The growing use of handheld Class 4 laser welding systems raises concerns about operator exposure to reflected and scattered radiation. The purpose of this study is to provide an assessment of the angular distribution and intensity of reflected laser radiation generated during manual welding of structural steel and aluminum alloy in butt and fillet joint configurations. It provides the first angle-resolved and height-resolved experimental characterization of reflected radiation in handheld welding, integrating material reflectivity, joint geometry, and observer position-parameters rarely examined together. Radiation intensity was measured at multiple angles, distances, and heights-including helmet-visor level-under controlled laboratory conditions, using identical welding parameters for both materials. Aluminum, with near-infrared reflectance of X75-78% compared with X14% for steel, produced broader and more persistent reflection fields. For butt joints, mean maximum intensities were comparable (X1912 ru for steel and X2049 ru for aluminum), but probe orientation and joint type strongly modulated exposure: lateral probe positions yielded X2.2-fold higher peak intensities than the forward direction for aluminum and more than fourfold higher for steel, while fillet joints increased the mean maximum intensity for steel by X109% relative to butt joints (3997 vs 1912 ru). The most hazardous conditions occurred within 10-15 cm of the weld and at probe angles between 30 degrees and 70 degrees, where both materials generated peak intensities above 1.5 & times; 104 ru, including at eye level (156 cm), highlighting a substantial risk of ocular overexposure during handheld laser welding. Helmet-level measurements confirmed attenuation of direct radiation. These findings show that effective protection requires PPE with high-optical-density filters, lateral shielding, and an optimized workstation layout, especially when welding reflective materials or working with fillet geometries. Material reflectivity and joint type strongly influence hazard-zone formation, with aluminum and fillet joints presenting the highest risks. Task-specific protective strategies are therefore essential to ensure compliance with exposure limits and maintain operator safety.

This study evaluates the mechanical performance, anisotropy, and spatial variability of 3D-printed cementitious and alkali-activated composites under laboratory, atmospheric, and freeze-thaw conditions. Alkali-activated composites exhibited substantially higher shrinkage than cement-based mixtures, reflecting differences in their reaction mechanisms and pore structure development. Compressive strength was measured in two orthogonal directions representing perpendicular (⟂) and parallel (∥) behaviour. Non-activated mixtures exhibited compressive strength of 11-12 MPa, whereas alkali-activated composites reached 19-20 MPa in the reference condition. Atmospheric exposure increased compressive strength by 10-22%, while freeze-thaw cycles did not significantly affect perpendicular strength. Flexural strength of non-activated mixtures remained low (3.7-5.3 MPa), whereas activated composites showed higher values in the reference state (8.8-15.0 MPa) but decreased after atmospheric exposure to 5.3-5.8 MPa. The degree of anisotropy increased significantly for alkali-activated mixtures (from 0.09 to 0.24) while remaining relatively stable for non-activated materials (0.04-0.11). Glass fibres showed no significant degradation after environmental and freeze-thaw exposure, while merino wool fibres exhibited only minor surface irregularities, confirming the potential of both fibre types for use in sustainable lightweight 3D-printed cementitious and alkali-activated composites.

In this study, the effects of Cu matrix morphology and Cu-coated SiC reinforcement ratio on the microstructure, mechanical, and electrical properties of Cu-SiC composites were investigated. Dendritic and flake morphologies were used as Cu matrix morphologies, while Cu-coated SiC particle ratios were selected as 5, 10, and 20% by volume. FESEM/EDS and XRD analyses confirmed that the surface of the SiC particles was homogeneously coated with Cu. This strategy was taken to enhance the matrix-reinforcement interface and achieve a more compact composite. Results show that matrix morphology is an important factor in the performance of the composites. Composites of flake Cu matrix have demonstrated increased relative density (90.96 vs. 87.82%), hardness (~ 135 vs. ~110 HB), tensile strength (~ 252 vs. 177 MPa), and electrical conductivity (88% IACS vs. 75% IACS) compared to composites of dendritic Cu matrix. The flake Cu matrix composite containing 10 vol% Cu-coated SiC reinforcement showed the most stable performance in terms of mechanical and electrical properties. In this context, this composite was shown to be a scalable and high-performance material candidate for the field of electrical materials.

This study investigated the mechanical properties and durability of novel multi-component cementless binders formulated entirely from industrial by-products, including co-fired fly ash (CFA), slag, reactive ultra-fine fly ash (RUFA), and fly ash (FA). The performance of these water-activated systems was compared with that of traditional alkali-activated materials (AAMs) through compressive strength monitoring, chloride migration tests, and microstructural analyses using MIP, XRD, and SEM. The results revealed that the water-activated binders demonstrated superior reliability, achieving compressive strengths of up to 22.2 MPa and exceptional resistance to chloride ingress, with chloride diffusion coefficients ranging from 1.91 x 10-12 m2/s to 2.82 x 10-12 m2/s. In contrast, the alkali-activated systems exhibited significant instability; specifically, high-slag AAMs suffered from severe strength loss (5.9 MPa) attributed to matrix brittleness and extensive microcracking. Microstructural analysis confirmed that the water-activated system employed a self-activation mechanism to form a dense C-A-S-H gel. In contrast, the incorporation of RUFA facilitated the growth of a unique, interlocked crystalline network dominated by Latiumite and Kottenheimite, which effectively severed pore connectivity. This research innovatively demonstrated that leveraging the self-activation potential of sulfate-rich CFA with ultra-fine particle modification could yield a sustainable, cementless binder with durability characteristics surpassing those of conventional alkali-activated systems.

This study investigates the sustainable production of high-purity copper powders obtained from recycled scrap copper sheets through the electrolysis method. With increasing environmental concerns and the growing need for resource efficiency, recycling-based copper powder production has emerged as an attractive and sustainable alternative to conventional production methods. The study aims to optimize electrolysis parameters affecting powder morphology and properties in order to enhance the industrial applicability of the material. The Taguchi method was applied to optimize current density, solution concentration, and electrode distance, focusing on their effects on average particle size and apparent density. An orthogonal array design and ANOVA analyses were employed to identify optimal processing conditions. Material characterization was performed using scanning electron microscopy (SEM), laser particle size analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized dendritic copper powders were grouped by average size (21.61 mu m, 52.24 mu m, and 87.97 mu m) and subsequently densified by hot-pressing to evaluate their physical, mechanical, electrical, and thermal properties. Samples with an average size of 52.24 mu m exhibited the best overall performance, achieving 98.5 % IACS electrical conductivity, 386 W/m & sdot;K thermal conductivity, 94 HB hardness, and 137 MPa tensile strength. The results demonstrate that recycled electrolytic copper powders can achieve high performance levels while simultaneously supporting sustainable production practices and improved industrial efficiency.

This study developed and verified a novel, alkali-free cementless material for 3D printing, formulated entirely from industrial by-products: circulating fluidized bed co-fired fly ash (CFA), blast furnace slag, fly ash, and reactive ultra-fine fly ash (RUFA). The research aimed to eliminate cement and hazardous liquid alkali activators by using the self-activated properties of CFA to activate the slag. The experimental program evaluated rheological properties for printability, compared the compressive strength of cast and 3D-printed specimens to assess anisotropy, and analyzed thermal conductivity and interlayer bonding using optical microscopy. Results showed the optimized cementless mixtures achieved stable fluidity and good extrudability, though with longer setting times than traditional alkali-activated materials (AAMs). While AAMs had superior compressive strength (over 60 MPa), their rapid hardening created weak interlayer bonding. Conversely, the cementless composites maintained continuous fusion and achieved lower thermal conductivity (minimum, 0.233 W/m K) due to an interstitial pore structure from RUFA. The study concluded that while AAMs were better suited for high-strength applications, the developed alkali-free composite offered a sustainable and energy-efficient solution for non-structural elements, striking a balance between buildability and thermal insulation. Its innovation lay in creating a self-activating, all-waste binder system that avoided corrosive chemicals while enabling tunable thermal properties in additive manufacturing.

Due to inherent characteristics of high reactivity and saturated vapor pressure, magnesium alloys put forward strict requirements to laser energy input of laser powder bed fusion (LPBF), significantly narrowing the processing windows for obtaining high processability and performance. In this work, WE43 magnesium alloys were fabricated at various laser energy densities of LPBF to investigate their influence on the forming quality, microstructure, and mechanical properties of the as-fabricated magnesium alloys. The results indicate that the laser energy density apparently affects the melting and evaporation of alloy powder, and wetting and the motion of melt under high energy laser irradiation. The surface roughness and area fraction of porosity of the laser-fabricated WE43 magnesium alloy at an optimal energy density of 185 J/mm3 reach minimal values of ∼11.2 μm and 0.1%±0.03%, respectively, indicating good laser processability. The microstructure consists of α-Mg matrix, flaky (Y, Zr)2O3 and submicron Mg3(Nd, Gd) precipitates, and an average grain size of ∼4.8 μm is obtained. As the laser energy density increases from 121 to 214 J/mm3, the hardness and elastic modulus of the laser-fabricated specimens continuously increase, exhibiting a trend of an initial increase followed by a subsequent decrease for the tensile ultimate strength. The WE43 magnesium alloy fabricated at 185 J/mm3 shows high comprehensive mechanical properties, with an ultimate tensile strength of ∼329 MPa and an elongation of ∼6.1%. This is ascribed to the combined effects of high forming quality and precipitation strengthening from fine Mg3(Nd, Gd) and (Y, Zr)2O3 precipitates. This work provides references for fabrication of high-quality and high-performance magnesium alloys by well modulating the laser energy input of LPBF.

Three-dimensional concrete printing (3DCP) is advancing rapidly, yet its sustainable adoption requires alignment with circular-economy principles. This study evaluates the substitution of natural aggregates with recycled constituents, 3DCP waste, brick debris, glass cullet, mixed rubble, fly ash, and slag, and the use of lightweight fillers (expanded perlite, lightweight expanded clay aggregate (LECA), and expanded polystyrene (EPS)) to reduce density and improve insulation. Key properties, such as particle-size distribution, printability, mechanical performance, thermal conductivity, and water absorption, were determined. Results indicate that grading strongly affected mixture behavior. Narrow distributions (fly ash, milled 3DCP waste) enhanced extrudability, while broader gradings (glass, rubble, slag) increased water demand and extrusion risks. Despite these differences, all systems remained within the printable window: flow spread decreased with most recycled additions (lowest for brick) and increased with glass. Mechanical responses were composition-dependent. Flexural strength typically decreased. Compressive strength benefited from broader gradings, with replacement levels up to ~6% enhancing strength due to improved packing. Loading anisotropy typical of 3DCP was observed, with perpendicular compressive strength reaching up to 13% higher values than parallel loading. Lightweight fillers significantly reduced thermal conductivity. LECA provided the best compromise between strength and insulation, perlite showed intermediate behavior, and EPS achieved the lowest thermal conductivity but induced significant strength penalties due to weak matrix-EPS interfaces. Water absorption decreased in recycled-aggregate mixes, whereas lightweight systems, particularly with perlite, retained higher uptake. The results demonstrate that non-reactive recycled aggregates and lightweight insulating fillers can be successfully integrated into extrusion-based 3DCP without compromising printability.

The study is focused on the technology for surface modification of AZ31 magnesium alloy for biomedical applications, in particular in implantology. The experimental procedure consists of intentional stages that involve chemical treatment in piranha solution, plasma chemical activation of the alloy surface using Ar and O2 as gaseous precursors, and biopolymer coatings deposition—based on polylactic acid (PLA) and poly(lactic-co-glycolic acid) (PLGA) with the addition of caffeic acid—utilizing the immersion method. In the course of the experiment, the validity of the investigated technology of surface modification of AZ31 magnesium alloy was confirmed. The pre-treatment step guaranteed obtaining a higher surface roughness, resulting in homogeneous and stable biopolymer coatings with proper adhesion to the substrate. Moreover, the corrosion studies conducted confirmed better corrosion behaviour of the modified samples in SBF corrosive medium, and no significant release of the alloy-related ions was observed. Furthermore, the biopolymer coatings ensured non-cytotoxicity towards the MG-63 cell line and promoted cell proliferation with proper morphology. Based on the obtained results, it may be concluded that the proposed technology can be treated as an interesting and promising surface-engineering strategy for implantology and biodegradable materials applications.

The advancement of modern 3D printing technologies has opened the possibilities to fabricate different spectrums of materials using these technologies. Binder jetting 3D printing is a shaping-debinding-sintering-based Additive manufacturing process that selectively fabricates the parts in a layer-by-layer fashion using the local imprinting of polymeric binder. This study aims to develop cobalt and nickel-free TiC-FeCr-based cermets that will contribute to the development of cermets towards green and cost-efficient materials. An effective approach to increase the densities of printed parts was to replace unimodal powder feedstocks with bimodal powders. Therefore, this work employed bimodal spherical powder (TiC and 430L ferritic stainless steel) to promote better densification of the cermet parts. Liquid phase vacuum sintering has been performed with different sintering temperatures to consolidate the cermet parts. Detailed analyses of the microstructure evolution, phase formation, and mechanical properties (hardness and fracture toughness) have been conducted. Further, thermodynamic simulations were conducted to calculate the phase diagram of the proposed cermet using the Thermo-Calc program. Microstructural analysis of consolidated cermets reveals a direct correlation between sintering temperature and carbide grain size, affecting their mechanical and physical properties. The best hardness and fracture toughness properties of TiC-FeCr-based cermets are 1102 +/- 13 HV30 and 12.74 +/- 1.38 MPa m1/2 respectively, were obtained after sintering at 1450 degrees C. Moreover, a systematic comparison is conducted with the same cermet composition fabricated with different additive manufacturing processes based on Laser powder bed fusion and Binder jetting 3D printing technology, demonstrating the potential and limitations of both technologies to fabricate brittle materials such as cermets.

The study investigates the potential of using Vietnam fly ash (FA) as a substitute for traditional Portland cement to reduce both the volume of landfilled waste and the carbon footprint of concrete mixtures, while maintaining adequate mechanical performance of the produced elements. Additionally, the incorporation of construction and demolition waste, recycled brick aggregate (BR), as a partial aggregate substitute was investigated to enhance the sustainability and resource efficiency of composite formulations. Five mixes, including a reference, were produced by casting and three-dimensional concrete printing (3DCP). Printability (flow table), water absorption (gravimetry and infrared thermography), and flexural/compressive behavior were assessed; printed specimens were tested parallel and perpendicular to the layer plane. Recycled additions reduced flow by 15–22%, yet all mixes remained printable. Printed specimens showed higher capillary uptake than cast ones. In flexure, modified mixtures composition exhibited 50% lower peak stress than the reference. Cast elements outperformed printed ones: the printed reference was 33% weaker than its cast counterpart, and other mixes were 10–15% lower. In compression, printed specimens loaded perpendicular to layers reached 6–7 MPa (35% below cast), whereas parallel loading yielded up to 3.5 MPa with larger scatter. The findings confirm the feasibility of utilizing secondary raw materials in 3DCP formulations to support resource efficiency and carbon footprint reduction in the construction industry.

This study investigates the influence of various reinforcing fibers, including coconut, basalt, glass, merino wool, and polypropylene, on the properties and processability of cementitious mixtures, with a particular emphasis on their application in 3D printing. The incorporation of fibers at a concentration of 1 wt.% was found to significantly hinder the printing process. Specifically, certain fibers, such as polypropylene, rendered extrusion impractical due to nozzle clogging. However, reducing the fiber content to 0.5 wt.% improved material flowability and minimized structural defects during printing. Fiber selection, in addition to its impact on mechanical properties, plays a crucial role in determining overall process efficiency. Mixtures incorporating coal slag as a dense filler, combined with stiff fibers such as basalt or glass, exhibited the highest flexural strength. Moreover, the inclusion of merino wool fibers enhanced the flexural performance of fly ash-based mixtures, achieving strength levels comparable to or exceeding those of stiffer fibers. These findings contribute to the advancement of sustainable construction practices. Notably, samples produced via 3D printing consistently demonstrated higher flexural strength than those fabricated using traditional molding techniques. This enhancement is attributed to microstructural modifications induced by the layer-by-layer deposition process. Depending on the sample composition and the type of reinforcing fiber, water absorption behavior varied significantly. Merino wool and coconut fibers exhibited the highest water absorption due to their hydrophilic nature and capillary action, particularly in 3D-printed samples with open-pore structures. In contrast, glass and basalt fibers, characterized by their higher density and hydrophobicity, exhibited lower water absorption levels. These results underscore the importance of optimizing fiber type, concentration, and processing methodologies to achieve tailored performance in fiber-reinforced cementitious mixtures. Such optimizations align with the principles of sustainable development and hold significant potential for advancing 3D-printed construction applications

In the face of accelerating urbanization and the growing demand for environmentally responsible materials and designs, this study presents the development and implementation of a modular parklet demonstrator fabricated using dual-material 3D printing. The structure integrates polylactic acid (PLA) and wood-filled PLA (wood/PLA), combining the mechanical robustness of pure PLA in the core with the tactile and aesthetic appeal of wood-based biocomposite on the surface. The newly developed dual-nozzle 3D printing approach enabled precise spatial control over material distribution, optimizing both structural integrity and sustainability. A comprehensive evaluation was conducted for developed filaments and printed materials, including optical microscopy, coupled thermogravimetry analysis and Fourier Transform Infrared Spectroscopy (TG/FTIR), differential scanning calorimetry (DSC), and chemical and mechanical resistance testing. Results revealed distinct thermal behaviors and degradation pathways between filaments and printed parts composed of PLA and PLA/wood. The biocomposite exhibited slightly increased sensitivity to aggressive chemical environments and mechanical wear, dual-material prints maintained high thermal stability and interlayer adhesion. The 3D-printed demonstrator bench and stools were successfully deployed in public spaces as a functional urban intervention. This work demonstrates the feasibility and advantages of using biocomposite materials and dual-head 3D printing for the rapid, local, and sustainable fabrication of small-scale urban infrastructure.

Rapid population growth and accelerating urbanization are intensifying the demand for construction materials, particularly concrete, which is predominantly produced with Portland cement and natural aggregates. This reliance imposes substantial environmental burdens through resource depletion and greenhouse gas emissions. Within the framework of sustainable construction, recycled aggregates and industrial by-products such as fly ash, slags, crushed glass, and other secondary raw materials have emerged as viable substitutes in concrete production. At the same time, three-dimensional concrete printing (3DCP) offers opportunities to optimize material use and minimize waste, yet it requires tailored mix designs with controlled rheological and mechanical performance. This review synthesizes current knowledge on the use of recycled construction and demolition waste, industrial by-products, and geopolymers in concrete mixtures for 3D printing applications. Particular attention is given to pozzolanic activity, particle size effects, mechanical strength, rheology, thermal conductivity, and fire resistance of recycled-based composites. The environmental assessment is considered through life-cycle analysis (LCA), emphasizing carbon footprint reduction strategies enabled by recycled constituents and low-clinker formulations. The analysis demonstrates that recycled-based 3D printable concretes can maintain or enhance structural performance while mix-level (cradle-to-gate, A1–A3) LCAs of printable mixes report CO2 reductions typically in the range of ~20–50% depending on clinker substitution and recycled constituents—with up to ~48% for fine recycled aggregates when accompanied by cement reduction and up to ~62% for mixes with recycled concrete powder, subject to preserved printability. This work highlights both opportunities and challenges, outlining pathways for advancing durable, energy-efficient, and environmentally responsible 3D-printed construction materials.

This study examines the pore structure and distribution in 3D printed and cast foamed concrete using protein-based and synthetic foaming agents alongside various stabilizing additives. In 3D printed samples, pores are irregular and flattened due to mechanical forces during printing, whereas cast samples display uniform, spherical pores from homogeneous foam distribution. Samples containing the CA stabilizer show higher apparent densities (up to 2.05 g/cm3 for printed samples), correlating with lower water absorption. Protein-based foaming agents (PS) produce smaller, more evenly distributed pores, while synthetic agents (AS) result in larger, less uniform pores. Stabilizers significantly influence pore characteristics: commercial stabilizers yield smaller, more uniform pores, while recycled industrial oil (UO) leads to larger, more variable pores. Protein-based agents improve structural stability and reduce water absorption through uniform pore distributions, while synthetic agents lower density and increase water absorption. The highest sorption values were observed in samples with AS without stabilizer (1.7 kg/m2h1/2) and AS and UO (1.6 kg/m2h1/2) in a vertical orientation, with the horizontal orientation of sample AS and UO achieving a peak value of 2.0 kg/m2h1/2. Moreover, stabilization using UO resulted in higher sorption coefficients than stabilization with CA. High porosity in M1 resulted in low strength (0.2 MPa bending, 0.1 MPa perpendicular compression), while M5 showed superior performance (11.5 MPa perpendicular compression). PS-foamed samples (M4, M6) with uniform pores had the highest strengths, with M6 achieving 3.8 MPa bending and 10.3 MPa perpendicular compression. Perpendicular compression (M5: 11.5 MPa) was up to three times stronger than parallel compression due to weak interlayer bonds in 3D printing.

Fiber-reinforced foamed composites have recently attracted growing interest due to their potential in sustainable construction and advanced additive manufacturing. However, their performance strongly depends on the type of matrix and fiber system used. The aim of this study was to perform a comparative analysis of matrix type and fiber composition on the porosity, thermal behavior, and mechanical performance of 3D-printed fiber-reinforced foamed composites. To this end, cementitious mixtures (M1-M3) were compared with alkali-activated hybrid binder systems (M4-M6). The results revealed marked differences in mechanical strength, dimensional stability, moisture transport, and interlayer cohesion. Alkali-activated specimens, particularly M5 and M6, exhibited superior compressive, flexural, and shear strength; reduced water penetration; and improved fiber-matrix bonding, associated with a denser and more homogeneous pore structure. In contrast, cementitious composites showed greater dimensional stability and easier process control, indicating practical advantages for large-scale on-site applications. The results highlight that while alkali activation and hybrid fiber reinforcement enhance structural performance, non-activated foamed concretes remain promising for applications prioritizing simplicity, reproducibility, and thermal insulation.

This study was conducted to comprehensively investigate the effect of mechanical milling parameters on the properties of electrolytic pure copper powders and hot pressed billets fabricated from recycled copper wastes. Three different milling speeds, five different milling times and three different ball to powder weight ratios were used to fully reveal the effect of the mechanical milling process on the properties of recovered Cu powders. The results show that as the milling time and milling speed increased, the initial dendritic morphology of the copper was transformed into a flake-like structure. At 400 rpm and a 5:1 BPR parameters, the average particle sizes of C3, C4, and C5 after 2, 4, and 8h were similar to 52 mu m, 83 mu m, and 71 mu m, respectively. This suggests that particle size initially increases due to shape change and cold-welding, but at longer durations, fracture becomes dominant. The I5 with d(0.5) = 69.32 mu m exhibited a high flow rate of 5.88 g/s with an apparent density of 2.9 g/cm(3).While the hardness value of the Cu samples (A1-bulk sample) produced by exposure to the lowest deformation during the mechanical milling is 95.02 HB, the hardness value of the Cu specimens (F5-bulk sample) showing the highest apparent density, best flow rate and highest density values is 109.31 HB. The electrical conductivity values were determined to be approximately 52.2 MS/m, 57.4 MS/m and 44.3 MS/m for A1-bulk, F5-bulk and H5-bulk, respectively. This study offers valuable insights into the relationship between milling parameters, powder characteristics, and final material properties.

The study used electric arc furnace oxidizing slag (EAFOS) to substitute natural fine aggregates. However, EAFOS replacement may cause volumetric instability. Therefore, a cement, fly ash, or slag layer was coated with EAFOS as a precoated technique. Then, the effect of EAFOS on engineering properties was investigated, and the optimum amount of EAFOS was identified. The amount of coated binders was set at 20

Three-dimensional concrete printing (3DCP) is an emerging additive manufacturing technology with increasing application potential in the construction industry, offering advantages such as reduced labor requirements, shortened construction time, and material efficiency. However, structural integrity remains a challenge, particularly due to weak interlayer bonding resulting from the layered manufacturing process. This study investigates the mechanical performance and anisotropy of 3D-printed mineral-based composites with respect to the time interval between successive layers. Specimens were printed with varying interlayer intervals (0, 25, and 50 min) and tested in different loading directions. Flexural, compressive, and tensile strengths (direct and splitting methods) were measured both parallel and perpendicular to the layer orientation. Results showed a clear degradation in mechanical properties with increasing interlayer time, particularly in the direction perpendicular to the layers. Flexural strength decreased by over 25% and direct tensile strength by up to 40% with a 25 min interval. Compressive strength also declined, though less dramatically. Compared to cast specimens, printed elements showed 3-4 times lower compressive strength, highlighting the significant impact of interlayer cohesion. This study confirms that both the time between layers and the loading direction strongly influence mechanical behavior, underlining the anisotropic nature of 3DCP elements and the need for process optimization to ensure structural reliability.

In response to escalating environmental concerns, the construction industry is under growing pressure to adopt sustainable practices. As a major consumer of natural resources and a significant emitter of greenhouse gases, it paradoxically holds the potential to become a leader in green transformation. This study investigates the development of innovative, fire-resistant, and alkali-activated hybrid binder foams incorporating recycled materials: fly ash, coal slag, and ground brick waste, as sustainable alternatives to traditional building materials. The fire resistance performance at a technical scale and the thermal behavior of fiber-reinforced, alkali-activated hybrid binder foams synthesized from recycled aluminosilicate precursors were determined. The properties of unreinforced composite were compared with the composites reinforced with merino wool, basalt fibers, polypropylene fibers, and coconut fiber. Small-scale fire-resistance tests revealed that merino wool-reinforced composites exhibited the best thermal insulation performance, maintaining structural integrity, that is, retaining shape and continuity without delamination or collapse for 83 min under fire exposure. Analyses combining chemical characterization (X-ray fluorescence) with microstructural methods (computed tomography and colorimetry) confirmed that fire performance is strongly influenced not only by fiber type but also by pore distribution, phase composition, and oxide migration under thermal loading. These findings demonstrate the potential of fiber-reinforced foamed, alkali-activated hybrid binder as eco-efficient, printable materials for fire-safe and thermally demanding construction applications.