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In this study, a TiNbCrTa refractory complex concentrated alloy (RCCA) was prepared using vacuum arc remelting. The microstructural evolution and mechanical properties of both as-cast and heat-treated RCCA samples were analyzed. Heat treatment (HT) was performed at 800–1200 °C for 1 h in a vacuum-sealed environment. These samples exhibited a formation of Cr2Nb and Cr2Ti Laves phases. A variation in elemental distribution was observed, with interdendritic (ID) regions showing higher fractions of Ti and Cr, while the dendritic regions had a greater concentration of Ta and Nb. Micro-segregation at the IDs was confirmed through energy dispersive x-ray spectroscopy mapping, which inferred the formation of Cr- and Ti-rich phases during HT at 800–1200 °C. High-temperature HT at 1200 °C for 1 h led to the evolution of the hcp omega phase. Prolonged HT at 1200 °C for 96 h resulted in the evolution of a Cr-rich Laves phase (Cr2Ta), which was homogeneously distributed within the microstructure, indicating an unstable microstructure. Furthermore, despite prolonged HT, a variation in the elemental distribution persisted due to the presence of dendritic and ID regions. Electron backscattered diffraction analysis revealed the presence of bcc and hcp phases in the dendritic and ID regions, respectively, of the as-cast and HTed samples. The as-cast samples demonstrated a high compressive strength of approximately 2 GPa. Micro-hardness values increased with the HT temperature up to 1000 °C. Further increases under HT conditions did not significantly reduce the microhardness value, whereas prolonged HT at 1200 °C led to an increase in the microhardness value. Overall, the newly developed TiNbCrTa RCCA exhibited high-strength behavior even after the phase transformation. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The purpose of this study was to determine the in vitro effects of a single exposure of bupivacaine on the mechanical properties of bovine cartilage explants at 3 weeks. DESIGN: Femoral condyle articular cartilage explants were aseptically harvested from juvenile bovine stifle joints before being exposed to chondrogenic medium containing 0.50% (wt/vol) bupivacaine, 0.25% (wt/vol) bupivacaine, or no medication (control) for 1 hour. Explants were then washed and maintained in culture in vitro for 3 weeks before testing. Cell viability, tensile and compressive mechanical properties, histological properties, and biochemical properties were then assessed. RESULTS: Explants exhibited a dose-dependent decrease in mean tensile Youngs modulus with increasing bupivacaine concentration (9.86 MPa in the controls, 6.48 MPa in the 0.25% bupivacaine group [P = 0.048], and 4.72 MPa in the 0.50% bupivacaine group [P = 0.005]). Consistent with these results, collagen content and collagen crosslinking decreased with bupivacaine exposure as measured by mass spectrometry. Compressive properties of the explants were unaffected by bupivacaine exposure. Explants also exhibited a trend toward dose-dependent decreases in viability (51.2% for the controls, 47.3% for the 0.25% bupivacaine-exposed group, and 37.0% for the 0.50% bupivacaine-exposed group [P = 0.072]). CONCLUSIONS: Three weeks after 1-hour bupivacaine exposure, the tensile properties of bovine cartilage explants were significantly decreased, while the compressive properties remained unaffected. These decreases in tensile properties corresponded with reductions in collagen content and crosslinking of collagen fibers. Physicians should be judicious regarding the intra-articular administration of bupivacaine in native joints.

Over the last decade, bioactive silicates have gained significant interest as bone graft substitutes due to their excellent ability to repair, replace, and regenerate damaged tissue in injured bone. In this work, a sol–gel combustion route was used to synthesize nanostructured barium-doped diopside (Ca1-XBaXMgSi2O6) using stoichiometric amounts of calcium nitrate, magnesium nitrate, and barium nitrate as oxidizers, and tartaric acid as a fuel. The resultant powder was examined by powder XRD to confirm the phase purity. Pure phase of diopside was achieved at 850 °C without any secondary phase. For functional group analysis, FT-IR was employed, and microscopic imaging (SEM/EDAX) was used to study morphological changes. Due to barium doping in the diopside matrix, the crystallite size was reduced, and the mechanical and degradation properties of the prepared pellets was enhanced after immersion in SBF medium over a period of time. The results show compressive strength of the doped diopside was found to be 169 MPa, closer to cortical bone strength and similar to previous findings. It can be concluded that barium can be considered as a dopant to improve bioactivity of Ca-Mg silicate for hard tissue application. [ABSTRACT FROM AUTHOR]

In this study, the feasibility of preparing a calcined laterite–phosphoric acid–Fe 3 O 4 -based geopolymer is investigated and its application for immobilizing radioactive borate liquid waste (RBLW) is explored. The addition of Fe 3 O 4 enhances the compressive strength of the geopolymer and mitigates the retardation effects on the geopolymer caused by RBLW. Reactions between Fe 3 O 4 and H 3 PO 4 not only promote the geopolymerization process by generating heat and forming additional geopolymer gel, but also produce amorphous iron–phosphorus phases, contributing to higher compressive strength of the waste forms. Moreover, partial replacement of [AlO 4 ] tetrahedra with [FeO 6 ] octahedra creates stable –Fe–O–P–O–Al–O–Si– network structures. The geopolymer waste forms exhibit remarkable leaching resistance after Fe 3 O 4 addition owing to the reduced open porosity, leading to radionuclide immobilization through physical encapsulation more efficiently. Furthermore, residual Fe 3 O 4 may contribute to Co2+ immobilization through magnetic adsorption. Overall, the calcined laterite–phosphoric acid–Fe 3 O 4 -based geopolymer waste forms exhibit excellent performance in immobilizing RBLW, offering a new strategy for RBLW treatment. [ABSTRACT FROM AUTHOR]

Achieving low thermal conductivity (κ) is an ideal goal for porous ceramics in high-temperature thermal insulation applications. In this study, a novel high-entropy (La 0.2 Ce 0.2 Sm 0.2 Eu 0.2 Gd 0.2)PO 4 (HE (5RE 1/5)PO 4) ceramic possessing the lowest intrinsic thermal conductivity has been screened from 21 kinds of potential high-entropy phosphate with five components. The porous HE (5RE 1/5)PO 4 ceramics with 30-50 wt% solid loading are fabricated by the particle-stabilized foaming method and the corresponding thermophysical properties are systematically investigated. The porous HE (5RE 1/5)PO 4 ceramics with 35 wt% solid loading display a better balance between compressive strength (1.51 MPa) and thermal conductivity (0.086 W m−1 K−1). Furthermore, porous HE (5RE 1/5)PO 4 ceramics possess a thermal insulating capability over 878 °C, indicating excellent thermal insulation performance. These excellent characteristics enable porous HE (5RE 1/5)PO 4 ceramics to be an excellent candidate material for high-temperature thermal insulation applications in the future. [ABSTRACT FROM AUTHOR]

Magnesium oxysulfate (MOS) is an emerging magnesium-based cementitious material gaining attention increasingly in construction and road maintenance because of its advantages. However, MOS cement made from lightly-calcined magnesia (LCM) with low activities (around 60 %) has too low setting rates. Increasing the MgO activity can accelerate the setting but often results in a material that sets too rapidly and is too weak to be useful in practical engineering operations. To address this challenge, we developed a novel method to produce MOS cement with the appropriate setting and mechanical strength required by practical engineering operations. The method involves ball-milling raw materials of LCM with an activity exceeding 80 % and magnesium sulfate heptahydrate (MgSO 4 ⋅7H 2 O) to effectively promote particle aggregation and bonding, thereby contributing to an enhanced ability to properly control the hydration reaction process in subsequent cement preparation. Based on this new method, we utilized both low- and high-activity raw LCM materials to prepare MOS cement samples and analyzed their characteristics, including setting time, mechanical strength, water resistance, chemical composition, and microstructure. The results indicate that with highly active MgO raw material, the new method can prepare the MOS cement samples that not only have a practical engineering-needed setting time of around 1 h but also increase the compressive strength fourfold. This study offers a promising technique for producing a cementitious material suitable for prompt emergency repairs of transportation roads and infrastructures. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, x ZrB 2 -AlCoCrFeNi (x = 0,5,10,15) (wt%) based high entropy alloy (HEA) composites were prepared by Spark Plasma Sintering (SPS). The influence of ceramic particle ZrB 2 content on the densification behavior, microstructural evolution, and mechanical properties of the composites was investigated through scanning electron microscopy, X-ray diffraction, and mechanical performance testing. The results indicate that the HEA composites undergo a phase transformation, from (FCC + BCC + B2) structure to (FCC + BCC + B2+Laves) structure with the addition of ZrB 2. The incorporation of ZrB 2 facilitates the emergence of the Cr precipitate phase, and the grain size of this phase enlarges as the ZrB 2 content rises. Additionally, when the ZrB 2 content is 10 %, the maximum compressive strength reached 2071 MPa. Furthermore, at the ZrB 2 content of 15 %, the composite material achieves a maximum densification of 99.13 % and a maximum hardness of 1222.2 HV. [ABSTRACT FROM AUTHOR]

This research mainly focused on studying the influence of various curing media on the properties of lightweight geopolymer composites. Here, Ground Granulated Blast furnace Slag (GGBS), Paddy straws, and the combination of sodium silicate and sodium hydroxide at the ratio of 2.5:1 were used to produce geopolymer composites. For this experiment, two different parameters, i.e., variation of paddy straw (0, 5, 10, 15, and 20%) and variation of curing media (Intermittent, Heat, and Saline water), were chosen. The compressive strength of a 20% addition of paddy straw is dramatically reduced by 88.6%, while the density is reduced to 40.42%. Maximum flexure and tensile strength were noted as 65.11 and 45.5%, respectively, for the 15% addition of paddy straw. An interesting fact found from the samples cured under Saline water enhanced the overall compressive strength, tensile and flexural strength by 12.85, 45.5, and 21.2%, respectively, compared to the other two curing media. [ABSTRACT FROM AUTHOR]

Direct ink writing (DIW) is one of the facile and versatile manufacturing techniques for additive manufacturing of ceramics. 3D printed porous boehmite structures fabricated via DIW can offer significant benefits in terms of their high specific surface area and robust mechanical properties, rendering them suitable for applications like catalysis, adsorption, etc. The characteristics of the boehmite structures produced through 3D printing are significantly influenced by several parameters associated with the DIW process, including but not limited to solids concentration in the ink, resolution, and drying time. In this work, for the first time, we try to optimize the DIW parameters for 3D printing of porous boehmite structures to achieve better shape stability, resolution, and mechanical properties. A shear-thinning boehmite ink was prepared by peptization of boehmite powder in nitric acid and the rheological properties were optimized by varying concentrations of boehmite and nitric acid. Boehmite ink with a solid loading of 37 % and a pH of 4 was found to have the optimal rheological properties and printability. A Menger sponge porous structure was printed by DIW using the optimized ink with different sample sizes and resolutions. The resolution and size were optimized for better shape accuracy of printing and structural integrity. Crack-free boehmite structures were obtained by optimizing the drying time. Boehmite structures printed with higher resolution resulted in enhanced compressive strength and energy absorption, i.e., compressive strength and energy absorption of 0.5 mm resolution boehmite structure is enhanced by 208 % and 144 %, respectively, compared to the 1 mm resolution structure. [ABSTRACT FROM AUTHOR]

Channel fracturing technology is designed to form fractures supported by non-uniform pillar proppants. Non-cured adhesive resin-coated proppant gradually becomes viscous after immersion and agglomerates during transportation. The pillars are stable after the fracture is closed. They not only maintain a certain compressive strength but also maintain long-term conductivity. Currently, there are few evaluations of coated proppant migration. Based on CFD-DEM method, a two-phase flow coupling model considering the adhesive contact force of coated proppant particles is established to study the cementation characteristics of coated proppant during transportation. The transportation mechanism of coated proppant are revealed by numerical calculation analysis. The results show that different from the conventional proppant, the migration process of the coated proppant is divided into four stages (1) the softening of the proppant contact; (2) the paving of the proppant agglomeration; (3) proppant pillars growth along fracture height; and (4) proppant pillars growth along fracture length. We have completed a preliminary geometric characteristics evaluation of sand bank formed by coated proppant by evaluating the pore volume ratio (the ratio of void volume between pillars to the sand bank volume) under various parameters. This evaluation offers some theoretical guidance for the optimization of channel fracturing proppant injection parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] Low mechanical strength is still the key question for collagen hydrogel consisting of nanofibrils as hard tissue repair scaffolds with no loss of biological function. In this work, novel collagen nanofibrous hydrogels with high mechanical strength were fabricated based on the pre-protection of trisodium citrate masked Zr(SO 4) 2 solution for collagen self-assembling nanofibrils and then further coordination with Zr(SO 4) 2 solution. The mature collagen nanofibrils with d -period were observed in Zr(IV) mediated collagen hydrogels by AFM when the Zr(IV) concentration was ≥ 10 mmol/L, and the distribution of zirconium element was uniform. Due to the coordination of Zr(IV) with ─COOH, ─NH 2 and ─OH within collagen and the tighter entanglement of collagen nanofibrils, the elastic modulus and compressive strength of Zr(IV) mediated collagen nanofibrous hydrogel were 208.3 and 1103.0 kPa, which were approximate 77 and 12 times larger than those of pure collagen hydrogel, respectively. Moreover, the environmental stability such as thermostability, swelling ability and biodegradability got outstanding improvements and could be regulated by Zr(IV) concentration. Most importantly, the resultant hydrogel showed excellent biocompatibility and even accelerated cell proliferation. [ABSTRACT FROM AUTHOR]

The dispersion of nano‐SiO2 (NS) in cement plays a critical role in enhancing the properties of cementitious materials. In this study, the combination of ultrasonic dispersion and polycarboxylic acid water reducing agent (PCE) was used to significantly improve the dispersion of NS. The effects of ultrasonic dispersion time, NS content, and PCE content on dispersion quality were investigated, alongside their impact on mechanical properties, electrical resistivity, and frost resistance. The results demonstrated that this synergistic method optimized the dispersion of NS, leading to superior mechanical properties and frost resistance. With an ultrasonic dispersion time of 40 min, NS content of 1.0 wt.%, and PCE content of 0.75 wt.%, the cement paste achieved its optimal performance. Compared to non‐dispersed samples, compressive strength increased by 33.7%. After 75 freeze–thaw cycles, the mass loss was 2%, the relative dynamic elastic modulus was 99.15%, and the strength loss was 13.74%. [ABSTRACT FROM AUTHOR]

Concrete is a constantly evolving building material whose demand is increasing due to population growth and urban development. This calls for more research on this composite material to improve its performance. However, concrete has some disadvantages, including that it is a brittle material and cannot withstand tensile stress. Therefore, rebars and fibers are incorporated into concrete to improve this property. Although previous works investigated the properties of concrete containing steel fibers, most of them were concerned with mechanical properties, while the durability properties still require further investigation to understand them. Thus, the purpose of this study is to ascertain how adding steel fibers to concrete in varying proportions (0.5, 1.0 and 1.5%) affects its mechanical and durability properties, including compressive strength, flexural strength, tensile strength, bulk density, water absorption, mode of failure, ultrasonic pulse velocity, dynamic modulus of elasticity and electrical resistance. Statistical relationships between the compressive strength and other characteristics were also established. The results indicated that all mechanical and durability characteristics significantly improved after adding steel fibers for all addition ratios, except for electrical resistivity, which showed lower values than the reference mixture for the 0.5 and 1% steel fiber proportions. Moreover, it was found that the best addition rate of steel fibers was 1.5%. At this percentage, the recorded increasing rates over the control sample were 29.3% in compressive strength, 83.7% in tensile strength, 27.9% in flexural strength, 50.1 in water absorption resistance, and 11.2% in electrical resistivity. [ABSTRACT FROM AUTHOR]

Low‐shrinkage porous mullite–zirconia ceramics were prepared using Al and ZrSi2 as raw materials and AlF3 as the whisker catalyst through foam‐gelcasting and freeze‐drying methods. The oxidation of Al and ZrSi2 combined with the Kirkendall effect and volume expansion was employed to reduce the sintering shrinkage, while the mullitization was promoted by the reaction between AlF3 and extra ZrSi2, and ZrO2 were generated to enhance the compressive strength as the reinforcing phase. The effect of AlF3 and ZrSi2 content on the microstructure and properties of porous mullite‐zirconia were explored. These ceramics exhibited high porosity (73.75%–85.02%) and compressive strength (2.98–17.71 MPa), low shrinkage (0.47%–10.89%) and thermal conductivity (0.228–0.462 W/(m·K)). In particular, the porous mullite–zirconia ceramics with great compressive strength (4.01 MPa) companied with near‐zero shrinkage (0.47%) at the AlF3 content of 15 wt% and extra ZrSi2 content of 20 wt% by introducing the reinforcing phase (ZrO2). Additionally, the temperature difference around 950°C of the porous ceramics during the heating test proved the exceptional application on thermal insulation. [ABSTRACT FROM AUTHOR]

Based on an orthogonal experimental design, this study introduces rubber powder particle size alongside rubber powder content, aggregate gradation, and cement content as factors. A total of 16 mix proportions were formulated. For each mixture, compaction tests and unconfined compressive strength (UCS) tests were conducted. Using Statistical Product and Service Solutions (SPSS) software, a multifactor variance analysis was performed to determine the influence levels of the four factors on maximum dry density and compressive strength. The optimal mix proportion was selected based on compressive strength. The results indicate that aggregate gradation and rubber powder content significantly affect the maximum dry density of the mixture, with aggregate gradation having the greatest impact. Rubber powder content has the most substantial effect on compressive strength, while rubber particle size has the least influence. The optimal formulation is 7% cement content, 30-mesh rubber powder, 0.5% rubber powder content, and a skeletal dense gradation close to the median. [ABSTRACT FROM AUTHOR]

Lepidolite ore contains abundant lithium resources; however, the extraction process generates a large number of tailings, which are environmentally hazardous solid waste. Currently, cemented fiber reinforcement and tailings filling technologies are commonly used methods for tailings treatment. The fiber length and geometric shape significantly affect the performance of fiber-reinforced cemented lepidolite tailing backfill (CLTB). However, there is limited research on the impact of these two factors on the performance of CLTB. Consequently, Polypropylene fiber-reinforced CLTB of four sizes and four fiber lengths were prepared and used for uniaxial compressive strength (UCS) tests. The max UCS of fiber-reinforced CLTB was 2.84 MPa, and the maximum increase percent was 83.7% compared with the non-fiber-reinforced CLTB. The experimental results show that when the fiber length was 12 mm the CLTB had the maximum UCS, longer fibers did not necessarily result in a higher UCS. The end effect was significant when the difference in cross-sectional area was small. The UCS of the L-40 sample was higher than that of the Y-50 sample under the same fiber length. The differences in the size effect and geometric shape were the main factors influencing their mechanical performance. When the fiber length was from 0 mm to 6 mm, the size effect was obvious, the UCS values gradually decreased with an increase in the volume ratio and cross-sectional area. However, the fiber length was the primary factor influencing the fitting curve of the UCS when the fiber length was from 12 mm to 19 mm. Additionally, the addition of fibers enhanced the integrity of CLTB. In other words, fiber-reinforced CLTB exhibited improving structural integrity. This study can provide theoretical references for the research and practical applications of fiber-reinforced fillers and size effects, as well as the treatment of lepidolite tailings, while also reflecting the CLTB performance under the action of different sizes and different fiber lengths, improving the filling efficiency, mining, and backfill safety. [ABSTRACT FROM AUTHOR]

Nowadays, when regenerable alternative green sources are attracting more caution under sustainability targets, kapok and coconut fibers, known as natural fibers, have come to the fore as a very significant raw material source. In this experimental study, compressive strength, thermal insulation, and pore structure characteristics of kapok fiber (KP)– and coconut fiber (CC)–incorporated concrete samples under different curing conditions were analyzed. For that purpose, randomly distributed fiber-incorporated concrete mixtures containing 0%, 0.5%, 1%, and 1.5% KP and CC fiber by the weight of cement were prepared and under H2O2 and NaClO curing conditions, the effects of KP and CC fiber inclusion on properties mentioned above of fiber-incorporated concrete samples were researched in detail. Experimental results depict that a maximum thermal conductivity coefficient decrease of 24.31% was detected at a content ratio of 1.5% by the reason of the pore modification effect of used natural fibers in the H2O2 curing group. Because of the remarkable pore modification effect of KP fiber incorporation into the cement matrix compared to the CC fiber inclusion cases, strong linear correlations revealing the insulation-strength mechanism could be detected for both H2O2 and NaClO curing cases. This work intends to promote sustainable development in the building industry by integrating natural fibers into concrete mixtures as an innovative design approach. [ABSTRACT FROM AUTHOR]

A key goal of environmental policies and circular economy strategies in the construction sector is to convert demolition and industrial wastes into reusable materials. As an industrial by-product, Waste marble (WM), has the potential to replace cement and fine aggregate in concrete which helps with saving natural resources and reducing environmental harm. While many studies have so far investigated the effect of WM on compressive strength (CS), it is undeniable that conducting experimental activities requires time, money, and re-testing with changing materials and conditions. Hence, this study seeks to move from traditional experimental approaches towards artificial intelligence-driven approaches by developing three models—artificial neural network (ANN) and hybrid ANN with ant colony optimization (ACO) and biogeography-based optimization (BBO) to predict the CS of WM concrete. For this purpose, a comprehensive dataset including 1135 data records is employed from the literature. The models' performance is assessed using statistical metrics and error histograms, and a K-fold cross-validation analysis is applied to avoid overfitting problems, emphasize the models' reliable predictive capabilities, and generalize them. The statistical metrics indicated that the ANN-BBO model performed best with a correlation coefficient (R) of 0.9950 and root mean squared error (RMSE) of 1.2017 MPa. Besides, the error distribution results revealed that the ANN-BBO outperformed the ANN and ANN-ACO with a narrower range of errors so that 98% of the predicted data points in the training phase by the ANN-BBO model experienced errors in the range of [-10%, 10%], whereas for the ANN-ACO and ANN models, this percentage was 85% and 79%, respectively. Additionally, the study employed SHapley Additive exPlanations (SHAP) analysis to clarify the impact of input variables on prediction accuracy and found that the specimen's age is the most influential variable. Eventually, to validate the ANN-BBO, a comparison was performed with the results of previous studies' models. [ABSTRACT FROM AUTHOR]

This paper aimed to research the role of zeolite and palm fiber in changing strength of cement-treated soil. The unconfined compressive strength (UCS) testwas mainly used to study the changes of strength of cement-treated soil by varied content of cement, zeolite, palm fiber under different curing period. The optimum substitution rate of zeolite for cement was researched for the purpose of increasing of strength of cement-treated soil and low carbon and environment protection, while the optimum content of palm fiber was explored for improving of strength and ductility of cement-treated soil by means of analytic software. Finally, the multiple regression technology was used to try to capture the relationship between strength of cement-treated soil and content of zeolite and palm fiber. The results show that the cement, zeolite, palm fiber and curing age have strong effect on the UCS of cement-treated soil. [ABSTRACT FROM AUTHOR]

AbstractIn this study, the life cycle and performance of normal concrete containing 35% limestone and 2% gypsum made in different ratios of water to binder (w/b) were examined. Its cost and CO2 emissions were found to be 13% and 35% lower compared to the control concrete. However, because of the greater replacement of cement with limestone filler, there is a reduction in its workability, the development of heat and strength, and the penetration resistance of water and chloride ions, especially in the early ages. The addition of gypsum marginally improved these concrete properties, but its quantity should be limited to 2% by weight of the binder. The use of gypsum beyond this limit led to a significant decrease in the properties of concrete. Anorthite, a calcium aluminosilicate mineral, was found in this concrete, and its fractured morphology was found to be more occupied with unreacted angular limestone particles. This low-carbon concrete showed an improvement in compressive strength with decreasing w/b ratios. The limestone reserve in India is abundant and spread evenly across its length and depth, and its use as the main replacement for cement in normal strength mixes would greatly reduce the impact of CO2 on the environment. [ABSTRACT FROM AUTHOR]

Deep‐sea equipment is generally made of lightweight and pressure‐resistant materials in order to meet the requirements of the actual work. In order to explore marine resources better, it is necessary to research lightweight buoyancy materials for loading on mining equipment. These buoyancy materials contribute not only to providing adequate buoyancy to the mining equipment but also to reducing economic expenses. In this paper, hollow glass microspheres reinforced epoxy hollow spheres (HGMSs‐EHSs) were prepared by the rolling ball method using expanded polystyrene (EPS), epoxy resin (EP), and HGMS as raw materials. Epoxy syntactic foam (ESF) was manufactured by blending EP, curing agent, HGMS, and HGMS‐EHS with molding method. Basalt fiber (BF) reinforced ESF was fabricated by adding BFs to form a fiber network inside the syntactic foam. The results revealed that the density and compressive strength of ESF increased progressively with the number of HGMS‐EHS layers. The density and compressive strength of ESF decreased prospectively with the increase of the stacking volume fraction of HGMS‐EHS. The density and compressive strength of ESF increased gradually with the enlargement of the length and content of BF. In the range of influencing factors mentioned above, the density of ESF remains around 0.3 g/cm3, which has a low density. When the number of layers of HGMS‐EHS was two, the stacking volume fraction was 90%, the length of BF was 12 mm, the content of BF was 4%, the density of BF‐ESF was 0.316 g/cm3, and the compressive strength was 6.93 MPa. The compressive strength of prepared buoyancy material can meet the pressure resistance requirements for operations in waters of a certain depth. With a density of only 0.316 g/cm3, it provides sufficient buoyancy to balance the gravity of the equipment. Compared with the current study, in this paper, BFs were used as the reinforcing phase to prepare solid buoyancy foam with low density and high compressive strength. The experimental results demonstrate that this economical fiber material can effectively improve the compressive strength of buoyancy materials. This buoyancy material may be suitable for loading on small equipment for extracting marine resources. This work provides a reference for the preparation of low‐density solid buoyancy materials. [ABSTRACT FROM AUTHOR]

Lightweight concrete, particularly polystyrene concrete, has been extensively utilized in civil engineering for decades. The incorporation of waste expanded polystyrene (EPS) as a filler material in the production of lightweight concrete presents significant advantages from a circular economy perspective. Prior research indicates that increasing the proportion of lightweight aggregates, such as EPS, typically results in reductions in strength and bulk density. The utilization of substantial amounts of EPS waste in the formulation of structural polystyrene concrete is crucial for advancing sustainable construction practices. This study investigates the effects of varying nano-silica content on the bulk density, compressive strength, flexural strength, splitting tensile strength, and water penetration depth of structural polystyrene concrete. Concrete specimens were prepared by substituting 25%, 50%, 75%, and 100% of sand with EPS waste, while evaluating nano-silica contents of 0.75%, 1%, and 1.25%. The findings reveal that increasing the volume fraction of EPS corresponds to a decrease in the concrete's bulk density. This research provides critical insights into optimizing structural lightweight concrete, thereby promoting advancements in sustainable construction applications. [ABSTRACT FROM AUTHOR]

This study analyzed the enhancement effects and mechanisms of steel, glass, and polypropylene fibers on the mechanical properties of concrete, aiming to guide the selection of suitable fiber types and dosages for shotcrete projects. Through laboratory tests, numerical simulations, and field experiments, it investigated the enhancement laws of flexural and compressive strengths of concrete with different dosages of these three fibers. Results showed: (1) After 28 days of curing, flexural strength peaked with 2.0% steel, 1.5% glass, and 2.0% polypropylene fibers, increasing by 118.6%, 42.86%, and 138.6%, respectively, over plain concrete. Compressive strength increased by 2.13%, 10%, and 18.3% at optimal dosages of 0.5%, 1.0%, and 2.0% for steel, glass, and polypropylene fibers. Fiber effects on compressive strength were less significant than on flexural strength, with polypropylene fibers outperforming the others. (2) Based on ABAQUS numerical simulations, microscopic analysis indicates that fibers, due to their high yield capacity, enhance the connections between concrete elements, reduce stress concentration, and improve the mechanical properties of concrete. (3) For shotcrete, 2.0% polypropylene fibers were preferred due to high flexural strength and reduced agglomeration. (4) The optimal dosage was applied to a mine's wet shotcrete support, effectively controlling tunnel deformation. These findings provide practical guidance for shotcrete applications. [ABSTRACT FROM AUTHOR]

Graphite/geopolymer composite is a promising smart material that can be used in various applications. This paper reports the design of strong self‐heating graphite/geopolymer composites with high graphite percentages up to 120 wt% of metakaolin. The physical, mechanical, electrical, and electrothermal performance of composites were investigated; the compressive strength was tested at various ages and the electrothermal performance was tested using AC and DC voltages. The results showed that a compromise between high compressive strength and high electrothermal conversion can be achieved when a specific balance between the percentage of the graphite and the water content is established. The current study specified the reason for the deterioration of the electrothermal performance of the graphite/geopolymer composites, that is, the formation of a barrier layer between the electrode and the sample surface; it has been found that this can be avoided by removing the free ions from the geopolymer via washing. A composite with 47 ± 1 MPa compressive strength and stable electrothermal performance of 98°C at 6 DC volts can be prepared using 90 wt% graphite and 57 mL water content. This work is a step in the future innovation of smart construction using self‐heating and antifreezing construction materials. [ABSTRACT FROM AUTHOR]

High-performance SiC aerogels are sought after for their superior thermal insulation and absorption properties, especially in applications such as electromagnetic stealth for aero engines and high-temperature radar stealth. However, achieving SiC aerogel with both temperature resistance and strong wave absorption while controlling their properties remains a significant challenge. This study investigates the influence of reactant concentrations on the structure, thermal insulation, and absorption performance of SiC aerogels synthesized via the sol-gel method. The aerogel synthesized with a n(C):n(Si) ratio of 1:2 showed superior thermal insulation. Additionally, it showed excellent electromagnetic wave absorption, with a minimum reflection loss of −53.80 dB at 6.16 GHz and a maximum effective absorption bandwidth of 3.10 GHz at a thickness of 2.40 mm. Furthermore, the maximum compressive strength of C/SiC@SiC reached 0.98 MPa, a notable improvement of 81.48 % compared to the pristine C/SiC matrix. The maximum effective absorption bandwidth of C/SiC@SiC was increased to 6.06 GHz at 2.35 mm, and the surface center temperature decreased from 183.1 °C for C/SiC to 130.1 °C for C/SiC@SiC. Overall, this study offers valuable insights into the development of advanced absorption and thermal insulation materials, providing a foundation for further research and innovation in this field. [ABSTRACT FROM AUTHOR]

The performance of the Ca(OH) 2 –Al 2 O 3 –SiO 2 –H 2 O hydroceramic system (with and without Al 2 O 3) as a potential well cementing material was investigated from both macroscopic and microscopic perspectives. To simulate the harsh conditions typical of deep wells, marked by high temperature and pressure, the material was cured at 240 °C and 50 MPa. Several hydroceramic systems with varying compositions were designed and a retarder was used to optimize the thickening time of all systems. Finally, the optimized hydroceramic systems were cured for different periods ranging from 2 to 90 days to investigate their long-term stabilities. It is found that the raw materials with finer particle sizes and higher reactivity (such as silica fume and nano-activated alumina) could improve the performance of the hydroceramic system, evidenced by increased compressive strengths and decreased permeability. Changing the Ca/Si molar ratio within the range from 2:1 to 1:1 had little effect on the physical and mechanical properties of the hydroceramic system, despite significant variations in the composition of hydration products. The hydroceramic systems exhibited good stability over a curing period from 2 to 30 days, but strength retrogression phenomenon was observed during longer curing periods from 30 to 90 days. Microscopic evaluations revealed that the strength retrogression could be due to the formation of reyerite in high calcium systems, while it was the conversion of amorphous C–S–H to xonotlite that led to the strength retrogression in low calcium systems. [ABSTRACT FROM AUTHOR]

In this work, the A 18 B 4 O 33 w (ABOw) was in-situ generated on the surface of Al 2 O 3 through the reaction of B 2 O 3 and Al 2 O 3 , resulting in the thorn structure. Then, the ABOw@Al 2 O 3 /AZ91 composites were fabricated through a combination of freeze casting and pressure casting. The influence of the initial content of B 2 O 3 on the microstructure and mechanical properties of ABOw@Al 2 O 3 /AZ91 composites was investigated. The results show that the lamellar structure of ABOw@Al 2 O 3 /AZ91 composites were weakened, which gradually changed to dendritic structure with the increasing B 2 O 3 content. The in-situ formation of ABOw on the surface of Al 2 O 3 was favorable to improve the compressive strength of both ABOw@Al 2 O 3 ceramic scaffold and ABOw@Al 2 O 3 /AZ91 composites, while also reducing the anisotropy of the composites. Furthermore, the in-situ generated ABOw within the ceramic layer could effectively relieve stress concentration and delay crack initiation and propagation, which led to the enhancement of the load-bearing capacity of ABOw@Al 2 O 3 /AZ91 composites. The ABOw@Al 2 O 3 /AZ91 composite exhibited the outstanding mechanical properties with the compressive strength of ∼685 MPa, when the B 2 O 3 's content is 5 wt%. [ABSTRACT FROM AUTHOR]