Search Results (109)

The dynamic behaviour of a column excited at the base, e.g., under an earthquake load, has been extensively studied. However, the column may also experience impact at the tip like a heavy-duty truck braking on a bridge. The caused base shear of the pier is very important. In this work, the dynamic behaviour, particularly the impact load from the tip to the base, was studied on two different composites: double basalt- and double flax fibre-reinforced polymer tube (DBFRP and DFFRP)-confined coconut fibre-reinforced concrete (CFRC). For each composite, two columns with a height of 1 m, an inner diameter of the outer tube of 100 mm, and an inner tube of 30 mm were fabricated. The column was fully fixed at the base and struck at the top with an impulse hammer. The base shear was calculated through an equivalent mass method using the acceleration at the tip. The results show that both DBFRP-CFRC and DFFRP-CFRC can dissipate a portion of the impact force, resulting in a reduction in force at the base of the specimens. The base shear of DFFRP-CFRC columns is larger and dissipates energy faster than that of DBFRP-CFRC columns. Full article

This study investigates hygrothermal durability of bio-epoxy composites reinforced with carbon, E-glass, basalt, and flax fibres. Fibre yarns and bio-composites were exposed for 3000 h at 60 °C and 98% relative humidity. The tensile strength reduction in the fibres and the interfacial shear strength (IFSS) reduction in the composites were assessed after ageing. Chemical deterioration was evaluated using energy-dispersive X-ray spectroscopy (EDS); morphological changes in fibres and composites fracture surfaces were examined using a scanning electron microscope (SEM). Results indicated that the durability was significantly influenced by fibre types. Tensile strength reduction was higher in carbon, glass and basalt compared to flax yarns because of chemical degradation of the sizing layer in synthetic fibres, while only physical damage was observed in flax. The IFSS reduction was highest in flax composites (10%), and lowest in carbon (4%). EDS indicated the hydrolysis and erosion of fibre sizing, with reduced silica content in glass and basalt fibres. SEM revealed matrix-dominated failure in carbon/bio-epoxy, interfacial debonding in glass and basalt composites, fibre slip and pull-out in flax/bio-epoxy. Overall, the results highlighted damage propagation pathways and demonstrated that bio-epoxy composites exhibited reasonable performance under hygrothermal ageing, supporting their potential as a sustainable alternative in durability-critical applications. Full article

This study investigates the adhesion of polypropylene (PP), steel and basalt fibres to geopolymer matrices of varying composition. Geopolymers formed via alkali activation of fly ash (FA) and ground granulated blast-furnace slag (GGBFS) offer significant environmental advantages over Portland cement by reducing CO₂ emissions and energy consumption. The addition of water treatment sludge (WTS) was also investigated as a partial or complete replacement for FA. Pull-out tests showed that replacing FA with WTS significantly reduces the mechanical properties of the matrix and at the same time the adhesion to the fibres tested. The addition of 20% WTS reduced the compressive strength by more than 50% and full replacement to less than 5% of the reference value. Steel fibres showed the highest adhesion (9.3 MPa), while PP fibres had the lowest, with adhesion values three times lower than steel. Increased GGBFS content improved fibre adhesion, while the addition of WTS weakened it. Calculated critical fibre lengths ranged from 50 to 70 mm in WTS-free matrices but increased significantly in WTS-containing matrices due to reduced matrix strength. The compatibility of the fibres with the geopolymer matrix was also confirmed via SEM microstructural observations, where a homogeneous transition zone was observed in the case of steel fibres, while numerous discontinuities at the interface were observed in the case of other fibres, the surface of which is made of organic polymers. These results highlight the potential of fibre-reinforced geopolymer composites for sustainable construction. Full article

To investigate the potential of metakaolin (MK) (5%, 10%, 15%, and 20% substitution of cement mass) and basalt fibre (volume contents of 0.1%, 0.2%, and 0.3%) in recycled aggregate concrete (RAC) products, RAC’s mechanical properties were first assessed with a singular incorporation of MK. The findings demonstrated that adding 15% MK optimised the compressive strength and flexural strength of RAC (at the recycled aggregate replacement levels of 30%, 45%, and 60% by weight). An orthogonal test was conducted to investigate the synergistic effect of MK and basalt fibre (BF), with the recycled coarse aggregate (RCA) replacement rate (mass ratio of RCA to natural coarse aggregates), MK content (cement mass substitution percentage), and BF content (volume dosage) identified as the influencing parameters. The variance analysis reveals that the influence of the replacement ratio of RCA on compressive strength surpasses that of MK content, which in turn exceeds that of BF content. Conversely, as for the flexural strength, BF is substantially more effective than that of MK. A model test of RAC curbs was performed based on the ideal mix ratio suggested by the single mixing of MK and MK and BF compound mixing inside the orthogonal test. The results demonstrate that the RAC curbs, with an RCA replacement rate of 30%, display optimal mechanical properties when 15% MK and 0.2% BF are incorporated. This surpasses the performance of 15% MK alone and illustrates that the mix incorporation of MK and BF is superior to that of MK alone. Full article

This study investigates the flexural performance, tensile splitting strength, and fracture behaviour of self-compacting concrete (SCC) reinforced with polypropylene (PP) and basalt (BF) fibres. A total of eleven SCC mixtures with varying fibre types and volume fractions (0.025–0.25%) were tested at 7 and 28 days. In this study, the term high-performance concrete (HPC) refers to SCC mixtures with a 28-day compressive strength exceeding 60 MPa, as commonly accepted in European standards and literature. The control SCC achieved 68.2 MPa at 28 days. While fibre addition enhanced the tensile and flexural properties, it reduced workability, demonstrating the trade-off between mechanical performance and flowability in high-performance SCC. The experimental results demonstrate that both fibre types improve the tensile behaviour of SCC, with distinct performance patterns. PP fibres, owing to their flexibility and crack-bridging capability, were particularly effective at early ages, enhancing the splitting tensile strength by up to 45% and flexural toughness by over 300% at an optimal dosage of 0.125%. In contrast, BF fibres significantly increased the 28-day toughness (up to 15.7 J) and post-cracking resistance due to their superior stiffness and bonding with the matrix. However, high fibre contents adversely affected workability, particularly in BF-reinforced mixes. The findings highlight a dosage-sensitive behaviour, with optimum performance observed at 0.05–0.125% for PP and 0.125–0.25% for BF. While PP fibres improve crack distribution and early-age ductility, BF fibres offer higher stiffness and energy absorption in post-peak regimes. Statistical analysis (ANOVA and Tukey’s test) confirmed significant differences in the mechanical performance among fibre-reinforced mixes. The study provides insights into selecting appropriate fibre types and dosages for SCC structural applications. Further research on hybrid fibre systems and long-term durability is recommended. The results contribute to sustainable concrete design by promoting enhanced performance with low-volume, non-metallic fibres. Full article

Dispersed reinforcement in cement mortars plays a key role in increasing their durability and strength. The fibres act as binding elements in the structure, preventing the development of microcracks that can weaken the material. Fibres increase mechanical strength, elasticity and resistance to tension and compression, which translates into better physical and mechanical parameters of the material compared to mortars without fibres. The aim of this study was to determine the physical and mechanical parameters of mortars with the addition of currently produced steel, glass and basalt fibres. The influence of the selected fibre type on the compressive and flexural strength, water absorption and capillary rise of mortars was investigated. The rheological properties of the mortars, i.e., consistency and volume density, were also investigated. Compressive and flexural strength was tested after 7, 28 and 56 days, while capillary rise and water absorption were tested after 28 days of curing. The frost resistance of the mortars was also determined. For the mortars tested, correlations were established between compressive strength and flexural strength, as well as between water absorption and capillary pull-up. A full statistical analysis was performed for two parameters, i.e., compressive strength and capillary pull-up. The introduction of basalt fibres into the mortars resulted in an increase in compressive strength by approximately 5% and in flexural strength by 48% after 56 days of curing. A lower mass increase of approximately 30% was also observed in relation to the reference series in the water absorption and capillary pull-up test for the series of mortars with glass fibres. Full article

This research paper employed novel sustainable alternative materials to reduce the environmental impact of thermoset/synthetic fibre composites. The effect of seawater hydrothermal ageing at 45 °C for 45 and 90 days on the physical and interlaminar fracture toughness (mode I and mode II) of a semi-unidirectional non-crimp basalt fibre (BF)-reinforced acrylic matrix and epoxy matrix composites was investigated. Optical and scanning electron microscopes were used to describe the fracture and interfacial failure mechanisms. The results show that the BF/Elium composite exhibited higher fracture toughness properties compared to the BF/Epoxy composite. The results of the mode I and mode II interlaminar fracture toughness values for the BF/Elium composite were 1280 J/m² and 2100 J/m², which are 14% and 56% higher, respectively, than those of the BF/Epoxy composite. The result values for both composites were normalised with respect to the density of each composite laminate. The saturated moisture content and diffusion coefficient values of seawater-aged samples at 45 °C and room temperature for the BF/Elium and BF/Epoxy composites were analysed. Both composites exhibited signs of polymer matrix decomposition and fibre surface degradation under the influence of seawater hydrothermal ageing, resulting in a reduction in the mode II interlaminar fracture toughness values. Enhancement was observed in mode I fracture toughness under hydrothermal ageing, particularly for the BF/Epoxy composite, due to matrix plasticisation and fibre bridging. Full article

This study introduced basalt fibres as a reinforcing material and employed notched beam three-point bending tests combined with digital image correlation (DIC) technology to comprehensively evaluate key fracture parameters—namely, initial fracture toughness, unstable fracture toughness, fracture energy, and ductility index—of expanded polystyrene (EPS)-based geopolymer concrete with different mix proportions. The results demonstrate that the optimal fracture performance was achieved when the basalt fibre volume content was 0.4% and the EPS content was 20%, resulting in respective increases of 12.07%, 28.73%, 98.92%, and 111.27% in the above parameters. To investigate the toughening mechanisms, scanning electron microscopy was used to observe the fibre–matrix interfacial bonding and crack morphology, while X-ray micro-computed tomography enabled detailed three-dimensional visualisation of internal porosity and crack development, confirming the crack-bridging and energy-dissipating roles of basalt fibres. Furthermore, the crack propagation process was simulated using the extended finite element method, and the evolution of fracture-related parameters was quantitatively analysed using a linear superposition progressive assumption. A simplified predictive model was proposed to estimate fracture toughness and fracture energy based on the initial cracking load, peak load, and compressive strength. The findings provide theoretical support and practical guidance for the engineering application of basalt fibre-reinforced EPS-based geopolymer lightweight concrete. Full article

To meet the European Green Deal targets, the construction sector must improve building thermal performance via advanced insulation systems. Eco-friendly sandwich panels offer a promising solution. Therefore, this work aims to develop and validate a new eco-friendly composite sandwich panel (basalt fibres and recycled extruded polystyrene) with enhanced multifunctionality for lightweight and energy-efficient building façades. Two panels were produced via vacuum infusion—a reference panel and a multifunctional panel incorporating phase change materials (PCMs) and silica aerogels (AGs). Their performance was evaluated through lab-based thermal and acoustic tests, numerical simulations, and on-site monitoring in a living laboratory. The test results from all methods were consistent. The PCM-AG panel showed 16% lower periodic thermal transmittance (0.16 W/(m²K) vs. 0.19 W/(m²K)) and a 92% longer time shift (4.26 h vs. 2.22 h), indicating improved thermal inertia. It also achieved a single-number sound insulation rating of 38 dB. These findings confirm the panel’s potential to reduce operational energy demand and support long-term climate goals. Full article

Three-dimensionally printed cement-based composites emerge as a research hotspot in the fields of construction engineering in recent years. Current research primarily focuses on the reinforcement mechanisms of individually incorporated fibres, while a significant gap remains in the synergistic effects of hybrid fibre systems. This study investigates the effects of mono-doping (0.2 wt.% and 0.4 wt.% by the mass of the cement) and hybrid-doping (0.1 wt.% + 0.1 wt.% by the mass of the cement) with 3 mm polypropylene, basalt, and carbon fibres on the fresh-state properties and mechanical behaviours. Through quantitative characterisation of the flowability and mechanical performance of short-fibre-reinforced 3D-printed cementitious composites (SFR3DPC), coupled with comprehensive testing including digital image correlation, X-ray diffraction, and scanning electron microscopy, several key findings are obtained. The experimental results indicate that the addition of excess fibres reduces fluidity, which affects the mechanical performance and make the anisotropy of the composites more pronounced. While the single addition of 0.2 wt.% CF shows the most significant improvement in flexural and compressive strengths, the hybrid combination of 0.1 wt.% CF and 0.1 wt.% BF shows the greatest increase in interlayer bond strength by 26.7%. The complementary effect of the hybrid fibres contributes to the damage mode of the composites from brittle fracture to quasi-brittle behaviour at the physical level. These findings offer valuable insights into optimising the mechanical performance and improving defects of 3D-printed cementitious composites with short fibres. Full article

Bioabsorbable polymer stents (BPSs) were developed to address the long-term clinical drawbacks associated with permanent metallic stents by gradually dissolving over time before these drawbacks have time to develop. However, the polymers used in BPSs, such as polylactic acid (PLA), have lower mechanical properties than metals, often requiring larger struts to provide the necessary structural support. These larger struts have been linked to delayed endothelialisation and an increased risk of stent thrombosis. To address this limitation, this study investigated the incorporation of high-strength basalt fibres into PLA to enhance its mechanical performance, with an emphasis on optimising the processing conditions to achieve notable improvements at minimal fibre loadings. In this regard, PLA/basalt fibre composites were prepared via twin-screw extrusion at screw speeds of 50, 200, and 350 RPM. The effects were assessed through ash content testing, tensile testing, SEM, and rheometry. The results showed that lower screw speeds achieved adequate fibre dispersion while minimising the molecular weight reduction, leading to the most substantial improvement in the mechanical properties. To examine whether a second extrusion run could enhance the fibre dispersion, improving the composite’s uniformity and, therefore, mechanical enhancement, all the batches underwent a second extrusion run. This run improved the dispersion, leading to increased strength and an increased modulus; however, it also reduced the fibre–matrix adhesion and resulted in a notable reduction in the molecular weight. The highest mechanical performance was observed at 10% fibre loading and 50 RPM following a second extrusion run, with the tensile strength increasing by 20.23% and the modulus by 27.52%. This study demonstrates that the processing conditions can influence the fibres’ effectiveness, impacting dispersion, adhesion, and molecular weight retention, all of which affect this composite’s mechanical performance. Full article

This research paper employed the recently developed Elium thermoplastic resin and basalt fabrics as an alternative to thermoset/synthetic fibre composites to reduce their environmental impact. Elium^® 191 XO/SA and Epoxy Prime^TM 37 resin were reinforced with mineral-based semi-unidirectional basalt fibre (BF). Physical, chemical, tensile, and flexural performance was investigated under the effect of hydrothermal seawater ageing at 45 °C for 45 and 90 days. The results show that the BF/Elium composite exhibited superior tensile and flexural strength, as well as good stiffness, compared with the BF/Epoxy composite. Digital images and scanning electron microscope images were used to describe the fracture and failure mechanisms. The tensile and flexural strength values of the BF/Elium composite were 1165 MPa and 1128 MPa, greater than those of the BF/Epoxy composite by 33% and 71%, respectively. The tensile and flexural modulus values of the BF/Elium composite were 44.1 GPa and 38.2 GPa, which are 30% and 12% greater than those of the BF/Epoxy composite. The result values for both composites were normalised with respect to the density of each composite laminate. Both composites exhibited signs of resin decomposition and fibre surface degradation under the influence of seawater ageing, resulting in a more recognisable reduction in flexural properties than in tensile properties. Full article

A fabric orientation angle has a significant influence on the failure mechanisms at the lamina level. Any change in this angle can lead to a sudden reduction in strength, potentially resulting in catastrophic failures due to variations in load-carrying capacity. This study examined the impact of off-axis fabric orientation angles (0°, 15°, 30°, 45°, 60°, and 90°) on the flexural properties of non-crimp basalt-fibre-reinforced acrylic thermoplastic composites. The basalt/Elium^® composite panels were manufactured using a vacuum-assisted resin transfer moulding technique. The results show that the on-axis (0°) composite specimens exhibited linear stress–strain behaviour and quasi-brittle failure characterised by fibre dominance, achieving superior strength and failure strain values of 1128 MPa and 3.85%, respectively. In contrast, the off-axis specimens exhibited highly nonlinear ductile behaviour. They failed at lower load values due to matrix dominance, with strength and failure strain values of 144 MPa and 6.0%, respectively, observed at a fabric orientation angle of 45°. The in-plane shear stress associated with off-axis angles influenced the flexural properties. Additionally, the degree of deformation and the fracture mechanisms were analysed. Full article

The increasing demand for environmentally friendly materials has driven researchers and industries to explore alternatives that combine performance with reduced environmental impact. In this framework, the possibility of replacing glass-fibre-reinforced composites (GFRCs) with basalt-fibre-reinforced composites (BFRCs) is attracting increasing attention. In this study, basalt–vinyl ester specimens and glass–vinyl ester specimens were mechanically characterized using both the Risitano Thermographic and Static Thermographic Methods. The results indicate that energy methods are effective for the mechanical characterization of complex materials like basalt and glass fibre composites. The average ultimate tensile strength was 374 ± 20.2 MPa for BFRCs and 295 ± 4.7 MPa for GFRCs, showing a 26.7% improvement with basalt. The fatigue limit was 96.5 ± 0.2 MPa for BFRCs and 104.8 ± 0.8 MPa for GFRCs, while the static stress limit estimated via thermography was 99.9 ± 6.45 MPa and 101.7 ± 5.24 MPa, respectively. Furthermore, the failure mechanisms of both BFRC and GFRC specimens were investigated. Additionally, a Life Cycle Assessment (LCA) was performed to evaluate the environmental impact of basalt and glass fibre composites. The results showed that BFRCs have lower environmental impacts, including 0.67 kg CO₂-eq with respect to climate change versus 0.81 kg CO₂-eq for GFRCs. This work highlights how the two materials are comparable in terms of their mechanical performance but different in terms of their sustainability and environmental impact. Full article

This study focuses on improving the recycled coarse aggregate (RCA) replacement ratio in recycled aggregate concrete products. First, the mix design and compressive performance of recycled aggregate concrete (RAC, RCA replacement percentages of 20%, 35%, and 50%) were evaluated using the monofactor analysis method and response surface methodology under three different conditions: single addition of nano-calcium carbonate (NC, dosages of 0.1%, 0.2%, and 0.3%), single addition of basalt fibre (BF, volume content of 0.1%, 0.2%, and 0.3%), and combined addition of both. The results show that the compressive strength of RAC at 7 and 28 days rises as the BF or NC content increases and then falls as the NC content increases. According to the sensitivity analysis, RAC’s compressive strength is significantly impacted by the replacement ratio of RCA, with NC having a more considerable effect on RAC’s 7-day compressive strength than BF, while BF affects the 28-day compressive strength more than NC does. Based on the desirability function, the ideal BF and NC content in RAC was optimised and confirmed by the compressive strength test. It demonstrates that the best compressive performance is achieved by RAC with 1% NC and 0.3% BF. Finally, concrete pavement brick models were created using the ideal mix proportion provided by the compressive strength test. The model compression test results show that RAC pavement bricks (RCA replacement ratio of 60%) with 1% NC and 0.3% BF had a 28d compressive strength of 5.7% and 15.8% higher than NAC and RAC pavement bricks, respectively. Full article