Search Results (905)

This article presents the results of experimental studies to determine the possibility of processing steelmaking slags into an artificial granulated filler for concrete by the method of forced carbonization and the stabilization of the obtained filler in the concrete matrix over time. The utilization of metallurgical waste and technogenic CO₂ is a global problem. In this work, the method of the granulation of finely ground converter (BOF) and electric steelmaking (EAF) slags was used to obtain artificial granules and their subsequent forced carbonization in the developed laboratory carbonization chamber. Within the framework of this study, the quantitative binding of CO₂ by granules based on BOF and EAF slags was established, which amounted to 5.2 and 7.8% by weight, respectively. It was determined that the mass loss during crushability testing, indirectly characterizing the actual compressive strength of the granule material, depending on the type of slag and grain size, ranges from 13.6 to 42.3%, which is quite sufficient for using this artificial filler in concrete production. Based on the developed batches of fillers, concretes were obtained that have a compressive strength of 30.7 to 37.8 MPa in 28 days of hardening, which generally corresponds to concrete class B25. The preliminary studies and the results obtained indicate the prospects of processing steel slags into artificial granulated fillers by forced carbonization and using this product in concrete production. Full article

This study examines the influence of steel fiber reinforcement on the mechanical properties of geopolymer concrete incorporating different slag to fly ash binder ratios (75:25, 50:50, and 25:75). Three fiber contents (0%, 1%, and 2%) by volume were used to assess their impact on compressive strength, flexural strength, initial stiffness, and toughness. Compressive tests were conducted at 1, 7, and 28 days, while flexural behavior was evaluated through a four-point bending test at 28 days. The results showed that geopolymer concrete with 75% slag and 25% fly ash experienced the highest compressive strength and modulus of elasticity, regardless of the steel fiber content. The addition of 1% and 2% steel fiber content enhanced the compressive strength by 17.49% and 28.8%, respectively, compared to the control sample. The binder composition of geopolymer concrete plays a crucial role in determining its compressive strength. Reducing the slag content from 75% to 50% and then to 25% resulted in a 15.1% and 33% decrease in compressive strength, respectively. The load–displacement curves of the 2% fiber-reinforced beams display strain-hardening behavior. On the other hand, after the initial crack, a constant increase in load causes the specimen to experience progressive strain until it reaches its maximum load capacity. When the peak load is attained, the curve gradually drops due to a loss in load-carrying capacity known as post-peak softening. This behavior is attributed to steel’s ductility and is evident in specimens 75S25FA2 and 50S50FA2. Concrete with 75% slag and 25% fly ash demonstrated the highest peak load but the lowest ultimate displacement, indicating high strength but brittle behavior. In contrast, concrete with 75% fly ash and 25% slag showed the lowest peak load but the highest displacement. Across all binder ratios, the addition of steel fibers enhanced the flexural strength, initial stiffness, and toughness. This is attributed to the bridging action of steel fibers in concrete. Additionally, steel fiber-reinforced beams exhibited a ductile failure mode, characterized by multiple fine cracks throughout the midspan, whereas the control beams displayed a single vertical crack in the midspan, indicating a brittle failure mode. Full article

This study investigated the structural behavior of slab-on-grade (SOG) specimens constructed using two materials: conventional concrete reinforced with steel mesh and high-ductility fiber-reinforced cement composites (HDFRCC) containing 1.2% polyethylene (PE) fiber without steel reinforcement. The compressive strengths of conventional concrete and HDFRCC were 37 MPa and 54 MPa, respectively. The average flexural tensile strength of HDFRCC was 3.9 MPa at first cracking and 9.7 MPa at peak load. Punching shear tests were performed under three loading configurations: internal (center), edge, and corner loading. Crack patterns and load–displacement responses were analyzed for both material types. Under center loading, the experimentally measured load-bearing capacities were 174.52 kN for conventional concrete and 380.82 kN for HDFRCC, with both materials exhibiting reduced capacities under edge and corner loading. Analytical predictions demonstrated close agreement with the experimental results for conventional concrete but significantly underestimated the load capacity of HDFRCC SOG. This discrepancy is attributed to the strain-hardening and crack-bridging mechanisms inherent in HDFRCC, which contribute to enhanced strength beyond conventional analytical predictions. In terms of failure mode, the conventional concrete SOG exhibited the expected flexural failure. In contrast, the HDFRCC SOG experienced either flexural failure or a combination of flexural and punching failure, in contradiction to the analytical prediction of exclusive punching shear failure. These findings indicate that the punching shear resistance of the HDFRCC SOG is substantially higher than predicted. Full article

This study evaluates glass and carbon fibre-reinforced concrete in terms of performance, durability, environmental impact, and a novel enzymatic self-healing method. An experimental program was conducted on seven concrete mixes, including a plain control and mixes with varying dosages of glass and carbon fibres. Glass and carbon fibres were incorporated at identical dosages of 0.12%, 0.22%, and 0.43% fibre volume fraction ($V_f)$ to enable direct comparison of their performance. The experimental investigation involved a comprehensive characterization of the concrete mixes. Fresh properties were evaluated via slump tests, while hardened properties were determined through compressive and split tensile strength testing. Durability was subsequently assessed by measuring the rate of water absorption, bulk density, and moisture content. Following this material characterization, a cradle-to-gate Life Cycle Assessment (LCA) was conducted to quantify the embodied carbon and energy. Finally, an evaluation of a novel Carbonic Anhydrase (CA)-based self-healing treatment on pre-cracked, optimised fibre-reinforced specimens was conducted. The findings highlight key performance trade-offs associated with fibre reinforcement. Although both fibre types reduced compressive strength, they markedly improved split tensile strength for glass fibres by up to 70% and carbon fibres by up to 35%. Durability responses diverged: glass fibres increased water absorption, while carbon fibres reduced water absorption at low doses, indicating reduced permeability. LCA showed a significant rise in environmental impact, particularly for carbon fibres, which increased embodied energy by up to 141%. The CA enzymatic solution enhanced crack closure in fibre-reinforced specimens, achieving up to 30% healing in carbon fibre composites. These findings suggest that fibre-reinforced enzymatic self-healing concrete offers potential for targeted high-durability applications but requires careful life-cycle optimisation. Full article

Single Event Transients (SETs) in clock-distribution networks are a major source of soft errors in synchronous systems. We present a practical framework that assesses SET risk early in the design cycle, before layout and parasitics, using a Vulnerability Function (VF) derived from Verilog fault injection. This framework guides targeted Engineering Change Orders (ECOs), such as clock-net remapping, re-routing, and the selective insertion of SET filters, within a reproducible open-source flow (Yosys, OpenROAD, OpenSTA). A new analytical Soft Error Rate (SER) model for clock trees is also proposed, which decomposes contributions from the root, intermediate levels, and leaves, and is calibrated by SPICE-measured propagation probabilities, area, and particle flux. When coupled with throughput, this model yields a frequency-aware system-level Bit Error Rate (${BER}_{sys}$). The methodology was validated on a First-In First-Out (FIFO) memory, demonstrating a significant vulnerability reduction of approximately 3.35× in READ mode and 2.67× in WRITE mode. Frequency sweeps show monotonic decreases in both clock-tree vulnerability and ${BER}_{sys}$ at higher clock frequencies, a trend attributed to temporal masking and throughput effects. Cross-node SPICE characterization between 65 nm and 28 nm reveals a technology-dependent effect: for the same injected charge, the 28 nm process produces a shorter root-level pulse, which lowers the propagation probability relative to 65 nm and shifts the optimal clock-tree partition. These findings underscore the framework’s key innovations: a technology-independent, early-stage VF for ranking critical clock nets; a clock-tree SER model calibrated by measured propagation probabilities; an ECO loop that converts VF insights into concrete hardening actions; and a fully reproducible open-source implementation. The paper’s scope is architectural and pre-layout, with extensions to broader circuit classes and a full electrical analysis outlined for future work. Full article

With the increasing application of manufactured sand, as one of the uncertain factors affecting the properties and performance of ready-mixed concrete proportioning with commonly used manufactured sand, residual flocculants in water-washed manufactured sand (WWMS) have received increased attention. Under certain prerequisites, a rapid detecting method for residual flocculants in WWMS was presented based on the pre-calibrated relationship between the Stormer viscosity of cement paste and the concentration of flocculants. Multi-dimensional and multi-factorial experiments were performed on cement paste, mortar and concrete orderly to explore the effects of flocculant content on the rheological (workability) and mechanical properties (compressive strength) of concrete. The results showed a good quantitative relationship between the Stormer viscosity and the flocculant content, and its mathematical formula depended on the type, molecular weight and content range of the flocculant. The residual flocculant contents in WWMS not only affected the workability of fresh concrete, but also the strength of hardened concrete to some extent. Full article

This study presents a novel approach to the development of self-compacting concrete (SCC) by partially replacing both cement and fine aggregate (sand) with waste marble sludge (WMS), a byproduct of the marble industry. The research aims to evaluate the feasibility of incorporating this industrial waste into SCC to enhance sustainability without compromising performance. To assess the fresh and hardened properties of the proposed mixtures, a comprehensive experimental program was conducted. Tests included slump flow, T₅₀, and V-funnel for evaluating workability, as well as measurements of specific gravity, compressive strength, flexural strength, Brazilian tensile strength, and water absorption at 28 days of curing. The results demonstrated that the mix containing 5% cement replacement and 20% sand replacement with marble sludge exhibited the highest mechanical performance, achieving a compressive strength of 48.2 MPa, tensile strength of 3.9 MPa, and flexural strength of 4.4 MPa. Furthermore, increasing the percentage of cement replacement led to enhanced flowability, as evidenced by an increase in slump flow diameter and a reduction in V-funnel flow time, indicating improved workability. Overall, the findings suggest that controlled incorporation of WMS can produce SCC with desirable mechanical and rheological properties, offering a promising pathway for sustainable concrete production. In addition to the technical performance, a carbon footprint analysis was conducted to examine the environmental benefits of marble sludge utilization. The mixture with 10% cement and 20% sand replacement exhibited the lowest carbon footprint, while the 7.5% replacement level provided the best balance between strength and sustainability. Full article

Three-dimensional concrete printing (3DCP) is rapidly emerging as a transformative construction technology, enabling formwork-free fabrication, geometric flexibility, and reduced labour. However, the lack of conventional reinforcement and the strict requirements for fresh and hardened properties present significant challenges. Fibre reinforcement and supplementary cementitious materials (SCMs), such as ground granulated blast furnace slag (GGBS), offer pathways to enhance printability while mitigating environmental impact. This study investigates the combined effect of natural cellulose microfibres and silica fume on the rheological, mechanical, and sustainability performance of 3D-printable mortars. Six mixes were prepared with 50% GGBS, 45% cement, and 5% silica fume, incorporating fibre dosages from 0% to 1%. Results showed that a 0.5% fibre dosage provided the most favourable balance. At this dosage, static yield stress increased to 9.35 Pa and thixotropy reached 8623 mPa·s, enhancing structuration for shape retention. Plastic viscosity remained stable at 4–5 Pa·s, ensuring adequate extrusion performance. Higher fibre dosages (≥0.75%) caused a significant increase in rheological resistance, with static yield stress reaching 208 Pa and thixotropy 135,342 mPa·s. This resulted in excessive structuration, fibre clustering, and poor extrudability. Compressive strength was achieved at 109.10 MPa (92% of silica fume-only mix) with 0.5% fibre. In comparison, flexural strength was 13.20 MPa at 0.5% fibre content and reduced gradually to 12.29 MPa at 1% fibre due to weak fibre–matrix bonding and porosity. Sustainability analysis confirmed that using 50% GGBS and 5% silica fume reduced embodied carbon compared to a 100% cement mix. This study also demonstrated that cellulose microfibres at 0.25–0.5% are optimal for balancing fresh properties, mechanical strength, and sustainability in 3D-printed mortars. Full article

Conventional strengthening measures for existing structures are usually not effective for the self-weight, which accounts for around 70% of the total load in reinforced concrete structures. Therefore, their effect on the overall load-bearing capacity is low. A self-weight-effective alternative for flexural strengthening is the thermal prestressing of additional reinforcement installed on the structure. In this method, reinforcing bars are slotted into the tensile zone, embedded in filler material, and tempered from the outside. They are thermally stretched, and once cooling starts, the bond with the hardened filler prevents re-deformation. The induced prestressing force counteracts dead loads and relieves the tensile zone, making the additional bars effective for the self-weight. In this paper, the effectiveness of the strengthening method is experimentally investigated in the serviceability and the ultimate limit states. Experiments involve strengthening a reinforced concrete beam under load by a thermally prestressed additional bar. Moreover, two reference tests are made to evaluate the method. An unstrengthened beam characterizes the lower capacity limit. Another beam with the same reinforcement amount as the strengthened one, but completely installed at casting, serves as the upper benchmark. All beams are loaded until bending failure. The strengthening method is assessed by means of the load-bearing behavior, deflection, crack development, and the strains in the initial as well as the added reinforcement. The results demonstrate the effectiveness of the strengthening method. The thermally prestressed bar achieves an effective pre-strain of approximately. 0.4‰ by heating at about 70 °C. The induced prestressing force and associated compression reduce tensile cracks by approx. 45% and increase stiffness. The strengthened beam reaches the maximum load of the upper benchmark, but with about 33% less deflection. The filler, which also expands thermally, generates an additional prestressing force that is effective up to about 20% of the load capacity. Beyond this, the filler begins to crack and its effect decreases, but the pre-strain in the reinforcing bar remains until maximum load. Full article

The objective of this study was to evaluate the technical properties and assess the durability of a novel high-performance concrete with aggregates composed entirely of reactive powders derived from chalcedonite—a mineral previously not utilized in HPC technology. Since there is insufficient information on chalcedonite-based concretes in the scientific literature, the presented research aims to address these knowledge gaps. The characterization of the chalcedonite powder involved the determination of specific gravity, particle size distribution, specific surface area, and particle morphology through microscopic analysis. The hardened chalcedonite-based and reference quartz-based high-performance concretes were subjected to a comprehensive suite of tests to determine their physical properties (bulk density, water absorption, and capillary absorption) and mechanical properties (flexural and compressive strength). Durability was further assessed based on compressive strength criteria, including frost resistance and carbonation resistance. To simulate long-term performance and better evaluate the durability of the high-performance concretes, specimens were tested following standard water curing and after additional maturation processes, including thermal treatment, which in the extreme case resulted in a seven-day compressive strength of 176.9 MPa, a value higher by 56.7 MPa (corresponding to an increase of 47.1%) compared to the strength of the identical concrete not subjected to thermal treatment. To explore the potential for architectural applications, particularly in outdoor environments, capillary absorption testing was of particular importance, as it provided insight into the material’s resistance to eventual pigment leaching from the mineral matrix. Full article

The conventional “one-pot” mixing method employed in concrete production restricts both efficiency and quality optimization. This study systematically investigates the effects of mixing duration and rotational speed on the compressive strength and microstructure of cement paste by varying these parameters. Results indicate that appropriately extending mixing duration and increasing rotational speed enhances the strength of cementitious paste. However, excessive duration or overly high speeds adversely affect strength. When the rotational speed is 250 r/min and the mixing time is 100 s, the compressive strength of the hardened cementitious pastes at all curing ages is good, with strengths of 50.1 MPa, 61.1 MPa, and 77.0 MPa at 3 days, 7 days, and 28 days, respectively. Microstructural analysis further reveals that this mixing condition produced lower porosity, denser morphology, and increased hydration product formation, collectively explaining the superior mechanical properties. Full article

This study focuses on the use of almond shell ash (ASA) obtained from agricultural waste through the pyrolysis process in concrete production while, at the same time, presenting an environmentally sustainable design. For this purpose, ASA was obtained from the biomass energy facilities (BEF) for use in concrete mixes. A total of 25 concrete series were prepared, including 1 control series. In these series, 5%, 10%, 15% silica fume (SF), 5%, 10% metakaolin (MK), and 1%, 3%, 5%, and 7% ratios of ASA were chosen to be substituted by volume with cement. Fresh and hardened concrete tests were performed on the specimens. Experiments have shown that the use of ASA in concrete production improves concrete performance up to a certain extent. With the data obtained from the test results, performance evaluation was performed in the artificial neural network. Because of this evaluation, a mathematical model able to predict the concrete compressive strength with high accuracy was developed. To evaluate the effectiveness of the developed model, it was tested again on control specimens to confirm its accuracy and applicability. A life cycle assessment (LCA) was also performed. The aim is to make a new contribution to the literature and practical application with the method to be developed because of the study and to pioneer future studies in this field. Full article

This research investigates the feasibility of producing eco-friendly self-compacting concrete (SCC) by partially replacing both fine and coarse natural aggregates with waste marble sludge (WMS), a byproduct of the marble industry. The objective is to evaluate whether this substitution enhances or compromises the concrete’s performance while contributing to sustainability. A comprehensive experimental program was conducted to assess fresh and hardened properties of SCC with varying WMS content. Fresh-state tests—including slump flow, T₅₀ time, and V-funnel flow time—were used to evaluate workability, flowability, and viscosity. Hardened properties were measured through compressive, flexural, and Brazilian tensile strengths, along with water absorption after 28 days of curing. The mix with 10% replacement of both sand and coarse aggregate showed the most balanced performance, achieving a slump flow of 690 mm and a V-funnel time of 6 s, alongside enhanced mechanical properties—compressive strength 48.6 MPa, tensile strength 3.9 MPa, and flexural strength 4.5 MPa—and reduced water absorption (4.9%). A complementary cost model quantified direct material cost per cubic meter and a performance-normalized efficiency metric (compressive strength per cost). The cost decreased monotonically from 99.1 $/m³ for the base mix to $90.7 $/m³ at 20% + 20% WMS (−8.4% overall), while the strength-per-cost peaked at the 10% + 10% mix (0.51 MPa/USD; +12% vs. base). Results demonstrate that WMS can simultaneously improve rheology and mechanical performance and reduce material cost, offering a practical pathway for resource conservation and circular economy concrete production. Full article

This study presents a rigorous experimental and numerical investigation of the synergistic effect of metakaolin (MK) and waste glass (WG) on the structural performance of reinforced concrete (RC) beams without stirrups. A two-phase methodology was adopted: (i) optimization of MK and WG replacement levels through concrete-equivalent mortar mixtures and (ii) evaluation of the fresh and hardened properties of concrete, including compressive and tensile strengths, elastic modulus, sorptivity, and beam shear capacity. Five beam groups incorporating up to 30% MK, 15% WG, and 1% steel fiber were tested under four-point bending. The results demonstrated that MK enhanced compressive strength (up to 22%), WG improved workability but reduced ductility, and the combined system achieved a 13% increase in shear strength relative to the control. Steel fibers further restored ductility, increasing the ductility index from 1.338 for WG-only beams to 2.489. Finite Element Modeling (FEM) using ABAQUS with the Concrete Damage Plasticity (CDP) model reproduced experimental (EXP) load–deflection responses, peak loads, and crack evolution with high fidelity. This confirmed the predictive capability of the numerical framework. By integrating material-level optimization, structural-scale testing, and validated FEM simulations, this study provides robust evidence that MK–WG concrete, especially when fiber-reinforced, delivers mechanical, durability, and structural performance improvements. These findings establish a reliable pathway for incorporating sustainable cementitious blends into design-oriented applications, with direct implications for the advancement of performance-based structural codes. Full article

Steel slag aggregate concrete (SAC) is widely recognized as a high-performance and sustainable construction material. However, its broader structural application has been impeded by the limited development of reliable constitutive models. Building upon the well-established non-uniform hardening plasticity theory, this study proposes a comprehensive theoretical framework to establish a stress–strain relationship model for SAC under complex stress states. To this end, a multiaxial elastoplastic constitutive model for SAC is developed through the following steps: (1) The Guo–Wang failure criterion is employed as the bounding surface, from which a yield criterion is formulated to capture the characteristic mechanical responses of SAC under multiaxial loading; (2) Based on fundamental plasticity theory, the stress–strain relationship is derived by integrating the proposed yield function with a non-associated flow rule using a Drucker–Prager-type plastic potential function, while ensuring consistency conditions are satisfied; (3) A parameter calibration methodology is introduced and applied using experimental data from uniaxial and multiaxial tests on SAC; (4) A numerical implementation scheme is developed in MATLAB 2024a, and the model is validated through computational simulations. The validation results confirm that the proposed model reliably captures the stress–strain behavior of SAC under complex loading conditions. Overall, this study not only delivers a robust multiaxial constitutive model for SAC, but also offers a systematic modeling approach that may serve as a reference for the further development of constitutive theories for steel slag-based concretes and their broader application in structural engineering. Full article