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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]

Fibrous porous ceramics have been receiving more and more applications in the thermal protection field of vehicles. In this study, we prepared Y 2 Si 2 O 7 fibrous porous ceramics (YFPCs) from Y 2 Si 2 O 7 fibrous membranes via the molding method. The influence of sintering time and binder concentration on the properties of YFPCs was studied, and the oxyacetylene ablation behavior with different heat fluxes was also investigated. The results showed that YFPCs obtained at 2 h sintering time had a stable component composition and constant mechanical strength. YFPCs prepared at 40 wt% binder concentration had the maximum density and compressive strength, 0.47 g/cm3 and 0.68 MPa, respectively. The as-prepared ceramics exhibited favorable ablation resistance after oxyacetylene ablation for 120 s. The minimum linear ablation rate was 2.02 μm/s when the ablated surface temperature reached 1390 °C. When the surface temperature increased to 1872 °C and 2200 °C, the fibers on the ablated surface began to melt, and the linear ablation rate increased to 9.63 μm/s and 77.63 μm/s, respectively. [ABSTRACT FROM AUTHOR]

Copper smelting slag (CSS) are waste slag obtained from smelters after reusing sulphur smelting slag. This study explores the potential of CSS to serve as a resource in cement mortar construction. Specifically, the study investigates the use of mechanical and chemical methods to enhance the volcanic ash activity of CSS, enabling them to replace up to 30 % of the cement content in cement mortar. The modified CSS was analyzed in terms of particle size and (Toxicity Characteristic Leaching Procedure) TCLP testing, while cement mortar specimens were subjected to a battery of tests including compressive strength, Freeze-thaw experiment, TCLP testing and cement stability testing. The results showed that compared with the unmodified CSS material, the copper smelting slag cement material with CaCO 3 meets the requirements of GB/T 1596–2017 on the standard compressive strength of OPC 42.5 grade, with a compressive strength of 38.88 MPa at 10 % CaCO 3 admixture, among which the CSS cement material with 10 % CaCO 3 is the best and meets the leaching toxicity standard. Moreover, the modified CSS reduced energy consumption by 7.15 %, CO 2 emissions by 27.41 %, and cost by 19.84 %. XRD, FTIR and SEM analysis showed that the mechanical activation of CaCO 3 doping more drastically damaged the crystal structure of CSS, and local lattice distortion occurred, which induced the transformation of CSS from crystalline phase to amorphous phase and destroyed the ordered structure of minerals, resulting in the volcanic ash activity increased. Overall, this study demonstrates that CSS can serve as a viable raw material in cement mortar samples, reducing environmental impact and achieving resourceful use of slag. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper proposes a novel strategy to fabricate porous calcium hex-aluminate (CA 6) ceramics using CaCl 2 -KCl as reactive medium. Effects of CaCl 2 -KCl content and sintering temperature on microstructure and properties of porous CA 6 ceramics are systematically studied. CaCl 2 -KCl serves as both a pore former and an additional source of CaO, eliminating the need for additional salt-washing treatment. By optimizing CaCl 2 -KCl content to 20 wt%, porous CA 6 ceramics with well cross-interlocking plate-like structures, possessing low thermal conductivity of 0.32 W·(m·K)−1 (1000°C), high apparent porosity of 68.28%, and desirable compressive strength of 6.76 MPa, are fabricated at 1300°C. This work not only validates the promising applicability of porous CA 6 materials for thermal insulation, but also introduces an auspicious fabrication methodology for thermal insulation materials. [ABSTRACT FROM AUTHOR]

Bioactive ceramic bone scaffolds are limited by their brittleness. To address this limitation, we developed a new method for preparing β-tricalcium phosphate (β-TCP)/polycaprolactone (PCL) porous composite scaffolds with a gradient structure using digital light processing technology and an impregnation process. The composite scaffolds exhibited compressive strength comparable to that of pure β-TCP scaffolds but with substantially higher toughness and reliability, especially during in vitro degradation. Owing to the gradient structure, the composite scaffolds could gradually shift from high strength and stiffness to moderate strength and low stiffness, which is beneficial for bone healing and remodeling. In femoral condyle defects without mechanical stimulation, the β-TCP/PCL composite scaffolds exhibited slightly lower cellular compatibility and osteoinductive ability than those of the pure β-TCP scaffolds. However, in radial defects, composite scaffolds demonstrated a better mechanical response and bone growth capacity. The composite scaffolds maintained their structural integrity after 2–4 months, whereas the β-TCP scaffolds fractured within 2 months. This study provides a novel methodology for the development of effective scaffold fabrication strategies for load-bearing or large segmental defects with complex stress applications for use in bone healing and remodeling. [ABSTRACT FROM AUTHOR]

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. Highlights: 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]

Thermoplastic polycarbonate provides minimal structural weight and ductility and is a recyclable material. However, investigation of the characteristics of hybrid composites reinforced with woven glass and polycarbonate sheets is limited. This current study investigated the effect of integration of polycarbonate sheets on glass fiber‐epoxy hybrid composite performance. Non hybrid laminate was fabricated from eight layers of woven glass fiber impregnated with epoxy resin (NG). However, the hybrid samples utilized various symmetric stacking patterns which were made by alternating two processed polycarbonate (PC) sheets with six layers of woven glass fiber embedded with epoxy matrix. The manufacturing was made using the hand layup procedure. Mechanical testing includes compressive, tensile, bearing, and hardness was performed on hybrid and non‐hybrid composites. The results showed that employing PC sheets instead of fibers affect the laminate's strength, ductility, bearing capacity, and hardness. Utilization of PC sheets reduces both compressive and tensile strength. However, an enhancement in tensile, compressive, and bearing failure strain was achieved by 2.5%, 31.25% and 31.7%, respectively with hybrid composite having PC in the skin layers as compared with NG. The extent of failure damage is correlated with the position of the PC sheets in the tested samples. Highlights: Novel hybrid composites of woven glass fiber and polycarbonate sheet as reinforcement with various stacking orders were successfully prepared by the hand lay‐up method.The compressive strain of hybrid PC samples are higher than NG sample.The hybrid PC composites showed an improved bearing strength and strain performance.The influence of sample configuration on the damage mechanisms has been investigated. [ABSTRACT FROM AUTHOR]

This research investigated the mechanical property and hydration process of sintered sludge cement (SSC) paste, focusing on the effects of calcination temperature of sludge, sintered sludge ash (SSA) content, curing age, and water‐binder ratio using isothermal calorimetry, X‐ray diffraction, scanning electron microscopy, and multiple regression. Increasing calcination temperature enhanced the compressive strength of SSC paste due to the decomposition of minerals like Clinochlore and Muscovite. The compressive strength decreased by 2.4%–49.4% when the SSA content increased from 0% to 50%, with more significant declines noted at higher water‐binder ratios. Notably, the 7‐day compressive strength of the cement paste with 10% SSA showed little change, and the 28‐day compressive strength actually increased at a water‐binder ratio of 0.4. SSA slowed down the hydration rate of cement and induced more Monocarbonate to form in the early stage. A multiple linear regression model was developed to predict SSC compressive strength with a 12% error margin. [ABSTRACT FROM AUTHOR]

Background: This study aims to evaluate the compressive strength, solubility, radiopacity, and flow of Bromelain (BR)-modified Biodentine (BD) for direct pulp capping (DPC). This is suggested to determine the impact of BR on the physical properties of BD. Methods: Eighty samples were prepared according to the ISO and ADA specifications and evaluated for compressive strength, solubility, radiopacity, and flow. The compressive strength was evaluated at 24 h and 21 days via a universal testing machine. The solubility was determined by weight loss after 24-hours immersion in deionized water. Radiopacity was assessed via X-ray with aluminum step-wedges, and flow was measured by the diameter of the discs under a standard weight. Independent sample t-tests were used to statistically assess the data. A significance level of 5% was considered. Results: The compressive strength was 41.08 ± 1.84 MPa for BD and 40.92 ± 1.80 MPa for BR + BD after 24 h, and 88.93 ± 3.39 MPa for BD and 87.92 ± 3.76 MPa for BR + BD after 21 days, with no significant differences. Solubility was slightly greater in the BR + BD (2.75 ± 0.10%) compared to BD (2.62 ± 0.25%), but not significantly different. The radiopacity was similar between BD (2.82 ± 0.11 mm) and BR + BD (2.73 ± 0.10 mm). BR + BD resulted in significantly greater flow (9.99 ± 0.18 mm) than did BD (9.65 ± 0.27 mm) (p ≤ 0.05). Conclusion: BR-modified BD maintains BD's physical properties, with improved flow, making it a promising DPC agent that warrants further study. [ABSTRACT FROM AUTHOR]

Sustainable structures are an important area of research, particularly for anticipated extended human presence on the Moon or Mars. Persistent human presence on the Moon will require building materials that are already present at the site to construct bases. The high cost associated with reinforcing metal (rebar) in mission payloads necessitates the exploration of alternative reinforcement methods for sustained lunar bases. Human hair is strong in tensile strength and will become available in any long-term mission. By using otherwise wasted hair instead of heavy metal, mission payloads and costs could be lowered. Concrete workability, compressive strength, and porosity were measured for a series of different cement compositions. These compositions consisted of combinations of Ordinary Portland Cement (OPC), lunar regolith, deionized (DI) water and human hair. Increased workability and porosity were found for increasing hair concentrations. Compressive strength slightly decreased with increased hair concentration. [ABSTRACT FROM AUTHOR]

This study examines the corrosion characteristics of weakly cemented sandstone under alkaline conditions, evaluating the effects of varying pH levels on its macroscopic degradation, micro-porosity, and mechanical properties, notably uniaxial compressive strength. Findings reveal that heightened alkalinity exacerbates rock damage, although a temporary alleviation in mass loss occurs between pH 9 and 11 due to pore clogging by complexes formed from cations like Ca2+ and Mg2+.Increased alkalinity induces marked changes in pore features, with an observed rise in pore numbers, transformation of pore shapes from elongated to more spherical, and adjustments in porosity, pore size, and roundness. Furthermore, the study confirms a decline in both the rock's compressive strength and elastic modulus as pH rises. These revelations shed light on the role of pH in the corrosion behavior of weakly cemented sandstone under alkaline conditions, providing a fresh perspective for understanding its corrosion mechanisms in such environments. [ABSTRACT FROM AUTHOR]

Translation abstract Use of 100 % recycled aggregates in concrete – report on practical applicationsThis article reports on eight practical examples of applications for concrete with 100 % recycled aggregates. The applications include reinforced/unreinforced bored piles, foundations, load‐bearing internal/external walls, columns and floor slabs as well as balcony elements. Some components were realised as architectural concrete components. The respective project is summarised together with the results of the concrete development and concrete testing as well as the experience gained from obtaining special approvals in individual cases. Based on the findings from the various practical projects, it can be concluded that concrete with 100 % RC‐GK can be used for a large number of applications, so far limited to up to XC4 and XF3. Compressive strength for ready‐mix concrete up to C35/45 with good workability even with pumped concrete (here: pumping distance 45 m) using 100 % RC‐GK type 1 were possible without any problems. A concrete with sufficient early strength and a final strength of C40/50 was developed for precast elements. In two examples, RC‐GK type 2 was used for the coarse grain fraction and RC‐GK type 1 for the sand. All the projects presented have already been completed or are nearing completion. The feasibility of 100 % RC concrete in practice has thus been successfully demonstrated in several cases. [ABSTRACT FROM AUTHOR]

The longevity of waste asphalt can be considerably improved through cold recycling techniques combined with various additives. This research investigates the cold regeneration of aged asphalt concrete using Reclaimed Asphalt Pavement (RAP), Portland cement, cationic bitumen emulsion, and additional aggregates. The primary goal is to evaluate the performance enhancements in terms of average density, compressive strength, water resistance, and swelling across different mix compositions. Three distinct mixtures were formulated and assessed. Mix No. 1, composed solely of RAP, showed the lowest average density and highest swelling, indicating poor performance due to the lack of binding agents. Mix No. 2, which incorporated RAP, Portland cement, and water, exhibited the highest density and compressive strength, highlighting the crucial role of Portland cement in improving structural integrity. Mix No. 3, a more complex mixture including RAP, aggregates, Portland cement, water, and bitumen emulsion, displayed balanced properties with enhanced moisture resistance and reduced swelling. The experimental findings emphasize the effectiveness of adding Portland cement and bitumen emulsion to improve the mechanical and durability characteristics of recycled asphalt mixtures. Specifically, Mix No. 2 and Mix No. 3 demonstrated significant performance improvements, making them suitable for road maintenance applications. This study advocates for the widespread use of cold recycling methods with additive integration to achieve sustainable and cost-effective pavement restoration solutions. [ABSTRACT FROM AUTHOR]

This study aimed to address the critical issue of age deterioration in prestressed concrete (PSC) structures by investigating the strengthening of aged PSC structures using a near-surface mounted (NSM) post-tensioned carbon fiber-reinforced polymer (CFRP). A total of nine PSC beams, each with a length of 6.5 m, were fabricated for a four-point bending test. Various experimental parameters were taken into account, including the strengthening method, compressive strength of concrete in the PSC beam, and the prestressing force of the PSC beam. The results indicated that the NSM post-tensioned CFRP strengthening system proved more efficient when compared to the NSM non-post-tensioned CFRP strengthening system. The flexural capacity of the NSM post-tensioned CFRP strengthening system, under the deteriorated low-strength PSC beam, increased by up to 30.9% compared to the PSC reference beam. Additionally, the experimental results were compared to a finite-element analysis, and a parametric study was conducted to examine the material properties of the PSC beam. Consequently, the NSM post-tensioned CFRP strengthening system is expected to be an effective solution for addressing the issue of deteriorated low-strength PSC structures. [ABSTRACT FROM AUTHOR]

A fairly high breakage rate can often occur in the cold-chain logistics of fresh eggs. In this study, the compression and freshness detection were designed for fresh eggs, with the storage temperature of the eggs and the coating material on the surface as the main parameters, and the storage time as the boundary conditions. The results demonstrated that the temperature of 2-8 ℃ retarded the rottenness of eggs for better pressure resistance. Whether at room temperature or low temperature, the relative elastic deformation with time was maintained at a high value. There was a small variation in the type of coating agent. The rottenness of eggs after coating was decelerated at room temperature. While the pressure resistance of eggs was improved to compromise at 2-8 ℃. Both the coating agent and the low temperature were superimposed to slow down the decrease of its freshness. A professional experimental group was organized to conduct the sensory scoring on different groups of eggs under various storage times. The Huff unit value and sensory scoring were similar to each other. Therefore, the freshness of fresh eggs decreased with the extension of storage time. After 14 days of storage, a small amount of egg contents were solidified in the non-coated group of eggs stored at 2 ℃. The sensory scores of the group were lower during that time period. A comprehensive evaluation model was established for the parameters of the cold-chain transportation using the analytic hierarchy process, particularly with the ultimate load, the relative elastic deformation, the Haugh unit value, and the sensory score of eggs as the decision-making indicators. The relative importance of each index was ranked to determine the importance discrimination matrix. The weights were calculated corresponding to each decision index, thus reflecting the importance of the decision index to the final. Four decision indicators were ranked in descending order of the Hough unit value, sensory score, ultimate load, and relative elastic deformation, according to the priority. The optimal parameters were achieved in the coldchain logistics temperature and the coating material for different transportation durations as follows. In the cold-chain logistics duration of 0-4 days, the transportation temperature was at 2 ℃ with no paints applied; In the duration of 4 -7 days, the transportation temperature was 5 ℃, with the chitosan solution chosen as the paints. In the duration of 7-10 days, the transportation temperature was selected at 2℃ with the polyvinyl alcohol solution chosen as the paint. For the duration of 10 to 14 days, the transportation temperature was 5 ℃ with no paints applied. The quality of stored eggs was generally better at low temperatures than that at room temperature. The coated eggs at room temperature were generally better than the uncoated eggs. While the coated eggs at low temperature were less than the uncoated eggs. The coating layer protected the eggs to reduce the damage from the external physical collisions in the cold-chain logistics of a short or medium distance, indicating the less rottenness of eggs. However, the coating layer on the eggs failed to protect them in the process of long-term cold-chain transportation. The coating layer deteriorated and even fell off in the low-temperature environment for a long time, leading to less pressure resistance and maintenance of the egg quality. The findings can provide theoretical support for the cold-chain logistics of fresh eggs. [ABSTRACT FROM AUTHOR]

Supersulfated cements (SSCs), as potential green alternatives to Portland cements, are in demand for developing new kinds of precursors instead of blast-furnace slag. A mixture of kaolin, quartz and sodium hydroxide was calcined to prepare SSC by grinding clinkers with lime and gypsum. Preparation factors were investigated and multiple characterisation methods were adopted to explore the calcination and hydration mechanisms. The sodium hydroxide additive was found to reduce the activation temperature of the kaolin and a moderate addition of sodium hydroxide improved the compressive strength of SSC made from calcined kaolin. Quartz added into the kaolin calcined with a moderate amount of sodium hydroxide also promoted the compressive strength. Comprehensive characterisations indicated that the alkali-added calcination of the kaolin generated pozzolanic zeolite and sodium aluminosilicates along with inert nepheline at a calcination temperature ≤950°C. The hydration of SSC pastes tended to produce C(N)–A–S–H/N(C)–A–S–H gels and crystalline ettringite. During sodium hydroxide-added calcination, quartz added into the kaolin hindered the generation of inert nepheline and produced cementitious N–S gels. The research facilitates the utilisation of the massive discharged coal gangues rich in kaolinite and quartz by synthesising SSCs economically. [ABSTRACT FROM AUTHOR]

The setting times and early strength of shotcrete are greatly affected by the gypsum content of the cement used. In this work, the setting times, compressive strength and microscopic analysis (X-ray diffraction quantitative analysis, thermogravimetric analysis and scanning electron microscopy) were used to determine the effects of changes in gypsum content on the hydration and mechanical properties of cement mixed with an accelerator at different temperatures. The results showed that an increase in the gypsum content of the cement promoted the formation of ettringite (AFt) and decreased the setting times of the cement pastes at 0°C, 20°C and 40°C. Mortar compressive strength tests showed that, after curing at 0°C, 20°C and 40°C, the highest compressive strength was exhibited with a final molar aluminate-to-sulfate ratio (C3A/SO3; henceforth called the MASR) of 0.84, 0.84 and 1.18, respectively. The mechanical properties of the hardened cement pastes were adversely affected by MASRs that were too high or too low. When the MASR was too high, the conversion of AFt to monosulfate (AFm) was facilitated and C3S hydration was slowed. Conversely, when the MASR was too low, this enabled large amounts of AFt to occupy the space where calcium silicate hydrate (C-S-H) gels were formed, resulting in decalcification of the C-S-H gels. [ABSTRACT FROM AUTHOR]

Fluorine-containing silicon residue (FSR) is a solid waste that is harmful to the environment. A new alkali-free liquid accelerator based on aluminium sulfate (LAFS) was prepared using FSR. The addition of LAFS to cement mortar shortened the setting times and significantly improved the early strength. With the addition of 8% LAFS, the initial and final setting times were 2.48 min and 11.83 min, respectively, and the 1-day compressive strength was 14.6 MPa, which was 200% of that of the mortar without LAFS. The mechanism of the action of LAFS was studied using isothermal calorimetry test, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and other analytical methods. The results showed that the LAFS rapidly generated a large amount of ettringite and promoted the formation of calcium silicate hydrate in the cement paste. A conceptual model of the early hydration process of cement paste with added LAFS was established based on the analytical results. [ABSTRACT FROM AUTHOR]

In construction projects in Khuzestan province in Iran, electric-arc steel slag (EASS) materials are used as fill materials. In this research study, bio-cementation practice on EASS materials is examined and compared with that on natural sand. For this purpose, direct shear, unconfined compressive strength (UCS) and constant head permeability tests, together with scanning electron microscopy images obtained using an instrument equipped with an energy-dispersive X-ray spectroscope, were used to analyse and compare untreated and treated materials. The results showed that despite higher urease activity and higher calcite production of EASS materials compared with natural sand, the latter showed slightly higher UCS, higher cohesion intercept enhancement and higher permeability decrease after bio-cementation treatment. [ABSTRACT FROM AUTHOR]

This study investigates clayey soil from a road project situated in the district of Lodhran, Punjab, Pakistan. The subgrade prepared with the soil distorted due to heaving after a certain period of its construction. First, laboratory tests were conducted to explore the reason for this problem, examining the fundamental engineering properties of soil. The test results show that the soil acts as a soft material when water content reaches 30%, significantly reducing its strength. The soft soil is generally considered unsuitable for civil work due to its poor performance behaviour. So, the performance of clayey soil was examined in the study at its soft state by coupling it with stronger materials, such as polyethylene polymeric reinforcement and sand, developing laboratory-scale foundation models. Based on the model studies, the study proposes a sustainable polyethylene–sand–soft soil model, which shows 155 and 56% higher ultimate bearing capacity (BC) than soft soil and sand-reinforced soft soil foundations. The changes in BC occur due to the reinforcement action of the polyethylene reinforcement, which is associated with its tensile membrane action effects and interlock bonding at the soil-reinforcement interface. Practically, the study can reduce the dependency of industry practitioners on sand materials. Using polyethylene in civil work is viable for environmental sustainability. [ABSTRACT FROM AUTHOR]

In the Kashmir region of Pakistan, the presence of Siwalik clays engenders serviceability issues to the infrastructure causing substantial loss of property. In this study, an attempt has been made to address these issues using polypropylene fibres (PPFs) as a sustainable modifier. These fibres were used in five different proportions, namely 0.25, 0.5, 0.75, 1 and 1.25% as partial replacement of base soil to analyse their impact on the engineering behaviour of matrices. Classification, compaction, indirect tensile, unconfined and triaxial compression, swell potential, consolidation and California bearing ratio (CBR) tests were conducted on controlled as well as reinforced-clay samples for comparative analyses. The maximum improvements were observed in unconfined compressive strength (109%), tensile strength (300%), cohesion (13%), friction angle (110%), soaked CBR (800%) and un-soaked CBR (550%). Besides, the reduction in swelling strain by 92% was also recorded corresponding to 1 kPa effective vertical stress. The capital cost analyses showed that PPFs reduced the costs of backfill behind the retaining wall and foundation soil beneath isolated footing by 21 and 44.5%, respectively. Moreover, the modifier had no adverse effect on the aqueous media. Conclusively, PPFs can be used as sustainable modifiers leading to a potential solution for serviceability issues. [ABSTRACT FROM AUTHOR]

Adhering to ASTM C109/C109M-20 standards ensures quality in cement mortar specimens. However, achieving the required sand gradation per ASTM C778-21 can be challenging. This paper presents a faster method for adjusting sand gradation without compromising ASTM quality standards. The proposed method involves analyzing six silica sand samples of different gradations, pre-screening sands, using Excel Solver for optimal mixture ratios, making automated gradation tweaks with precise calculations, and validating the gradation to ensure ASTM compliance. After making the adjustments, compressive strength tests were conducted on mortars with the modified sands, and the results were compared with those of standard-graded sand. Based on statistical analysis, the new method yielded reliable outcomes with compressive strengths similar to standard sands. This innovation offers a more efficient alternative, paving the way for streamlined practices in civil engineering. [ABSTRACT FROM AUTHOR]

In situ TiC/corundum–mullite electrically conductive ceramics were prepared by carbon‐bed sintering method using bauxite, clay and Ti3SiC2 powders as raw materials. The phase composition, microstructure, shrinkage, apparent porosity, bulk density, compressive strength, and resistivity of samples were investigated. The X‐ray diffraction results indicate that the TiC is completely generated by desilicidation reaction of the Ti3SiC2 at 1 300°C. When the sintering temperature is 1 300°C and Ti3SiC2 powder addition is 22 wt.%, the properties of the sample are optimum, with a longitudinal shrinkage of 2.04%, a radial shrinkage of 2.56%, an apparent porosity of 19.01%, a bulk density of 2.53 g/cm3, a compressive strength of 181 MPa, and a resistivity of 267 Ω·cm. The electrically conductive phase TiC is connected into a complete electrically conductive network. The shrinkages of samples decrease with increasing sintering temperature, which indicates that the samples expand due to secondary mullitization. The continuous electrically conductive network of TiC is destroyed. As the Ti3SiC2 powder addition increases from 14 to 20 wt.%, the resistivity of the samples decreases significantly, but the further increase in the Ti3SiC2 powder addition has no significant effect on the resistivity. [ABSTRACT FROM AUTHOR]

Magnesium potassium phosphate cement (MKPC) presents a broad application prospect in engineering fast repairing, reinforcement, hazardous material, and national defense construction, due to its good properties such as fast hardening and early strength, high bonding strength, and wide environmental adaptability. In this work, the effect of slag with different particle size on the workability, mechanical properties, and hydration products of MKPC was investigated. The results showed that the compositions of slag in the particle size range 75–300 µm are quite different. A decrease in the particle size of slag resulted in reduction of the fluidity of MKPC from 175 to 108 mm and shortening the setting time from 1300 to 850 s. The compressive strength of MKPC (curing for 3 h) does no change much as the particle size of slag varies, and slag with the particle size in the range of 115–300 µm slightly increase the 3‐h‐compressive strength of MKPC, since the compressive strength values are in the vicinity of 13 ± 2 MPa. As the curing age increases, physical effect and hydration activity of slag concurrently dominate the mechanical properties of MKPC, and when the hydration activity of the slag exceeds the adverse effect caused by fine particles, the compressive strength increases. Slag particle size can significantly improve the long‐term compressive strength of MKPC, which can effectively reduce the cost and can be used as a repair material with better durability. [ABSTRACT FROM AUTHOR]

The polygonal honeycomb core has been vertically rotated and spliced to form a new three-dimensional polygonal honeycomb (TPH) structure lattice. Young's modulus and Poisson's ratio for the three main directions of the TPH structure had been derived from Castigliano's second theorem and Moore's theorem. The theoretical results show good agreement with the numerical and experimental results. Meanwhile, the compressive strength of the TPH structure has been analyzed. The results show that the geometric parameters have a significant effect on the elasticity and strength of TPH structures, and the mechanical properties of the TPH structures can be programmed by adjusting the geometric parameters. In addition, the TPH structure exhibits a bidirectional zero Poisson's ratio (ZPR) during compression. This structure shows promise for applications in aerospace, construction, and other fields. This study provides guidance for further research on polygonal honeycomb structures. [ABSTRACT FROM AUTHOR]

In the current study, the effects of cement or lime content, fibre content, partial cement or lime replacement with zeolite and curing time on the Unconfined Compressive Strength (UCS) of sand have been investigated. The results reveal that increasing cement or lime content increases Maximum Dry Density (MDD) and Optimum Water Content (OMC). However, increasing zeolite replacement percentage decreases MDD and OMC. Increasing the fibre content from 0 to 4% reduces the MDD and increases OMC. The optimum combination of the stabiliser and fibre has been derived from an array of tests. Results comparison shows the 0.5% fibre content and 8% stabiliser results in maximum effect. Also, the optimum percentage of 80% replacement of lime and 30% and 40% replacement of the cement with zeolite leads to the maximum UCS. Observing failure patterns demonstrates the influential performance of fibre content such as controlling the crack length and brittle behaviour. Moreover, SEM analysis was conducted to compare the microscale behaviour. [ABSTRACT FROM AUTHOR]

Robust models based on Artificial Neural Network and simplified linear regression were proposed to predict the Unconfined Compressive Strength (UCS) of Lime Treated Soils (LTS). In total, an experimental database using 1120 test specimens was created. Critical examination of the collected experimental data suggested that there are eight key parameters that govern the attained strength gain. These input parameters are liquid limit, plastic limit, dry unit weight, water content, fine content, lime content, curing temperature and curing time whereas the only output dependent parameter is the UCS. The parameters of the proposed model including weights, biases and transfer functions were successfully converted to an explicit mathematical model relating the UCS with the key input parameters. Based on the results of the statistical evaluation, it was shown that a three-layered Artificial-Neural-Network model with 19 hidden neurons was capable to predict the UCS of (LTS) with a high degree of accuracy that was better than that achieved by the developed regression model. A coupling effect of the input parameters and weights analysis were conducted for the developed Artificial-Neural-Network-model to assess the importance of the key parameters. Analysis of weights of the model showed that curing time was the most significant factor affecting strength gain. [ABSTRACT FROM AUTHOR]

This article investigates the durability of recycled self-compacting concrete in relation to its resistance against freeze-thaw cycles and alkali-silica reactions. It explores the properties of fresh concrete, investigates the impact of various additives, and evaluates key factors such as spalling, weight loss, compressive strength, expansion rate, and ultrasonic properties in hardened concrete samples incorporating different levels of recycled aggregates. The findings illustrate the feasibility of achieving self-compacting recycled concrete by increasing the use of superplasticizers and adding 10% beach sand. Furthermore, incorporating 10% micro-silica and 7.5% wollastonite in the recycled mix enhances the strength of all samples, with the 25% recycled material sample demonstrating the highest strength and durability. Despite a decrease in strength and increased expansion as recycling percentages and freeze-thaw cycles rise, the recycled samples maintain acceptable durability. Additionally, this study employs the R programming language to elucidate the relationship between compressive strength and modulus of elasticity, offering valuable insights into recycled concrete performance and behavior. [ABSTRACT FROM AUTHOR]

Research into leveraging nanomaterials to enhance building material performance has shown significant progress in recent decades. Silica nanoparticles (SiO2), a prevalent chemical element in ceramics, glass, sand, cement, and binders, have been a focus. This study delved into the impact of varying nanosilica (NS) percentages (ranging from 0 to 2.5% of LRP weight) on lime-based pastes for roofs and screeds (LRP), commonly used in building insulation. Specimens underwent demolding after 48 h, with 75% treated at 40, 60, and 80 °C for 7 h and then cured at room temperature for 3, 7, and 28 days. Analysis revealed that SiO2 and CaO in LRP transformed into calcium silicate and calcium carbonate during hydration. The addition of NS notably enhanced compressive strength by facilitating calcium silicate formation and reducing pore structures, with the best results at 40 °C. Thermogravimetric analysis indicated a significant weight loss reduction (2.3 times less) in samples with 2.5% NS content compared to those without. Optimal NS content percentages of 1.5% and 2.5%, replacing LRP at water/binder ratios of 0.6 and 0.75, respectively, were identified based on tensile and compressive strengths and desirable flowability. [ABSTRACT FROM AUTHOR]

In practical applications, it is typical for different types of sheathings (referred to as dissimilar) to be connected at both flanges of the stud (lipped channel-section) in cold-formed steel (CFS) panelised construction (e.g. one-side has interior sheathing and the other exterior sheathing). However, limited studies are available on the axial behaviour of CFS studs with different combinations of sheathings present at both-flanges of a stud. This novel experimental study investigates the structural behaviour of fourteen (14) CFS panels with sheathing on one-side only and different sheathing on both flanges of the wall panel using combinations of seven (7) different sheathing boards [fibre-cement boards (FCB) (8 mm/10 mm/12 mm thick); calcium silicate boards (CSB) (12 mm thick); and heavy duty FCB (6 mm/9 mm/12 mm thick)]. The ultimate axial strength, load-deformation behaviour and failure patterns are the parameters compared. Analytical/semi-analytical design methodologies namely; Rayleigh-Ritz (R-R) method, finite-strip method based on direct strength method (DSM) and differential equation of equilibrium method (DEEM) are validated based on the experiments. Limited studies are available to verify the efficacy of these methods to estimate the axial strength of CFS wall panels with dissimilar sheathing on both flanges. Results establish that DSM may be used efficiently rather than the R-R method and DEEM. [ABSTRACT FROM AUTHOR]

Accurate prediction of tunnel boring machine (TBM) penetration rates is of great significance for intelligent TBM construction. Traditional empirical and theoretical models of TBM penetration rates are difficult to adapt to complex and changeable formation environments. To improve the adaptability, this paper proposes a TBM penetration rate prediction model based on the particle swarm optimization (PSO)-Elman algorithm fusion. Particle swarm optimization (PSO) was used to find the optimal connection weight matrix, which was inserted into the Elman network, and the TBM penetration rate was predicted by the machine learning method. This study examined field data from two distinct tunnel sections, focusing on their geological conditions, construction challenges, and environmental impacts. By analyzing the characteristics unique to these sites, the research offers a comparative perspective on tunnel engineering in diverse settings. Five parameters—uniaxial compressive strength (UCS), rock integrity index (Kv), cutter head thrust (Fn), cutter head speed (RPM), and penetration degree (P)—were selected as the input parameters. The TBM penetration rate was estimated by neural network training of the model. The results show that the PSO method effectively can overcome the problem of being prone to a local minimum using the single Elman method, and the PSO-Elman model has a fast convergence speed and high accuracy. In the 20 groups of experimental samples selected, the mean absolute percentage error (MAPE) was 3.38%, and the coefficient of determination (R2) was 0.936. The prediction quality was better than that of the single Elman method or the backpropagation neural network (BP) method. The study yields specific insights into efficient tunnel construction methodologies and practical neural network tools for risk management, highlighting innovative approaches in environmental preservation and safety enhancement in tunnel engineering. [ABSTRACT FROM AUTHOR]

This study delved into the utilization of chamotte particles in varying contents (0–50 wt%) as reinforcing agents in both fresh and hardened states within potassium‐based geopolymer (KGP) composites. Although the previous research predominantly underscored the high‐temperature stability of chamotte in composites subjected to extreme conditions, this study focuses on expanding their potential applications at ambient temperature. The experimental findings showed that the flowability of the pastes experienced a slight reduction up to 20 wt% chamotte, followed by a substantial decrease, ultimately resulting in complete shape retention at 50 wt%. Squeeze flow and standard rheological tests supported these observations, revealing elevated work‐to‐squeeze values peaking at 1.3 J. X‐ray diffraction data showed that crystallinity prevailed in chamotte, establishing its efficacy as a nonreactive reinforcement. In the hardened state, the inclusion of chamotte enhanced the mechanical properties of the composites, specifically compressive, flexural, and splitting tensile strengths, reaching up to 61.7, 13.2, and 5.6 MPa, respectively. Young's modulus (E) and shear modulus (G) also exhibited an upward trend with increasing chamotte content, reaching values of up to 17.7 and 7.7 GPa at 50 wt%, respectively. Scanning electron microscopy (SEM) analysis validated particle interlocking and crack‐bridging mechanisms. In general, this study highlights the effectiveness of chamotte particles in improving the mechanical properties of KGP composites at room temperature. It also emphasizes the necessity of considering the mentioned parameters in the design of particulate‐reinforced geopolymer compositions for diverse applications. [ABSTRACT FROM AUTHOR]

The present study reports the investigation of the influence of naphthalene–camphor binary solvent and the densification process on the pore structure formation of α‐alumina monoliths using the freeze‐casting technique with a freezing temperature control mechanism. Freeze‐casting technique allowed a controlled production of monoliths with high porosity (65%–70%) and distinct pore morphologies based on the adjustment of solvent composition (hypoeutectic, eutectic, and hypereutectic) and sintering time. In general, the longer the sintering time, the greater the average pore diameter (8–10 µm), the larger the grain size (∼319–596 nm), the higher the material density (∼1450–1650 kg/m3), the lower the open porosity (∼60%–49%), the higher the closed porosity (5%–18%), and the greater the compressive strength of the monoliths (hypoeutectic: 23.56 MPa; eutectic: 4.81 MPa; hypereutectic: 23.49 MPa). The study also reveals that the solvent composition directly influenced the alignment of the pore structure, as the pores of the final monolith resemble frozen solvent crystals. Hydraulic tortuosity varied from 1.30 to 1.53 for selected samples. Finally, solvent composition and sintering time proved to be important parameters that should be considered in the manufacturing process of porous ceramic structures via freeze casting. [ABSTRACT FROM AUTHOR]