Physical-mechanical Properties Research Articles

An investigation of the physic-mechanical properties of the expanded perlite mortars with thermal-activated concrete waste and microencapsulated paraffin

In the transition to zero waste and sustainable development, it becomes essential to use phase change materials and recycled cement in construction projects to improve energy efficiency and encourage sustainable building practices. The primary goal of this study is to determine how the properties of expanded perlite mortars are affected when Portland cement is partially replaced with recycled cement, produced by thermally treating concrete waste at 550˚C. Recycled cement substituted Portland cement in various percentages (10%, 30%, and 50%). Also, microencapsulated phase change material (m-PCM) was incorporated into the mortar in a proportion of 2 wt.% and 5 wt.%. Cement-based mortars with a 1:3 aggregate volume ratio have been developed for evaluation. The mortars were analyzed in terms of mechanical strength (flexural and compressive), water absorption, thermal properties, differential scanning calorimetry, and microstructure. The experimental results revealed a decrease in mechanical strength values when Portland cement is substituted by recycled cement, regardless of percentage. Recycled cement in proportion of 30% positively influenced the water absorption. The thermal conductivity of reference mortar was higher than that of 30% recycled cement. The reference mortar's specific thermal conductivity values were 0.466 W/(m·K) at 25°C, 0.525 W/(m·K) at 30°C, and 0.589 W/(m·K) at 35°C. On the other hand, the mortar containing 30% recycled cement exhibited much lower heat conductivity throughout these temperatures, suggesting superior insulating qualities. DSC analysis verified that adding m-PCM to the mortars increased their thermal storage capacity, which is essential for raising the energy efficiency of building materials. Nevertheless, the mechanical strength decreased as m-PCM was added. Despite decreases, all mortars satisfied the SR EN 998–1 standard's CS IV classification for interior plaster applications, which is based on compressive strength requirements. Overall, this study shows how using m-PCM and recycled materials can improve the performance of cement-based materials.

Moisture ageing effects on the mechanical performance of eco-friendly sandwich panels made of aluminium skins, bamboo ring core and bio-based adhesives

Recent research has been focused on developing high-performance sandwich structures using renewable resources. The adoption of bamboo rings as a core material and bio-based adhesives has emerged as a promising sustainable design solution for panel construction. It is therefore critical to conduct accelerated ageing tests on these materials to evaluate the impact of environmental humidity on their degradation and durability. This study assessed the effects of moisture ageing on the physic-mechanical properties of eco-friendly sandwich panels and their constituents (aluminium skins, bamboo ring core and castor oil bio-adhesive). Mechanical evaluations of sandwich panels with compacted and spaced bamboo ring cores were performed under varying humidity conditions. Bamboo rings exhibited variable bulk density due to swelling and loss of organic material over time. They also demonstrated increased compressive properties after 2 years of natural ageing but reduced performance after 30 days at 100% relative humidity. The mechanical properties of the bio-based polymer were enhanced through water-ageing exposure. Sandwich panels constructed with compacted bamboo ring cores exhibited higher bending properties than those with spaced ring core architecture, with the latter showing failures characterised by a wrinkling effect on both skins followed by debonding.

Study on the polymerization shrinkage and mechanical-physical properties of dental resin composite modified by polyurethane dimechacrylate and glass flake fillers: Short title: Aging resistance for dental resin composites with low shrinkage

ObjectivesWe intend to explore the polymerization shrinkage and mechanical-physical properties of the dental resin composite modified by polyurethane oligomer PU-MA and glass flakes fillers, and provide some experimental information for developing new dental materials. MethodsBased on Bis-GMA/TEGDMA, the new dental resin composite was hand fabricated by combining PU-MA with different content (65 wt% ∼ 75 wt%) of glass flakes/Si-Al-borosilicate glass mixed fillers. The kinetics of polymerization shrinkage was investigated by using an experimental set-up based on laser triangulation. The mechanical-physical properties of specimens after 60 days water immersion and 5000 times thermo-cycles were measured by three-point bending test and micro vickers hardness tester. Data were submitted to one-way ANOVA/LSD-test (α = 0.05). Independent sample T test was used to analyze the data before and after aging. Two-way ANOVA was adopted to analyze the effect of composition and aging condition on the mechanical-physical properties (α = 0.05). ResultsPU-PG-75% performs lower volume shrinkage (1.35 %). As the increase of filler content, the water sorption and solubility increased and the depth of cure decreased significantly (P < 0.05). After aging, the flexural strength, elasticity modulus and vickers hardness of commercial products dropped obviously and PU-PG-75wt% was relatively stable. Conclusions20 wt% PU-MA could decrease the volume shrinkage of dental resin composite effectively. 60 days water immersion and 5000 times thermal cycles simultaneously resulted in a significant reduction in the flexural properties for experimental materials. PU-PG-75% may have the potential to be taken as a low shrinkage dental resin composite with good mechanical properties. Clinical SignificanceThis new synthesized composite could perform low polymerization shrinkage and better mechanical resistance, which may provide a new idea for improving the lifespan of direct restoration.

Assessment of Physical and Mechanical Parameters of Spun-Bond Nonwoven Fabric.

The selection of an appropriate fabric for technical applications, such as protective masks, hinges on a thorough understanding of the fabric's physical and mechanical properties. This study addresses the challenge of selecting the optimal material structure for the upper layer of a protective mask, aiming to ensure adequate breathability while providing effective filtration against airborne particles and contaminants. We assessed and compared the physical-mechanical properties of five polymer spun-bond nonwoven fabrics from different suppliers. Our comprehensive evaluation included, as follows: a visual inspection; light permeability analysis; mass and thickness measurements; elongation and tensile strength tests; breathing resistance assessments; and filter penetration tests with paraffin oil. The results revealed significant variations in performance among the samples, with one fabric consistently outperforming the others across multiple parameters. Notably, this top-performing fabric met or exceeded the EN 149:2001+A1:2009 standard for breathing resistance and filtration efficiency and, in combination with additional filter layers, met the requirements or exceeded class FFP2 (filtering face piece). This study underscores the importance of meticulous material selection and quality control in optimizing PPE (personal protective equipment) performance and user safety, providing valuable insights for mask manufacturers and healthcare professionals.

Performance evaluation of waste phosphogypsum-based solidified sludge: From laboratory test to field application

Massive dredged sludge is being landfilled without effective use due to its high-water content and poor engineering properties, which not only leads to soil resources waste, but also occupies a large amounts of land sources. In this study, ternary stabilizer, including waste phosphogypsum (PG), ground granulated blast-furnace slag (GGBS), and lime (LM) with a mixing proportion of PG: GGBS: LM = 35:60:5, was adopted to improve the mechanical and environmental behaviors of sludge for subgrade filling purpose. The initial water content of sludge was controlled using two different dehydration methods for comparison. A series of laboratory tests, including unconfined compressive strength (UCS), organic matter content, and pH value were tested to understand its physical-mechanical properties. Thereafter, field application model equipped with a mini weather monitoring station was constructed to monitor the influence of solidified matrix on the surrounding water and soil environment. Time -dependent parameters such as plant growth, temperature, humidity, total nitrogen, phosphorus/potassium content, electrical conductivity, and pH value were monitored. Results indicate that the incorporation of PG-GGBS-LM ternary stabilizer significantly improves the mechanical and environmental properties of dredged sludge. The optimal dosage of the ternary stabilizer is 36%, which can result in a UCS value of the 2.0 MPa (slightly higher than ordinary Portland cement) after 28 days of curing. Field application reveals that plants could grow normally in solidified sludge. The environmental related parameters (i.e., total nitrogen, phosphorus/potassium content, electrical conductivity, and pH value) were similar with those in conventional planting soil, suggesting the advantage of the proposed PG-GGBS-LM ternary stabilizer in mechanical, economic and environmental aspects.

Evolution of TiAlSi thin film coatings under varying target power in DC magnetron sputtering

This study, for the first time, presents the growth, nucleation, and characteristics of TiAlSi thin films sputtered from a partially sintered Ti30Al16Si10 (at. %) composite target under controlled conditions of target power. The TiAlSi thin films were grown on soda-lime glass substrates through Direct Current (DC) sputtering at varying levels of the target power: 73.2 W, 151.2 W, and 269.5 W. The other deposition parameters: the deposition temperature, time, argon mass flow rate, substrate rotation, and deposition pressure, were kept constant at 23 °C, 150 min, 25 sccm, 5 rpm, and 10−3 mbar, respectively. The pre-sputter power, argon flow rate, and time were also kept constant at 73.2 W, 20 sccm, and 5 min, respectively. The physical properties, microstructure, crystal structure, topography, and mechanical properties of the thin film coatings were analysed. The thickness and rate of deposition of the TiAlSi thin films increased with an increase in the target power (73.2 W – 269.5 W) from 414.6 nm and 0.046 nm/s to 1358.8 nm and 0.151 nm/s, respectively. The chemical composition of all the thin films remained constant, with the formation of a uniform TiAlSi alloy with no segregation of elements. However, a thin (wetting) interlayer consisting of Si and O elements was observed between the TiAlSi layer and the glass substrate. Further, the structure sizes and roughness values of the TiAlSi thin films increased with an increase in the target power, with a maximum of 75.4 nm for the size and 4.78 nm for the RMS roughness of thin films deposited at the maximum target power (269.5 W). Lastly, mechanical analysis of the TiAlSi thin films depicted an increase in the hardness as the target power increased, with the highest hardness at maximum power (269.5 W) obtained as 4.76 GPa. Despite having the lowest elastic modulus (50.5 GPa), the coating deposited at the highest power exhibited the highest plasticity index (H/E) and plastic deformation factor (H3/E2) of 0.094 and 0.042 GPa, respectively, which indicated the high resistance to abrasive wear, cracking, and deformation, compared to thin films deposited at the lowest target power (H/E = 0.066 and H3/E2 = 0.015 GPa). This study demonstrates that target power is a significant factor in determining the growth of TiAlSi thin films during the sputtering process and can be used for better control of their physical, structural, and mechanical properties.

Influence of high cis-1,4-liquid polydienes on properties of carbon-black filled composites

High cis-1,4 liquid polybutadiene (cLBR) and polyisoprene (cLIR) with narrow molecular weight distribution were prepared by the chain-transfer coordination polymerization. The effects of cLBR and cLIR on the physical and dynamic mechanical properties of carbon-black filled composites containing single polybutadiene (PBR) or a blend of PBR/polyisoprene (PIR), were investigated. The results showed that cLBR and cLIR effectively ameliorated filler dispersion compared with the treated distillate aromatic extract (TDAE) oil. The wet skid resistance and rolling resistance of vulcanized PBR/PIR composites plasticized with 5 phr cis-1,4 liquid rubbers were significantly improved. Therefore, a new type of plasticizers cLBR and cLIR that are environmental benign and highly compatible with matrix rubbers, has been discovered to replace the conventional TDAE oil used in fabricating the “green” tyres.

Insight on physical–mechanical properties of one-part alkali-activated materials based on volcanic deposits of Mt. Etna (Italy) and their durability against ageing tests

In recent years, there has been a growing interest in one-part alkali-activated materials, which utilize solid-form alkali activators, within the construction industry. This approach is becoming popular due to its simpler and safer application for cast-in-situ purposes, as compared to the conventional two-part method. At this purpose, we have pioneered the use of volcanic deposits of Mt. Etna volcano (Italy) as precursor for the synthesis of a unique one-part formulation. This was done to assess its performance against both traditional and two-part alkali-activated materials. The study employed a comprehensive range of investigative techniques including X-ray powder diffraction, Fourier transform infrared spectroscopy, hydric tests, mercury intrusion porosimetry, ultrasound, infrared thermography, spectrophotometry, contact angle measurements, uniaxial compressive strength tests, as well as durability tests by salt crystallization and freeze–thaw cycles. The key findings on the studied samples are as follows: i) small size of pores and slow absorption-drying cycles; ii) satisfying compactness and uniaxial compressive strengths for building and restoration interventions; iii) high hydrophily of the surfaces; iv) lower heating dispersion than traditional materials; v) significant damage at the end of the salt crystallization test; vi) excellent resistance to freeze–thaw cycles. These newly developed materials hold promises as environmentally friendly options for construction applications. They offer a simplified mixing process in contrast to the conventional two-part alkali-activated materials, thus providing an added advantage to this class of materials.

Alternative Tree Species for Sustainable Forest Management in the Brazilian Amazon

The scarcity of hardwoods from tropical forests makes the search for alternative species necessary for commercialization. This study aimed to establish groups of timber species from the Amazon Forest with potential for logging purposes through the assessment of their physical-mechanical properties, aiming to identify alternative species that can meet the market demands. We utilized data from the Forest Products Laboratory (LPF) (containing information on basic density and other wood mechanical properties) and the Timberflow platform, as well. We applied a multivariate cluster analysis technique with the aim of grouping species based on the technological characteristics of their wood and evaluating similarity among them to obtain homogeneous groups in terms of economic potential and utilization. The results indicated four homogeneous groups: Cluster 1 (40.72% of species, basic density-db: 690 kg m−3), Cluster 2 (13.92%, db: 260 and 520 kg m−3), Cluster 3 (27.32%, db: 550 and 830 kg m−3), and Cluster 4 (18.04%, db: 830 kg m−3). Most of the 20 listed species are classified as more commercially viable (70%), with high wood density. Species identified as alternatives include Dialium guianense and Zollernia paraensis for Dipteryx odorata, Terminalia argentea for Dinizia excelsa, Terminalia amazonia and Buchenavia grandis for Goupia glabra, and Protium altissimum and Maclura tinctoria for Hymenaea courbaril. The analysis highlighted the overexploitation of a restricted group of species and the need to find alternatives to ensure the sustainability of forest management. This study contributed to identifying species that can serve as alternatives to commercial ones, promoting a more balanced and sustainable forest management.

REPAIR OF PORTICO ELEMENTS AND DRAINAGE SYSTEM OF THE HUSEJNIJA MOSQUE IN GRADAČAC

In 2004, the Commission for the Preservation of National Monuments declared the "Architectural Complex of Husejnija (Husein-kapetan Gradaščević) Mosque in Gradačac" a national monument of Bosnia and Herzegovina. The mosque belongs to the type of central domed mosque with a portico covered by three small domes. In September/October 2023, cracks were observed on six arches, the capitals of two columns, and the base of one column in the portico of the mosque. Geotechnical investigative works included the creation of three excavations and two boreholes with continuous Standard Penetration Tests (SPT). The excavations reveal layers below the ground level, consisting of a well-bound sandy artificial fill from the ground surface to a depth of 1.35 meters, a layer of poorly bound artificial stony material from 1.35 to 2.45 meters, and a layer of natural clay at greater depths. It is assumed that over time, due to water seepage from the hillside and rainfall runoff from the mosque, there has been a change in the physical-mechanical properties of the foundation soil and partial settling of the portico structure. In addition to the existing channel on two sides of the mosque, a drainage ring around the building and a drainage curtain on the uphill slope have been designed. Also, underpinning of the portico foundations in alternating segments has been designed to strengthen the stone masonry layer and prevent further settling and development of cracks in the portico elements. After the works are completed, a 12-month monitoring period is planned, followed by an analysis and repair of the cracks.

3D bioprinting of fish skin-based gelatin methacryloyl (GelMA) bio-ink for use as a potential skin substitute.

Gelatin methacryloyl (GelMA), typically derived from mammalian sources, has recently emerged as an ideal bio-ink for three-dimensional (3D) bioprinting. Herein, we developed a fish skin-based GelMA bio-ink for the fabrication of a 3D GelMA skin substitute with a 3D bioprinter. Several concentrations of methacrylic acid anhydride were used to fabricate GelMA, in which their physical-mechanical properties were assessed. This fish skin-based GelMA bio-ink was loaded with human adipose tissue-derived mesenchymal stromal cells (ASCs) and human platelet lysate (HPL) and then printed to obtain 3D ASCs + HPL-loaded GelMA scaffolds. Cell viability test and a preliminary investigation of its effectiveness in promoting wound closure were evaluated in a critical-sized full thickness skin defect in a rat model. The cell viability results showed that the number of ASCs increased significantly within the 3D GelMA hydrogel scaffold, indicating its biocompatibility property. In vivo results demonstrated that ASCs + HPL-loaded GelMA scaffolds could delay wound contraction, markedly enhanced collagen deposition, and promoted the formation of new blood vessels, especially at the wound edge, compared to the untreated group. Therefore, this newly fish skin-based GelMA bio-ink developed in this study has the potential to be utilized for the printing of 3D GelMA skin substitutes.

Synergic effects of physio‐mechanical performances on sliding‐rolling tribological and abrasion behaviors of polyisoprene based aviation tire treads

AbstractAbrasion and tribological properties of tread rubber play a crucial role in governing the service life of aviation tires and the safety of aircrafts. Polyisoprene (IR) with the same chemical structure as natural rubber shows great potential for application in aviation tires. Herein, the abrasion and tribological behaviors of IR based composites under sliding‐rolling conditions were investigated in relation to the carbon black (CB N234) content, sliding‐rolling ratio, ambient temperature, and counterparts in order to provide guidance for the development of high‐performance aviation tire treads. Moreover, the relationship between wear performances and physical–mechanical properties was discussed to establish a prediction model. The results revealed that physical and mechanical properties affected wear performances in a synergetic manner, which could be described as a negative linear correlation of the folding wear with the product of hardness and rebound resilience (H4R) and the ratio between rebound resilience and tensile strength ((1‐R)/σ) even at elevated temperature and sliding‐rolling ratio regardless of the counterpart. The increase in CB N234 content and sliding‐rolling (s‐r) ratio resulted in a transition of the wear mechanism from folding to abrasion due to the formation of soft rubber particles with a certain fluidity and a lubricating transfer film that was located at the friction interface and was generated by the thermal‐mechanical degradation of the IR matrix when it was rubbed against steel counterparts, which marred the aforementioned negative linear relationship.Highlights The increase in temperature improved the abrasion resistance of tire treads. The folding wear was negatively and linearly related to H4R and (1‐R)/σ. Increasing CB N234 content and s‐r ratio made a transition of wear mechanism.

Towards gradient design of TPMS lattices and laser powder bed fusion processing– Role of laser strategies and lattice thickness

The ability to manufacture complex design geometries via Additive Manufacturing (AM) has led to a rapid growth in advancing the design methods, fabrication, and application of Triply Periodic Minimal Surface (TPMS) lattices with minimal surface topologies. Due to its zero-mean curvature, TPMS lattices can be additively manufactured without any sacrificial support structures and offer both design and manufacturing engineers, unprecedented control over the local physical properties (surface area, relative density, etc.) and local mechanical properties (flexural strength, Young’s modulus, etc.). TPMS lattices are of high interest for a wide range of applications such as biomedical implants, energy absorption, and surface fluidic applications such as heat exchangers, and energy storage. Recent advancements in functionally graded TPMS lattice design by varying local lattice geometry has shown to result in different mechanical performance. However, there have been limited studies in understanding the functional grading of AM process conditions (e.g., Laser-Powder Bed Fusion in this study) and lattice sheet thickness to better map the design-processing conditions-properties. The goal of this study is to achieve similar mechanical properties in TPMS sheet lattices with two different TPMS sheet thicknesses by varying laser processing conditions (e.g., contour and hatch conditions in this study). Quasi-static tensile testing of solid samples with corresponding AM conditions and 3-point bending tests of TPMS lattices were performed in accordance with ASTM E8 and ASTM E290, respectively. It was observed that the flexural properties of the 0.75 mm and 0.25 mm TPMS lattices are similar and exhibit different properties with different scan strategies and speed variations under contour-only and hatch-only laser scanning strategies. Also, the 0.75 mm TPMS sheet lattices exhibited 79 % higher flexural stiffness than the 0.25 mm sheet lattices. It was also observed that this observed trend was reversed in the case of tensile properties. Findings from this study can provide new directions towards achieving gradient TPMS lattice designs with varying local mechanical performance by grading the laser scanning strategies to achieve desired mechanical properties and surface topologies.

Synergistic action and effect mechanism of coal gangue powder and red mud on the properties of concretes

Red mud and coal gangue powder were employed as substitutes for cement to prepare red mud concrete, coal gangue concrete, and red mud-coal gangue concrete. The effects of red mud and coal gangue powder on the physical properties, workability, and mechanical properties of concretes were evaluated, and the hydration reaction mechanisms were elucidated through microanalysis. Furthermore, the reaction process was investigated through thermogravimetric analysis. The results indicated that the individual addition of red mud and coal gangue powder had negative effect on the strength, workability, and porosity of concretes. However, the combination of red mud and coal gangue powder significantly improved the strength and porosity of the concrete compared to red mud concrete and coal gangue concrete. The red mud-coal gangue concrete with 15 % red mud and 15 % coal gangue powder had lower porosity, and comparable compressive strength with the cement concrete. The microscopic results and thermogravimetric analyses indicated that the synergistic effect of red mud and coal gangue led to the improvement of the strength of red mud-coal gangue concrete. The red mud exhibited the promotion effect on the hydration of coal gangue powder to generate new C-S-H, filling the pores. The denser structure in the red mud-coal gangue concrete was formed, thereby improving the pore space and mechanical properties of the concretes.

Environmentally Friendly Paving Block Based on Wood Waste: The Effect of Rubber Wood Waste Content on the Physical-Mechanical Properties of Paving Block

The wood sawing industry generates significant waste, consisting of wood chips, wood scraps, and sawdust. This research aims to evaluate the effect of rubber wood sawdust addition on the moisture content, water absorption capacity, and compressive strength of paving blocks. The study was conducted in August–September 2023, starting with preparing raw materials, composition planning, and test specimen fabrication. The parameters in this study included density testing, moisture content, water absorption capacity, and compressive strength. The density test results for treatments P0 were 1.11 g/cm3, P1 1.09 g/cm3, P2 1.07 g/cm3, P3 1.08 g/cm3, and P4 1.09 g/cm3. The moisture content test yielded values of 11.38% for P0, 12.56% for P1, 12.94% for P2, 13.24% for P3, and 13.80% for P4. The water absorption capacity values obtained were, for P0, 5.17%; P1, 5.40%; P2, 6.36%; P3, 8.11%; and P4, 9.27%. Compressive strength tests produced values for P0 at 7.19 N/mm2, P1 at 5.67 N/mm2, P2 at 4.22 N/mm2, P3 at 3.48 N/mm2, and P4 at 3.07 N/mm2. The addition of rubber wood sawdust to paving blocks significantly influences density, moisture content, water absorption capacity, and compressive strength values. Keywords: Composition, Compressive strength, Paving block, Sawdust waste.

Identification of mineralogical ore varieties using ultrasonic measurement results

Purpose. To improve the measurement and information base of ultrasonic measurements rock characteristics to assess their mineralogical varieties. It is proposed to use a combination of measurement results of the acoustic quality factor of the test sample in relation to longitudinal and transverse ultrasonic waves, as well as the characteristic coefficient based on the dispersion and the average amplitude value of the received signal, for fuzzy identification of mineralogical and technological varieties of iron ore. Methods. As elastic waves propagate through the rock mass, they undergo attenuation due to absorption and dissipation of ultrasonic signal energy. The degree of attenuation, as well as the wave propagation velocity, is dependent on the physical-mechanical and chemical-mineralogical properties of the medium through which they travel. In this paper, we analyze a rock characterized by a complex structure comprising ore inclusions and surrounding matrix, each of which differs in its physical-mechanical and chemical-mineralogical properties. In particular, in iron ore samples, the distribution of mineral grains and aggregates exhibits significant heterogeneity in terms of both amount and size. Findings. An iterative method of fuzzy identification of mineralogical-technological iron ore varieties, based on the analysis of their properties in vector space of features, allows, by minimizing the sums of weighted distances between the analyzed and reference values of ultrasonic measurement results, to attribute them with a certain degree of belonging to the main technological types of ores mined at the deposit, and define them as magnetite quartzite with a confidence probability of 0.93. Originality. As an information base for identification of mineralogical iron ore varieties, the results of measuring the velocity and attenuation of longitudinal and transverse ultrasonic waves of appropriate frequency are used, on the basis of which the acoustic quality factor of the rock sample is calculated, as well as the characteristic parameter S, which is determined by the dispersion and average values of the received ultrasonic signal intensity, which has traveled a certain distance in the studied environment. Practical implications. The results of tests and practical approbation of the method for identifying mineralogical iron ore varieties based on the data of ultrasonic well logging testify to its high efficiency, which allows recommending the developed scientific-technical solutions for wide industrial application at mining enterprises.

Physical and mechanical properties of special cementitious materials modified by nano-particles

Compared to ordinary Portland cement (OPC), sulphoaluminate/ferroaluminate cement (SAC/FAC) and aluminate cement (CAC) are the most promising repair materials due to their excellent early strengths, but the later strengths of SAC/FAC develop slowly, and the later strengths of CAC are obviously declined. This paper studied the effects of nano-SiO2 and nano-ZnO on the physical properties, mechanical properties and early hydration processes of three special cement-based materials and compared them with OPC-based materials. The strength development and early hydration mechanism were revealed by hydration heat, scanning electron microscopy and X-ray diffraction. The test results showed that with the increasing content of nano-SiO2, the setting time of the four cement pastes was gradually shortened, the fluidity of four fresh mortars was gradually reduced, and their compressive and flexural strengths at all ages were improved to different degrees. Nano-ZnO significantly prolonged the setting time of OPC paste and increased the fluidity of OPC mortar, which had a negative effect on its early compressive and flexural strengths, but enhanced its late strengths. After the addition of 1 % nano-ZnO, the initial and final setting time of OPC were about 12 times and 13.4 times that of ordinary OPC paste, respectively. The effect of incorporating nano-ZnO on the physico-mechanical properties of three special cements was similar to that of nano-SiO2. The strength loss of CAC mortar with two kinds of nanoparticles was greatly reduced. The incorporation of nano-SiO2 and nano-ZnO could promote the hydration process of three special cements, resulting in the denser microstructure and higher crystallinity of hydration products.

Physical, mechanical and thermal properties of novel bamboo/kenaf fiber-reinforced polylactic acid (PLA) hybrid composites

This study investigates the physical, mechanical, and thermal properties of bamboo (BF) and kenaf (KF) fiber-reinforced polylactic acid (PLA) hybrid composites. Three hybrid (30BF-70KF, 50BF-50KF, and 70BF-30KF) and two non-hybrid (BF-PLA and KF-PLA) composites were developed through twin screw extrusion and compression molding techniques. The physical properties (density, void content, crystallinity via XRD, and chemical interactions via FTIR), mechanical properties (tensile, flexural, compressive, impact, and hardness), and thermal properties (Thermogravimetric analysis-TGA and Differential scanning calorimetry-DSC) were thoroughly analyzed. BF reinforcement reduced the composites’ density to 1.1826 g/cm³, while the inclusion of KF increased it to 1.2479 g/cm³. 50:50 blend of bamboo-kenaf reinforcement achieved the lowest void content of 0.27 %. The XRD patterns revealed heightened crystallinity in the BF-PLA composite. FTIR analysis showed stable functional groups, with O–H absorption bands indicative of cellulosic fibers. The BF-PLA non-hybrid composite exhibited the highest tensile strength at 25.95 MPa and compressive strength at 173.15 MPa, with the 30BF-70KF hybrid composite showing notable impact strength. Fractured morphology by FESEM revealed superior fiber-matrix adhesion for BF-PLA composite. TGA demonstrated a variation in thermal degradation temperatures, with the BF30-KF70 composite showing the highest onset of degradation at 484 °C. DSC analysis indicated a reduction in the glass transition temperature (Tg) across all fiber-reinforced samples and revealed significant adjustments in melting and crystallization temperatures. This research highlights the potential of BF-KF/PLA hybrid composites in the development of eco-friendly plastic furniture and consumer products.

Life cycle assessment as a circular economy strategy to select eco-efficient raw materials for particleboard production

Life Cycle Assessment (LCA) is applied for choosing and comparing circular alternatives, comprising a bicomponent polyurethane resin based on castor oil (PU) and sugarcane bagasse (SB) particles to conventional materials using urea formaldehyde (UF) and eucalyptus particles, for the production of 1 m3 of medium-density particleboard (MDP), from cradle-to-gate, with five different formulations. Databases were used in life cycle inventory and the ReCiPe impact method was selected at midpoint level. The eco-efficiency index, based on modulus of rupture and CO2 emissions, revealed that the best condition was the panels using alternative materials, as it can reduce up to 74 % the environmental burdens investigated. The panel using only circular materials showed feasible technical performance according with the physical-mechanical properties considered, generating the best eco-efficiency indicator (0,154 MPa/CO2 eq.). These results build a foundation for reconsidering the selection of raw materials in large-scale MDP production, potentially leading to the adoption of more sustainable practices.

Preparation, Mechanical and Thermal Insulation Properties of Graphene Oxide/Polydopamine/Polyurethane Foam‐Based Tunnel Insulation Liner Material

This article designs a novel tunnel insulation liner material based on polyurethane foam (PUF), aiming to improve the liner material's mechanical properties, hydrophobicity, thermal insulation properties and to reduce the self‐weight of the material. Firstly, PUF is self‐made using a one‐step method, and the optimal parameter combination is optimized through the single‐parameter (SP) method. Secondly, based on the optimal parameter combination of PUF, a new process is employed to prepare polydopamine (PDA)/graphene oxide (GO)/PUF. Compression experiments and contact angle tests are conducted to assess the physical mechanical properties of PDA/GO/PUF. Infrared thermography and combustion experiments are employed to characterize the thermal insulation performance of PDA/GO/PUF. Microscopic mechanisms are explained through thermogravimetric analysis (TG), scanning electron microscopy (SEM), and Fourier‐transform infrared spectroscopy (FTIR). The results show that: the optimal parameter combination of tin(II) bis(2‐ethylhexanoate) (TEH), water (H2O), and toluene‐2,4‐diisocyanate (TDI) content optimized by the SP method is 4 parts, 2.8 parts, and 19 parts. PUF prepared based on the optimal parameter combination exhibits a dense and uniform cell structure with low density. Under cyclic loading, PDA/GO/PUF composite material exhibits excellent mechanical stability and fatigue resistance; the hydrophobicity, thermal insulation, and thermal stability of PDA/GO/PUF are significantly improved compared to PUF.