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In this study, TiC particle-reinforced high-manganese-steel (Mn18Cr2) matrix composites were successfully prepared using an in-situ method, and a millimeter micrometer dual-scale architecture was constructed in the composites to further enhance their mechanical properties. The effects of different moderator contents in the precursor on the size, volume fraction, mechanical properties, and impact wear resistance of the generated TiC particles were primarily investigated. The results showed that the moderator considerably influenced the microstructure and mechanical properties of the composites. As the moderator content increased, the size, volume fraction, mechanical properties, and wear resistance of TiC particles decreased. The optimal comprehensive performance of the composites was obtained when the moderator content was 20 wt%., average TiC particle size was 1.21 μm, volume fraction was 64.9 %, bulk hardness was more than three times that of the matrix, compressive strength was ∼2 GPa, and relative wear resistance was 2.47 times that of the matrix. The main wear behaviors of composites included grooves, microcutting, pits, and plastic deformation. In conclusion, this study guides the design and synthesis of steel matrix composites with tunable in-situ ceramic particle sizes and volume fractions to enhance wear resistance. [ABSTRACT FROM AUTHOR]

Reactive powder concrete (RPC) is used in structures such as radioactive storage plants, tall buildings and power plants. The performance of RPC after high-temperature exposure is therefore important. RPC (110 MPa) was prepared with different fibres (polypropylene fibres (PPF), polyester fibres (PEF) and their combination) at an optimum fibre dosage of 0.5% by weight of cement. The fibre-reinforced RPCs were exposed to temperatures of 200–800°C for different durations (30–120 min). Physical characteristics like colour change, fracture formation, weight loss, water absorption and residual compressive strength were evaluated. Ultrasonic pulse velocity tests were conducted. Scanning electron microscopy was used to observe the microstructure and assess the deterioration of hydrated substances after exposure to extreme temperatures for different durations. An increase in compressive strength was found for all fibre-reinforced RPCs after heating to 200°C for up to 120 min. The strength increased for 30-min exposure to 400°C. The strength of the fibre-reinforced RPCs decreased for all durations of 600°C and 800°C exposure. At these temperatures, the PEF-reinforced RPC had 10–15% greater residual strength than the RPCs. The PPF-reinforced RPC absorbed 6–12% more water than the RPCs made with PEF fibres after 120 min exposure to 800°C. [ABSTRACT FROM AUTHOR]

Porous mullite ceramics with high porosity and low thermal conductivity are urgently required as high-temperature thermal insulators in harsh environments. How to improve the strength of Porous mullite ceramics dramatically under the premise of no sacrificing its thermal insulating properties has remained an extremely challenging. Inspired by the freezing rain phenomenon in nature, high-strength and high-temperature resistant phosphate coatings were applied to the surface of mullite fibers, which significantly improved the mechanical properties of porous mullite ceramics without significantly increasing their thermal conductivity. The Al(H 2 PO 4) 3 solution concentration significantly affected the mechanical and thermal properties of the composite material, where the mechanical performance improved with an increasing Al(H 2 PO 4) 3 solution concentration. The phosphate coating phase stabilized with an increasing calcination temperature. The mechanical properties of the ceramics were improved by the excellent interfacial bonding strength between the coating and mullite fiber, and the forms of phosphate in the porous ceramics. The optimum composite preparation process increased its compressive strength by approximately nine-fold to 4.1 MPa and resulted in a thermal conductivity of only approximately 0.09 W/(m·K), demonstrating that the composite exhibited a significantly higher comprehensive performance than other previously reported porous ceramics and aerogels. Such new composites with excellent mechanical and thermal insulation properties exhibit excellent potential for high-strength thermal insulation in the chemical, metallurgical, pharmaceutical, aerospace, and other fields. [ABSTRACT FROM AUTHOR]

Porous CeO 2 materials have attracted great attention in solar thermochemical CO 2 splitting due to their superiorities on oxygen ion mobility and fuel production kinetics. Porous CeO 2 ceramics with interconnected pores at micron scale have been firstly prepared via Pickering emulsion. Derived from emulsion template, the conversion from closed pore structure to open pore structure can be realized by regulating solid content, water-oil ratio and polyvinyl alcohol (PVA) content due to its competitive adsorption at water/oil interface of Pickering emulsions with modified CeO 2 particles. The obtained porous CeO 2 ceramics present pores with average pore size of 5.56–65.36 µm, bulk density of 0.66–1.03 g/cm3, high porosity of 81.9–90.8%, and compressive strength of 1.91–6.60 MPa. Their CO production for two thermal cycles is 3.226 g/ml and 3.014 g/ml respectively, showing an advantage over counterparts from conventional methods, which are expected to be applied for solar thermochemical CO production. [ABSTRACT FROM AUTHOR]

For the first time in this paper, a composite sandwich panel with a novel circular-shaped core reinforced with silica nanoparticles (SNPs) is designed and fabricated using the vacuum-assisted resin transfer molding (VARTM) method. Carbon fibers and epoxy resin are utilized to construct the composite sandwich panels, followed by polyurethane foam injection. After fabrication, the sandwich panels undergo uniform compression testing to examine their mechanical behavior and properties. In this study, the effects of various parameters, such as core length, core height, weight percentage (wt.%) of SNPs, and polyurethane foam, on the compressive strength of the structure are evaluated. To validate the results, a finite element simulation of the sandwich panel compression test is performed using ABAQUS software, and the results obtained are compared with experimental data, showing good agreement. The results of this research demonstrate that adding SNPs within a specific range results in a considerable enhancement of the structural strength. Adding SNPs up to 3% leads to approximately a 19% increase in the compressive strength of the structure. However, adding 4 wt.% SNPs results in a decrease of about 12% in the strength of the sandwich panel. Additionally, the core's geometry significantly influences the control of compressive strength and rigidity of the sandwich panel. In other words, by increasing the core length, the compressive strength increases by 38%, while increasing the core height decreases compressive strength by about 30%. Also, it is found that adding polyurethane foam to the sandwich panel, despite a slight increase in weight, leads to a significant increase in compressive strength by about 32% and postpones its ultimate failure. Eventually, the hybrid specimen exhibits a strength approximately 57% greater than that of the pure foamless sandwich panel. [ABSTRACT FROM AUTHOR]

The significant effect of desert sand on cement-based composites was observed in the previous investigation. However, how the composition of fine aggregate affects the formation of air void structure remains to be investigated. In this paper, mortars composed of five different sand mixtures were prepared, and the specific surface area (SSA) of the sand mixture with different content of fine aggregate was calculated. It was observed that the air void content decreased as the SSA value of the sand mixture increased. A negative-slope linear relation was observed between the SSA values and air void content in the composite construction sand fiber reinforced mortar system. With the increase of SSA, the air void number of every high-strength fiber reinforced mortar decreased from 12,446 to 6652. With the gradual increase of desert sand content, the count of air void number decreased. When the fine aggregate was completely desert sand, the air void content of the fiber-reinforced mortar dropped from 1.21% to 0.98%. Through the analysis of the 3D air void system, it can be concluded that the mixture of fine aggregate with different particle size distributions plays a positive role in optimizing the air void characteristics. Reasonable utilization of desert sand can significantly improve the pore structure characteristics and compressive strength of cement-based composites, which provides an effective theoretical basis for the development and utilization of desert sand resources. The function of different kinds of construction sand in the formation of air-void structure was investigated by X-CT technology. A negative-slope linear relationship was discovered between specific surface area (SSA) values and the entire air void content in the composite construction sand fiber reinforced mortar system. The mixture of river sand and desert sand plays a positive role in optimizing the air void characteristics and compressive strength. [ABSTRACT FROM AUTHOR]

This paper investigates the flexural behaviour of hybrid reinforced concrete (RC) beams having aramid fibre reinforced concrete (AFRC) in the tension zone and high-strength concrete (HSC) in the compression zone. In two series of experimental investigations, the depth of AFRC layer and the concrete strength in the compression zone were varied. The hybrid beams were tested in series 1 to explore the effects of the depth of AFRC layer on load-carrying capacity and flexural toughness. The effects of compressive strength of the concrete in the top half of the hybrid beams on load-deflection behaviour, failure mode and cracking pattern were studied in series 2. The experimental results reveal that the use of AFRC only in the bottom half of the beam enhanced load-carrying capacity and flexural toughness by 62.44% and 87.66%, respectively, compared to the control specimen with no AFRC. The hybrid beam with AFRC-HSC exhibited 5% higher load-carrying capacities, 45% higher ductility and better cracking behaviour than the conventional RC beam. These enhanced structural performances are beneficial for specific purposes such as structures in marine environment where rebar corrosion is the main concern, or structures under extreme loadings where high ductility is required. [ABSTRACT FROM AUTHOR]

In this study, the aim is to investigate and predict the compressive strength of geopolymer concrete (GPC). The effects of curing method, curing time and concrete age on the compressive strength of GPC were evaluated experimentally. Four curing methods, namely room temperature (25°C), mobile dryer (50°C), heating cabinet type 1 (80°C) and heating cabinet type 2 (100°C) were adopted. Additionally, three curing times, of 8 h, 16 h and 24 h, as well as three concrete ages, of 7 days, 14 days and 28 days, were considered. To predict the compressive strength of GPC, 679 test results were collected to develop various machine learning models. The test results indicated that increasing the curing temperature, curing time and concrete age all led to improvements in the compressive strength of GPC. The mobile dryer showed promise as a curing method for cast-in-place GPC. The proposed machine learning models demonstrated good predictive capacity for the compressive strength of GPC with relatively high accuracy. Through sensitivity analysis, concrete age was identified as the most influential variable affecting the final compressive strength of GPC. [ABSTRACT FROM AUTHOR]

Across the world, the acceptance criterion for concrete made with non-potable water (SA) is stipulated for mean strength with reference to similar concrete made with potable water (SP). The basis for the strength design of concrete is the characteristic strength. The effect of the acceptance criteria on the characteristic strength of SA and SP was examined using statistical simulations, for the first time. It was found that, compared with a two-sample set, using a three-sample set would improve the characteristic strength of SA. A higher allowable ratio between the means of SA and SP and a lower deviation of individual samples from the mean would improve the characteristic strength of SA. The effect of the coefficient of variation (CoV) of the original population on the characteristic strength of SA varied. On the one hand, a higher CoV reduced the characteristic strength of SP, thereby increasing the probability of SA strength being higher than SP strength. On the other, a higher CoV of SP meant a wider spread of the samples and that could increase the CoV of SA, thereby reducing the characteristic strength of SA. Probabilistic charts were developed for the characteristic strengths of SA and SP for different combinations of the aforementioned variables, with guidance for practical application. [ABSTRACT FROM AUTHOR]

Excavation disturbance and groundwater actions can lead to initial damage in granites, posing a long-term stability threat to underground structures. Due to the lack of quantification methods for initial damage, it is hard to investigate the mechanical characteristics of granites under the combined effects of the excavation-induced damage and the water-rock weakening damage. In this investigation, granite samples were saturated in water for one year and subjected to different pre-loading to induce various levels of initial damage using Damage Stress Ratio (DSR) method. Uniaxial tests, acoustic wave tests, and microscopic examinations were performed on granites to analyze their mechanical behavior. The key findings are as follows: (1) A novel constitutive model is proposed, capturing the combined influence of pre-loading and water-induced weakening as a damage variable. It accurately describes the stress-strain curves of granites under this combined action, including the void-compaction stage. (2) Granites experience transgranular failure along fish-scale-like joint planes, contributing to their low strength. A one-year saturation period results in a softening coefficient of 0.83 in this specific granite, which emphasizes the performance of water-induced degradation. Furthermore, escalating the initial damage variable results in a reduction in uniaxial compressive strength, axial strain at failure, and the volume expansion point, while instigating a gradual augmentation in lateral strain. (3) A linear direct correlation is observed between strength and P wave velocity in both saturated-for-one-year and dried granites. Additionally, a linear correlation is established between the initial damage variable and the Damage Stress Ratio (DSR). These findings provide valuable insights for the characterization and prediction of their strength and damage properties. [ABSTRACT FROM AUTHOR]

A micromechanics based analytical model under combined loading for unidirectional composites has been developed. The peak compressive load predicted from the combined loading analytical model is compared with the experimental results of carbon epoxy pultruded rod having a volume fraction 60%. The specimens were subjected to torsional load under rotational control and longitudinal compressive load using displacement control. The model captures the compressive strength of the composite subjected to remotely applied shear stress. It is observed that the peak compressive strength of the composite decreases linearly with an increase in shear stress. The analytical modeling results are in good agreement with the experiment data. The analytical model and the experimental results are used to find the effect of shear stress on longitudinal compressive loading. The peak compressive strength caused in the presence of applied shear stress and compressive load and the effect of shear on the compressive strength are predicted using a 2D analytical model in this study. The model results are confirmed using experimental data from combined loading. [ABSTRACT FROM AUTHOR]

This experimental investigation involves adaptation of constrained simplex mixture design optimization technique for modeling of the mechanical behavior of soil–saw dust ash (SDA) which is a derivative from industrial byproducts to provide efficient waste management practices. The soil enhancement protocols deployed were to improve its engineering properties for pavement foundation purposes. The statistical analyses engaged in this research study were achieved using Design Expert software for the formulation and imposition of the components constraints, derivation of the mixture experimental runs and design proportions of ingredients. The experimental responses obtained from the laboratory works showed a maximum unconfined compressive strength (UCS) and California bearing ratio (CBR) results of 248 kN/m2 and 35% with mixture fraction of 0.875:0.125 for soil and SDA two component mixture respectively. For the investigation and development of the Extreme Vertex Design (EVD)-model, information from experimental exercises was used. The procedures included statistical assessment, ANOVA, diagnostic tests, and influence statistics, as well as numerical optimization utilizing the desirability function to examine the datasets. Desirability score of 1.0 was derived at a mix ratio of 0.8125: 0.1875 for the two components of soil–SDA to produce maximized CBR and UCS response of 35.053% and 257.152 kN/m2 respectively. Furthermore, the adequacy of the model generated was assessed by statistical validation and simulation exercises using student's t-test and F-test with P(T < = t) one-tail of 0.490 and 0.499 for F-test and P(F< = f) two-tail of 0.960 and 0.977 for t-test calculated for CBR and UCS responses, respectively. The calculated statistical results with P-value > 0.05 signified that there is no significant difference between the actual and EVD-model simulated results. [ABSTRACT FROM AUTHOR]

During the development process of heavy oil with steam huff and puff, the wellbore undergoes alternating conditions of temperature rise and fall, leading to a significant decline in the strength of the cement sheath. This work studied the inhibition effect and mechanism of the composite material composed of mullite and basalt fiber on the strength decline of cement stone (the hardened body of cement slurry) under simulated wellbore temperature alternating conditions from 80 °C to 260 °C. The pore structure distribution of cement stone was investigated by mercury intrusion porosimetry (MIP), the microstructure and phase composition of cement stone was characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), together with quantitative X-ray diffraction (XRD) analysis. After 4 rounds of curing under alternating temperature conditions, the compressive strength of cement stone containing mullite and basalt fiber composite material was 28.6 MPa at 260 °C, which was only 9.2 % lower than that at 80 °C. However, the compressive strength of the blank cement stone without composite materials decreased to 22.5 MPa at 260 °C, which was 20 % lower than that at 80 °C. After 4 rounds of alternating temperature cured, the harmful pores of the cement stone without composite materials increase, and the xonotlite flakes and stacks together. The cement stone added with mullite has a finer pore structure after 4 rounds of alternating temperature cured because mullite reacts with portlandite to form C-A-S-H gel. The xonotlite remains fibrous, and a small amount of new phase hibschite is formed. Furthermore, basalt fiber can react with C-A-S-H gel at high temperatures, and the two phases are closely combined to further improve the high-temperature resistance of cement stone. [ABSTRACT FROM AUTHOR]

The complex structure of Ti/HA (HA: hydroxyapatite) implants prepared by additive manufacturing technology plays an essential role in its application in bone repair. Digital light processing (DLP) is widely used to prepare bioceramics with complex structures. However, it is a challenge to prepare Ti/HA biomaterials by DLP due to the high ultraviolet (UV) absorption of Ti powder. In the present work, TiH2 powder coated with a TiO2 layer is selected to reduce the UV absorption and improve the curing depth for DLP printed green bodies of TiO2@TiH2/HA, because the TiO2@TiH2 powder can be reduced by 12.7% compared to the TiH2 powder without any oxidation. Then, the shell layer of TiO2 undergoes dehydrogenation and reduction reaction with the core phase of TiH2 during the sintering process to transfer TiO2@TiH2/HA into TixOy@Ti/HA. In addition, the effects of HA content on compressive strength and biocompatibility are investigated in the TixOy@Ti/HA biomaterials. The results show that when adding 60 vol%HA, the maximum monolayer curing depth of the slurry reaches 90.1 ± 3.5 µm. 40%TixOy@Ti/60%HA shows the maximum effect in promoting the pre‐osteoblast differentiation and a relatively high compressive strength of 48.7 ± 3.5 MPa. This work provides an experimental basis for the preparation of ceramic–metal composites with high UV absorptivity using DLP. [ABSTRACT FROM AUTHOR]

Under seismic loading, corroded reinforced concrete (RC) columns are prone to brittle shear failure, which poses a significant threat to existing structures. However, due to the mechanical defects and insufficient parameters included in the equations available in codes, the literature exhibits a lack of precision in predicting the shear strength of such columns. In this paper, a shear strength equation for the RC column was established based on the truss-arch model theory. On this basis, the effect of corrosion on key parameters such as the cross-sectional area of rebar, yield strength, compressive strength of concrete, and displacement ductility was fully considered to establish the shear strength equation of corroded RC columns. To assess the accuracy and applicability of the proposed equation, a database consisting of 215 specimen parameters was compiled. Comparative analyses were conducted with existing equations from the literature. The results indicate that the mean values and coefficient of variation for the ratio of calculated values to the tested values of the equation were 1.098 and 0.601, respectively, which proves the equation's high computational accuracy and low dispersion. Consequently, the proposed equation offers a more effective calculation method for predicting and assessing the shear strength of corroded RC columns. This method holds significant potential for enhancing the resilience of structures in seismic-prone regions. [ABSTRACT FROM AUTHOR]

Cemented gangue backfill bodies (CGBBs) are characterized by high brittleness and poor toughness in backfill mining technology. According to different types of waste tires corresponding to different processing and crushing means, waste tire steel fiber (WTSF) was divided into S-WTSF, P-WTSF, and H-WTSF. The influence of CGBBs with different types and amounts of WTSF on the early mechanical properties of the modified samples was studied. Uniaxial compressive strength (UCS) and scanning electron microscopy (SEM) tests on the modified CGBB samples were carried out. The results show that as the WTSF content increased from 0% to 1.5%, the UCS of CGBB samples modified with S-WTSF, P-WTSF, and H-WTSF at a curing time of 3 d first increased and then decreased; the turning point for S-WTSF and P-WTSF was 1%, and the turning point for H-WTSF was 0.5%, whereas the UCS of these modified CGBB samples at a curing time of 7 d decreased continuously with the increasing addition of WTSF content. The addition of WTSF made CGBB samples change from brittleness to ductility. With the increasing content of S-WTSF and P-WTSF, the toughness of the modified CGBB samples at a curing time of 3 d first increased and then decreased (the turning point was 1%), and that at the curing time of 7 d continued to increase. The toughness of CGBB modified with H-WTSF first increased and then decreased (the turning point was 0.5%) with the increase of the H-WTSF content. The toughness enhancement mechanism of CGBB modified by WTSF can be illustrated from a microscopic perspective as follows: WTSF is wrapped by hydration products, and the inlaying and bridging effects of WTSF are formed in the CGBB matrix. This research provides a basis for the improvement of mechanical properties of CGBB modified by WTSF and a new method for the reuse of discarded tires. [ABSTRACT FROM AUTHOR]

Recent disasters involving upstream raised tailings dams in Brazil have caused regulatory agencies to prohibit the construction of new upstream dams and demand the decommissioning of existing ones. As such, new alternatives are being sought to safely dispose of iron ore exploitation byproducts. The dry stacking of filtered tailings is an option to diminish the risks associated with tailings storage facilities and cope with new legislation. Accordingly, this paper studies new solutions for enhancing the performance of tailings for dry stacking purposes. The behavior of reinforced and nonreinforced iron ore tailings-alkaline-activated cement (AAC) blends was studied through unconfined compressive strength tests and conventional triaxial testing. The AAC is produced from the residues of iron ore exploitation (waste and tailings). The addition of fibers has enhanced the performance of cemented iron ore tailings with increased strength regardless of the fiber content and ductility. Also, reinforcement effectiveness values were greater than those reported for other cement agents, due to the lower stiffness of the cemented matrix from AAC compared with others. A comparative analysis between using only AAC and ACC plus 0.5% of fibers within the η/Biv framework was proposed. The dosage curves for the same qu value yielded an AAC=20.80% for AAC only and AAC=3.80% when using 0.5% of fibers. Therefore, using fibers can collaborate with the feasibility of using a new waste-based AAC to construct dry stacking facilities. [ABSTRACT FROM AUTHOR]

The incorporation of supplementary cementitious materials (SCMs) into cementitious materials can be used to offset the overall carbon footprint of cement in addition to improving performance and promoting circular economy. Synthesized silicomanganese fume (SiMnF), silica fume (SF), and ordinary portland cement (OPC) based binary and ternary cementitious mortar specimens were designed and optimized using the Taguchi method. Four factors with three levels each were investigated—SiMnF content of 0%–40% and SF content of 0%–10% (by mass) of the total cementitious, sand-to-binder of 1.5–2.5, and water-to-binder ratio of 0.35–0.45. Based on the orthogonal array proposed by the Taguchi method, nine mortar mixes were batched and their flow after mixing and compressive strength at 3, 7, and 28 days of casting were measured. The strength data were statistically analyzed using ANOVA to investigate the effects of the chosen experimental variables. It was observed that the strength is considerably reduced from the addition of SiMnF, but the reduction is marginal from increasing the sand-to-binder ratio. The addition of 5% SF increased the strength. A restricted analysis indicated that specimens prepared with 20% SiMnF, or 20% SiMnF and 5% SF can yield mortar strengths of up to 30.5 MPa and 48.8 MPa, respectively. Microstructural investigations revealed that the mixes with SiMnF have detectable pores at 1,000× magnification, however, the addition of 5% SF densifies the matrix with no visible pore at the same magnification. This corroborates the strength data. The life-cycle assessment (LCA) indicates that the utilization of SiMnF in the mortar mixtures can reduce CO2 emissions by up to 25% at a reasonably acceptable compressive strength. [ABSTRACT FROM AUTHOR]

Nanopore-rich high porosity aerated cement (NHPAC) was prepared by introducing nanomontmorillonite slurry (NMS) into aerated cement paste, and the rheology of slurry, pore structure (air voids and microscopic pores), performance of NHPAC, and related mechanisms were investigated. The results indicated that NMS can generate rich microscopic pores in NHPAC and successfully achieve the part replacement of air void, increasing 0% to 30% of NMS rose microscopic pore porosity from 40.4% to 57.2% and from 40.5% to 54.9% for density grade of 250 and 400 kg/m3 , respectively. In addition, the content of air voids below 0.5 mm increased with increasing NMS. Due to the creation of small air voids, the replacement of air voids by microscopic pores, the pozzolanic reaction of nanomontmorillonite, and the performance of NHPACs were enhanced. 20% of NMS improved 56-day compressive strength by 34.8% and 10.9%, and reduced thermal conductivity by 15.3% and 9.3% for density grades of 250 kg/m3 and 400 kg/m3 , respectively. This development might allow for the use of high porosity aerated cement. [ABSTRACT FROM AUTHOR]

The great development of transpiration cooling technology challenges the coolant medium seriously. In this paper, porous ZrO2–ZrO2 ceramics have been satisfactorily prepared to meet the requirements of the coolant medium in transpiration cooling. The results illustrate that porous ZrO2–ZrO2 ceramics have excellent compressive strengths; meanwhile, percentages of compressive strength difference (parallel and perpendicular to the mold‐pressing direction) have an upward trend due to the increasing fiber contents. Besides, the failure mode has a huge distinction between parallelity (45° oblique section) and perpendicularity (wedge shape). These ceramics have unimodal pore size distribution (2–10 µm), and their wettability has a substantial improvement reflected by contact angle from 118° to 0°. Permeability behavior across these ceramics has been accurately described using the Darcy–Forchheimer equation, while obtaining viscous and inertial resistance coefficients, respectively. This work can provide an essential reference for coolant medium in transpiration cooling. [ABSTRACT FROM AUTHOR]

Bi2Te3‐based alloys have historically dominated the commercial realm of near room‐temperature thermoelectric (TE) materials. However, the more widespread application is currently constrained by its mediocre TE performance and inferior mechanical properties resulting from intrinsic hierarchical structure. Herein, microstructure modulation and carrier transport optimization strategies are employed to efficiently balance the electro‐thermal transport performance. Specifically, the weighted mobility increases by 24%, while the lattice thermal conductivity decreases by 31% at 350 K compared to the matrix. Consequently, the Bi0.5Sb1.496Cu0.004Te2.98 sample attains a peak ZT of 1.45 at 350 K and an average ZT of 1.20 (300–500 K). Moreover, intricated microstructure design, exemplified by the gradient twin structure, significantly enhances the mechanical performance metrics, including Vickers hardness, compressive strength, and bending strength, to notable levels of 0.94 GPa, 224 MPa, and 58 MPa, respectively. Consequently, the constructed 17‐pair TE modules demonstrate a maximum conversion efficiency of 6.5% at ΔT = 200 K, surpassing the majority of reported Bi2Te3‐based modules. This study provides novel insights into the synergistic enhancement of TE and mechanical properties in Bi2Te3‐based materials, with potential applicability to other TE systems. [ABSTRACT FROM AUTHOR]

In reinforced concrete structures, GFRP bars are becoming acceptable as internal reinforcement subject to compressive load and hygrothermal environments. The paper presents an experimental study on the compressive behavior, thermodynamic properties, and degradation mechanism of the glass fiber‐reinforced polypropylene (GFRPP) bars after aging in distilled water (DW), alkaline solution (AS) and seawater and sea sand concrete (SWSSC) solution at 21, 40, and 60°C up to 120 days. The effect of specimen assembly methods, and slenderness rations (Lu/Db) on the compressive behavior was evaluated on the control GFRPP bars. After immersion, the compressive strength of the GFRPP bars was significantly affected by the type of solution, immersion time, and temperature. Typically, the compressive strength retention was decreased by 25.8%, 30.0%, and 33.0% at 60°C in DW, AS, and SWSSC solutions, respectively. The degradation mechanism of the compressive behavior of GFRPP bars was revealed through SEM images and FTIR spectroscopy analysis, and the debonding of fiber‐resin interfaces, chemical etching of glass fibers, and changes in polypropylene functional groups were confirmed or discovered. Finally, based on the Arrhenius theory, the long‐term life prediction of compression strength in three typical service environments was conducted to provide the design guideline for reinforcement concrete. Highlights: Effect of specimen assembly and Lu/db on compressive behavior of GFRPP barsThermodynamic behavior of the GFRPP bars under different aging environmentsRevealed the degradation mechanism of GFRPP bars under hygrothermal environmentsPredicted the service life of GFRPP bars in typical service environments [ABSTRACT FROM AUTHOR]

Phosphoric acid-based geopolymer (PGEO) belongs to acidic material and has many applications in environmental disposal. The curing method has an important impact on the mechanic performance of geopolymers, the existing research concerning PGEO synthesized from fly ash (FA) and phosphoric acid (PA) are performed on the specimens cured at sealed environment, but no related research on the PGEO cured at an open environment is found. Therefore, to investigate the mechanic performance, pH and of PGEO cured in an open environment, the unconfined compressive strength tests were conducted on PGEO specimens cured in an open environment, and its mechanism was investigated using Scanning Electron Microscope, X-Ray diffraction, and Fourier transform infrared reflection (FTIR) tests. Moreover, the thermogravimetric was measured using the thermogravimetric tests. The results showed that in the scope of this study, the compressive strength of the PGEO decreased with the PA concentration and the liquid–solid ratio (L/S) increasing. When the L/S was a fixed value, as the curing time increased, an obvious strength loss was observed for the PGEO with the content of 40 and 50%, but the compressive strength increased first and then, reduced for the PGEO with the content of 40 and 50%, a maximum strength was obtained at 60 days of curing. The open curing for the PGEO is not conducive to the later growth of compressive strength. As the PA concentration and L/S increased, the pH descended. As the curing time lengthened, the pH first raised and then droped, the maximum pH was obtained at 60 days. Furthermore, the compressive strength increased with the pH with a good correlation. The microscopic analysis showed that the crystalline compounds AlSiP3, Ca2P2O7(H2O)2, molecular sieve SAPO-20 (Al0.47Si0.13P0.4)O2, AlPO4-5 (AlPO4), CaHPO4, and AlPO4 in PGEO were detected. Overall, the open curing environment is not conducive to PGEO, and sealed curing should be used in engineering applications. [ABSTRACT FROM AUTHOR]

Ultra-high temperature ceramics (UHTCs) are considered as promising thermal insulation materials applied in ultra-high temperature environments (> 2000 °C). However, the high thermal conductivity and high density limit their further development and application. Herein we adopt the strategies of introducing porous structure and high-entropy effect to solve the above problems. Thus porous high-entropy (Zr0.25Hf0.25Nb0.25Ti0.25)C ceramics were prepared. In order to obtain the uniform pore structure and high mechanical property, the camphene-based freeze-casting method was used in this study. The as-prepared porous samples exhibit high porosity of 92.01–73.57% and homogeneously interconnected pore structure with average pore size of 40.8–19.6 μm. Besides, this work realizes the aims of lightweight (0.65–2.15 g/cm3) and low thermal conductivity (0.29–1.53 W/(m·K)). More importantly, porous samples still have the merit of high compressive strength (0.38–29.02 MPa) due to the even microstructure. The results show that highly porous high-entropy (Zr0.25Hf0.25Nb0.25Ti0.25)C with good overall properties can be an excellent candidate material for ultra-high temperature thermal insulation. [ABSTRACT FROM AUTHOR]

Sintering red mud (SRM) is an industrial alkaline waste residue generated from the sintering process in alumina production, which is often directly discarded and causes environmental issues. In this study, an innovative magnesium-modified wet carbonation method was proposed to convert sintering red mud to valuable calcium carbonate whiskers using CO 2 -containing flue gas. The effects of carbonation conditions including temperature, MgCl 2 concentration, and duration on the composition, microstructure, and morphology of carbonated products were systematically investigated. It was found that a high whisker content of 60% with an aspect ratio of ∼6 could be obtained under the optimal conditions of 80 °C, 0.4 M MgCl 2 , and 2 h reaction time. Besides the formation of whiskers, amorphous aluminosilicate gel was also generated during SRM carbonation. The effects of the as-prepared whisker-rich materials as partial cement replacement on the mechanical properties of cement paste were evaluated with 5 wt% replacement, the 28 d compressive strength was significantly improved by 20.5% compared to the control specimen. The effective reinforcement was ascribed to the fibrous whiskers and enhanced interfacial bonding. This method enables high-value utilization of SRM waste and CO 2 fixation, providing a green and low-cost approach to producing high-performance cementitious materials. [ABSTRACT FROM AUTHOR]

AbstractThe major focus of the present study is the use of pond ash to replace fine river sand in the production of plaster. In this study, the physical, mechanical, and microstructure characteristics of mortar are investigated for different replacement levels of sand with pond ash. The results show that the dry density of pond ash mixes is reduced by increasing the replacement level, which is due to the higher water absorption and pond ash’s porousness. It is worth mentioning that at a replacement rate of 20%, compressive and flexural strengths are higher than those of control specimens. On the other hand, drying shrinkage is 31% lower than the control, but the achieved strength is more than the required strength as per the Indian code. Scanning electron microscopy with energy dispersive x-ray spectroscopy shows that a rise in silicon content (12%) for samples having a 20% replacement of pond ash has a high C–S–H gel density, thus exhibiting higher compressive and flexural strengths. X-ray diffraction results show that the lower strength of 40% pond ash replacement is due to the presence of sodium sulfate. Hence, the results indicate that fine pond ash can be partially replaced with fine river sand for internal plaster and to produce mortar and blocks. [ABSTRACT FROM AUTHOR]

This study examines the effect of coarse recycled aggregates (CRAs) and processed coarse recycled aggregates (PCRAs) on the behaviour of alkali-activated concrete (AAC) before and after exposure to marine seawater and acidic environments (5% HCl and 5% H2SO4 solutions). Measurements of compressive strength and the microstructure changes were conducted over periods of 56 and 90 days to assess these effects. The experimental design included varying the replacement levels of NAs with CRAs and PCRAs from (0–100%) and using ground-granulated blast furnace slag and fly ash as constant components. In addition to durability tests, sorptivity assessments were conducted to gauge the material's porosity and water absorption capabilities. Advanced microstructure techniques, such as scanning electron microscopy (SEM) and X-ray diffraction (XRD), were employed to detail the pre and post-exposure mineralogical and microstructural transformations within the AAC blends. The AAC mixtures incorporating PCRAs emerged as durable, showcasing better strength and a denser, more compact matrix facilitated by the synergistic formation of NASH and CASH gels after exposure to aggressive agents compared to untreated CRAs. In addition, the results show that the samples exposed to marine seawater exhibited improved mechanical performance compared to those exposed to acidic environments. The novelty of this study lies in its exploration of the effects of recycling plant-based CRAs and PCRAs on AAC for marine and acid exposure. [ABSTRACT FROM AUTHOR]

The stratified structural plane caused by stratified backfill will reduce the strength of backfill, and the introduction of retarder will make up for the defect. Three retarders, sodium tripoly-phosphate, citric acid and sucrose, were introduced. After determining the optimal dosage of retarder, they were added into the filling slurry with a ratio of lime to sand of 1:6 and a mass concentration of 75%. Based on the hydration reaction mechanism and damage mechanics theory of cement, the setting time test and uniaxial compressive strength test were carried out. With the help of scanning electron microscopy and X-ray diffraction, the influence mechanism of retarder on the physical characteristics of stratified cemented filling was investigated.The main research contents and achievements are as follows:. The results showed that the three retarding agents can delay the setting time of the cement filling slurry, and the retarding effect is sucrose > citric acid > sodium tripolyphosphate. The addition of retarder can improve the uniaxial compressive strength and integrity of stratified consolidated backfill, and the best filling interval time (FIT) is 12 h. Appropriate addition of retarder will increase the amount of cement hydration products, make the structure of hydration products more dense, reduce the formation of stratified structural plane, and help to improve the strength of stratified cemented backfill. [ABSTRACT FROM AUTHOR]

The uniaxial compressive strength (UCS) and elasticity modulus (E) of intact rock are two fundamental requirements in engineering applications. These parameters can be measured either directly from the uniaxial compressive strength test or indirectly by using soft computing predictive models. In the present research, the UCS and E of intact carbonate rocks have been predicted by introducing two stacking ensemble learning models from non-destructive simple laboratory test results. For this purpose, dry unit weight, porosity, P‐wave velocity, Brinell surface harnesses, UCS, and static E were measured for 70 carbonate rock samples. Then, two stacking ensemble learning models were developed for estimating the UCS and E of the rocks. The applied stacking ensemble learning method integrates the advantages of two base models in the first level, where base models are multi-layer perceptron (MLP) and random forest (RF) for predicting UCS, and support vector regressor (SVR) and extreme gradient boosting (XGBoost) for predicting E. Grid search integrating k-fold cross validation is applied to tune the parameters of both base models and meta-learner. The results demonstrate the generalization ability of the stacking ensemble method in the comparison of base models in the terms of common performance measures. The values of coefficient of determination (R2) obtained from the stacking ensemble are 0.909 and 0.831 for predicting UCS and E, respectively. Similarly, the stacking ensemble yielded Root Mean Squared Error (RMSE) values of 1.967 and 0.621 for the prediction of UCS and E, respectively. Accordingly, the proposed models have superiority in the comparison of SVR and MLP as single models and RF and XGBoost as two representative ensemble models. Furthermore, sensitivity analysis is carried out to investigate the impact of input parameters. [ABSTRACT FROM AUTHOR]

Assessment of compressive strength is crucial for ensuring the safety of concrete structures. However, existing works mainly focus on wet concrete rather than fully saturated concrete underwater and neglect the influences of mix parameters. To this end, this study develops a testing system to measure ultrasonic waves underwater and investigates the influence of water-cement (W/C) ratio (ranging from 0.35 to 0.54), sand-aggregate (S/A) ratio (ranging from 0.57 to 0.87), and average diameter (Da) of coarse aggregate (ranging from 7.5 to 17.44) on the relationships between compressive strength and the velocities of pressure (P) and Rayleigh (R) waves. Ultrasonic and destructive experiments are performed on 96 concrete blocks with 32 mix parameters. The W/C and S/A ratios have a more significant influence on the relationship than the Da. Therefore, a set of formulas is developed to assess compressive strength based on the velocity of P and R waves considering the influence of W/C and S/A ratios. The developed formulas improve the accuracy by 32% to 57% compared to existing formulas, guiding the assessment of underwater infrastructures. [ABSTRACT FROM AUTHOR]

Highlights Delamination is one form of damage in composite laminates. The effects of delamination damage locations (thickness direction of laminates) on the residual compressive strength and failure mechanism of carbon fiber/polyphenylene sulfide (CF/PPS) composites are studied by damage morphology, full‐field strain and finite element simulation. The closer the delamination is to the center of the composite, the lower the residual compressive strength. The failure mode of composites is dominated by 0° fiber fracture, which is divided into bulging, delamination propagation, and fracture. The delamination locations significantly affect the first two stages. Constructing delamination damage in composites by interlayer preset defects. Simulation and damage analysis to reveal the mechanism of compression failure. The relationship between delamination depth and damage stage is revealed. [ABSTRACT FROM AUTHOR]

Background: An ideal synthetic spacer for medial opening wedge high tibial osteotomy (MOWHTO) has not yet been developed. The authors have developed a new β-tricalcium phosphate (β-TCP) spacer with 60% porosity (N-CP60) by modifying the micro- and macro-pore structures of a conventional β-TCP spacer (CP60) that is widely used in clinical practice. The purpose of this study was to compare the absorbability, osteoconductivity, and in vivo strength of the N-CP60 spacer with those of the CP60 spacer, when used in MOWHTO. Methods: First, the porosity, diameter distribution of macro- and micropores, and compressive strength of each β-TCP block were examined using methodology of biomaterial science. Secondly, a clinical study was performed using a total of 106 patients (106 knees) with MOWHTO, who were followed up for 18 months after surgery. In these knees, the N-CP60 and CP-60 spacers were implanted into 49 tibias and 57 tibias, respectively. The absorbability and osteoconductivity were radiologically evaluated by measuring the area of the implanted spacer remaining unabsorbed and assessing with the Hemert's score, respectively. The incidence of cracking in the implanted spacers was determined using computed radiography. Statistical comparisons were made with non-parametric tests. The significance level was set at p = 0.05. Results: The N-CP60 and CP60 blocks had almost the same porosity (mean, 61.0% and 58.7%, respectively). The diameter of macropores was significantly larger (p < 0.0001) in the N-CP60 block than in the CP60 block, while the diameter of micropores was significantly smaller (p = 0.019) in the N-CP60 block. The ultimate strength of the N-CP60 block (median, 36.8 MPa) was significantly greater (p < 0.01) than that of the CP60 block (31.6 MPa). As for the clinical evaluations, the absorption rate of the N-CP60 spacer at 18 months after implantation (mean, 48.0%) was significantly greater (p < 0.001) than that of the CP60 spacer (29.0%). The osteoconductivity of the N-CP60 spacer was slightly but significantly higher (p = 0.0408) than that of the CP60 spacer only in zone 1. The incidence of in vivo cracking of the posteriorly located N-CP60 spacer at one month (mean, 75.5%) was significantly lower (p = 0.0035) than that of the CP60 spacer (91.2%). Conclusions: The absorbability, osteoconductivity, and compressive strength of the new N-CP60 spacer were significantly improved by modifying the macro- and micro-pore structures, compared with the conventional CP60 spacer. The N-CP60 spacer is more clinically useful than the CP60 spacer. Trial registration number: H29-0002. [ABSTRACT FROM AUTHOR]

Difunctional devices have great potential in the application of many areas, they can perform two functions simultaneously, and structural difunctional supercapacitor is one of them. The difunctional supercapacitor can carry out bearing capacity and storge electric energy, but it's difficult to keep the balance between bearing capacity and energy storage capacity. In this work, the montmorillonite based geopolymer has a compressive strength of 31.6 MPa after curing for 28 days, and a compressive strength of 30.5 MPa after repolymerization. We use the geopolymer as the framework, and inject 0.5 M Na 2 SO 4 into the geopolymer to prepared a structural electrolyte. Then, the structural electrolyte membrane, electrodeposited MnO 2 , and an activated carbon are assembled into a difunctional supercapacitor. The maximum specific capacity reaches 2216.7 mF cm−2 at 1 mA cm−2 under 15 MPa, achieving a good balance between compressive strength and energy storage capacity. [ABSTRACT FROM AUTHOR]

In order to overcome the serious corrosion problem of furnace hearth refractory materials for smelting reduction ironmaking, the Cr 2 O 3 –Al 2 O 3 –MgO–ZrO 2 refractories were synthesized, and the phase component, microstructure, mechanical characteristics, and slag erosion behavior of composite refractories were investigated and evaluated. The results indicate that the composite refractories mainly consist of Mg(Al, Cr) 2 O 4 spinel phase, (Al, Cr) 2 O 3 solid solution and ZrO 2. The content of Mg (Al, Cr) 2 O 4 spinel significantly increases with the increasing MgO content, while the content of (Al, Cr) 2 O 3 obviously decreases. Furthermore, the comprehensive mechanical properties of the MgO modified composite refractories can be obviously enhanced by increasing the MgO content, and sample S4 presents the best mechanical characteristics when the MgO addition is 10 wt%. The corresponding hardness, compressive strength and bending strength are 14.22 GPa, 267.14 MPa and 80.0 MPa, respectively. This is mainly because the formation of Mg(Al, Cr) 2 O 4 significantly improves the densification of composite refractories, and a large number of high-strength Mg (Al, Cr) 2 O 4 spinel "bridge" formed between the large-sized (Al, Cr) 2 O 3 grains. The erosion test results indicate that increasing the MgO content can significantly improve the slag infiltration resistance of composite refractories, because the formation of Mg (Al, Cr) 2 O 4 spinel layer significantly improves the densification of MgO reinforced composite refractories. Although the slag corrosion resistance of Mg(Al, Cr) 2 O 4 is lower than that of (Al, Cr) 2 O 3 , the Cr 2 O 3 –Al 2 O 3 –MgO–ZrO 2 refractories still presents good erosion resistance, permeability resistance, and excellent mechanical characteristics. [ABSTRACT FROM AUTHOR]

As a material masonry is anisotropic in nature as it is constituted of various components that differ each other in many ways. Though, the ideas of modeling of concrete are also valid for masonry, still there are difficulties in determining the exact behavior of masonry. The micro modeling (simplified) approach has been adopted in this study for modeling masonry samples subjected to various nature of loadings. The brick masonry units were modeled as discrete elements and linked together by interface element. The coulomb friction model was used to describe the interface element as mortar joint. Damage was assumed to be governed by the compressive strength of both the constituents i.e., mortar and brick. The mechanical properties of the masonry samples were determined by means of variety of tests and those properties then served as input parameters in the constitutive model. The results clearly indicate that numerical model predicted the behavior of the experimentally tested samples, in compression as well as tension prims for both unconfined and confined cases. The proposed model is suitable for modeling any type of brick masonry walls. [ABSTRACT FROM AUTHOR]

Alkali‐activated waste glass (AA‐WG) has received much attention because to its high mechanical properties achieved with low energy demand. However, AA‐WG exhibits low stability, including volume expansion, porosity increment, and a reduction in compressive strength. Enhancing the stability of AA‐WG could improve its commercial viability and expand its range of applications. Therefore, this study aims to evaluate the role of calcite CaCO3 (CC) and magnesite MgCO3 (MC) in enhancing the physicomechanical properties and phase composition of AA‐WG at elevated temperatures. The proposed strategy includes replacing WG with different contents of CC and MC, followed by activation with a 4 M NaOH solution and curing at 100°C for 24 h. The hardened samples were then exposed to 800°C for a 2 h holding time to evaluate the thermal stability of the AA‐WG, AA‐WG‐CC, and AA‐WG‐MC mixtures. The results demonstrated that increasing the CC content up to 50 wt.% significantly enhanced the compressive strength of the AA‐WG when cured at 100°C, while the incorporation of MC caused a negative effect. Surprisingly, an opposite trend was observed at a higher temperature of 800°C, where the samples containing MC exhibit better mechanical and physical performance compared to those with CC. The variation in the type, composition, and weight loss upon ignition of the carbonate‐based minerals significantly influenced the stability and phase composition of the thermally exposed AA‐WG. Although the sample with 50 wt.% MC showed higher volume shrinkage, it demonstrated higher compressive strength (~82 MPa) at 800°C than the sample with 50 wt.% CC (~7 MPa). This difference can be attributed to the formation of diopside CaMgSi2O6 and forsterite Mg2SiO4, which have higher crystallinity, specific gravity, and hardness compared to wollastonite CaSiO3 and the tri‐calcium silicate phases Ca3SiO4. [ABSTRACT FROM AUTHOR]

The research focuses on ultra-lightweight foam concrete with a dry density below 200 kg/m3, primarily used as insulation material. Factors that may affect material properties are categorized into mixing techniques and material composition, and experimental investigations were conducted on the impact of these factors on the rheological properties of cement slurry, density at different time intervals, compressive strength, and thermal conductivity of foam concrete samples. The experimental results indicate the influence of mixing speed and mixing duration on the instrument during the cement slurry production and mixing process with foam. Additionally, variations in foam concrete sample properties are observed due to the water-to-cement ratio, foam content, and foam density in the selected material compositions. By analyzing the material density at different time intervals, the relationship between the ambient air trapped during the mixing process and the viscosity of the material can be indirectly observed. This analysis can also reveal the correlation between the unplanned air content and the properties of the material. [ABSTRACT FROM AUTHOR]

Improvement of hydrophysical properties and corrosion resistance of self-compacting concrete to the effects of alternate freezing–thawing and aggressive soils of Southern and Central Kazakhstan is of interest to a wide range of researchers from the side of practical application of the obtained results in construction practice. It is proposed to form a spatially reinforced fine crystalline structure of a cement matrix with the maximum dense packing by using a complex modifier (hyperplasticizer + polymer + microsilica + fibro fibers) in the composition of self-compacting concretes (SCCs). The introduction of the calculated amount of the above additives increases the operational reliability of the current SCC compositions, increasing the water resistance to W16, frost resistance to F = 500, increasing the compressive strength by 20%, and reducing the mass loss of samples during corrosion leaching to 50%. It has been experimentally established that the proposed addition of the complex modifier (hyperplasticizer + polymer + microsilica + fibro fibers) to the SCC composition allows obtaining self-compacting concrete of high quality with improved performance characteristics (compressive strength, water resistance, frost resistance, and corrosion resistance). Studies have shown that the complex modifier-modified SCC compositions have a high degree of resistance in aggressive environments and leaching corrosion. Based on the results of the conducted tests, it is possible to recommend the obtained SCC compositions for the production of building products working in the zone of alternating freezing–thawing and aggressive soils. [ABSTRACT FROM AUTHOR]

This study investigated the influences of ultrafine fly ash (UFA) and ultrafine slag powder (USL) on the compressive strengths, autogenous shrinkage, phase assemblage, and microstructure of magnesium potassium phosphate cement (MKPC). The findings indicate that the aluminosilicate fractions present in both ultrafine fly ash and ultrafine slag participate in the acid–base reaction of the MKPC system, resulting in a preferential formation of irregularly crystalline struvite-K incorporating Al and Si elements or amorphous aluminosilicate phosphate products. UFA addition mitigates early age autogenous shrinkage in MKPC-based materials, whereas USL exacerbates this shrinkage. In terms of the sustained mechanical strength development of the MKPC system, ultrafine fly ash is preferred over ultrafine slag powder. MKPC pastes with ultrafine fly ash show greater compressive strength compared to those with ultrafine slag powder at 180 days due to denser interfaces between the ultrafine fly ash particles and hydration products like struvite-K. The incorporation of 30 wt% ultrafine fly ash enhances compressive strengths across all testing ages. [ABSTRACT FROM AUTHOR]

The aggregation of graphene oxide (GO) during the hydration process limits its wide application. Polymer superplasticizers have been used to improve the dispersion state of GO due to their adsorption and site-blocking effects, though the formation of a large amount of foam during the mixing process weakens the mechanical properties of cement. A highly dispersed amphoteric polycarboxylate superplasticizer-stabilized graphene oxide (APC/GO) toughening agent was prepared by electrostatic self-assembly. Results demonstrate that the APC/GO composite dispersed well in a cement pore solution due to the steric effect offered by the APC. Additionally, the well-dispersed GO acted as an antifoaming agent in the cement since GO nanosheets can be absorbed at the air–liquid interface of APC foam via electrostatic interactions and eliminate the air-entraining effect. The well-dispersed APC/GO sheets promoted cement hydration and further refined its pore structure owing to the nucleation effect. The flexural and compressive strength of the cement containing the APC/GO composite were enhanced by 21.51% and 18.58%, respectively, after a 7-day hydration process compared with a blank sample. The improved hydration degree, highly polymerized C-S-H gel, and refined pore structure provided enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

Negative thermal expansion (NTE) ceramics Sm0.85Zn0.15MnO3 (SZMO) and ZrMgMo3O12 (ZMMO) were selected to prepare Sm0.85Zn0.15MnO3-ZrMgMo3O12/Al-20Si (SZMO-ZMMO/Al-20Si) composites using ball milling and vacuum heating-press sintering processes in this study. The synergistic effect of the SZMO and ZMMO NTE ceramic reinforcements on the microstructure, mechanical properties, and coefficient of thermal expansion (CTE) of the composites was investigated. The results show that the processes of ball milling and sintering did not induce the decomposition of SZMO or ZMMO NTE ceramic reinforcements, nor did they promote a reaction between the Al-20Si matrix and SZMO or ZMMO NTE ceramic reinforcements. However, the excessive addition of SZMO and ZMMO NTE ceramics led to their aggregation within the composite. Adding a small amount of SZMO in combination with ZMMO effectively increased hardness and yield strength while reducing CTE in the Al-20Si alloy. The improvement in strength was primarily provided by SZMO, while the inhibition effect on CTE was primarily provided by ZMMO. An evaluation parameter denoted as α was proposed to evaluate the synergy effects of SZMO and ZMMO NTE ceramic reinforcements on the mechanical properties and CTE of the composites. Based on this parameter, among all composites fabricated, adding 2.5 vol% SZMO NTE ceramic and 10 vol% ZMMO NTE ceramic resulted in an optimal balance between CTE and strength for these composites with a compressive yield strength of 349.72 MPa and a CTE of 12.55 × 10−6/K, representing a significant increase in yield strength by 79.20% compared to that of Al-20Si alloy along with a notable reduction in CTE by 26.44%. [ABSTRACT FROM AUTHOR]

Low-grade limestone (LGL) is not used to produce cement clinker, but this leftover material in cement quarries increases the water demand when used as a filler in concrete production. In this study, the effect of six commercial superplasticizers on the performance of cement mixes containing 35% LGL and 2% gypsum was investigated. The optimal doses of these superplasticizers were found in a range of different water/binder (w/b) ratios by conducting several Marsh cone and mini-slump tests. The addition of a superplasticizer with a higher active solid content produced a maximum cement flow, regardless of the w/b ratios. The LGL-based mortar samples admixed with this superplasticizer obtained a maximum compressive strength of about 36 MPa at the end of 28 days. SEM and XRD results showed the formation of a new calcium-rich mineral in their microstructure. These findings highlight the impact of the type and properties of superplasticizers on the performance of concrete mixes containing LGL as a supplementary cementitious material. [ABSTRACT FROM AUTHOR]

Lightweight and high-strength insulation materials have important application prospects in the aerospace, metallurgical, and nuclear industries. In this study, a highly porous silica fiber reinforced phenolic resin matrix composite was prepared by vacuum impregnation and atmospheric drying using quartz fiber needled felt as reinforcement and anhydrous ethanol as a pore-making agent. The effects of curing agent content on the structure, composition, density, and thermal conductivity of the composite were studied. The mechanical properties of the composite in the xy direction and z direction were analyzed. The results showed that this process can also produce porous phenolic resin (PR) with a density as low as 0.291 g/cm3, where spherical phenolic resin particles are interconnected to form a porous network structure with a particle size of about 5.43 μm. The fiber-reinforced porous PR had low density (0.372~0.397 g/cm3) and low thermal conductivity (0.085~0.095 W/m·K). The spherical phenolic resin particles inside the composite were well combined with the fiber at the interface and uniformly distributed in the fiber lap network. The composite possessed enhanced mechanical properties with compressive strength of 3.5–5.1 MPa in the xy direction and appeared as gradual compaction rather than destruction as the strain reached 30% in the z direction. This research provides a lightweight and high-strength insulation material with a simple preparation process and excellent performance. [ABSTRACT FROM AUTHOR]

In this study, a data‐driven model was developed to predict compressive strength of concrete columns after confining with Fiber‐Reinforced Polymer (FRP). Through application of Response Surface Method (RSM), interactions of input parameters are investigated in addition to their individual influence. Moreover, RSM is utilized in conjunction with unification to enhance model's accuracy. Furthermore, sensitivity analysis is employed together with RSM, to determine the effect size of statistically significant parameters. It is revealed that the real behavior of FRP confined concrete cannot be predicted by single‐parameter studies. Therefore, interaction terms should be included in the model to yield a more accurate prediction. Moreover, the model shows the highest sensitivity to FRP failure strength which this sensitivity decreases as corner radius increases. Therefore, regarding rounded‐corner sections, high improvements are achievable even by utilizing low strength FRPs. It is also shown that higher improvement may be limited due to premature debonding which elastic modulus mismatch between different phases is supposed to be responsible for it. [ABSTRACT FROM AUTHOR]