irradiation at 4.85 kW. The results demonstrated a linear decrease in uniaxial compressive strength and elastic modulus correlating with increasing irradiation durations. Acoustic emission data indicated increased normalized crack closure stress and decreased normalized crack initiation and damage stress, suggesting complex crack propagation and evolution patterns under microwave influence. 3D Digital Image Correlation revealed that as heating time increased, the macrocrack leading to specimen failure shifted from being load-dominated to involving both load and microwave-induced thermal cracks. A simple four-parameter damage constitutive model for granite (a 1, r 1 , a 2, and r 2) effectively described the damage evolution under the coupling effect of microwave and uniaxial load. The model accurately characterized the complete stress–strain curves, including both microcrack compaction and post-peak stages, revealing that initial damage escalates with longer heating, though the progression rate decreases.

Influence of β Grain Orientation on the Stress‐Induced Martensite Formation in Cold‐Rolled Metastable β Ti–5Mo–5V–5Al–3Cr Alloy

Solution‐treated metastable β Ti–5Mo–5V–5Al–3Cr (Ti 5553) alloy processed through cold rolling at strain levels of 5–45% results in stress‐induced martensitic transformations (SIMT). Further, the cold‐deformed sample is annealed at 860 °C for 5 min to achieve recrystallization and relieve internal stresses. The influence of recrystallized β grain orientations on Ti‐5553 deformation behavior is characterized using nanoindentation tests. As β grain orientation changes from near <111> to <001> direction, the alloy exhibits an increase in hardness (from ≈6.3 to ≈6.6 GPa) and a decrease in elastic modulus (from ≈127 to ≈120 GPa). It can be inferred that a threshold stress is necessary to activate SIMT in each orientation due to the stress gradient from the top surface to the indent tip at a certain penetration depth in the sample. Additionally, the influence of alloying elements (e.g., Mo, V, Al, and Cr) on β phase stability as a function of grain orientations is confirmed using the electron probe microanalyzer. Observations indicate that <111> grain orientation is most preferred, followed by <101> for promoting stress‐induced martensite, while <001> is least preferred.

Three-dimensional free-standing heterostructures out of MoS2 and rGO with infused PDMS towards electromechanical pressure sensing

Abstract The behavior of two-dimensional (2D) materials constructed as three-dimensional structures is studied to bring such materials one step closer to the real-life application. Lattices structures of gyroid triply periodic minimal surface (TPMS) were fabricated out of 2D materials, namely, molybdenum disulfide (MoS2), and reduced graphene oxide (rGO), forming for the first time free-standing MoS2 (FSM) lattice and free-standing hetero-structural lattice of MoS2 and rGO (FSH) out of TPMS. These 2D materials were also integrated with polydimethylsiloxane (PDMS) elastomer, forming FSM/PDMS and FSH/PDMS composites. Mechanical characterization, including compression and cyclic tests, were conducted on FSM, FSH, and the composites. Additionally, electromechanical characterization was conducted to evaluate the sensing potential of these structures. It is worth noting that the elastic modulus of the 10 unit-cells with either FSM or FSH was higher than the other lattices of the same type. FSH tends to have a higher modulus at 1504.4 kPa in the 10 unit-cells. This modulus is even higher at 3 MPa when PDMS is added to the FSH lattice. Due to the brittle fracture, FSM or FSH lattices follow the layer-by-layer failure mechanism. Samples with PDMS are more stable towards such cyclic tests without noticeable failures or a decrease in elastic modulus. Finally, the 10 unit-cell lattices of FSH/PDMS composite have the highest conductivity at 2.5 mA, and a comparable sensitivity at 0.365 kPa−1 over the range of 0–100 kPa.

A FDEM study on the mechanical properties and failure behavior of soft-hard interbedded rocks considering the size effect

Soft–hard interbedded rocks are widely distributed at the Earth’s surface, and their mechanical properties and failure behavior directly affect the stability of local tunnel and slope engineering projects. Previous studies have rarely considered the influence of size effects on the mechanical properties and failure behavior of such rocks. Therefore, this paper used the combined finite–discrete element numerical method (FDEM) to study the mechanical properties and failure behavior of soft–hard interbedded rock samples considering the size effect. First, appropriate input parameters were calibrated and verified by using a new parameter calibration method. Second, the effects of the element size and loading rate were studied to obtain appropriate model parameters. Finally, the effects of the layer number, sample size, and height–diameter ratio of composite rock samples on their mechanical properties and failure behavior at different layer dip angles and layer thickness ratios were investigated. The results support the following findings: (1) For the composite rock samples with a layer thickness of 10 mm, reliable simulation results can be obtained by using a 2.2 mm element size, and the loading rate should not exceed 0.2 m/s in FDEM numerical modeling. (2) The number of layers in the sample should be at least 5, and when the height–diameter ratio is a constant 2.0, the height of the sample should not be less than 110 mm. (3) As the height–diameter ratio of the composite rock samples increases, both the compressive strength and elastic modulus decrease for all layer dip angles considered, but the rock failure mode changes for layer dip angles of 15–75°; in addition, the sample size effect is most significant for layer dip angles of 60° and 75°. (4) Taking horizontally layered composite rock samples as examples, both the compressive strength and elastic modulus of samples with different layer thickness ratios decrease with increasing height–diameter ratio and their failure modes also depend on the height–diameter ratio.

Experimental and simulation studies on damage characteristics, crack development patterns, and strength reduction mechanisms of sandstone under laser irradiation

In order to explore the damage characteristics and crack development laws of hard rock under laser irradiation, laser irradiation experiments on sandstone were conducted considering the interaction of three laser parameters: spot diameter, laser power, and irradiation time. Subsequently, uniaxial compression experiments were conducted on sandstone samples before and after laser irradiation. In addition, based on the maximum principal stress intensity criterion and finite element software, laser induced fracturing sandstone simulation experiments were conducted. Research has found that: Laser irradiation significantly reduces the uniaxial compressive strength of sandstone, with a maximum reduction of about 88.9%, and is also accompanied by a significant decrease in elastic modulus. The degree of sandstone damage escalates with increasing laser power and irradiation time, alongside a reduction in spot diameter. Strong correlations were observed between the strength reduction rate and crack metrics like opening, area, and depth, enabling the establishment of a high-precision regression model. Cracks originate internally within sandstone, initially extending diagonally upwards toward the specimen’s surface before propagating outward. These findings elucidate the mechanisms behind sandstone’s strength reduction and crack propagation under laser irradiation, providing some insights for the practical application of laser rock breaking technology in engineering.

Mesoscopic Numerical Simulation of Freeze–Thaw Damage in Hydraulic Concrete

To investigate the impact of freeze–thaw damage on the mechanical properties of concrete, this study utilized Python in combination with ABAQUS 2016 to generate a two-dimensional meso-scale model of concrete. Uniaxial compression tests were conducted on the concrete after freeze–thaw cycles to study the evolution of its mechanical properties. Using “relative compressive strength” as a variable, the relationships between this variable and the parameters of the freeze–thaw damage model were determined, leading to the establishment of the freeze–thaw damage model and the simulation of compressive tests on concrete after freeze–thaw cycles. This study also explored the changes in the mechanical properties of concrete with variations in ITZ parameters and coarse aggregate content. The conclusions drawn are as follows: A comparison with experimental data showed that the model ensures that the relative error of each mechanical property parameter does not exceed 7%, verifying the model’s rationality. Increasing the ratio of ITZ parameters improved the mechanical properties of the ITZ, enhancing the overall mechanical performance, but had almost no effect on the elastic modulus. Compared to ratios of 0.7 and 0.8, concrete with a ratio of 0.9 showed slower rates of decrease in compressive strength and elastic modulus and slower rates of increase in peak compressive strain after freeze–thaw cycles. The increase in coarse aggregate content had a similar effect on the strength and freeze–thaw resistance of concrete as the ratio of ITZ parameters. Concrete with a coarse aggregate content of 60% exhibited slower rates of change in mechanical properties after freeze–thaw cycles.

Flexural properties of bamboo scrimber under different temperature conditions: Experimental study and mathematical model

Changes in ambient temperature significantly affect the flexural properties of bamboo scrimber. From the perspective of structural safety, temperature is one of the most important conditions to be considered when using structural components made of bamboo scrimber. This experimental study investigated the flexural performance of bamboo scrimber across a broad temperature range of −30 °C to 250 °C, providing essential data for its use as a structural member under different temperature conditions. Through a series of tests conducted at different temperature conditions with utilization of scanning electron microscopy, the damage modes and failure mechanism of bamboo scrimber were analyzed at both macroscopic and microscopic levels. It was found that the failure modes of bamboo scrimber under different temperature conditions were mainly categorized as simple tensile fracture damage, split tensile damage and brittle tensile fracture damage, in which the brittle tensile fracture damage only occurred in the specimens at a temperature of 250 °C. In general, the flexural strength and modulus of elasticity decrease with increasing temperature; when the temperature was increased from 20 °C to 250 °C, the specimens' flexural strength and modulus of elasticity decreased by 87.95 % and 90.25 %, respectively. Microscopic analysis revealed that these variations were correlated with alterations in the shape, structure and composition of the internal cells. Moreover, based on the Hognestad model, a mathematical relationship model between the load-displacement curves of bamboo scrimber and the temperature was derived, which can accurately predict the flexural load capacity of bamboo scrimber under varying temperature conditions.

A methodology for evaluating damage in thin-walled cylindrical shells using bounded ultrasonic beam scattering

This paper introduces an ultrasonic detection methodology specifically designed to assess damage in thin-walled cylindrical shells, which crucially relies on the interaction between a bounded ultrasonic beam and a thin-walled cylindrical shell immersed in fluid, considering both water-filled and air-filled cavities. Initially, we derive the scattered sound field expression for a bounded ultrasonic beam obliquely striking the shell. Subsequently, through finite element simulations and experimental verification, we observe that when the incident bounded beam is emitted at the critical angles defined in this study, early damage significantly enhances the received sound pressure amplitude detected by a symmetrically positioned receiver. Notably, a mere 5 % decrease in the shell's elastic modulus leads to a notable 233.69 % increase in the area under the amplitude-frequency curve of the received sound pressure for water-filled cavities and a remarkable 642.85 % surge in area for air-filled cavities. Experimental data further validates the sensitivity of this method towards varying corrosion damage states. This approach combines the reliability of linear ultrasonic methods with the enhanced sensitivity of nonlinear ultrasonic techniques, offering a significant advancement over traditional ultrasonic detection methods for inspecting cylindrical shells. The proposed assessment method holds immense potential in providing novel insights for inspecting cylindrical shells in practical applications.

Physical Properties of Cellulose Derivative-Based Edible Films Elaborated with Liposomes Encapsulating Grape Seed Tannins.

Combined use of edible films (EF) with nanoencapsulation systems could be an effective alternative for improving the films' physical properties and maintaining bioactive compounds' stability. This research work focuses on the combined use of EF of cellulose-derived biopolymers enriched with liposomes that encapsulate grape seed tannins and on the subsequent evaluation of the physical properties and wettability. Tannin-containing liposomal suspensions (TLS) showed 570.8 ± 6.0 nm particle size and 99% encapsulation efficiency. In vitro studies showed that the release of tannins from liposomes was slower than that of free tannins, reaching a maximum release of catechin of 0.13 ± 0.01%, epicatechin of 0.57 ± 0.01%, and gallic acid of 3.90 ± 0.001% over a 144 h period. Adding liposomes to biopolymer matrices resulted in significant decrease (p < 0.05) of density, surface tension, tensile strength, elongation percentage, and elastic modulus in comparison to the control, obtaining films with greater flexibility and lower breaking strength. Incorporating TLS into EF formulations resulted in partially wetting the hydrophobic surface, reducing adhesion and cohesion compared to EF without liposomes. Results indicate that the presence of liposomes improves films' physical and wettability properties, causing them to extend and not contract when applied to hydrophobic food surfaces.

Evaluating impact damage on carbon fiber-reinforced polymer plates utilizing zero-group-velocity Lamb waves

This paper presents an effective method for evaluating the impact damage of composite plates using zero-group-velocity (ZGV) Lamb waves. A finite element (FE) model of the carbon fiber-reinforced polymer (CFRP) plate is established to analyze in detail the propagation characteristics of the S1-ZGV Lamb wave mode with a specified propagation direction. The study investigates the changes in the S1-ZGV mode with varying damage levels, characterized by a decrease in elastic moduli. Results indicate that as the damage level increases, the corresponding S1-ZGV frequency and amplitude decrease proportionally. The spectral amplitude (SA) at the initial S1-ZGV frequency exhibits a consistent and significant decrease with increasing damage levels, offering a reliable method for accurately assessing damage in CFRP plates. Additionally, the S1-ZGV mode of the CFRP plate is experimentally excited using the pitch-catch technique with air-coupled ultrasonic transducers to explore the variations in the S1-ZGV mode with different impact damages. Experimental findings show that the SA of the S1-ZGV mode at the initial S1-ZGV frequency decreases monotonically and sensitively with an increasing number of impacts. These experimental results correlate with the FE analysis, validating the effectiveness of accurately evaluating impact damage in CFRP plates based on the SA of S1-ZGV modes.

Comparative study on mechanical properties and biomineralization of hooks in the diaspores of three epizoochorous plant species

Most of the plants using epizoochory show adaptations to this diaspore dispersal strategy by having the diaspores covered by barbs, hooks, spines or viscid outgrowths, which allow diaspores to easily attach to an animal surface. Many previous studies have been mainly focused on the dispersal distances and efficiency, or effectiveness of diverse attachment structures depending on their size, anatomy, and morphology. However, the knowledge about the mechanical properties of these structures remains rather poor. In this study, we use a combination of scanning electron microscopy, energy dispersive X-ray element analysis and nanoindentation, to examine the microstructure, biomineralization and mechanical properties of single hooks in Arctium minus, Cynoglossum officinale and Galium aparine. Both the biomineralization and mechanical properties of the hooks strongly differ in examined plant species; mechanical properties depend on the biomineralization pattern, such as the accumulation of silicon and calcium. Elastic modulus and hardness decrease in the series C. officinaleG. aparineA. minus. Anisotropic mechanical properties are found between the radial and longitudinal directions in each single hook. By characterizing the mechanical properties and biomineralization of plant hooks, this paper contributes to the understanding of attachment biomechanics related to seed dispersal. Statement of significanceThe dispersal of seeds is essential for plant survival. Many of the plants that use the outside surface of animals to transport the seeds show adaptations to this dispersal strategy by having the seeds covered with hooks. Although these hooks have various sizes, morphologies and anatomical structures, all of them provide mechanical interlocking to animal surfaces. To reduce the risk of interlocking failure, the hooks are usually reinforced by mineralization. However, the relationship between mineralization, mechanical properties and specialized function of plant hooks has been largely overlooked. Here we perform a characterization study on the hooks of three plant species. Our results deepen the current understanding of the mineralization-material-function relationship in specialized hooks of plant seeds.

Research Progress in the Application of Calcium-based Expansive Agents as Compensation for Autogenous Shrinkage in High-strength Concrete

In this study, comprehensive investigation of the shrinkage compensation mechanisms of calcium-based expansive agents (CEAs), their effects on the properties of (ultra) high-strength concrete (HSC/UHSC), and the existing problems in applying this methodology was conducted. Analyses showed that the rational use of CEAs under certain conditions could greatly or completely inhibit the development of autogenous shrinkage of HSC/UHSC, and significantly reduce the risk of associated cracking. However, it was found that the hydration of the CEAs affected the hydration process of other binders, thereby altering the microstructure of concrete. This was in turn observed to lead to a degree of decrease in compressive strength, flexure strength and elastic modulus, and the decrease rate increasing as with the rise in proportion of CEAs. Moreover, when attempting to improve the shrinkage compensation effects, increasing the amount of CEA presented a risk of delayed expansion cracking of HSC/UHSC. Neither the expansion mechanism, expansion conditions, nor the inhibition methods have yet been fully clarified in the current stage. Lastly, newly proposed Ca-Mg composite EAs were outlined, and the research prospects of Ca-Mg composite EAs in HSC/UHSC were explored.

Effect of temperature on the nanoindentation behavior of monocrystalline silicon by molecular dynamics simulations

Monocrystalline silicon (Si) undergoes complex phase transformations under external loads, significantly affecting its performance and processing. In this study, molecular dynamics (MD) simulations are performed from 1 to 900 K to explore temperature effects on the mechanical properties and deformation behavior of monocrystalline silicon during nanoindentation. Results indicate that hardness and elastic modulus decrease with rising temperature. At lower temperature, the activation of plastic deformation is delayed. The suddenly release of stored elastic energy manifests as a pop-in event. The indentation creates a quadruple symmetric phase transformation zone, primarily consisting of Si-II at the core, flanked by Si-XIII and bct-5. Increasing temperature advances the plastic deformation of the sample. High temperatures facilitate the formation and subsequent phase transformation of Si-XIII, reduce the stability of bct-5 during unloading, and promote the amorphization of silicon. At high temperatures, the dislocation of silicon nucleates at the subsurface, resulting in the formation of a substable phase. The anisotropy of deformation is evident from the atomic perspective, based on the orientation dependence of the phase transformation. This research provides new insights into the deformation behavior and phase transformations of monocrystalline silicon, supporting manufacturing and application of silicon products.