Search Results (3,942)

3D concrete printing (3DP) enables automated construction with reduced material waste and enhanced geometric flexibility. However, its structural performance remains sensitive to anisotropy, mix design, and printing parameters, thereby complicating quality control. Self-sensing cementitious materials provide a promising approach by enabling intrinsic strain monitoring during fabrication and service. In this study, a hybrid multi-material printing strategy was developed using a conductive cement-based mix incorporating graphite (G), milled carbon microfibers (MCMF), and chopped carbon microfibers (CCMF), alongside a plain cement-based matrix. Based on percolation analysis, an optimal composition of 2 wt.% G, 0.25 wt.% MCMF, and 0.0625 wt.% CCMF was selected. Reinforced beam specimens were fabricated with the conductive material embedded in either the tensile (bottom) or compressive (top) region, combined with two internal architectures: diagonal infill and solid-base configuration. Four configurations were defined: Pattern 1 (bottom/diagonal), Pattern 2 (bottom/solid-base), Pattern 3 (top/diagonal), and Pattern 4 (top/solid-base). Cyclic three-point bending tests with spatially distributed electrical measurements were conducted to evaluate the electromechanical response in the elastic range. Specimens with the conductive layer located in the tensile region (Patterns 1 and 2) consistently exhibited higher gauge factors than those in the compressive region (Patterns 3 and 4). Pattern 2 exhibited the best sensing performance, with an average gauge factor of 556 and SNR of 31. Across all configurations, SNR decreased with increasing electrode spacing, with reductions of up to 31.0%, demonstrating the effect of current path length on sensing performance. Full article

Interface shear transfer (IST) is a critical mechanism governing composite action in reinforced concrete (RC) structures. While the IST behavior in steel-RC is well established, its application to glass fiber-reinforced polymer (GFRP)-RC remains uncertain due to the scatter of experimental data and the absence of a unified design model. This study assesses the accuracy of current IST design provisions and analytical models for GFRP-RC using a database of 107 push-off tests from the literature, including 56 specimens with an as-cast interface, 20 specimens with an intentionally roughened interface, 26 specimens with a monolithic interface, and five specimens with a smooth interface. Predictions of available models were compared with experimental peak loads. The results show that current provisions in design codes and standards either significantly underestimate or overestimate the IST capacity. The proposed analytical strain-based models in the literature improved predictions but exhibited inconsistencies across different interface conditions. Accordingly, a modified IST model is proposed based on regression analysis, incorporating a cohesion parameter as a function of the concrete strength with a GFRP strain limit of 0.003. The proposed model provides accurate, yet conservative, predictions across different interface conditions. Full article

High-performance fiber-reinforced cementitious composite (HPFRCC) has shown considerable potential as a strengthening material for improving the crack resistance, integrity, and deformation capacity of masonry structures. In aging concrete hollow block masonry walls subjected to long-term eccentric compression, material degradation may lead to premature cracking, local crushing, stiffness deterioration, and reduced safety margins, thereby adversely affecting structural reliability and service performance. However, studies on the eccentric compression behavior of HPFRCC-strengthened concrete hollow block masonry walls with simulated material degradation remain limited. In this study, experimental, finite element, and theoretical analyses were conducted on three HPFRCC-strengthened specimens with an eccentricity ratio of 0.5y, namely a 30 mm double-sided strengthened specimen, a 45 mm double-sided strengthened specimen, and a 30 mm single-sided strengthened specimen. The failure modes, load–displacement responses, lateral deformation, strain development, and DIC strain distribution characteristics were investigated. The results showed that, under the test conditions considered in this study, the double-sided strengthened specimens exhibited higher load-bearing capacity, greater stiffness, and better structural integrity than the single-sided strengthened specimen. Among them, the 45 mm double-sided strengthened specimen reached the highest peak load of 1643 kN, whereas the 30 mm double-sided strengthened specimen exhibited a gentler post-peak response, more dispersed crack development, and better deformation compatibility. The finite element results were generally consistent with the experimental results; the ratios of the experimental to numerical peak loads ranged from 0.96 to 1.01, while the corresponding peak displacement ratios ranged from 1.02 to 1.09. Within the parameter range considered in the numerical analysis, increasing the strengthening thickness was generally beneficial to the eccentric compression capacity. The proposed preliminary sectional bearing capacity model showed acceptable agreement with the test results for the specimens considered in this study; however, its broader applicability requires further validation using additional specimens. Full article

Limited research exists on the behavior of square CFDST slender columns, especially under the consideration of the relation global buckling and confinement effect. This study evaluates square concrete-filled double-skin steel tubular (CFDST) columns using nonlinear finite element analysis (FEA) to simulate structural behavior under axial and eccentric loads until failure. Parametric analyses of extensive specimens of square CFDST pin-ended columns evaluate various parameters, providing design insights for engineering applications. The study was conducted over a wide range of slenderness ratios. Four concrete varieties with compressive strengths were tested: normal concrete (NC), engineered cementitious composites (ECCs), high-strength concrete (HSC), and ultra-high-strength concrete (UHSC). Parametric variables included inner to outer steel tube thickness ratios, hollow ratios with a wide range, inner tube steel grades, and load eccentricities. An increasing slenderness ratio reduced the axial capacity, causing failure to change from yielding to buckling. By increasing the inner thickness, the capacity increased for intermediate columns compared to very long (i.e., slender) columns. The ideal hollow ratio is () for short columns compared to () for slender columns. UHSC improved short columns. Concrete’s performance was impacted by eccentric loading, which decreased the capacity, particularly in long columns. Designers should take into consideration the diminished efficacy of material strength enhancements under eccentric loading and prioritize stability in long, slender columns. The design formula was modified to enhance the strength estimates of square CFDST columns. Full article

This study proposes and investigates a modular assembled steel–ultra-high-performance concrete (UHPC) composite cable support bridge consisting of upper prefabricated UHPC ducts and a steel truss underneath. Finite element (FE) analysis is conducted to investigate the mechanical performance of the medium-span (L = 36 m) cable support bridge under service-loading conditions. The FE results indicate that under combined action of vertical and horizontal loads, the tensile damage in the UHPC ducts reaches approximately 10%, mainly concentrated near the end-support sections. The peak stress in the steel truss is far below its yield strength. The peak vertical displacement of the bridge is approximately L/225, below the allowable limit of L/150, and the peak horizontal displacement is negligible. A parametric analysis is performed for web sections in the midspan and end of the cable support bridge. Results show that the peak stress located at the lower chord increases with larger midspan web section. The increase in the midspan web section triggered a stress redistribution in the end webs and, consequently, a rise in the peak stress under the same load case; the peak vertical displacement decreases while the horizontal displacement exhibits marginal change. Appropriately scaling down the end diagonal web sections optimizes the material distribution, achieving a reduction in self-weight with negligible impact on the overall structural performance. Full article

The composition and interface quality of jointed concrete can significantly influence chloride ion penetration, especially in coastal environments. This study investigates the transport behavior of chloride ions in concrete flexural members with varying joint configurations—no joint, smooth wet joint, and roughened wet joint—under different bending loads. After 28 days of curing, specimens were subjected to bending loads and immersed in an 8% NaCl solution for 300 days. Chloride ion concentrations were then measured at different depths and locations. Results revealed that joints, particularly smooth wet joints, significantly accelerate chloride ion transmission, and that chloride accumulation at the joint is consistently higher than in adjacent areas or jointless concrete. The apparent diffusion coefficient of chloride ions was notably higher at joint interfaces and increased with bending load level due to microcrack formation. Notably, the incorporation of Cementitious Capillary Crystalline Waterproofing (CCCW) in the concrete mix improved resistance to chloride ion penetration. A dosage of 1% CCCW proved most effective, reducing the diffusion coefficient at the joint by approximately 10%—demonstrating an optimal balance between performance and material efficiency. These findings provide practical guidance for improving the durability of jointed concrete structures in chloride-rich environments. Full article

Rapid urbanization has increased the demand for building materials, depleting natural resources used in cement production and prompting the use of alternative and waste materials. This research verifies that eggshell powder waste can fully replace limestone in clinker synthesis. Five clinkers were produced using eggshell powder, aluminum sources (bentonite, zeolite, fly ash, and kaolinitic–illitic clay), Fe-slag, and quartz sand, with mechanical preprocessing (10–30 min) before sintering at 1300 °C. Experimental tests assessed the effects of mix design and mechanical activation on clinkerization, phase formation, temperature, and mechanical properties. XRD, FTIR, and SEM/EDS confirmed consistent phase compositions and primary cement minerals. Aluminum source raw materials contributed significantly to tricalcium aluminate and tetracalcium aluminoferrite formation. Eggshell and fly ash promoted tricalcium silicate and dicalcium silicate synthesis, enhancing cement strength at early and late ages. Longer mechanical pretreatments hindered clinkerization. Eggshell-based cements untreated or pretreated for 10 min are suitable for structural concrete; 20–30 min pretreatment is appropriate for low-demand or non-structural applications. The proposed methodology reduces clinker manufacturing temperature by about 100 °C from the typical range of 1400–1450 °C while maintaining mechanical properties comparable to ordinary Portland cement. Full article

Fish-derived products are extensively acknowledged for their substantial role in fostering balanced diets and supporting a healthy way of life. This research is aimed at formulating, analyzing and evaluating a fish-based food product. The methodology adopted in this study adheres to contemporary food safety standards, prioritizing the utilization of minimal technological processes and natural ingredients, a focus that is gaining prominence within contemporary industrial practices. Thus, the proposal for a formulation obtained by integrating powders and extracts from plant byproducts (Citrus) represents a concrete application direction with real potential for commercialization. The product has been enriched with biocomponents derived from orange peel, namely orange extract (OE) and orange peel powder (PPO). The research focused on product development and the in situ evaluation of the effects of OE and PPO. The physicochemical composition, bioactive compound content, and antioxidant activity were evaluated, along with the microbiological status under post-opening refrigeration conditions, in order to simulate actual consumer use. In addition, the product’s color parameters and sensory attributes were analyzed. The results highlight significant potential for the development of a clean-label fish-based product, characterized by a simplified and easily implementable formulation, aligned with current production and consumption requirements. Compared to the control sample, both OE and PPO significantly influenced the analyzed parameters. Differences in physicochemical composition were observed in the experimental samples. In addition, PPO increased the antioxidant activity of the samples and the profile of bioactive compounds. Microbiological analysis, performed on day 0 and after 3 and 7 days of storage at 4 °C showed opening, confirmed the absence of Escherichia coli and Staphylococcus aureus in all samples and had an influence on the growth of fungi. The acceptability of fish-based products is often limited by odor perception, which is one of the main factors leading to consumer rejection. Sensory evaluation demonstrated that citrus-enriched samples were distinguished by the perception of particular sensory attributes. This formulation presents a practical solution to address this constraint, thereby enhancing the product’s sensory acceptability. The integration of OE and PPO yielded a more harmonized sensory profile, as evidenced by elevated hedonic scores and an intermediate placement in both principal component analysis (PCA) and external preference mapping. This research furnishes a thorough characterization of a fish-based food product, underscoring its potential as a viable option for balanced dietary regimens. Simultaneously, the findings support the product’s adherence to sustainability principles through the utilization of bioactive compounds sourced from plant byproducts, thus satisfying contemporary requirements for foods that possess an optimal nutritional profile and a diminished environmental footprint. Full article

Chinese Traditional Concrete (CTC), known as “San-he-tu,” has ensured the long-term durability of ancient coastal structures, yet its underlying material design logic remains insufficiently understood. This study investigates the Chongwu Ancient City Wall (Quanzhou, China), a Ming Dynasty granite fortification exposed to over 600 years of marine weathering, to elucidate the structure–property–function relationships of CTC across three functional layers: the horse-track surface, wall core backfill, and masonry bonding layer. A multi-technique analytical framework (XRF, XRD, TG, and SEM) was employed to characterize chemical composition, mineral phases, thermal behavior, and microstructure. Results reveal a deliberate “functional adaptability” material design. The surface layer adopts a rigid protective formulation with high quartz (76.9%) and CaO (17.06%), forming a dense, low-porosity matrix resistant to abrasion and weathering. The wall core exhibits a flexible filling strategy with high porosity (35.44%), enabling moisture dissipation and deformation accommodation. The bonding layer, enriched in kaolinite (~29.8%) and reactive Al–Fe components, promotes pozzolanic reactions that generate hydraulic gels, ensuring durable interfacial adhesion under humid coastal conditions. These findings demonstrate that ancient builders engineered zone-specific material compositions to meet distinct structural and environmental demands, forming a functionally graded system analogous to modern material design concepts. This study provides a scientific basis for adopting partitioned, differentiated restoration strategies in coastal heritage conservation. Full article

Concrete and cementitious composites exhibit brittle failure under shear stress, limiting their resilience in seismic and high-load applications; this study investigates whether crimped NiTi shape memory alloy (SMA) fibers can enhance pure shear strength and ductility of mortar specimens, with particular focus on the effect of thermal activation. Z-shaped mortar specimens were prepared with SMA fiber volume fractions of 0%, 1.0%, and 1.25%, tested under both non-heated and heated conditions using a Universal Testing Machine, with deformation monitored via LVDTs and Digital Image Correlation. SMA fiber reinforcement increased peak shear strength by 13% and 14.5% for 1.0% and 1.25% fiber volumes, respectively, under ambient conditions, reaching up to 22% enhancement after thermal activation due to recovery-stress-induced prestressing; the 1.0% fiber volume achieved the highest ductility index of 4.05 compared to 1.03 for plain mortar, while SMA fibers had negligible influence on initial shear modulus but substantially improved post-cracking response and crack bridging. These findings demonstrate that crimped SMA fibers effectively improve shear resilience of cementitious composites, with 1.0% fiber content offering the optimal balance between strength and ductility, though activation protocols require careful calibration to minimize thermal degradation of the matrix. Full article

When conventional FRP composites are applied to confine rectangular concrete columns, strength enhancement is often limited due to the highly non-uniform lateral expansion of sections with a large aspect ratio (e.g., 2.0). High ductile FRP (HDFRP), a composite of glass fibers and polypropylene (PP) fibers, improves column strength while alleviating corner stress concentration in square sections, demonstrating its promising application potential for strengthening members with rectangular cross-sections. Yet existing studies on HDFRP have primarily focused on circular and square sections. To explore its applicability to rectangular cross-sections, this study conducted axial compression tests on HDFRP-confined rectangular short concrete columns (HDFRP-CRCC), investigating the effects of aspect ratio, corner radius, and FRP thickness on their mechanical behavior. The test results demonstrate that the HDFRP composite material can significantly enhance the overall strength and axial deformability of rectangular concrete columns, thereby effectively overcoming the limited strength enhancement associated with conventional FRP systems. Based on the experimental results, a design-oriented model is developed to offer theoretical support for the application of HDFRP in strengthening rectangular frame structures. Full article

Cross-Laminated Timber (CLT) has gained increasing attention as sustainable and efficient material for slab systems in construction. However, the lack of standardized design guidelines and comprehensive performance comparisons between different CLT-based slab solutions limits its widespread application, particularly in emerging markets with limited local expertise. This study aims to fill this gap by evaluating the structural performance and applicability of four CLT slab systems: (i) CLT slabs, (ii) CLT–concrete composite slabs, (iii) CLT–glued-laminated timber (GLT) beam ribbed slabs, and (iv) CLT–steel beam composite slabs. A comprehensive design methodology based on the Gamma method and Eurocode 5 is developed, critically applied, and its limitations discussed for each system, considering both ultimate and serviceability limit states, with special attention to vibration criteria and shear connection efficiency. The systems are compared in terms of maximum span, self-weight, thickness, and dynamic response under residential and office load categories. Results show that ribbed slab systems with timber or steel beams achieve the longest spans (up to 14 m for residential use), with lower self-weight, while CLT and CLT–concrete slabs exhibit maximum spans of 9 m with reduced thickness. Serviceability limit states, particularly vibration, were identified as the governing design constraints in most cases. This study provides a systematic comparison of CLT slab solutions, contributes to the development of reliable design tools, and identifies priorities for experimental validation, supporting the broader adoption of CLT in regions with growing timber construction sectors, such as Portugal. Full article

This paper innovatively employs an epoxy-free composite layer with basalt fiber-reinforced polymer (BFRP) and engineered cementitious composite (ECC) to reinforce the two-way concrete slab structure. Five strengthened slabs and one reference slab were tested under biaxial bending moments with four-side simply supported conditions. The thickness of ECC (15, 25, 35 mm) and BFRP grid (1, 2, 3 mm) were selected as two main variables in the test program. The experimental results showed that the cracking and ultimate load of the strengthened slabs were substantially improved. Notably, the cracking pattern was shifted from diagonally concentrated cracks to discontinuous short cracks, with no apparent debonding of the composite layer. As the thickness of the BFRP grid and ECC increases, both the flexural capacity and stiffness improve, with decrease in the maximum deflection and effective utilization rate of steel reinforcement and BFRP grid at mid-span. Furthermore, a theoretical model considering different positional distribution of yield line was proposed to predict the bearing capacity of the strengthened slabs, with the calculated values aligned well with the experimental results. This research highlights the FRP–ECC composite as a robust reinforcement method for two-way slabs, and offers a good design-oriented reference basis in the field. Full article

This study examines a cold-press manufacturing method for laminated bamboo and bamboo–timber composites, together with a cradle-to-gate carbon footprint analysis of the produced materials. The proposed material systems are assessed as alternatives to conventional engineered bamboo and to widely used construction materials such as structural steel, concrete, and aluminum. Existing engineered bamboo products are typically manufactured using hot pressing and formaldehyde-based adhesives, both of which contribute to their environmental burden. The present work therefore considers a more practical and environmentally responsible route based on lower-energy processing and lower-emission adhesive systems. Following a cradle-to-gate carbon footprint analysis of the produced materials, the embodied carbon values obtained for the four systems are 473.3, 322.3, 314.2, and 210.3 kg CO₂e/m³ for the BBE, BPA, CBE, and CPA specimens, respectively. Relative to conventional hot-pressed laminated bamboo, these values correspond to embodied carbon reductions of 26.8%, 50.1%, 51.4%, and 67.5%, respectively. When the biogenic carbon stored in the bamboo and pine biomass is included, the net carbon balances become −415.5, −607.1, −597.0, and −618.6 kg CO₂e/m³, respectively. These results show that the proposed engineered bamboo and bamboo–timber composites offer feasible low-carbon options for construction applications. Full article

To investigate the influence of basalt fiber (BF) on the mechanical properties and crack evolution of coal gangue–slag geopolymer concrete, geopolymer concrete specimens were prepared using coal gangue powder calcined at 700 °C and slag as precursors, with BF contents ranging from 0 to 1.25%. Mechanical testing combined with digital image correlation (DIC), scanning electron microscopy (SEM), and X-ray diffraction (XRD) was conducted to evaluate the effects of BF on macroscopic mechanical behavior, crack evolution, and underlying microstructural mechanisms. The results demonstrate that BF effectively enhances both the mechanical performance and crack-control capacity of coal gangue–slag geopolymer concrete, exhibiting a clear content-dependent trend. Compressive strength initially increases and subsequently decreases with increasing BF content. The 28-day compressive strength reaches a maximum value of 84.05 MPa at a BF content of 0.5%, representing an 11.92% improvement compared with the control group. Splitting tensile strength and flexural strength attain their peak values at a BF content of 1%, increasing by 37.88% and 25.81%, respectively. DIC analysis indicates that BF delays strain localization and effectively restrains the propagation of dominant cracks. Specifically, the compressive strain field becomes more uniformly distributed at 0.5% BF content, while crack propagation during splitting failure is more stable at 1% BF content. SEM observations reveal that the primary strengthening mechanisms include crack bridging, interfacial load transfer, and energy dissipation associated with fiber pull-out. XRD analysis shows that BF incorporation does not significantly alter the phase composition of the coal gangue–slag geopolymer system; thus, performance enhancement mainly arises from fiber bridging and interfacial reinforcement rather than changes in primary reaction products. Full article