Interlocking Effect Research Articles

Discrete Element Analysis of the Dynamic Mechanical Characteristics of Ballasted Track on Bridges Under Train Loading

The operation and service performance of ballasted track on bridges face significant challenges due to high-speed railway train operations. To investigate the mechanical characteristics of ballasted track on bridges, field experiments were conducted. A coupling model of ballasted track on a simply-supported girder bridge was established using the coupling method of discrete element and multi-flexible body dynamics and analyzes the changes in ballast bed settlement deformation, stiffness and energy with increasing load cycles. The findings reveal that dynamic loading alters the original contact state of ballast particles, displaying notable anisotropy vertically and longitudinally and isotropy horizontally. The vibration of ballast particles on bridges is more pronounced than on the subgrade, with vibration acceleration under the sleeper at 150[Formula: see text]mm depth on the bridge being 2.89 times that on the subgrade foundation. As the system stabilizes, the interlocking effect among granular ballast particles strengthens, reducing mutual sliding and increasing ballast bed stiffness by approximately 7.8–9.5% compared to the initial state, while total energy and dissipated energy gradually decrease. It is recommended to monitor the quality of ballast particles under the sleeper of ballasted tracks on bridges, implement vibration mitigation measures, or periodically replace ballast particles.

Study on the Morphological Distribution and Modeling Methods of River Particles in Upstream and Downstream Sections

This study investigates the morphological evolution of river particles and their mechanical behavior during sediment transport. River particles exhibit distinct shape differences between upstream and downstream sections, with particles becoming progressively rounded downstream. The rounding process is quantitatively described using morphological indices. The analysis reveals upstream particles are more angular, while downstream particles become increasingly rounded due to erosion and abrasion, modeled by a unified abrasion function. The Loop subdivision method effectively simulates this gradual rounding process. Additionally, the Discrete Element Method (DEM) calculates the natural angle of repose for particles with varying erosion levels, showing angles ranging from 38.2° for angular particles to 34.4° for rounded particles, closely matching field observations. The numerical results effectively demonstrate the interlocking effect caused by particle morphology. This research enhances the understanding of sediment transport dynamics and provides a robust framework for modeling particle shape evolution.

Formation of the Interlock Morphology and Its Role in Refill Friction Stir Spot Welding of Aluminum Alloy to Steel

Considering energy conservation and emission reductions, lightweight automobiles have become a research focus in the automotive industry. Steel/aluminum joining is regarded as an ideal lightweight structure, which can not only reduce the energy consumption but also ensure safety and is already attracting extensive attention. In this study, aluminum alloy 6061 and B410LA steel sheets were successfully joined by refill friction stir spot welding. The tensile properties, microhardness distribution and interfacial microstructure characteristics of the steel/Al welded joints were investigated. The maximum tensile load of the steel/Al joint was 4.3 kN. The mechanical properties of the steel/Al refill friction stir spot welded joint were largely determined by the bonding quality of the sleeve-plunging zone. With the stirring of the sleeve and the pin during the refill friction stir spot welding, work hardening occurred in the stir zone (SZ). The microhardness of the SZ was significantly higher than that of the steel base metal (BM) and could be detected on the steel side. The Fe-Al intermetallic compound (IMC) layer was continuously distributed at the interface of the sleeve-plunging zone, revealing good uniformity in the thickness. In particular, a hook-and-vortex-like structure formed during the refill friction stir spot welding process in the sleeve-plunging zone, producing a mechanical interlock effect at the interface. The ideal mechanical properties of the welded joint could be attributed to the good quality of the metallurgical and mechanical bonding at the interface, especially the mechanical interlock effect, thereby depending on the hook-and-vortex-like structure.

Precision-induced localized molten liquid metal stamps for damage-free transfer printing of ultrathin membranes and 3D objects

Transfer printing, a crucial technique for heterogeneous integration, has gained attention for enabling unconventional layouts and high-performance electronic systems. Elastomer stamps are typically used for transfer printing, where localized heating for elastomer stamp can effectively control the transfer process. A key challenge is the potential damage to ultrathin membranes from the contact force of elastic stamps, especially with fragile inorganic nanomembranes. Herein, we present a precision-induced localized molten technique that employs either laser-induced transient heating or hotplate-induced directional heating to precisely melt solid gallium (Ga). By leveraging the fluidity of localized molten Ga, which provides gentle contact force and exceptional conformal adaptability, this technique avoids damage to fragile thin films and improves operational reliability compared to fully liquefied Ga stamps. Furthermore, the phase transition of Ga provides a reversible adhesion with high adhesion switchability. Once solidified, the Ga stamp hardens and securely adheres to the micro/nano-membrane during the pick-up process. The solidified stamp also exhibits the capability to maneuver arbitrarily shaped objects by generating a substantial grip force through the interlocking effects. Such a robust, damage-free, simply operable protocol illustrates its promising capabilities in transfer printing diverse ultrathin membranes and objects on complex surfaces for developing high-performance unconventional electronics.

Impact sensing, localization and damage assessment in Fiber-Reinforced composites with ZnO Nanowires-Based sensor array

The structural integrity and monitoring of load distributions in composites are critical for safety and economic efficiency but still challenging. Herein, zinc oxide nanowires (ZnO NWs) were embedded into a carbon fiber-reinforced composite serving as mechanical reinforcement and sensing components. The presence of ZnO NWs in the composite material increased the flexural strength, interlaminar, and interfacial shear strength by respectively 4.9 %, 8.8 %, and 19.9 % due to the strong bonding at the fiber/resin interface and the mechanical interlocking effect. Additionally, the piezoelectric nature of ZnO NWs with an asymmetric crystal structure generated piezoelectric charges under stress, thereby enhancing the sensitivity of capacitive monitoring. A self-developed algorithm was then designed to analyze the array capacitance changes collected from the prepared composite laminate to determine the impact load with high precision with an error margin of 3 mm and not exceeding 0.25 MPa. Furthermore, damage was also able to be detected by monitoring capacitance changes. Overall, the proposed high-precision and minimally aggressive approach for load localization and quantification provides a promising direction and strategic pathway for the development of smart self-monitoring composites.

Simultaneous enhancement in mechanical properties and flame retardancy of reed charcoal/polypropylene composites by graphene oxide interfacial modification

Biochar/polypropylene composites (BPCs) have great potential in automobiles and building materials due to their ease of processing and light weight. However, the inferior interfacial bonding strength between biochar and polypropylene (PP) and flammability of PP often result in the weak mechanical properties and poor flame retardancy of BPCs, which limit the practical applications of BPCs. Herein, graphene oxide (GO) is used as an active interfacial modifier to prepare graphene-reed charcoal/polypropylene (G-RC/PP) composites. Benefiting from the mechanical interlocking effect formed by GO, the G-RC/PP composites exhibit higher tensile and flexural strengths. When 1 % of GO was added (relative to mass of RC), the tensile and flexural strengths were 22.84 MPa and 50.8 MPa, respectively, which are 16 % and 22.7 % higher than pure PP. Additionally, the barrier-adsorption-dilution synergetic effects of GO enhance both the thermal stability and flame retardance of the composites. The total heat release rate of G-RC/PP composites is reduced by 71.6 % compared to RC/PP when GO was added at 1 %, resulting in a substantial reduction in fire hazards. This study offers a fresh perspective on the development of biochar/plastic composites with exceptional mechanical properties and high fire safety towards extensive applications as automotive parts and building structures.

A review of mixture design and preparation methods for high-performance recycled aggregate concrete

Recycled aggregate concrete (RAC) has been widely investigated for recent decades, during which there are a great deal of findings on the modification of RAC to overcome the drawbacks of RA, i.e. high absorption and low strength. In this paper, four methods for designing and preparing RAC are reviewed, including the particle packing method (PPM), equivalent mortar volume (EMV) method, two-stage mixing approach (TSMA) and distributing-filling coarse aggregate (DFCA) process, and their effects on the properties of RAC is compared to reveal the effective approaches to high-performance preparation of RAC. Among these methods, only TSMA presents a positive effect on the workability of RAC. In terms of the properties of hardened RAC, TSMA improves the compressive strength and penetration resistance by densifying the ITZs around RA, and the developed TSMAsc containing silica fume exhibits better efficiency in improving the properties of RAC. The EMV method and DFCA process are beneficial to the compressive strength, elastic modulus and volumetric stability of RAC, and the effectiveness of the DFCA process is superior to the EMV method, indicating that enhancing the coarse aggregate interlocking effect is an effective approach to obtain high-performance RAC. Furthermore, the combination of TSMA and EMV methods can synthesize the enhancements of ITZs and coarse aggregate interlocking effect, contributing to a further improvement in the properties of hardened RAC. It is conceived that the TSMA and DFCA process can be integrated as a promising combination to realize the high performance of RAC.

An efficient synergistic double-sided friction stir spot welding method: A case study on process optimization, interfacial characteristics and mechanical properties of 2198-T8 aluminum‑lithium alloy joints

Friction stir spot welding has important applications in the joining of thin metallic plates. However, the asymmetric thermomechanical action inherent in the single-sided friction stir spot welding inevitably generates the hook defect at the joint interface, and the defect deteriorates with the improvement of the interfacial metallurgical bonding, which causes the irreconcilable contradiction and significantly restricts the breakthrough of the process stability and welding efficiency. The synergistic double-sided probeless friction stir spot welding (SDP-FSSW) technology proposed in this study adopts a dual-axis synergistic control system, which introduces intense plastic deformation from both sides of the interface to form a wavy hook by accurate axial motion during the welding process. This innovative process solves the problem of hook warpage while realizing rapid metallurgical bonding and mechanical interlocking at the interface, thus obtaining AA2198-T8 aluminum‑lithium alloy spot joints with a tensile/shear strength exceeding 9kN in a short dwell time (0–3 s). Through response surface methodology, the optimal process parameters are identified, i.e. rotation speed of 603 rpm, dwell time of 3 s, and plunge depth of 0.26 mm, at which condition the average joint strength is 13.0 ± 0.5kN, a 47 % increase compared to an optimized joint of single-sided probeless friction stir spot welding (8.9kN). The optical microscope examination shows that the wavy hook can be adjusted by the rotation speed and the higher rotation speeds will make the wave disappear and produce an approximately straight interface. The fractographic analysis shows that the wavy hook can inhibit crack propagation and has good mechanical interlocking effect, but the flat hook at high rotation speeds leads to crack propagation directly along the interface, and the failure mode is changed from plug-pull fracture to interfacial fracture. Therefore, the joint strength at 1000 rpm is only 7.0kN, which decreases by about 47 % compared with the optimal strength. The electron backscattering diffraction analysis shows that continuous dynamic recrystallization occurs in the hook region and good metallurgical bonding is formed, and there are also some discontinuous dynamic recrystallized grains distributed between the large grains due to the larger strain rates and lower temperature at the interface during the SDP-FSSW process. It has been found that the wavy hook with good metallurgical bonding and mechanical interlocking can be introduced in spot welded joints by controlling the interface forming, which is a viable method to create high quality, efficient and reliable spot joints.

Realization of Joints of Aluminosilicate Glass and 6061 Aluminum Alloy via Picosecond Laser Welding without Optical Contact.

To achieve laser direct welding of glass and metal without optical contact is hard, owing to the large difference in thermal expansion and thermal conductivity between glass and metal and an insignificant melting area. In this study, the high-power picosecond pulsed laser was selected to successfully weld the aluminosilicate glass/6061 aluminum alloy with a gap of 35 ± 5 μm between glass and metal. The results show that the molten glass and metal diffuse and mix at the interface. No defects such as microcracks or holes are observed in the diffusion mixing zone. Due to the relatively large gap, the glass collapsed after melting and caulking, resulting in an approximately arc-shaped microcrack between modified glass and unmodified glass or weakly modified glass. The shape of the glass modification zone and thermal accumulation are influenced by the single-pulse energy and linear energy density of the picosecond laser during welding, resulting in variations in the number and size of defects and the shape of the glass modification zone. By reasonably tuning the two factors, the shear strength of the joint reaches 15.98 MPa. The diffusion and mixing at the interface and the mechanical interlocking effect of the glass modification zone are the main reasons for achieving a high shear strength of the joint. This study will provide reference and new ideas for the laser transmission welding of glass and metal in the non-optical contact conditions.

Fracture properties and acoustic emission characteristics of manufactured sand recycled fine aggregate concrete

To promote the application of recycled fine aggregates, fracture characteristics of concrete beams containing manufactured sand (MS) and recycled fine aggregate (RFA) were investigated. The fracture properties and acoustic emission (AE) characteristics of manufactured sand recycled fine aggregate concrete (MSRFAC) with 0 %, 25 %, 50 %, 75 % and 100 % RFA replacement rates were evaluated by three-point bending test of single-sided notched beams. The fracture mechanisms of MSRFAC beams were explored using AE and digital image correlation (DIC) techniques, and fracture process zone (FPZ) was qualitatively and quantitatively analyzed. The results indicated that the critical nominal stiffness, initial fracture toughness, fracture energy and characteristic length of MSRFAC decreased significantly with the increase of RFA replacement rate, up to 20.2 %, 37.7 %, 22.8 %, and 26.6 %, respectively, while the unstable fracture toughness was insensitive to the variation of RFA. Moreover, the AE activity, the tensile crack, large-scale crack, high amplitude, and high peak frequency in MSRFAC increased with increasing RFA replacement rate. According to the FPZ characteristics of MSRFAC, its FPZ length increased with the increase of RFA replacement rate, while the FPZ width decreased with the increase of RFA replacement rate. The critical FPZ lengths of MSRFAC with different RFA replacement rates were about 20.2–30.0 mm, and the maximum FPZ widths were about 26.0–36.7 mm. The RFA weakened the friction mechanism and interlocking effect between aggregates of MSRFAC, resulting in a faster FPZ propagation rate and smaller damage width of MSRFAC than normal manufactured sand concrete.

New OpenSees material model for simulating reinforced concrete shear walls subjected to coupled axial tension and cyclic lateral loads

In high-rise buildings, reinforced concrete (RC) shear walls, particularly those forming part of coupled wall systems or core wall systems, may be subjected to coupled axial tension and cyclic lateral loads during strong seismic events. A new two-dimensional material model named the “Fixed Angle Model Considering Crack Sliding” (FAM-CS) was proposed for simulating the nonlinear behavior of RC walls subjected to axial tension and cyclic lateral loads. The proposed model was implemented in the OpenSees platform. Nonlinear constitutive models for shear aggregate interlock effects of concrete and dowel action of rebars were incorporated into the proposed model to represent the shear transfer mechanisms along concrete cracks. The proposed model was validated against the test data of six wall specimens subjected to coupled axial tension and cyclic lateral loads. The results indicated that the proposed model reasonably predicted the lateral strength capacity (an average error of 6.2 %) and the residual strength at the maximum drift loading (an average error of 12.3 %) of the specimens. For comparison, three other commonly used models, the Shear-Flexure Interaction Multiple-Vertical-Line-Element-Model, the multi-layer shell element model and the Cyclic Softened Membrane Model were adopted for the simulation of the specimens. Compared with the three existing OpenSees models, the newly implemented material model provided improved predictions of the wall hysteretic behavior with respect to lateral strength capacity, lateral strength degradation, pinching characteristics and cyclic stiffness degradation. In addition, the proposed model reasonably captured the localized failure pattern as well as the energy dissipation characteristics of the test specimens. Finally, a mesh sensitivity study was conducted to assess the robustness of the proposed model. The results revealed that the proposed model was robust regarding the lateral load-drift responses of RC walls, with a mesh size ranging from approximately one to three times the average crack spacing.

Ionic Liquid-Accelerated Growth of Covalent Organic Frameworks with Tunable Layer-Stacking.

Layer-stacking behaviors are crucial for two-dimensional covalent organic frameworks (2D COFs) to define their pore structure, physicochemical properties, and functional output. So far, fine control over the stacking mode without complex procedures remains a grand challenge. Herein, we proposed a "key-cylinder lock mimic" strategy to synthesize 2D COFs with a tunable layer-stacking mode by taking advantage of ionic liquids (ILs). The staggered (AB) stacking (unlocked) COFs were exclusively obtained by incorporating ILs of symmetric polarity and matching molecular size; otherwise, commonly reported eclipsed (AA) stacking (locked) COFs were observed instead. Mechanistic study revealed that AB stacking was induced by a confined interlocking effect (CIE) brought by anions and bulky cations of the ILs inside pores ("key" and "cylinder", respectively). Excitingly, this strategy can speed up production rate of crystalline powders (e.g., COF-TAPT-Tf@BmimTf2N in merely 30 minutes) under mild reaction conditions. This work highlights the enabling role of ILs to tailor the layer stacking of 2D COFs and promotes further exploration of their stacking mode-dependant applications.

Ionic Liquid‐Accelerated Growth of Covalent Organic Frameworks with Tunable Layer‐Stacking

AbstractLayer‐stacking behaviors are crucial for two‐dimensional covalent organic frameworks (2D COFs) to define their pore structure, physicochemical properties, and functional output. So far, fine control over the stacking mode without complex procedures remains a grand challenge. Herein, we proposed a “key‐cylinder lock mimic” strategy to synthesize 2D COFs with a tunable layer‐stacking mode by taking advantage of ionic liquids (ILs). The staggered (AB) stacking (unlocked) COFs were exclusively obtained by incorporating ILs of symmetric polarity and matching molecular size; otherwise, commonly reported eclipsed (AA) stacking (locked) COFs were observed instead. Mechanistic study revealed that AB stacking was induced by a confined interlocking effect (CIE) brought by anions and bulky cations of the ILs inside pores (“key” and “cylinder”, respectively). Excitingly, this strategy can speed up production rate of crystalline powders (e.g., COF‐TAPT‐Tf@BmimTf2N in merely 30 minutes) under mild reaction conditions. This work highlights the enabling role of ILs to tailor the layer stacking of 2D COFs and promotes further exploration of their stacking mode‐dependant applications.

Development of self-sensing cement composites by incorporating hybrid biochar and nano carbon black

The self-sensing cement composites (SSCC) containing traditional conductive carbon materials are of great significance but cause serious pollution. In this study, the green SSCC is innovatively developed utilizing the synergistic effects of nano carbon black and biochar from coconut shell. The SSCC mixtures are compared in terms of fluidity, mechanical properties, resistivity, microstructure and comprehensive properties. The results indicate that in SSCC containing nano carbon black, the addition of biochar can obtain comparable compressive strength for its internal curing, interlocking and bridging effects. Besides, 4.5 % carbon material prolongs the crack initiation stage during compression, and 9 % carbon material causes the multiple cracks. Moreover, the addition of 4.5 % biochar can reduce the 35-day resistivity of sample with 1.5 % biochar and 3 % nano carbon black by 35.6 % owing to the increasing tunneling effect and contact conduction. It is also found that in conductive SSCC, the slope Kc of the non-contact resistivity curve is dominated by the conductive additives rather than cement hydration. And the self-sensing cement composites exhibit excellent piezoresistivity. The rates of change in resistivity of samples after cycle loading are exponentially related to residual damages, with R2 values greater than 0.95. Finally, multi-indicator evaluation analyses show that the sample containing more biochar is more environmentally friendly. This study provides a new pathway for the sustainable development of SSCC.

Improvement of interfacial properties and hygrothermal resistance of CF reinforced epoxy composites by fluorine-containing sizing agent

To enhance the interfacial bonding performance between carbon fibers (CFs) and epoxy resin, the fluorine-containing sizing agent was prepared by the unique characteristics of fluorine. The incorporation of C-F bonds endows the interfacial layer with a higher degree of homogeneity, effectively mitigating stress concentrations that arise from surface imperfections. This mitigation is attributed to the repulsive interactions among fluorine atoms. The test results showed that the interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy composites (CFREs) can be increased to a maximum of 66.01 MPa, representing a notable enhancement of 15.79 % in comparison to unsized CFREs. The enhancement of interfacial bonding ability is primarily ascribed to the synergistic effects of mechanical interlocking and chemical bonding interactions at the interface between CFs and resin. Concurrently, the hygrothermal resistance of CFREs was subjected to rigorous testing. The electron cloud of fluorine atoms exerts a pronounced shielding effect on the carbon chains, thereby significantly bolstering the hygrothermal resistance of CFREs. This enhancement is critical for the CFREs ' application in environments with high humidity and temperature. Moreover, the sizing agent developed in this study boasts a streamlined production process, which is expected to be applied in the commercial large-scale production of CFs.

EXPRESS: Getting the Board on Board: Marketing Department Power and Board Interlocks

Although the power held by the marketing department can determine key organizational outcomes, including firm performance, this power seemingly has been decreasing. To address this apparent disconnect, the authors propose that the board of directors is a critical but overlooked antecedent of marketing department power (MDP). In particular, the authors demonstrate that directors’ exposure through board service at other firms (i.e., board interlocks) affects MDP in the firms on whose boards they also serve (i.e., focal firms). A sample of 6,008 firms, spanning 2007–2021, reveals that MDP in board-interlocked firms has a positive effect on MDP in focal firms. Despite evidence that board interlock effects have diminished or even disappeared, the findings suggest the board interlock effect remains a potent antecedent of MDP—and this effect did not decrease during the observation period. Adapting the 3R (reach–richness–receptivity) framework, the authors also find that the board interlock effect increases with greater reach and richness of a focal firm’s board interlock network and its executives’ receptivity to information. The marketing department’s decreasing power is concerning for the discipline; the robust results of this study suggest that firms need to get the board “on board” to stem this diminishing trend.

Study on Low Temperature Cracking Resistance of Carbon Fiber Geogrid Reinforced Asphalt Pavement Surface Combined Body.

Currently, there are limitations in the research on the use of carbon fiber geogrids to prevent low-temperature cracking in asphalt pavements. This study aims to comparatively investigate the effects of carbon fiber-based geogrid type and dense-graded asphalt concrete mixture (AC) surface combined body (SCB) type on the low-temperature cracking resistance of reinforced asphalt pavement through low-temperature bending damage tests. Two geogrid types were prepared: a carbon fiber geogrid (CCF) and a glass/carbon fiber composite qualified geogrid (GCF). Two SCB types were studied: AC-13/AC-20 and AC-20/AC-25. The results show that the improvement in the flexural tensile strength of CCF is similar to that for GCF. Moreover, under reinforced conditions, the improvement in the low-temperature cracking resistance of AC-20/AC-25 is better than that for AC-13/AC-20 by 16.26-24.57%. Based on the analysis, the reasonable ratio range of the aperture sizes to the major particle sizes in the dense gradation can achieve a more effective interlocking effect. This can improve the low-temperature cracking resistance of carbon fiber-based geogrid-reinforced samples. Then, increasing the bending absorption energy is a key way of improving the low-temperature cracking resistance of carbon fiber-based geogrid reinforcements. Eventually, the fracture type of carbon fiber-based geogrid-reinforced samples is a mixed plastic-brittle fracture. These results can provide a reference for the road failure analysis of geogrid-reinforced asphalt pavement.

Ultra-strong bonding of 30-wt% GF/PET-A2024 aluminium alloy via collaborative promotion of ultrasonic-assisted FeCl3+N2H4 corrosion and the coordination bonds by Zr4+

Enhancing the bonding strength between metals and polymers is advantageous for hybrid structures used in aerospace and power electronics applications. This study, conducted for the first time, involves the preparation of multi-scale “honeycomb-meteorite crater” morphologies on the surface of A2024 aluminium alloy through a multi-step ultrasonic-assisted corrosion treatment. The ultrasonic-assisted FeCl3/N2H4 corrosion process increased the interfacial tensile shear strength of a 30-wt% glass fibre reinforced PET-A2024 aluminium alloy joint (expressed as 30-wt% GF/PET-A2024) to 32.0 MPa. Coating Zr4+ substantially enhances the hydrophilicity of the A2024 surface; however, the coordination bonding effect of Zr4+ can only be activated after prolonged heat treatment (100 °C, 3 h). With the combined effects of multi-scale mechanical interlocking and coordination bonding of Zr4+, the tensile shear strength of the 30-wt% GF/PET-A2024 joint can reach 56.5 MPa, surpassing existing works by a significant margin. Experimental results and Density Functional Theory (DFT) calculations demonstrate that the optimal concentration for Zr4+ treatment is 1.5 wt%. Excessive Zr4+ would lead to ion-dipole interactions, which diminish the interface bonding strength; when the concentration of Zr4+ is 2 wt%, The joint strength dropped sharply to 39.1 MPa. This study provides a comprehensive discussion on ultrasonic-assisted corrosion and the effect of Zr4+, offering valuable insights for future research aimed at enhancing the interfacial bonding strength between polymers and metals.

Environmentally friendly lime melting slag-GBFS-titanium gypsum cementitious material: Mechanical properties, hydration characteristics and microstructure

Lime melting slag (LMS) is the solid waste produced when high-purity magnesium hydroxide is made utilizing the ammonia-lime combination technology. This study discusses the impact of LMS on the strength growth and hydration behavior of the granulated blast furnace slag (GBFS)-titanium gypsum (TG) system, with the aim of realizing the resource utilization of LMS. XRD, FTIR, SEM-EDS NMR and hydration heat characterization were employed to identify the types and development processes of hydration products at various stages. The findings indicate that incorporating 2 % LMS into the sample yields the most effective excitation, enhancing the mechanical characteristics of cementitious materials at various curing stage, particularly after 3d. The 3d compressive strength of the samples with 2 % LMS was 99.2 %, 36.9 %, 43.6 % and 72.4 % higher than that of the samples with 0 %, 4 %, 6 % and 10 % LMS, respectively. The undissolved Ca(OH)2 in the LMS can selectively adsorb dissolved Ca2+ and OH- to form a double layer structure. The higher the content of undissolved Ca(OH)2 in GBFS- titanium gypsum system, the higher the adsorption capacity of Ca2+ and OH-, and the relative content of ions used in alkali excitation slag decreased. Therefore, in the GBFS-titanium gypsum system, with the increase of LMS content, the hydration degree of GBFS gradually slows down, and the generation of hydration products correspondingly decreases, which shows that the compressive strength decreases on the macro level. The analysis of hydration products shows that the appropriate amount of LMS can promote the dissolution of GBFS, generate a large number of C-(A)-S-H gels and ettringite, form an interlocking effect in three-dimensional space, and improve the mechanical properties of hydration products. However, CO2 in the air dissolves in the water pool of the curing test block to form CO32-, which reacts with the three-dimensional network gel to form fine needle-like thaumasite, resulting in a decline in the flexural strength of GTL2, but this does not affect the development of the compressive strength of the test block. GTL cementitious materials also have good ecological and environmental benefits. This study provides a new idea for the resource utilization of LMS, and provides a rich theoretical basis for the research of solid waste cementitious materials.

Analyzing the mechanical behavior of granular materials: A multi-morphological approach using spherical harmonics and LS-DEM

This paper investigates the micro-to-macro response of granular materials influenced by multi-scale morphological characteristics using spherical harmonics and LS-DEM. Our simulation results reveal that particle elongation plays the primary role in governing the shear strength and dilatancy, with surface roughness also affecting these macroscopic behaviors of non-elongated assemblies while marginally influencing elongated assemblies. At the microscale, more elongated particles with a higher degree of roughness present a stronger interlocking effect. Furthermore, we quantitatively establish a connection with the system stress ratio through the stress-fabric-force (SFF) relationship, enabling us to comprehend the shape-dependent macroscopic shear strength from microscopic anisotropy perspectives. Our results indicate that more elongated and rougher particles lead to a more significant fabric anisotropy at the critical state. Additionally, a mechanics-based shape parameter, known as rotational resistance angle, is found to correlate linearly with the critical shear strength of all explored assemblies, which can be explained by the microscopic linkage between all partitioned anisotropy components and the adopted shape parameter.