Search Results (2,956)

Seawater sea sand-engineered cementitious composites (SS-ECCs) provide a potential solution to the shortage of freshwater and sand resources for coastal and offshore construction. However, systematic studies on the combined effects of fiber parameters in SS-ECC systems remain limited. This study examines the effects of polyethylene (PE) fiber content (0%, 1%, 1.5%, and 2%) and length (12 mm, 18 mm, and 24 mm) on the mechanical properties of SS-ECC via compressive, tensile, and bending tests. The results indicate that increasing the volume fraction of PE fibers effectively enhances the tensile strength, flexural strength, and flexural toughness of SS-ECC. SS-ECC attained its highest tensile strength with a 24 mm PE fiber length, showing increases of 41.1% and 44.2% over specimens with 12 mm and 18 mm fibers, respectively. Furthermore, based on 28-day curing, the utilization of seawater and sea sand led to increases in tensile and flexural strengths by 12.3% and 17.2%, respectively, relative to ECC prepared with freshwater and river sand, though it resulted in a reduction in toughness. A predictive model for tensile strength is established considering the characteristic value of PE fiber with an R² of 0.8461, indicating reasonable correlation within the tested range. Results from this paper can help to develop a favorable PE fiber-reinforced SS-ECC for ocean engineering. Full article

Low-carbon and highly printable cementitious materials are crucial for the practical application of extrusion-based three-dimensional concrete printing (3DCP). This study develops and optimizes a one-part alkali-activated concrete suitable for 3D printing through an integrated experimental and evaluation approach. An orthogonal experimental design was employed to investigate the effects of precursor ratio (ground granulated blast-furnace slag, GGBFS, to fly ash, FA), water-to-binder ratio, activator dosage, and retarder content on fresh-state properties, rheological behavior, setting characteristics, and mechanical performance. The optimal mixture was determined using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) multi-criteria decision method. The mixtures exhibited suitable rheology, with a yield stress of 90–141 Pa and a plastic viscosity of 3.5–7.2 Pa·s, a setting time of 40–96 min, and mechanical performance with compressive and flexural strengths of 29–71 MPa and 4.2–6.9 MPa, respectively. The optimal mixture provided a 95-min printing open time and an acceptable pumping pressure of 1.77 MPa, while full-scale tests confirmed stable extrusion and good print quality. Furthermore, within the defined cradle-to-gate, materials-stage boundary and the adopted inventory factors, the optimized alkali-activated mixture exhibited an embodied CO₂ emission of 0.113 kg CO₂/L, which is approximately 61% lower than that of the reference cement-based printable mixture. The proposed approach provides a systematic framework for designing low-carbon, high-performance one-part alkali-activated materials for extrusion-based 3D concrete printing applications. Full article

The durability characteristics of inorganic mixtures incorporating recycled aggregates from rural residential construction and demolition waste with high red brick content remain inadequately elucidated. To illuminate their long-term serviceability, two types of recycled aggregate inorganic mixtures (RAIMs) were formulated and implemented in a test road section, with their mechanical properties and fatigue resistance systematically monitored and assessed. Comparative analysis indicated that RAIMs exhibit comparable resistance to permanent deformation and analogous fracture failure mechanisms to natural aggregate inorganic mixtures (NAIMs), yet their elastic deformation recovery capability is compromised. Specifically, RAIMs attained parity with NAIMs in terms of unconfined compressive strength, indirect tensile strength, flexural tensile strength, and static compressive resilient modulus. However, their dynamic compressive resilient modulus, indirect tensile resilient modulus, and flexural tensile resilient modulus were lower than those of NAIMs by over 30%. Furthermore, probabilistic fatigue prediction models for RAIMs were established, facilitating reliable estimation of the service life of RAIMs under various stress intensity levels. This study holds considerable significance for dispelling the inherent perception of RAIMs’ inferior service performance and augmenting the theoretical foundation for their resourceful utilization in road engineering. Full article

Background: This study aimed to investigate the biomechanical behavior of conservative inlay restorations fabricated from different CAD/CAM materials by combining experimental flexural strength testing with finite element analysis. Methods: Five CAD/CAM materials were evaluated: feldspathic ceramic (Cerec Blocs), leucite-reinforced ceramic (IPS Empress CAD), resin nano-ceramic (Lava Ultimate), polymer-infiltrated ceramic network (VITA Enamic), and lithium disilicate ceramic (IPS e.max CAD). Young’s modulus and Poisson’s ratio were experimentally determined using three-point bending and nanoindentation tests and used as inputs for 3D FEA. Von Mises (VM) stress distributions within the inlays were analyzed under simulated occlusal loading. Results: Maximum VM stresses showed an inverse relationship with material elasticity. IPS e.max CAD exhibited the highest maximum VM stress (45.571 MPa), whereas the resin nano-ceramic showed the lowest (25.419 MPa). Despite higher stress concentrations in high-modulus ceramics, VM values for all materials remained well below their FS limits. Conclusions: All materials demonstrated adequate mechanical stability under physiological loading. Lithium disilicate showed a comparatively larger margin between stress levels and flexural strength, while lower-modulus materials tended to promote greater stress transfer to supporting structures. Full article

This study investigated the flexural behavior of concrete one-way slabs reinforced with CFRP grids as longitudinal reinforcement, employing both experimental and finite element (FE) methods. A total of eight concrete one-way slabs were tested, including one with a steel grid and seven with CFRP grids. The test variables considered were concrete strength grade, grid size, and concrete cover thickness. The experimental results revealed that the CFRP grid-reinforced slabs underwent significant deformation without failure. Concrete strength grade was found to significantly influence the cracking load, with an increase of 64.1% observed when the grade was raised from C20 to C40. Reducing the cover thickness proved most effective in enhancing serviceability load capacity, yielding a 44.9% increase when the cover was reduced from 30 mm to 10 mm. Additionally, a finite element model was developed and validated against the experimental results, showing good agreement. Full article

The strengthening of reinforced concrete (RC) beams requires repair systems that can enhance strength, stiffness, and energy dissipation without significantly increasing self-weight or compromising durability. This study explores the structural response of RC beams strengthened using an integrated shear–flexure system combining near-surface-mounted carbon fiber-reinforced polymer (NSM-CFRP) ropes and steel-reinforced geopolymer overlays in the compression zone. Monotonic three-point bending tests were performed on two RC beam specimens, one unstrengthened control and one strengthened beam, to obtain preliminary observations of load–deflection behavior, stiffness, ductility, and energy absorption. The strengthened specimen exhibited increases in ultimate load (28.6%), stiffness (13.6%), and energy absorption (7.65%) relative to the control beam, suggesting the potential for effective composite action between the CFRP ropes and geopolymer material. A three-dimensional nonlinear finite element model was developed using ATENA to support interpretation of the experimental response, incorporating detailed constitutive models for concrete, steel reinforcement, and CFRP ropes. The numerical predictions showed reasonable agreement with the experimental results. Within the limitations of the test matrix, the results indicate that the proposed dual strengthening system may offer a viable and sustainable approach for enhancing the shear–flexural performance of RC beams. Full article

Wood used in construction varies in density, leading to differences in strength and rigidity. Wood densification has recently emerged as a promising technique to address these limitations and enhance material performance. This study explores the potential of two abundant and low-cost invasive hardwood species in South Africa—Prosopis glandulosa (Honey Mesquite) and Acacia mearnsii (Black Wattle)—as sources for producing densified wood. A range of strengthening methods, including chemical, pressure, and heat treatments, were applied and compared. After partial delignification and hot pressing, sample thicknesses were reduced by 40% for Prosopis and 50% for Acacia, yielding substantial increases in flexural strength of 216% (22.61 MPa) for Prosopis and 334% (24.65 MPa) for Acacia. In addition to SEM anatomical imaging, analyses of lignosulphonate content, and thermogravimetric profiling, the study also evaluated several practical, carpentry-relevant mechanical properties. These included comparative tests for flexural and compressive strength, nailing and sanding performance, as well as assessments of water absorption, electrical resistivity, and flame-holding capacity. Full article

Based on the dual requirements of building energy efficiency and construction industrialization, along with the development of high-strength, high thermal resistance (low thermal conductivity) foamed concrete (HLFC), this study proposes a new prefabricated high-strength foamed concrete thermal self-insulating shear wall system (called HFSW shear wall) suitable for multi-story buildings, which could address the core shortcomings of existing organic insulation materials in buildings, such as poor fire resistance and short life cycles. Concerning the research gap in the flexural performance of this wall type, this study conducted seismic tests on two full-scale wall models and systematically analyzed the fundamental performance parameters under quasi-static loading, including bending failure phenomena, load-bearing capacity, stiffness degradation, energy dissipation capacity, and ductility. The results show that HFSW walls with large shear span ratios generally exhibit typical bending failure characteristics. However, due to the relatively low material strength, extensive development of shear and flexural–shear cracks occurs, leading to minimal differences in typical seismic performance indicators compared to shear-dominated failure scenarios in traditional shear walls (indicating significant flexural–shear coupling effects). Finally, a finite element model was used to simulate the wall capacity under various parameters, including axial compression ratio, wall thickness, and longitudinal reinforcement in edge columns. Based on the validated and calibrated finite element results, and in accordance with the wall failure mode as well as the load transfer mechanism, a calculation model for the flexural strength of HFSW shear walls was established to guide design and engineering application, achieving a theoretical calculation accuracy of 0.97. The research findings provide meaningful guidance for the design and application of this wall system. Full article

This study evaluates bamboo–coir hybrid composite panels developed for formwork applications using an 80:20 fiber–matrix ratio and a 50:50 bamboo-to-coir distribution. The novelty of this study lies in the combined assessment of formwork-relevant mechanical performance, Mode I and Mode II fracture behavior, finite element validation and post-fracture microstructural correlation for a high fiber volume fraction natural fiber hybrid panel. Mechanical, durability, fracture, numerical and microstructural investigations were performed and benchmarked against 10 mm thick construction-grade plywood. The hybrid panels exhibited a density of 805 ± 10.84 kg/m³, which is within 0.7% of plywood, a tensile strength of 50.20 ± 2.85 MPa, representing an increase of 41.8% over plywood, and a flexural strength of 38.60 ± 2.10 MPa, corresponding to an increase of 12.9% as compared to plywood. The impact energy absorption of hybrid panels was 7.85 ± 0.62 J, which is 26.6% greater than plywood. Mode I fracture testing yielded a fracture toughness of 456.65 ± 15.42 J/m², corresponding to an increase of 9.3% over plywood, while Mode II fracture toughness yielded a value of 792.42 ± 30.18 J/m², representing an increase of 13.7% over plywood. Finite element predictions deviated from experimental load–displacement responses by 5–13%. SEM observations identified fiber bridging, fiber pullout and interfacial sliding in the hybrid panels, consistent with the measured fracture energy values. The results indicate that bamboo–coir hybrid panels satisfy the mechanical and fracture performance requirements for reusable formwork systems. Full article

Synthetic microfibres released during textile drying are considered an emerging source of microplastic pollution, yet this waste stream is generally discarded without treatment. This study investigates a valorisation route by incorporating waste dryer-filter microfibres into a potassium-based/metakaolin geopolymeric coating for architectural applications, with the dual objective of preventing environmental release and enhancing material performance. Geopolymer pastes containing 0.1–0.3 wt.% of synthetic microfibres were characterised in terms of physical, mechanical and microstructural behaviour. Microfibre addition produced a marked toughening effect, with flexural strength increasing from about 3 MPa for the unreinforced matrix to 7.5 MPa for the composite containing 0.3 wt.% fibres, while compressive strength decreased moderately due to the presence of a compliant fibrous phase. Microstructural observations confirmed fibre dispersion and fibre–matrix bonding, supporting crack-bridging mechanisms. Density, porosity and water absorption measurements indicated a stable geopolymer gel structure with a connected pore network. Thin-layer applications onto clay brick exhibited satisfactory workability and adhesion, confirmed by pull-off testing (~0.12 MPa) and interfacial microscopy. The results demonstrate that textile-derived microfibres can be effectively immobilised within a potassium geopolymer matrix while improving flexural performance, offering a feasible circular strategy for microfibre waste reuse in mineral coatings. Full article

In order to better understand the mechanical properties of lightweight cement-based composite concrete (LWC), expanded polystyrene (EPS) beads are used as lightweight aggregate (LWA) in this paper. 50%, 70%, and 90% of EPS foam beads by volume are used to partially replace normal fine aggregate in different EPS concrete compositions. In addition, Ordinary Portland cement (OPC) was substituted with silica fume (SF) in EPS concrete at varying weight percentages of 15%. Nine mixes are made in order to examine the properties of EPS concrete. In the testing program, fresh density, slump, compressive strength, splitting tensile strength, flexural strength, thermal conductivity, and absorption are all determined. Although workability is improved, the mechanical properties of concrete are generally decreased when EPS beads are used. The addition of silica fume (SF) successfully counteracted the mixture’s overall decline in mechanical properties across all the mixtures that have been used. More solid material can be found per square inch of surface area in materials with a higher density, which results in more continuous heat-conduction pathways. In comparison to the control mix, the compressive strength of the polystyrene modified mixes showed a noticeable decline, falling by roughly 62% for P-50%, 69% for P-70%, and 71% for P-90%. In contrast, mixes P-90%-1.2, P-90%-1.4, and P-90%-1.6 reduced absolute strength compared to P-90%; their performance is nonetheless noteworthy because of their extraordinarily high EPS content. Despite having lesser absolute strengths than P-90%, mixes of P-90%-1.2, P-90%-1.4, and P-90%-1.6 nevertheless performed admirably considering their remarkably high EPS content. Full article

This study aims to evaluate the feasibility of replacing the minimum shear reinforcement in high-strength self-compacting lightweight concrete (HSLC) beams with hooked-end steel fibers at a volume fraction of 0.75 vol.% and to quantitatively assess the contribution of steel fibers to the shear capacity of the beams. Six HSLC beam specimens were tested to determine load-bearing behavior and failure modes under different reinforcement schemes, including beams without steel fibers or stirrups, beams reinforced with either steel fibers or stirrups, and beams incorporating both steel fibers and stirrups. The experimental results indicate that replacing the minimum shear reinforcement with 0.75 vol.% hooked-end steel fibers increased the flexural capacity, ultimate deflection, and energy absorption capacity by 2.5%, 7.8%, and 16.1%, respectively, thereby confirming the feasibility of using hooked-end steel fibers as a substitute for minimum shear reinforcement. The fiber shear capacity, calculated from experimental data, was compared with various prediction equations. Models containing the fiber factor demonstrated better agreement with test results, showing a minimum difference of 10.1%. Full article

The increasing demand for bricks has raised environmental concerns related to natural clay depletion, land degradation, and agricultural waste disposal. To address these challenges, this study utilizes rice husk ash (RHA) as a sustainable partial replacement for clay in fired clay bricks. Brick mixtures were casted with varying RHA dosages (up to 80%), and the effect of 2% lime addition was also examined. Mixtures were fired at 1000 °C and 1200 °C and were tested for compressive strength, flexural strength, and water absorption. Microstructural and mineralogical characteristics were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). At 1000 °C, increasing RHA content and lime addition increased porosity and reduced mechanical strength due to limited vitrification. In contrast, firing at 1200 °C promoted extensive verification and densification, resulting in improved strengths surpassing the severe-weathering requirements of ASTM C62. Compressive strengths of 74.62 MPa and 52.55 MPa were achieved for bricks containing 20% and 40% RHA, respectively, exceeding ASTM C62 severe weather grade requirements. Results demonstrate that RHA can be utilized at high replacement levels when appropriate firing conditions are applied, supporting sustainable fired brick production and agricultural waste valorization. Full article

The rising environmental burden of Portland cement production has intensified the demand for eco-friendly binders that support sustainable construction. This study investigates the development and performance of eco-friendly self-compacting geopolymer concrete (SCGC) produced from industrial by-products, including fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume (SF), metakaolin (MK), and glass waste powder (GWP). Twenty-one binder formulations were evaluated for fresh-state workability, mechanical performance, durability, and microstructural characteristics under different curing regimes. Fresh properties were assessed using slump flow, V-funnel, L-box, and J-ring tests, while hardened-state evaluations included compressive and flexural strength, Young’s modulus, and water absorption. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were performed on selected mixes to examine microstructural features and crystalline phase development. Results highlight a strong dependency of SCGC performance on binder composition and curing conditions. Mixes rich in GGBFS and SF demonstrated superior mechanical and durability performance, achieving compressive strengths of up to 102.4 MPa under water curing and 107.6 MPa under heat curing, along with negligible water absorption, reflecting a dense and well-developed gel matrix. SEM micrographs confirmed homogeneous, compact microstructures in high-performing mixes, while XRD analysis revealed broad amorphous humps indicative of well-formed N-A-S-H and C-A-S-H gel phases with minimal crystalline residues. In contrast, FA-dominant mixes displayed delayed strength development, and MK-GWP-rich systems exhibited higher porosity and reduced strength. This study underscores the significance of precursor synergy, optimized curing strategies, and microstructural refinement in tailoring SCGC for high-performance, durable, and low-carbon applications in sustainable construction with values ranged from 38.64 GPa (Mix 21) to 25.04 GPa (Mix 19) at 28 days. Stiffer mixes corresponded to denser matrices containing GGBFS and silica fume, whereas lower values were linked to weaker bonding and higher porosity. Full article

The increasing adoption of digital light processing (DLP) three-dimensional (3D) printing in prosthodontics has enabled the rapid fabrication of denture bases with improved dimensional accuracy and reproducibility. However, the mechanical performance and surface characteristics of 3D-printed denture base resins remain inferior to those of conventional heat-polymerized polymethyl methacrylate (PMMA), limiting their long-term clinical reliability. This study aimed to investigate the effect of incorporating zinc oxide (ZnO) and samarium oxide (Sm₂O₃) nanoparticles, individually and as hybrid nanofiller systems, on the mechanical and wettability properties of a DLP 3D-printed denture base resin. ZnO and Sm₂O₃ nanoparticles were incorporated into a photopolymerizable denture base resin at concentrations of 1 and 2 wt.%, producing seven experimental formulations, including a control group. A total of 280 specimens were fabricated using a DLP 3D printer and subjected to standardized post-processing. Nanoparticle dispersion and morphology were examined using field-emission scanning electron microscopy (FE-SEM), while Fourier-transform infrared spectroscopy (FTIR) was employed to assess possible chemical interactions between the nanofillers and the polymer matrix. Mechanical performance was evaluated through impact strength, transverse strength, and flexural strength tests, and surface wettability was assessed using static water contact angle measurements. Statistical analysis was conducted using one-way ANOVA followed by Tukey’s post hoc test (α = 0.05). The results demonstrated that all nanoparticle-reinforced groups exhibited significantly enhanced mechanical properties compared with the unmodified control resin. The incorporation of 1 wt.% nanofillers yielded the most pronounced improvements, with the 1 wt.% ZnO group achieving the highest transverse strength and the 1 wt.% ZnO–Sm₂O₃ hybrid group exhibiting the maximum flexural strength. Increasing the nanofiller concentration to 2 wt.% resulted in partial reductions in impact and flexural strength, which were attributed to nanoparticle agglomeration and increased light scattering during photopolymerization. FTIR analysis revealed no evidence of chemical bonding between the resin matrix and the nanofillers, indicating that the observed enhancements were primarily governed by physical reinforcement mechanisms. Wettability analysis showed that Sm₂O₃-containing formulations significantly reduced the water contact angle, indicating increased surface hydrophilicity, whereas ZnO incorporation produced more hydrophobic surfaces. Within the limitations of this in vitro study, the findings suggest that low-concentration incorporation of ZnO and Sm₂O₃ nanoparticles represents an effective strategy to enhance the mechanical integrity and tailor the surface properties of DLP 3D-printed denture base resins. These results suggest potential clinical relevance of nanoparticle-reinforced printed denture bases, emphasizing the importance of optimized filler loading to avoid agglomeration-induced performance degradation. Full article