Search

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Concrete is a constantly evolving building material whose demand is increasing due to population growth and urban development. This calls for more research on this composite material to improve its performance. However, concrete has some disadvantages, including that it is a brittle material and cannot withstand tensile stress. Therefore, rebars and fibers are incorporated into concrete to improve this property. Although previous works investigated the properties of concrete containing steel fibers, most of them were concerned with mechanical properties, while the durability properties still require further investigation to understand them. Thus, the purpose of this study is to ascertain how adding steel fibers to concrete in varying proportions (0.5, 1.0 and 1.5%) affects its mechanical and durability properties, including compressive strength, flexural strength, tensile strength, bulk density, water absorption, mode of failure, ultrasonic pulse velocity, dynamic modulus of elasticity and electrical resistance. Statistical relationships between the compressive strength and other characteristics were also established. The results indicated that all mechanical and durability characteristics significantly improved after adding steel fibers for all addition ratios, except for electrical resistivity, which showed lower values than the reference mixture for the 0.5 and 1% steel fiber proportions. Moreover, it was found that the best addition rate of steel fibers was 1.5%. At this percentage, the recorded increasing rates over the control sample were 29.3% in compressive strength, 83.7% in tensile strength, 27.9% in flexural strength, 50.1 in water absorption resistance, and 11.2% in electrical resistivity. [ABSTRACT FROM AUTHOR]

There is a growing trend toward employing sustainable materials to address the drawbacks of traditional construction materials. This experimental study explores the utilization of basalt and steel fibers, both independently and in combination, alongside fly ash and desert sand. The findings reveal that the introduction of further basalt fibers led to a reduction in concrete workability, density, and compressive strength. The optimal compressive strength for concrete made from desert sand was achieved in the mixed concrete incorporating 1% steel fibers, measuring at 50.6 MPa. Meanwhile, the highest flexural and tensile strengths were observed in a concrete mixture of 0.3% basalt fiber and 1% steel fiber, measuring 7.35 MPa and 4.6 MPa. Scanning Electron Microscopy, Energy Dispersive Spectroscopy, and X-ray Diffraction tests were conducted to examine the concrete microstructure. The results demonstrate that including a low content of hybrid steel and basalt fibers significantly improved the concrete microstructure. This study recommends conducting further studies to investigate the durability of concrete mixtures containing desert sand and basalt fibers and enhance sustainability in the construction industry. [ABSTRACT FROM AUTHOR]

This study investigates the behavior of the shear strength of fibrous concrete I-beams made from normal and lightweight concrete that have the same compression strength, of about 30 MPa. Lightweight aggregate concrete was made by replacing 75% of the coarse aggregate with lightweight aggregate (Bonza stone). Fourteen concrete I-beams with dimensions of 1000x210x175 mm were divided into two groups. In the first group, the web area was reinforced with steel fiber added in 0.5%, 1%, and 1.5% of the mix volume. The second group was reinforced with glass fiber added in the same percentage as the steel fiber. The results showed that the shear strength of a Normal Concrete Beam with Steel Fibers (NCSF) is increased by 3.5%, 13.5%, and 13.3% for the addition ratios of 0.5%, 1%, and 1.5%, respectively, compared to the Normal Concrete Beam without Fibers (NC). Webs with glass fibers gain an increase of about 3.7% and 14.05% for the addition ratios of 0.5% and 1%, respectively, while the shear strength decreased by 6.21% for the addition ratio of 1.5%. On the other hand, the Lightweight Concrete Beam with Steel Fibers (LWCBSF) achieved greater shear strength than the Lightweight Concrete Beams without Fibers (LWCB) by 4.8%, 13.5%, and 10.9%; for the three additional percentages, respectively. The shear strength increased by 8.4% and 11.04% for the Lightweight Concrete Beam with Glass Fibers (LWCBGF) at 0.5% and 1% ratios, while the shear strength decreased by 11.9% for the 1.5% glass fibers ratio compared to the Lightweight concrete Beam without Glass Fibers (LWCB). The best performance, according to the ultimate load, was achieved when fibers were added at a ratio of 1% in normal and lightweight concrete compared to other ratios. [ABSTRACT FROM AUTHOR]

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Construction using eco-friendly materials reduces environmental impact and promotes sustainable practices. This research uses sawdust and steel fibers to design sustainable concrete. The main goal is to improve mechanical properties and reduce embodied carbon emissions. This study examines the mechanical properties of concrete with different sawdust and steel fiber combinations to fill a gap in the literature. In this research synergistic effect of saw dust and steel fiber on concrete characteristics have been studied. The research also examines these pairings' environmental benefits. This study used a response surface methodology (RSM) to design an experimental program and assess the effects of input variables (sawdust and steel fiber percentages) on output responses like compressive strength (CS), split tensile strength (STS), flexural strength (FS), modulus of elasticity (MOE), embodied carbon (EC), and eco-strength efficiency (ESE). Established testing methodologies and RSM provided an optimum prediction model based on specimen mechanical properties. Sawdust and steel fibers enhances concrete's mechanical properties. Varying proportions of both materials were added in mix; sawdust (0%-12%) and steel fiber (0%-2%). The experimental findings suggest that the optimized composition achieved the following mechanical properties: 13.85 MPa compressive strength, 1.4 MPa split tensile strength, 3.67 MPa flexural strength, 18.027 GPa modulus of elasticity, 211.272 kg CO2e/m3 embodied carbon, and 0.065487 eco-strength efficiency. This research showed that the aims of improving mechanical properties and reducing embodied carbon were achieved. As per multi-objective optimization, optimal percentages of saw dust and steel fibers in concrete are 11.81% and 0.063% respectively. The investigation yielded many suggestions. To test the optimal blend composition of ecologically friendly concrete in real-world building projects, start with realistic projects. Finally, life cycle evaluations and cost studies are needed to determine the environmental and economic impacts of eco-friendly concrete compared to standard options. [ABSTRACT FROM AUTHOR]

Concrete is a constantly evolving building material whose demand is increasing due to population growth and urban development. This calls for more research on this composite material to improve its performance. However, concrete has some disadvantages, including that it is a brittle material and cannot withstand tensile stress. Therefore, rebars and fibers are incorporated into concrete to improve this property. Although previous works investigated the properties of concrete containing steel fibers, most of them were concerned with mechanical properties, while the durability properties still require further investigation to understand them. Thus, the purpose of this study is to ascertain how adding steel fibers to concrete in varying proportions (0.5, 1 and 1.5%) affects its mechanical and durability properties, including compressive strength, flexural strength, tensile strength, bulk density, water absorption, mode of failure, ultrasonic pulse velocity, dynamic modulus of elasticity and electrical resistance. Statistical relationships between the compressive strength and other characteristics were also established. The results indicated that all mechanical and durability characteristics significantly improved after adding steel fibers for all addition ratios, except for electrical resistivity, which showed lower values than the reference mixture for the 0.5 and 1% steel fiber proportions. Moreover, it was found that the best addition rate of steel fibers was 1.5%. At this percentage, the recorded increasing rates over the control sample were 29.3% in compressive strength, 83.7% in tensile strength, 27.9% in flexural strength, 50.1 in water absorption resistance, and 11.2% in electrical resistivity.

This study focuses on the development and evaluation of a novel cement-free gamma-ray-resistant ultrahigh-performance concrete (UHPC), known as UHPC-CAS. UHPC-CAS is composed of calcium oxide–activated slag, iron and barite powders, and steel fibers, making it a type of ultrahigh-performance geopolymer concrete (UHPGC). In this study, the effects of replacing silica sand with varying percentages of iron and barite powders on the mechanical and radiation properties of UHPC-CAS were investigated. The optimal replacement ratio of iron powder was found to be 50%, resulting in the highest compressive, tensile, and bending strengths among all mixtures without fibers. Furthermore, the UHPC-CAS samples reinforced with steel fibers and containing barite powder exhibited a more pronounced softening zone than those containing iron powder. With 100% iron powder and 3% steel fibers, UHPC-CAS achieved superior resistance to gamma rays, as evidenced by the highest attenuation coefficient of 0.234 cm and the lowest half-value layer of 2.96 cm. This research demonstrates the potential for developing sustainable cement-free UHPC for use in nuclear facilities and other applications requiring high radiation shielding. [ABSTRACT FROM AUTHOR]

This study investigated the behavior of reinforced concrete columns using high-performance concrete (HPC) filled in prefabricated steel tubes to serve as reinforcement. The experimental setup involved HPC with a compressive strength of 1,515 kg/cm², filled into steel tubes with diameters of ¾, 1, and 1¼ inches, replacing the reinforcement in concrete columns sized 150x150x600 mm. The concrete used for casting the sample columns had a compressive strength of 257 kg/cm². The columns were tested for axial and eccentric loading at displacements of 20, 40, and 60 mm to determine the maximum compressive strength, bending moment, interaction diagrams, and failure patterns of the steel-reinforced concrete columns. The experimental results showed that the axial compressive strength of columns using HPC in steel tubes as reinforcement was higher than that of the control concrete columns. The compressive strength at various eccentricities showed a slight increase compared to the control columns. The comparison between experimental compressive strengths and bending moments with calculated values indicated a consistent trend. Furthermore, the failure patterns of the concrete columns revealed both compression and tension failures.

Deep beams are crucial for construction projects due to their load-carrying capacity, shear resistance, and architectural adaptability. Ultra-high strength concrete and ultra-high-performance concrete (UHPC) are used in their production. Basalt fiber is used as an alternative due to its corrosion resistance, tensile strength, and thermal stability. This study investigates the behavior of UHPC deep beams reinforced with basalt fibers. Three sets of 11 specimens were constructed without transverse reinforcement and reinforced with either fibers or steel fibers. The study also analyzes the impact of parameters like shear strength capacity, crack development, and load-deflection behavior on UHPC deep beams. The study discovered that the inclusion of basalt fibers in UHPC deep beam can effectively postpone the onset of diagonal cracks. Incorporating basalt fiber at concentrations of 0.5, 0.75, and 1.0% led to respective increases of 48.17, 70.07, and 86.66% in the diagonal fracture force, as compared to the inclusion of steel fibers which resulted in increases of 18.24, 56.93, and 98.54% in diagonal fracture loads. The ideal ratio for enhancing the maximum shear capacity was found to be 0.75% of basalt. This specific percent resulted in the highest measured force out of the three percentages that were examined. The addition of basalt fibers at concentrations of 0.5, 0.75, and 1.0% resulted in respective improvements of 11.62, 30.08, and 28.69% in the ultimate shear capacities. During that period, steel fibers significantly enhanced the ultimate shear capacity, resulting in an increase of 19.83, 34.49, and 55.24% compared to specimens without fiber reinforcement. Regarding the second parameter of this investigation, a drop in the shear span ratio is linked to an augmentation in shear capacity and a reduction in mid-span deflection to varying extents for both the utilization of basalt and steel fibers.

The use of fibers is often aimed at increasing the ductility and load-bearing capacity of the desired concrete, and controlling the spread of cracks by adding fibers to the concrete causes this. The fibers improve the behavior of the concrete after the first crack due to the bridging property on the micro-cracks. In this paper, 15 concrete mixing designs in the form of 90 cubic specimens with dimensions (15 * 15 * 15) cm for the compressive strength test and 42 specimens with dimensions (15 * 15 * 60) cm for the flexural strength test have been made. Three mixing designs were made as a reference with 3 water-to -cement ratios (0.24, 0.29, 0.34) without fibers and with fibers with 3 different lengths of polypropylene fibers with lengths of (6, 12, 18) mm, respectively. A mixing scheme with 40 mm long hook metal fibers and another mixing scheme with a combination of 40 mm hooked metal fibers and 12 mm polypropylene fibers were investigated. Microsilica gel and super-lubricant were used to increase the smoothness and efficiency of concrete. The highest average compressive strength of 28 days was related to samples with composite fibers with a resistance of 72.52 MPa, which was 12.9% higher than the reference sample. The concrete sample with metal fibers with an average bending strength of 12.85 MPa has the highest strength among all the concrete mixing designs of this research and shows a 60% increase in bending strength compared to the sample without fibers. In the concrete samples tested with polypropylene fibers, after the compressive strength test, with the increase in the length of the polypropylene fibers, the workability and compressive strength of the concrete decreased, but the plasticity of the concrete samples increased. After the flexural strength test, the flexural strength and ductility of the concrete samples increased with the increase in the length of the polypropylene fibers, but it led to a decrease in the workability of the concrete.

Abstract This study investigates the influence of LDHs (Layered Double Hydroxides) microparticles and steel fibers on the mechanical properties of lightweight concrete. Through a combination of experimental analysis and finite element modeling, the effects of LDHs and steel fibers on flexural strength and crack resistance were evaluated. The experimental results demonstrate a significant increase in flexural strength and toughness with the incorporation of LDHs microparticles and steel fibers. The finite element model corroborates these findings, highlighting the synergistic enhancement of mechanical properties due to LDHs and steel fibers. Additionally, the study discusses the frontier applications of LDHs in improving fracture characteristics and highlights the potential of hybrid reinforcement strategies in lightweight concrete. The findings reveal that both the quantity of microparticles and steel fibers significantly impact the concrete's residual strength. In scenarios without steel fibers, an optimal weight fraction of approximately 1 wt.% LDHs demonstrate a 39% increase in bearing capacity. Notably, under comparable conditions, the influence of LDHs microparticles on enhancing concrete mechanical characteristics appears to surpass the effects induced by steel fibers. However, at 2 wt.% LDHs usage, a decrease in load capacity by 3.3% is observed compared to the 1 wt.% LDHs configuration. This research provides valuable insights into optimizing concrete properties through novel material combinations and paves the way for future advancements in structural engineering.

Steel fiber reinforced high-strength concrete (SFRHSC) is a composite material composed of cement, coarse aggregate, and randomly distributed short steel fibers. The excellent tensile strength of steel fiber can significantly improve the crack resistance and ductility of high-strength concrete (HSC). In this study, experimental and numerical investigations were performed to study the cyclic behavior of the HSC beam-column joint. Three SFRHSC and one HSC beam-column joint were prepared and tested under cyclic load. Two different volume ratios of steel fibers and three stirrups ratios in the joint core area were experimentally studied. After verification of the experimental results, numerical simulations were further carried out to investigate the influence of steel fibers volume ratio and stirrups ratio in the joint core area on the seismic performance. Evaluation of the hysteretic response, ductility, energy dissipation, stiffness, and strength degradation were the main aims of this study. Results indicate that the optimal volume fraction of steel fibers is 1.5%, and the optimal stirrups ratio in the joint core area is 0.9% in terms of the enhancement of the seismic performance of the SFRHSC beam-column joint. [ABSTRACT FROM AUTHOR]

The presence of toxic elements in manganese slag (MSG) poses a threat to the environment due to potential pollution. Utilizing CO curing on MS offers a promising approach to immobilize toxic substances within this material, thereby mitigating their release into the natural surroundings. This study investigates the impact of CO cured MS on various rheological parameters, including slump flow, plastic viscosity (η), and yield shear stress (τ). Additionally, it assesses flexural and compressive strengths (f and f), drying shrinkage rates (DSR), durability indicators (chloride ion migration coefficient (CMC), carbonization depth (CD)), and the leaching behavior of heavy metal elements. Microscopic examination via scanning electron microscopy (SEM) is employed to elucidate the underlying mechanisms. The results indicate that CO curing significantly enhances the slump flow of ultra-high performance concrete (UHPC) by up to 51.2%. Moreover, it reduces UHPC's η and τ by rates ranging from 0% to 52.7% and 0% to 40.2%, respectively. The DSR exhibits a linear increase corresponding to the mass ratio of CO cured MS. Furthermore, CO curing enhances both f and f of UHPC by up to 28.7% and 17.6%, respectively. The electrical resistance is also improved, showing an increase of up to 53.7%. The relationship between mechanical strengths and electrical resistance follows a cubic relationship. The CO cured MS demonstrates a notable decrease in the CMC and CD by rates ranging from 0% to 52.6% and 0% to 26.1%, respectively. The reductions of leached chromium (Cr) and manganese (Mn) are up to 576.3% and 1312.7%, respectively. Overall, CO curing also enhances the compactness of UHPC, thereby demonstrating its potential to improve both mechanical and durability properties. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The utilization of recycled materials in concrete technology has gained significant attention in recent years, promoting sustainability and resource conservation. This paper investigates the behavior of lightweight self-compacting concrete (LWSCC) with recycled tire steel fibers (RTSFs). The effects of RTSFs on the flowability of the composite material and its density were assessed. The mechanical properties of the developed material were examined and beam tests were performed, aiming to assess its feasibility for structural applications. The compressive and tensile strengths were determined to evaluate the mechanical properties of the developed concrete mixtures. The beam tests were conducted to assess the flexural behavior of the beam specimens. Three different steel fiber contents of 0, 0.5, and 1% volumetric fractions of concrete were used in this study. The test results indicate that incorporating the fibers did not negatively impact the flowability and density of the LWSCC mixtures. In addition, the use of RTSFs enhanced the tensile strength of the developed concrete mixtures, where fibrous concrete showed increases in the splitting tensile strength in the range of 38 to 76% over that of non-fibrous concrete. On the other hand, the compressive strength of the mixtures was not affected. The test beams with RTSFs exhibited improved flexural performance in terms of delaying and controlling cracking, enhancing ultimate load, and increasing ductility. Compared with the control non-fibrous beam, the increases in the cracking load, ultimate load, and ductility index were up to 63.8, 9.3, and 16%, respectively. The test results of the beams were compared with theoretical predictions, and good agreement was found. [ABSTRACT FROM AUTHOR]

This study investigates the influence of steel fiber content (0%, 0.3%, 0.6%, 0.9%) on the axial compressive performance of ceramsite concrete. Four types of ceramsite concrete specimens were prepared and the cube compressive strength of each type of ceramsite concrete was tested. Four sets of uniaxial compression tests on prismatic specimens of ceramsite concrete were conducted. The failure process and characteristics of the specimens were analyzed, and the uniaxial compressive performance of each group of specimens was systematically studied. Additionally, the stress-strain curves equations were proposed. The research indicates that, after the addition of steel fibers, the strength and ductility of ceramsite concrete are significantly enhanced. The compressive strength of cubic specimens can increase by up to 42.6%, axial compressive strength can increase by up to 25.6%, and residual stress can increase by more than 300%. Ceramsite concrete with a steel fiber volume fraction of 0.9% demonstrates clear advantages. Its energy dissipation coefficient has increased by 17%, ductility coefficient has improved by 33%, toughness coefficient has enhanced by 68%, and stiffness degradation has noticeably become more gradual. The stress-strain curve model proposed in this study aligns well with the experimental results, accurately describing the stress-deformation characteristics of steel fiber ceramsite concrete under uniaxial compression. It demonstrates good applicability. The research findings of this study can provide a theoretical foundation for the structural analysis and design of such concrete, which is of significant importance for the utilization of ceramsite concrete as both a structural material and as a component in prefabricated lightweight wall panels. [ABSTRACT FROM AUTHOR]

Geogrids, first developed in the late 20th century, revolutionized soil reinforcement using polymer materials in grid-like structures to enhance soil stability, reduce erosion, and strengthen infrastructure, marking a pivotal advancement in geotechnical engineering. However, geogrids typically find limited application in structural engineering, especially reinforced concrete (RC) columns. The present research explores the feasibility of geogrids in concrete columns, thus optimizing construction practices by exploring innovative reinforcement methods beyond conventional steel, aiming to bolster durability and performance in diverse structural scenarios. The traditional method of using steel stirrups to confine circular columns was substituted with a new approach; i.e., geogrids were introduced partially as confining material alongside steel stirrups. Furthermore, the research examines the performance of concrete columns confined partially with geogrid, both with and without the inclusion of steel fibers, in comparison to traditional columns reinforced with steel. Columns, 16 in number, with different steel stirrup spacing, concrete types, and geogrid configurations, were cast and put under axial load. Load-deflection curves were obtained, and parameters including ultimate load, maximum axial displacement, ductility, secant stiffness, and energy dissipation were assessed and compared. The findings indicated that incorporating geogrids with greater tensile strength alongside steel fibers could uphold a peak load value 10.16% higher than the control column, improved stiffness, and enhanced energy dissipation, indicating a promising approach for reinforcing columns in conjunction with steel fibers. [ABSTRACT FROM AUTHOR]

With the addition of electrically conductive steel or carbon fibers, Ultra-High-Performance Concrete (UHPC) possesses an intrinsic self-sensing capability. This opens up the possibility of combining the resilience and sustainability of UHPC with the development of self-sensing solutions for structural applications. In this study, the self-sensing behaviour of a proprietary nano-engineered UHPC material subjected to tension was investigated. To assess the self-sensing performance of the material, bulk resistivity measurements were used on direct tension and pure flexure tests, while a novel wireless approach that operates on was used on out-of-plane bending tests. The wireless approach used alternate current (AC) measurements while the bulk resistivity methods were performed through direct current (DC) and the four-probe method. In both methods, the fractional change in resistance was correlated to the state of deformation. The disposition of the actual strain field was evaluated using Digital Image Correlation (DIC). It was found that in the case of direct tension and pure flexure, the fractional change of resistance was initially decreased up to the onset of strain localization, while it gradually increased in the post-peak range, where the separation of the localized crack gradually increased. In the case of the wireless approach using AC, the onset of cracking was successfully predicted with an abrupt increase in resistivity. The wireless strain-sensing approach also captured the Poisson's effect due to the loading. [ABSTRACT FROM AUTHOR]

In this study, the properties of steel strand-reinforced reactive powder concrete (RPC) with mixed steel fibers and basalt fibers were investigated. The volume ratios of steel fibers and basalt fibers ranged from 0% to 2%. The reinforcement ratio of steel strands was 1%. The flexural strength and toughness were measured. Moreover, the impact toughness was determined. The studies were carried out under an erosion environment with chlorides and sulfates. The electrical resistance and the ultrasonic velocity were obtained to assess the salt corrosion resistance performance of steel strand-reinforced RPC. The results show that the addition of basalt fibers and steel fibers can improve the mechanical strength, ultrasonic velocity, flexural toughness, and impact toughness and decrease the performance degradation of the steel strand-reinforced RPC under the conditions of dry–wet alternations of NaCl and Na2SO4 solutions. Basalt fibers and steel fibers can improve the steel strand-reinforced RPC's flexural strength by rates of up to 13.1% and 28.7%, respectively. Moreover, the corresponding compressive strength increases by 10.3% and 18.3%. The flexural strength decreases by 11.2%~33.6% and 7.3%~22.7% after exposure to the NaCl and Na2SO4 dry–wet alternations. Meanwhile, the corresponding compressive strength decreases by 22.1%~38.9% and 14.6%~41.3%. The electrical resistance increases with the addition of basalt fibers and decreases with the increasing dosages of steel fibers. The steel strand-reinforced RPC with the assembly units of 1% steel fibers and 1% basalt fibers shows the optimal mechanical properties and salt resistance considering its wet–dry alternation performance. The properties of steel strand-reinforced RPC decrease more rapidly after undergoing NaCl erosion than Na2SO4 erosion. [ABSTRACT FROM AUTHOR]

This study investigates the influence of LDHs (Layered Double Hydroxides) microparticles and steel fibers on the mechanical properties of lightweight concrete. Through a combination of experimental analysis and finite element modeling, the effects of LDHs and steel fibers on flexural strength and crack resistance were evaluated. The experimental results demonstrate a significant increase in flexural strength and toughness with the incorporation of LDHs microparticles and steel fibers. The finite element model corroborates these findings, highlighting the synergistic enhancement of mechanical properties due to LDHs and steel fibers. Additionally, the study discusses the frontier applications of LDHs in improving fracture characteristics and highlights the potential of hybrid reinforcement strategies in lightweight concrete. The findings reveal that both the quantity of microparticles and steel fibers significantly impact the concrete's residual strength. In scenarios without steel fibers, an optimal weight fraction of approximately 1 wt.% LDHs demonstrate a 39% increase in bearing capacity. Notably, under comparable conditions, the influence of LDHs microparticles on enhancing concrete mechanical characteristics appears to surpass the effects induced by steel fibers. However, at 2 wt.% LDHs usage, a decrease in load capacity by 3.3% is observed compared to the 1 wt.% LDHs configuration. This research provides valuable insights into optimizing concrete properties through novel material combinations and paves the way for future advancements in structural engineering. [ABSTRACT FROM AUTHOR]

AbstractThis study explores the use of cutting-edge materials to improve the strength and longevity of concrete constructions, with a particular emphasis on the design and functionality of light gauge steel hollow sections (LGSHS) that are filled with concrete reinforced with steel fibers (SFRC) under flexural stress scenarios. Because of its remarkable fire resistance, SFRC enhances the capabilities of Ordinary Portland cement (OPC). Examining member shape, fire being exposed, both concrete and steel buildings, and structural response, the study examines the mechanical qualities and reaction of LGSHS filled with SFRC. A curved trend in force against the midpoint of the displacement and a continuous 12% rise in maximum load capacity is revealed by a comparative comparison between practical and numerical results, demonstrating the synergy of composite components. Infilling LGSHS with SFRC enhances load-bearing capacity, ductility, and toughness. Characterization techniques such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR) are utilized at temperatures up to 1050 °C. The objective of the investigation is to determine the load-carrying capacity, strain, deformation capacity, ductility, and failure characteristics of specimens at both ambient and elevated temperatures. Experimental and analytical findings are juxtaposed with theoretical values proposed by various code provisions. [ABSTRACT FROM AUTHOR]

The use of alkali‐activated concrete (AAC) as an alternative construction material to Portland cement‐based concrete (PCC) has been widely encouraged by its enhanced mechanical and durability performance and environmental benefits. However, AAC exhibits low flexural and tensile strength, limiting its application in areas where high post‐cracking flexural and tensile load‐bearing capacity are needed. Steel fibers can be added to improve the composite ductility and toughness. Steel fiber‐reinforced alkali‐activated concrete (SFRAAC) is a new emerging technology with research studies evaluating the effect of fiber addition on its mechanical properties still in the early stages. To promote the application of SFRAAC, analytical models predicting their mechanical performance are needed. This study evaluates the applicability to SFRAAC of previously published analytical models developed for steel fiber‐reinforced cement‐based concrete (SFRPCC). Experimental data available in the literature have been collected to create an extensive database to validate and then calibrate these currently available correlations between mechanical properties for SFRAAC. The prediction models considered in this study correlate the mechanical performance of SFRAAC, that is, compressive strength, modulus of elasticity, splitting tensile strength, flexural and residual flexural strength, to the compressive strength of the reference concrete without fibers, the fiber volume fraction and the fiber reinforcing index. Thus, by knowing the performance of the AAC matrix and the fiber properties and dosage, it is possible to predict the overall mechanical behavior of the steel fiber‐reinforced composite. [ABSTRACT FROM AUTHOR]

This research aims to develop sustainable high-strength concrete (SHSC) by replacing 100% fine and/or coarse aggregates with fine recycled aggregate (RA) and/or coarse RA. Due to the high surface water absorption of coarse RA, a surface treatment method was adopted, consisting of immersing it in a cement and silica fume slurry. Moreover, to improve the performance of the produced SHSC, steel fibers were employed at a relatively low volume fraction (0.5%). Eleven blends were cast and tested in this experimental study. A control SHSC mix (without RA) and ten other mixtures, including fine natural and RA, treated and untreated coarse RA, with and without steel fibers, were prepared. Compressive, splitting, and flexural strengths, water absorption, density, and ultrasonic pulse velocity (UPV) of the resulting SHSC were conducted. The results indicated that the use of RA in SHSC resulted in an average drop of 25% in its mechanical properties and an increase of about 30% in water absorption. However, using treated RA compensated the compressive and tensile strength reductions in SHSC by 9% and 7%, respectively, compared to mixes containing untreated RA. On the other hand, adding fibers helped improve compressive, flexural, and splitting tensile strengths by about 8%, 23%, and 31%, respectively, compared to the corresponding control mix. Consequently, the results showed that it is possible to produce durable SHSC made from 100% RA and 0.5% steel fibers with a reduced density and improved mechanical performance to a comparable level or even superior to high-strength concrete (HSC) with only natural aggregates (NAs). [ABSTRACT FROM AUTHOR]

In the present study, the mechanical properties of heavy weight geopolymer concrete reinforced with steel fibers including compressive and splitting tensile strength were investigated. In addition, fracture parameters were also investigated according to WFM and SEM methods. In this research, first, a sample containing natural aggregates without fibers was tested. Then, an example in which heavy recycled aggregates were considered as a complete substitute for natural aggregates. Then, steel fibers were added to the same sample in volume fractions of 0.5, 0.75, 1, 1.25 and 1.5% and its effects were investigated. The results obtained from the tests showed that the addition of steel fibers with any volume fraction led to an increase in indirect compressive and tensile strengths. The results showed that the fracture energy (GF) obtained by the fracture mechanics method (WFM) in the sample with steel fibers with 1.5 percent is higher than the control sample. However, increasing the percentage of steel fibers has led to an increase in fracture energy. Examining Cf values showed that in samples with 0.5% and 0.75% steel fibers, its value is lower than the control sample and in other samples it is higher than the control sample. However, increasing the percentage of steel fibers has steadily led to an increase in Cf. The GF/Gf ratio for different designs in this research was between 0.81 and 1.14. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Construction using eco-friendly materials reduces environmental impact and promotes sustainable practices. This research uses sawdust and steel fibers to design sustainable concrete. The main goal is to improve mechanical properties and reduce embodied carbon emissions. This study examines the mechanical properties of concrete with different sawdust and steel fiber combinations to fill a gap in the literature. In this research synergistic effect of saw dust and steel fiber on concrete characteristics have been studied. The research also examines these pairings’ environmental benefits. This study used a response surface methodology (RSM) to design an experimental program and assess the effects of input variables (sawdust and steel fiber percentages) on output responses like compressive strength (CS), split tensile strength (STS), flexural strength (FS), modulus of elasticity (MOE), embodied carbon (EC), and eco-strength efficiency (ESE). Established testing methodologies and RSM provided an optimum prediction model based on specimen mechanical properties. Sawdust and steel fibers enhances concrete’s mechanical properties. Varying proportions of both materials were added in mix; sawdust (0%–12%) and steel fiber (0%–2%). The experimental findings suggest that the optimized composition achieved the following mechanical properties: 13.85 MPa compressive strength, 1.4 MPa split tensile strength, 3.67 MPa flexural strength, 18.027 GPa modulus of elasticity, 211.272 kg CO2e/m3 embodied carbon, and 0.065487 eco-strength efficiency. This research showed that the aims of improving mechanical properties and reducing embodied carbon were achieved. As per multi-objective optimization, optimal percentages of saw dust and steel fibers in concrete are 11.81% and 0.063% respectively. The investigation yielded many suggestions. To test the optimal blend composition of ecologically friendly concrete in real-world building projects, start with realistic projects. Finally, life cycle evaluations and cost studies are needed to determine the environmental and economic impacts of eco-friendly concrete compared to standard options.

Abstract To aid in the creation of sustainable structures, scientists have utilized waste materials found in the environment to serve as alternatives for traditional resources in the construction sector. They have undertaken extensive investigations pertaining to this matter. In this particular study, tempered glass as waste glass coarse aggregate (WGCA) was substituted for natural coarse aggregate (NCA) at varying proportions of 15%, 30%, and 45% in the formulation of eco-friendly self-compacting concrete (SCC), combined with hooked-end steel fibers (SFs) at various volumes. The study assessed concrete’s flowability, permeability, compressive strength, and fracture parameters at 28 and 56 days. A total of 240 edge-notched disc bending samples (ENDB) and 60 cubic samples (150 × 150 mm) were tested to assess fracture resilience and compressive strength, respectively. The results showed that increasing SF and WGCA content reduced slump flow diameter and blockage ratio, particularly at higher levels. The solidified characteristics of all specimens incorporating SF and WGCA displayed heightened attributes when contrasted with the reference sample. Among the entire array of specimens, WG15SF0.5 and WG30SF0.5 exhibited the most superior performance, demonstrating an average percentage elevation of 20.29 and 27.63 in both compressive strength and fracture toughness assessments across the different curing periods. SF had the most significant impact on post-cracking behavior by enhancing load-bearing capacity through a bridging fiber mechanism. Through a comparison of the influence of SFs and WGCA on the fracture toughness of pure mode III, it was observed that the inclusion of SF in samples with a 30% replacement of WGCA resulted in an average increase of approximately 15.48% and 11.1% in this mode at the ages of 28 and 56 days, respectively, compared to the control sample.

Due to its inherent properties, concrete exhibits brittle failure once it attains its peak compressive and tensile strengths. As concrete is weak in tension, it is usually reinforced with steel bars to resist tensile stresses produced by the applied loading in its superstructure and infrastructure. However, over the last few decades, steel fibers have also been used in preparing concrete for the construction of structural components. Based on some published studies, it has been observed that the use of steel fibers significantly decreases the brittleness associated with concrete and causes an increase in peak compressive and tensile strengths. Furthermore, it was also observed that its behavior significantly differs under increasing compressive loading rates when compared under static loads. However, these studies have been unable to identify the causes of this change in behavior under increasing loading rates; therefore, in this study, a detailed numerical investigation has been carried out using non-linear finite-element analysis software, ABAQUS. It was found that the behavior exhibited by steel fiber reinforced concrete specimens under high rates of compressive loading represents a structural response rather than material behavior.

This paper investigates the effects of silica fume (SF) and metakaolin (MK) as cement substitutes on the mechanical properties, shrinkage, and toughness performances of steel fiber reinforced concrete (SFRC). Initially, a reference concrete mix with a water-to-binder ratio of 0.4 is blended with different volume fractions of steel fibers with varying geometries (crimped steel and straight steel), both individually and in combination, to examine their mechanical properties. Also, the possible influence of pozzolans on the variation of drying shrinkage and flexural toughness of hybrid steel fiber reinforced concrete (Hy-SFRC) was evaluated. An increase in workability was observed as a result of hybridization of steel fibers. Pozzolanic steel fiber reinforced concrete (SFRC) exhibited a more significant enhancement in compressive strength and flexural strength compared to non-pozzolanic SFRC. The hybrid combination of CS 1.5 % and SS 0.5 % was found to be the best in terms of mechanical properties. The addition of SF and MK reduced the shrinkage strain by up to 50 % compared to the reference mix. The flexural toughness values for both binary and ternary pozzolanic Hy-SFRC were notably higher than those for non-pozzolanic Hy-SFRC, indicating a stronger bond between the fibers and the matrix. Hy-SFRC containing a ternary pozzolanic mix of SF 10 % and MK 10 % gave the best results in flexural toughness. The results were consistent with morphology analysis, which revealed an increase in hydration products at the interface between the aggregate and concrete matrix, as well as between the steel fiber and concrete matrix, due to the ternary blending of SF and MK.

The use of fossil fuel and wood for cooking poses health, environmental, and economic challenges, especially with the growing population. This has led to an increase in the trend towards the use of clean and sustainable cooking sources, including solar cookers. This experimental study aims to contribute by enhancing the performance of a solar box cooker (SBC) according to the concept of porous media via adding steel fibers inside the box as a modified SBC and comparing it with a conventional SBC. The stagnation test to determine the first figure of merit and the load test to determine the second figure of merit, standard boiling time, and cooker optothermal ratio were conducted under the outdoor conditions of Baghdad city. Also, an energy and exergy efficiency analysis, and calculating the rate of heat loss by three water loads heating and cooling tests. The results revealed that the modified SBC has a higher thermal performance than the conventional SBC. [ABSTRACT FROM AUTHOR]

In light of the effort for decarbonization of the energy sector, it is believed that common geopolymer binding materials such as fly ash may eventually become scarce and new geological aluminosilicate materials should be explored as alternative binders in geopolymer concrete. A novel, tension-hardening geopolymer concrete (THGC) that incorporates high amounts of semi-reactive quarry wastes (metagabbro) as a precursor, and coarse quarry sand (granite) was developed in this study using geopolymer formulations. The material was optimized based on the particle packing theory and was characterized in terms of mechanical, physical, and durability properties (that is, compressive, tensile, and flexural resistance; Young's modulus; Poisson's ratio; absorption; drying shrinkage; abrasion; coefficient of thermal expansion; and chloride-ion penetration, sulfate, and salt-scaling resistance). The developed THGC, with an air-dry density of 1940 kg/m³ (121 lb/ft³), incorporates short steel fibers at a volume ratio of 2%, and is highly ductile in both uniaxial tension and compression (uniaxial tensile strain capacity of 0.6% at an 80% post-peak residual tensile strength). Using digital image correlation (DIC), multiple crack formation was observed in the strain-hardening phase of the tension response. In compression, the material maintained its integrity beyond the peak load, having attained 1.8% compressive strain at 80% post-peak residual strength, whereas upon further reduction to 50% residual strength, the sustained axial and lateral strains were 2.5% and 3.5%, respectively. The material exhibited low permeability to chloride ions and significant abrasion resistance due to the high contents of metagabbro powder and granite sand. The enhanced properties of the material, combined with the complete elimination of ordinary portland cement from the mixture, hold promise for the development of sustainable and resilient structural materials with low CO2 emissions, while also enabling the innovative disposal of wastes as active binding components. [ABSTRACT FROM AUTHOR]

To aid in the creation of sustainable structures, scientists have utilized waste materials found in the environment to serve as alternatives for traditional resources in the construction sector. They have undertaken extensive investigations pertaining to this matter. In this particular study, tempered glass as waste glass coarse aggregate (WGCA) was substituted for natural coarse aggregate (NCA) at varying proportions of 15%, 30%, and 45% in the formulation of eco-friendly self-compacting concrete (SCC), combined with hooked-end steel fibers (SFs) at various volumes. The study assessed concrete's flowability, permeability, compressive strength, and fracture parameters at 28 and 56 days. A total of 240 edge-notched disc bending samples (ENDB) and 60 cubic samples (150 × 150 mm) were tested to assess fracture resilience and compressive strength, respectively. The results showed that increasing SF and WGCA content reduced slump flow diameter and blockage ratio, particularly at higher levels. The solidified characteristics of all specimens incorporating SF and WGCA displayed heightened attributes when contrasted with the reference sample. Among the entire array of specimens, WG15SF0.5 and WG30SF0.5 exhibited the most superior performance, demonstrating an average percentage elevation of 20.29 and 27.63 in both compressive strength and fracture toughness assessments across the different curing periods. SF had the most significant impact on post-cracking behavior by enhancing load-bearing capacity through a bridging fiber mechanism. Through a comparison of the influence of SFs and WGCA on the fracture toughness of pure mode III, it was observed that the inclusion of SF in samples with a 30% replacement of WGCA resulted in an average increase of approximately 15.48% and 11.1% in this mode at the ages of 28 and 56 days, respectively, compared to the control sample. [ABSTRACT FROM AUTHOR]

High-strength concrete is extensively used in the construction industry due to its higher stiffness and modulus, but it is inherently brittle. In order to reduce its brittle behavior, steel fibers are being used to increase their application in the construction industry. In this experimental study, a fixed volume fraction (Vf = 1.5%) of steel fiber was used in the concrete, whereas the type of confinement (steel tube and carbon fiber-reinforced polymer CFRP strip) was varied. Five high-strength concrete beams with and without steel fibers strengthened with different confinements (steel sheet and CFRP) were cast and evaluated for flexural performance. (Four-point loading tests were done here.) Conventional steel was used for reinforcing concrete as it has the same lateral and longitudinal strengths. The high initial cost of steel tubes is compensated by eliminating the cost of formwork required for casting regular concrete members. For conventional reinforcement, a balanced steel ratio was used. All specimens were tested under monotonic loading. The tested structural elements showed good plasticity and increased flexural capacity. The improved ductility and energy absorption capacity of the members indicate their promising use in building structures. [ABSTRACT FROM AUTHOR]

The rehabilitation of concrete structures has been a subject of extensive investigation, exploring various facets. One such avenue involves the incorporation of fiber additives into concrete materials. In parallel, the construction of reinforced concrete structures inevitably encounters construction errors, necessitating constant efforts from researchers to devise solutions for mitigating their impact. In the context of this research, a series of experiments was conducted involving the construction and testing of five reinforced concrete moment-resisting frames. The initial sample served as the control, while two additional samples were integrated with polypropylene and metal fibers. The subsequent two samples deliberately introduced a manufacturing error through the application of air-entraining admixture materials at the beam-to-column connection. This deliberate error aimed to assess the influence of additive fibers on frames affected by manufacturing errors. Several critical parameters were subjected to evaluation, including ultimate strength, stiffness, ductility, energy dissipation capacity, and strength reduction factor. The results of these assessments demonstrated that the utilization of additive fibers contributes to an enhanced overall performance of the frames, as inferred from the aforementioned seismic parameters. Furthermore, it was established that the incorporation of these additive fibers substantially alleviates the impact of manufacturing errors on moment-resisting reinforced concrete frames. Although a significant reduction in energy dissipation capacity was observed in samples with manufacturing errors, the other seismic parameters remained relatively unaffected. Subsequently, numerical models were generated in ABAQUS software to validate the experimental findings, and their outcomes were compared with the results derived from the physical experiments. [ABSTRACT FROM AUTHOR]

Several efficient applications of ultrahigh‐performance fiber‐reinforced concrete (UHPFRC). Among them are UHPFRC jackets utilized for strengthening or permanent formworks of the steel reinforcing normal strength concrete (NSC) columns since UHPFRC jackets could enhance the compressive strength and other properties of the NSC column. However, the efficiency of a UHPFRC jacket simultaneously depends on its thickness and the added steel fiber volume fraction. The paper aims to explore the interaction effect of UHPFRC jacket thickness and steel fiber volume fraction on the behavior of UHPFRC jackets confining the NSC core under compressive load. The circular ultrahigh performance concrete jacket filled inside with the normal strength concrete, named NSC‐UHPFRC column specimen, is tested under loading on the NSC core. UHPFRC jacket thickness of 18‐49 mm with three adding steel fiber volume fractions was conducted for the experimental study. The investigation and analysis of the effect of the UHPFRC jacket and the steel fiber volume fraction on compression behaviors of NSC‐UHPFRC columns proceeded after the compressive strength test results were validated using Richart's model. This comprised a review of various parameters such as specimen failure pattern, stress–strain relationship, and ductile indices. The Weibull distribution was employed to explain the interaction effect on the variation in the experimental results. Finally, an interaction model was proposed and used to discuss the interaction effect of UHPFRC jacket thickness and steel fiber volume fraction and the optimum condition of the compressive strength of the NSC‐UHPFRC columns. [ABSTRACT FROM AUTHOR]

In today's world, concrete structures are exposed to various influences, including explosive actions. With the increasing use of fiber-reinforced concrete (FRC), it is essential to investigate its response to blast effects. As there are few studies on this topic worldwide, this research is dedicated to the question of how blast effects affect the damage and properties of six different types of reinforced concrete (RC) slabs. These samples differ in concrete classes (C30/37 and C50/60) and in the type of fibers added (steel and polypropylene). Visual inspections and non-destructive measurements are carried out before and after blasting. The damaged area of the concrete surface is determined by visual inspection, while non-destructive measurements evaluate parameters such as the rebound value of the Schmidt hammer, the electrical resistivity of the concrete, the velocity of the ultrasonic wave, and the dynamic modulus of elasticity. Equal amounts of explosives are applied to five of the RC slabs to enable a comparative analysis of the resulting damage. Based on the comparison of the measured data from these five RC slabs, conclusions are drawn regarding the effects of the explosive impacts on conventionally reinforced concrete slabs compared to those with added fibers. In addition, one of the RC slabs with steel fibers is exposed to approximately three times the amount of explosives to assess the extent of increased damage and to evaluate the suitability of military standards in the calculation of explosive charges for blasting RC elements with fibers. [ABSTRACT FROM AUTHOR]

Due to its inherent properties, concrete exhibits brittle failure once it attains its peak compressive and tensile strengths. As concrete is weak in tension, it is usually reinforced with steel bars to resist tensile stresses produced by the applied loading in its superstructure and infrastructure. However, over the last few decades, steel fibers have also been used in preparing concrete for the construction of structural components. Based on some published studies, it has been observed that the use of steel fibers significantly decreases the brittleness associated with concrete and causes an increase in peak compressive and tensile strengths. Furthermore, it was also observed that its behavior significantly differs under increasing compressive loading rates when compared under static loads. However, these studies have been unable to identify the causes of this change in behavior under increasing loading rates; therefore, in this study, a detailed numerical investigation has been carried out using non-linear finite-element analysis software, ABAQUS. It was found that the behavior exhibited by steel fiber reinforced concrete specimens under high rates of compressive loading represents a structural response rather than material behavior. [ABSTRACT FROM AUTHOR]

In recent years, the alarming number of terrorist attacks has highlighted the critical need for extensive research aimed at fortifying structures against explosion-induced loads. However, the insufficient energy absorption and brittleness of conventional concrete make it ineffective in withstanding blast loading, encouraging researchers to explore innovative strategies for augmenting the energy dissipation capabilities of construction materials. This study specifically delves into the incorporation of recycled rubber, a sustainable and environmentally friendly solution to the pressing issue of scrap tire disposal. The primary focus of this research revolves around the integration of rubber recycling and steel fibers into concrete, with the ultimate goal of enhancing the dynamic response of reinforced concrete (RC) beams. This novel approach not only contributes to the structural resilience required for resisting blast impacts, but also aligns with eco-friendly practices by reusing recycled rubber. A meticulous numerical investigation was undertaken to comprehensively assess the static and blast response of these augmented beams. The numerical study involved developing finite element (FE) models using ABAQUS version 6.14 for static implicit analysis and LS-DYNA R11 for blast explicit simulations. The ABAQUS model was validated against previous experimental testing for load–displacement and failure patterns. Similarly, the LS-DYNA model was validated for blast pressure in accordance with UFC-3-340 standards and for material response under blast loading, utilizing existing experimental data. The numerical models were designed to accommodate varying weight percentages of rubber, ranging from 5% to 20%, and a consistent 1.0% incorporation of steel fibers. This comprehensive analysis aims to provide valuable insights into the efficacy of these materials in improving the structural integrity and blast resistance of RC beams, thereby contributing to the development of more secure and sustainable construction practices. By reducing the reinforcement ratio in order to meet the minimum code requirements, it became evident that the failures of the rubberized RC beams tended to exhibit ductility on the tension side under static loading. In addition, the increase in the reinforcement ratio correlated with a higher failure load and decreased deflection. Furthermore, the findings indicated an optimal concrete mixture characterized by improved ductility, energy absorption, and blast load capacity, achieved by combining 5–10% rubber with steel fibers. [ABSTRACT FROM AUTHOR]

Concrete is the most used construction material in the world. Today, there are various concretes with different applications in the industry. One of the types of concrete is fiber concrete. In this study, several concrete samples were made with steel, glass and polypropylene fibers and the effect of the volume and weight percentages of each of the fibers in improving the compressive strength of the samples at temperatures Different has been checked. In order to check the results and the possibility of comparing it with the behavior of normal concrete, a type of concrete without fibers was also made using common materials and similar tests were performed on it. Based on the investigations, the results showed that the concrete samples with steel fibers tolerated higher temperature levels and had higher resistance compared to other samples. In the samples, by adding 0.25% and 0.5% by volume of steel fibers to concrete, respectively, the compressive strength of the sample at high temperatures was improved. The strength of concrete samples with 3400 Kg/m was slightly decreased by increasing the percentage of fibers from 0.5% to 0.75%. The compressive strength of concrete containing steel fibers is 20% higher than that of concrete containing propylene fibers. [ABSTRACT FROM AUTHOR]