Hooked Steel Fibers Research Articles

Effects of aging to the mechanical properties of geopolymer concrete with addition of hooked steel fibers cured at ambient temperature

The development of compressive and flexural strength versus aging time for steel fiber reinforced geopolymer concrete (SFRGC) cured at ambient temperature was studied. SFRGC is produced by mixing of Malaysian fly ash, alkali activator, aggragates, and hooked steel fibers. At the first stage, the addition of steel fibers in geopolymer concrete are by volume fraction which are 0 %, 0.5 %, 1.0 %, 1.5 %, and 2.0 % and cured at room temperature for 28 days. The optimum addition of steel fibers will be selected for further investigation related to the mechanical properties versus aging days. Chemical composition of Malaysia fly ash shows this fly ash is classified as class F. Result indicates 1.0 % of steel fibers addition exhibit the best performance for both compressive and flexural strength. Aging days show an improvement to mechanical properties where the compressive and flexural strength increases as the aging day increased. These mechanical properties improvement is almost similar to the mechanical growth exhibited by OPC concrete.

Environmental and economic benefits of steel, glass, and polypropylene fiber reinforced cement composite application in jointed plain concrete pavement

Conventional plain concrete (PC) leads to large design thickness when used in applications where high flexural strength is required. Therefore, to minimize the consumption of natural resources and to avoid large design thickness, it is fundamental to upgrade the flexural strength of PC by using supplementary materials i.e. steel rebars, fibers. This study evaluated the environmental and economic performance of the pavements designed with different fibrous concrete composites (FCCs). FCCs were manufactured by incorporating 0.5 and 1.0% volume fractions of glass fiber (GF), hooked steel fiber (HSF), and polypropylene fiber (PPF) in the normal strength concrete (C30). Initially, the flexural properties of FCCs were evaluated and then these properties were utilized to design the thickness of jointed plain concrete pavement (JPCP). Using the cost and carbon emissions per cubic meter of each concrete mix, the environmental and economic performance of JPCP construction was estimated. The performance of different FCCs in the JPCP was compared with that of the conventional PC. The results of mechanical testing showed that HSF-FCC outperforms both PPF-FCC and GF-FCC by a significant margin. Despite inferior mechanical performance compared to HSF-FCC, both PPF-FCC and GF-FCC are very effective in reducing the carbon footprint and cost of JPCP. JPCPs with GF-FCC and PPF-FCC are also ecofriendly and economical than the JPCP with conventional PC for the same load-carrying capacity. Overall, FCC can yield cheaper and eco-friendlier pavements compared to conventional PC if the dosage and type of fiber are correctly chosen as recommended in this study.

A model for optimizing hooked end steel fibre reinforcements in cracked cement composites

The addition of metallic fibres in concrete is a widely used technique to increase its resistance to crack opening, energy absorption capacity, and durability. The properties of the resulting composite strongly depend on the geometry of the fibres, which usually dispose of an hooked end, as well as on the mechanical properties of both the fibre and the concrete. The optimization of the fibre reinforcement mechanisms can only be achieved by an approach that takes into account adequately these aspects. Therefore, in this work, a computational model incorporating the key features of a hooked end fibre embedded in a cement matrix is proposed. The fibre is modelled as a Timoshenko beam, whereas a cohesive interface is used to model the interaction with the surrounding concrete. Different failure mechanisms are defined including fibre debonding or fibre tensile rupture and concrete spalling at fibre exit point. The model is calibrated by using the results of an experimental campaign conducted by authors. A multi-step optimization algorithm is used to find the optimal geometry and model’s constitutive parameters that maximize the peak pull-out force and the energy absorption capacity in a fibre pull-out test. The analysis suggests that the use of concrete with high strength has the potential to increase both peak force and energy absorption capacity by designing the proper geometry of the fibre.

Analysis of steel fiber reinforced concrete wall panels under compression, flexural and impact loading

Fiber reinforced concrete is a concrete strengthened through discrete strings of reinforcing material. Reinforcing material as fibers can be of steel, glass or any synthetic or any natural material. Fiber increases the structural integrity of concrete. Steel Fiber Reinforced Concrete (SFRC) is extensively being handled in construction nowadays. This paper revolves around design of SFRC wall panel and analyses of its performance characteristics as compared to conventional concrete (CC) wall panels. The SFRC wall panels and cubes were casted with different percentages (0%, 1%, 1.75% and 2.5%) of steel fibers (hooked type) as a volume of total mixture. Under this study, the SFRC wall panels and the CC wall panels were exposed to flexural and impact loading. Also, cubes were examined at 7 and 28 days for compression strength. The compression strength test on concrete showed higher values on addition of hooked steel fibers. Likewise, flexural strength of wall panels made with steel fiber also was increased with the growth in the percentage steel fibers. The graph of peak load v/s deflection was plotted and it showed the optimum peak load at 1.75% fiber content. Also, in the impact test, the value of impact blows was found more for the higher concentration of fibers.

Flexural strength and toughness of steel fiber reinforced concrete beams

This study has proposed to evaluate the flexural response of reinforced concrete (RC) beam elements of size 150 mm × 200 mm × 1000 mm (with conventional steel rebars of reinforcement ratio of 0.6%) with and without steel fibers of varying reinforcement index (RI) (product of fiber aspect ratio, AR and volume fraction, Vf%). The mechanical strength (compressive, split tensile and prismatic flexural strength) of concrete are ascertained with hooked steel fibers (HSF) and crimped steel fibers (CSF) in RI of 0.25–1.50 in comparison to controlled concrete (CC) with no fibers. RC beams (with and without HSF and CSF of RI = 0.5–1.0) have been tested under flexure and the loads and deflection at first cracking, yielding, peak and ultimate failure points show that the performance of fibrous beams are higher than non-fibrous beams, and CSF is effective than HSF in RC beams. The RC beams with CSF has higher residual strength and toughness (at deflection point, L/150, L being the span), and total absorbed energy than the specimens with HSF. The residual strength and toughness (at L/150) and the total absorbed energy (TAE) of RC beams with HSF and CSF are higher than the control beams (without fibers). The experimental reserve flexural capacity (ERFC) of RC beams ≥ 1.30. The stiffness of the fibrous RC beams at initial pre-cracking, post-cracking and pre-peak stages are higher than the non-fibrous beams. The deflection ductility indices (yield and peak) have shown an increase when RI is increased from 0.5 to 1.0. The flexural test results have shown that addition of HSF and CSF has improved the first cracking, yielding and peak loads of RC beams (at RI = 0.5, 0.6 and 1.0). The crack spacing and width of flexural cracks in the RC beams have reduced due to the addition of steel fibers, and CSF has shown better cracking behavior than HSF in the beams. The equivalent flexural strength (toughness factor) and strength ratio of RC beams (with conventional reinforcement) with CSF are higher than the beams with HSF, and, therefore, crimped fibers are recommended for effective use in construction.

Effect of steel fibre on fracture toughness of concrete

The project focuses on fracture toughness of steel fibre reinforced concrete. M30 grade concrete is used in this project. 5%0.10%, 15%,20%, 25% and 30% of Ground Granulated Blast Furnace Slag (GGBFS) is replaced with cement. The hooked end steel fibre addition is kept constant as 3% by weight of binder content. 5%, 10%, 15%, 20%, 25%, and 30% of foundry sand is replaced with fine aggregate. Specimens of size 500 × 50 × 50 mm are used with notch of constant width 3 mm with notch depth ratios of 0.1, 0.2, 0.3, and 0.4. The fracture toughness is determined by using three-point bending test. The results are compared with the results of ordinary concrete mix.

A novel approach to characterize the direct shear pullout behavior of single hooked steel fibers

Fibers crossing sliding crack planes have a positive influence on capacity because they can transfer shear load as dowels. Such behavior was evidenced by several researches that investigated the direct shear performance of Fiber-Reinforced Concrete. However, there is limited literature on the direct shear pullout behavior of single fibers, which certainly provides a deeper understanding of the mechanisms involved in direct shear. Therefore, this paper presents a new approach to perform direct shear pullout (or dowel pullout) of single fibers with a developed portable test apparatus, which enables performing the typical pullout with aligned fiber and load as well. From the comparison between the dowel and aligned pullouts, the energy dissipation capacity and the bond strength of the samples tested under direct shear were found 3.13 and 1.77 times greater than the aligned ones, respectively. The remarkable differences are attributed to the increase in fiber/matrix friction due to the shear load and the continuous occurrence of plastic strains, evidenced by the fiber shape at the end of the dowel pullout. Both mechanisms can be associated with the snubbing effect. Furthermore, the test methodology presented small coefficients of variation (CV) for pullout work and bond strength. For the direct shear pullout, the CVs were 9.57% and 10.42%, respectively, and for the aligned pullout were 16.73% and 18.95%, respectively.

Evolution of the Mechanical Properties and Cracking Pattern of Cementitious Composites Reinforced with Hooked Steel Fibers

Abstract Degradation and disintegration of concrete depend on the formation of cracks and micro cracks intensively. With increase loading, micro cracks are linked together and form cracks. To solve the problem and to provide the homogenous condition, a series of thin fibers having been spread through the volume of concrete are used in the several last decades and they are called as fibers. In the study, the steel fibers integrated in the different percentages of weight have been investigated. The performance of fibers has been studied how to increase compressive strength, tensile strength, and bending strength. To survey compressive strength, tensile strength, and bending strength in the produced concrete, three plans of mixtures including the different percentages of the steel fibers have been examined. The results show that compressive strength in the concrete reinforced with steel fibers relies mainly on the quality of mortar. The added steel fibers cause the inconsiderable changes in the compressive strength of concrete. The results demonstrate that the concrete reinforced with steel fibers increase tensile strength considerably. The more the volume of steel fibers is, the more tensile strength is. Pozzolanic materials used in the specimens reinforced in steel fibers improve tensile strength. To investigate bending strength of the specimens reinforced with steel fibers, the study has used 4-point loading system. Generally, steel fibers used in the concrete increase bending strength of the concrete. The results indicate the increased steel fibers enhance bending strength in three plans of mixtures. Among the specimen reinforced with steel fibres, the most mechanical properties are related to the plans including 1, 1.5, and 2 percentages of dramix hooked steel fibers in the study. To examine crack pattern of the matrix tensile specimen reinforced with the different percentages of fibers, parameters such as the number of cracks, width of cracks, and distance between them are investigated.

A novel steel-PAFRC composite fender for bridge pier protection under low velocity vessel impacts

Steel fenders are frequently employed in bridge pier shields to engross collision energy due to vessel impact. However, vulnerability to corrosion is a major drawback in existing steel fenders. To end this, an innovative composite fender structure consisting of corrugated steel and Preplaced Aggregate Fibre Reinforced Concrete (PAFRC) is introduced. Corrugated plates of steel are intended to absorb energy and stiff guard outer panels made with PAFRC exhibit enhanced resistance to impact and ductility. Six steel-PAFRC fenders were prepared with the steel plates of two different thicknesses, where the four top panels of the PAFRC are reinforced with short and long hooked end steel fibres while bottom panels are made with non-fibrous preplaced aggregate concrete (PAC). All steel-PAFRC fenders were tested through a drop weight impact testing device to investigate their impact behaviour and failure mechanism. Collision energy at crack initiation and the ultimate crack of PAFRC panels, crushing deformation of corrugated plates and failure configuration were also examined. Additionally, a numerical model of composite fenders was developed and verified through experimental evidence. Research revealed the crashworthiness of PAFRC panel was higher when compared to the PAC panel. The relative resistance of corrugated plates of steel and the PAFRC panels had a dramatic effect on the composite fender’s impact response.

Shear Capacity Contribution of Steel Fiber Reinforced High-Strength Concrete Compared with and without Stirrup

This study presents the shear capacity of eco-friendly high-strength concrete (HSC) beams reinforced by 0.75% (by volume) of hooked steel fibers or shear stirrups with various spacings. Five large-scale HSC beams with steel fibers or stirrups were tested and investigated with respect to shear capacity, failure mode, and crack patterns. The test results indicate that all five tested beams finally failed by a shear-critical failure mode and that the use of 0.75 vol% of steel fibers significantly improved the shear strength although it decreased the diagonal crack angle of HSC beam in the case of without stirrups. There are some different properties compared with ACI 318-19 recommendation, but the use of 0.75 vol% steel fibers exhibited approximately 13.2% higher shear strength when compared with that of minimum shear reinforcement for the HSC beam. Furthermore, the shear capacity of steel fibers calculated by experimental data, and it was compared with several prediction equations. The prediction models containing fiber factor were more closely agreeable with test results with a minimum of 10.9% difference.

Spacing and bundling effects on rate-dependent pullout behavior of various steel fibers embedded in ultra-high-performance concrete

This study examines the effects of fiber geometry, spacing, and loading rate on the pullout resistance of steel fibers in ultra-high-performance concrete (UHPC). For this, three different types of steel fibers, four different fiber spacings, and three different loading rates ranging from 0.018 to 740 mm/s were considered. Test results indicated that the single straight fiber in UHPC was most rate sensitive for pullout resistance, followed by the single twisted and then hooked fibers. The bond strengths and pullout energy of specimens with multiple straight fibers were improved by increasing the loading rate but were not affected by fiber spacing. Closer fiber spacing had a detrimental effect on the dynamic pullout resistance of multiple hooked steel fibers in UHPC, while no enhancement of average bond strength of multiple twisted fibers was observed as fiber spacing and loading rate varied. The average bond strengths of single and bundled hooked and twisted steel fibers in UHPC were clearly improved by increasing the loading rate. Bundling of fibers enhanced the impact pullout resistance of all the steel fibers in UHPC. The highest dynamic increase factors for the bundled straight, hooked, and twisted fibers were approximately 3.78, 1.57, and 1.41, respectively, at the impact loads.

Shear Behavior of Concrete Beam Reinforced with Carbon Coated Steel Fiber

The project discussing concrete shear behavior analysis with varying percentage of steel fiber. D6,The fibres of hooked end steel fibre, which are used at varying proportions, namely 1%, 1.5% and 2%. The strength tests show that the addition of fibre used better result when compared with conventional concrete. Various analyzes were conducted, such as compressive strength, split tensile strength, and flexural strength. The outcome of the experimental study shows, that incorporating carbon coating steel fibre enhances the properties of plain concrete.

Determination of mechanical properties and environmental impact due to inclusion of flyash and marble waste powder in concrete

The production of marble waste powder (MWP) and flyash is one of the significant source of pollution in developing countries. Both MWP and flyash are generated in enormous quantities, and their disposal poses a big problem. Due to their binding properties, both flyash and MWP can be effectively used in concrete to enhance its properties. In this study, MWP is used to replace fine aggregate up to 30%, and PPC, consisting of approximately 30% flyash, is used to manufacture eco-friendly concrete. Also, hooked steel fibres are added from 1% to 3% to enhance the mechanical properties of concrete. The results of the experimental study indicate an enormous increase in mechanical properties in comparison to previous research works. The environmental impact assessment is performed using recipe midpoint and endpoint analysis, which shows a positive impact due to the inclusion of flyash and marble waste powder in concrete. The economic feasibility study indicates a cognitive enhancement of cost, which is justified in return for an excellent improvement in mechanical and permeability properties along with a positive impact on the environment leading to sustainable development.

HYBRID FIBER REINFORCED CONCRETE WITH POZZOLANIC MATERIALS

This paper investigates the possibility of combining steel fibers with different weight percentages along with their functions in increasing compressive strength, indirect tensile strength and bending strength. It`s been considered an important economic issue for a long time the ability to service and increase the load-bearing capacity of structural materials. Concrete as a widely used structural material is widely used today. Despite its remarkable properties including high ductility, high durability, longevity, availability and low cost, concrete is a brittle material and performs extremely poor under flexural and tensile loads. In general, the breakdown and destruction of concrete is strongly dependent on the formation of cracks and micro-cracks. As the loading increases, the micro-cracks interconnect and form cracks. In order to address this problem and to create homogeneous conditions, a series of thin filaments has been used throughout the concrete in recent decades; They are called fibers. Steel fiber is one of the most commonly used fibers in concrete. In this study, the compressive strength of concrete was investigated which in some specimens reinforced with steel and containing pozzolanic materials, the compressive strength of control samples increased with the use of fiber etc. In the present study, the flexural and tensile strength of steel fiber reinforced specimens were investigated. According to the results, flexural strength increases with increase in steel fibers. The designs contain 1%, 1.5% and 2% of the Dramix hooked steel fibers used in the research. By reinforcing the specimens with steel fibers, the behavior of tensile concrete is much more flexible than that of non-steel specimens.

Geopolymer Concrete: an Emerging Green Material for Modern Construction

Nowadays the environmental health is considered to be the most important topic for concern. The emission of CO2 and other harmful gases to the atmosphere become a serious problem and the root cause of environmental alteration. In other ways, the production of cement is reducing continuously due to the unavailability of resources and a large amount of carbon footprint. To overcome all these problems the low CO2 emitting and alumina silicate rich sources are used as binders instead of ordinary cement. The paper reviews all the recent and experimental works done by the researchers in order to study the physical and mechanical properties of Geopolymer Concrete with different mixtures of binders and additives introduced for increasing the strength and durability. The use of different industrial by-products in concrete development is encouraged and the workability, effects of temperature variation, use of admixture, fibers and effects of water- binder ratio for the Geopolymer Concrete are examined. Reviews indicate that the compressive strength of the Geopolymer Concrete with additional hooked end steel fibers are more than that of controlled Geopolymer Concrete mix.

Effect of polypropylene and steel fibers on web-shear resistance of deep concrete hollow-core slabs

Twelve shear tests were conducted on fiber-reinforced precast/prestressed concrete hollow-core (PCHC) slabs to quantify the effectiveness of polypropylene (pp) and steel fibers (hooked and high-strength/straight types) on shear resistance. Different volume fractions of pp fibers (0.11 and 0.22%) and steel fibers (0.51 and 0.89%) were investigated. The experimental results showed that there were moderate increases in shear strength with the use of pp fibers while substantial increases in shear resistance were observed with the use of steel fibers. In addition, shear strength increased with steel-fiber content. Moreover, with the same steel fiber content of 0.89%, specimens with high-strength/straight fibers exhibited superior performance in shear resistance compared to specimens using hooked steel fibers. In addition, web-shear failure occurred in the majority of specimens. However, as steel fiber content was increased up to 0.89%, in some instances, failure mode shifted from web-shear to flexural-shear failure. In addition, the 2010 fib model code formula for shear strength of steel-fiber-reinforced-concrete (SFRC) members was used to estimate shear capacity of the tested slabs using steel fibers. The calculations showed that the fib model code was overly conservative for shear-strength predictions of SFRC hollow-core slabs reported in this investigation. A semi-empirical formula to calculate shear strength of hollow-core slabs with steel fibers was proposed. It was verified using a database including the 6 shear-test results from this study and another 39 shear-tests on SFRC hollow-core slabs compiled from literature. The formula had a mean value of 1.12 for the ratio of experimental shear strength to calculated shear strength with a coefficient of variation of 0.21.

The Effect of Steel Fiber and Internally Curing on the Strength of Self-Consolidated Concrete

The main idea of this study is to find the effect of steel fiber on the strength and internally curing of self-consolidated concrete (SCC), by using lightweight aggregate (LWA) from available porcelain.  The work includes two stages; the first stage involved making several experimental mixes and then choosing the one that corresponds to international standards with natural properties. The second stage was adding lightweight aggregate (LWA) by replacing 15% of sand with saturated fine lightweight aggregate (LWA) as internal curing material to study the change in the Mechanical properties of SCC. Four concrete mixes were used with different volume fractions of hooked steel fibers were incorporated 0%, 0.5%, 1%, and 1.5%.  Results showed that adding steel fibers provides a slight increase in compressive strength while significant enhancement in tensile properties was observed. Furthermore, replacement of fine aggregate by (LWA) causes an increase in hydration which leads to higher compressive and tensile strengths. Results of the rate of absorption indicate that adding steel fibers has beneficial effects.

Effect of nitric acid on Rice Husk Ash steel fiber reinforced concrete

Concrete is globally used construction material and nowadays its durability is the main concern. Acid is one of the chemicals influencing the durability of concrete. Nitric acid (HNO3) is one such acid. Several mineral admixtures are used to improve the durability of concrete. Rice Husk Ash (RHA) is one of such admixtures. This paper make known the results of an experimental programme intended to explore the durability aspects of Normal Concrete (NC) and Steel fiber Rice Husk Ash Concrete (SFRHAC). M25 grade of concrete using normal constituents was designed and used for referral. The RHA was used for partial replacement of Ordinary Portland Cement (OPC). The different replacement levels considered were 10, 15, 20 and 25%. It is found that workability of concrete decreased with increase in the replacement level. The optimum replacement level was found to be 15%, with respect to the compressive strength. The hooked steel fiber was added (by volume) to the RHA and Steel fiber concrete. The cubes of both NC and SFRHAC were cured in Tap water as well as in 5% Nitric acid solution till 90 days. Nitric acid is based on acid rain, sewage and industrial waste etc. The compressive strength of cubes was determined after 7, 28, 56, and 90 days. The compressive strength of water cured SFRHAC is higher than the NC. The compressive strength of both NC and SFRHAC was found to decrease in acidic solution for all the exposure periods; however, the decrease was lower in case of SFRHAC. The XRD analysis was carried out to estimate the effect of nitric acid on the constituents of concrete. The higher peaks of Calcium Silicate Hydrate (C-S-H) are detected in SFRHAC samples.

Effects of the strain rate and fiber blending ratio on the tensile behavior of hooked steel fiber and polyvinyl alcohol fiber hybrid reinforced cementitious composites

The strain rate effect on the tensile behavior of high performance hybrid fiber reinforced cementitious composites was evaluated according to the blending ratio of hooked steel fiber (HSF) and polyvinyl alcohol fiber (PVA). The tensile strength, strain capacity, peak toughness, and softening toughness were investigated. In the experimental result, specimen with 1.5 vol% HSF and 0.5 vol% PVA (HSF1.5PVA0.5) exhibited the highest tensile strength and softening toughness. However, the strain capacity and peak toughness were less than those of the specimen with 2.0 vol% HSF (HSF2.0). Nevertheless, HSF1.5PVA0.5 exhibited the highest dynamic increase factors (DIFs) for the tensile strength, strain capacity, and softening toughness. HSF2.0 showed a higher DIF for the peak toughness than HSF1.5PVA0.5. But HSF1.5PVA0.5 is expected to exhibit a higher DIF for the peak toughness than HSF2.0 at high strain rates (>101 s−1), because it have highest strain rate sensitivity of tensile strength and strain capacity.

Strength and Durability Studies on Steel Fibre Reinforced Self Compacting Concrete

This paper presents the studies on the strength and durability properties of Steel Fibre Reinforced Self Compacting Concrete (SFRSCC) of different grades. Compressive strength and durability performance of Steel Fibre Reinforced Self Compacting Concrete (SFRSCC) using hooked end steel fibres is reported in terms of Chemical Resistance, Initial Absorption Test (ISAT). The rational mix design procedure is used for designing the SCC mixes satisfying the EFNARC (2005) guidelines. In the first phase, the mechanical properties like compressive strength and in the second phase durability properties like Acid-Durability factors, sorptivity were studied for the Plain SCC (SCCP) and Steel Fibre Reinforced SCC (SFRSCC) and comparisons are made. Based on the studies, it is observed that the compressive strengths of the SFRSCC were found to be about 2% to 10% more compared to SCCP. The Sorptivity of SFRSCC is found to be reduced, with the addition of steel fibres and increase in the grade of concrete. Acid weight loss factor, the loss of dimension stability, acid strength loss percentage decreases with increase in grade of concrete. With increase in the period of immersion of the concrete in 5% concentration of acids and sulphates like Na2SO4, HCL, H2SO4, there was a damage of concrete near the corners of the cubes and such disruption in SFRSCC was less than that in SCCP. When compared to the plain SCC, the SFRSCC was found to be more durable against both acids and sulphates.