Recycled Steel Fibers Research Articles

Investigation of the mechanical and shrinkage properties of plastic-rubber compound modified cement mortar with recycled tire steel fiber

To facilitate the recycling of waste solids in cement-based materials, plastic-rubber (PR) compound modified mortar (PRM) samples and recycled steel fiber (RSF)-reinforced plastic-rubber modified mortar (PRSRM) samples were prepared and tested to evaluate their mechanical and drying shrinkage properties. PR compound particles, with a mesh size of #8, replaced the natural aggregates with four volume percentages: 2%, 5%, 7.5%, and 10%. The fiber was added with a constant volume fraction of 0.2%. Accordingly, control mortar, PRM mortar with different PR replacement ratios, and PRSRM mortar with RSF were prepared and tested. A numerical splitting tension test model was also established based on the two-dimensional Distinct Element Method (DEM) to investigate the crack initiation and propagation mechanism of the PRM samples. The mechanical test results indicated that the addition of RSF enlarged the compressive strength by 14–27% PRM samples. Meanwhile, both PR and RSF improved mortar flexural behavior by increasing the fracture energy. The SEM image of a fracture surface and DEM simulation showed the crack propagation path was changed by PR particles due to its lower stiffness. Meanwhile, the 7-days drying shrinkage length change was reduced by about 25% due to the PR’s porous structure and water-retaining ability. Overall, the sustainable material design with the combination of PR and RSF would promote the full-recycling of waste tires in cement-based materials.

Steel fibers from waste tires as reinforcements in concrete: Analysis of bond mechanism

This paper mainly studies the bond performance between a single recycled steel fiber and concrete, to attain the overall bond strength of recycled steel fibers reinforced concrete. By measuring the load displacement curve of the recycled steel fibers under pullout, we ascertain the maximum bonding stresses of the recycled steel fibers with different depths, angles and shapes while undergoing interfacial pull-out. At the same time, through observations and calculations, the failure phenomena of three stages and the changing trend of bond stresses of recycled steel fibers along the anchorage section are obtained. It is evidenced that the recycled steel fibers reinforced concrete has good interfacial bonding performance. Numerical simulation results of fiber pull-out process via the finite elements provide conditions for the analysis of bond strength of recycled steel fibers reinforced concrete cubes under different circumstances.

Study on bonding compression-shear performance between industrial green fiber-reinforced concrete and old concrete

Industrial green fiber-reinforced concrete, a new hybrid high performance environmental protection material, can be made by adding recycled steel fibers into concrete in a certain proportion. As a composite material used in the construction industry, it can provide a new research direction for national green and sustainable development. This paper studied the interface bonding mechanism of normal steel fiber-reinforced old and new concrete and industrial green fiber-reinforced concrete and old concrete by using a self-made new fixture, and discussed the influence of compressive stress, types of steel fibers and recycled steel fiber content on the bonding compression-shear performance of specimens. The results show that the bonding compression-shear performance of specimens gradually increases with the increases of the compressive stress acting perpendicular to the shearing surface within the range of low compressive stress, and when the compressive stress is from 0.2 MPa to 1.0 MPa, the increased amplitude of the bonding compression-shear performance of specimens gradually increases, when the compressive stress is from 0.6 MPa to 1.0 MPa, the increased amplitude of the bonding compression-shear performance of specimens reaches the maximum, and when the compressive stress is from 1.0 MPa to 1.4 MPa, the increased amplitude of the bonding compression-shear performance of specimens decreases. Under the same conditions, the effect of the recycled steel fibers on improving the bonding compression-shear performance between old and new concrete is better than normal steel fibers. The bonding compression-shear performance between old and new concrete gradually increases with the increases of the volume ratio of recycled steel fibers, and when the fiber content is from 0.0 % to 1.0 %, the increased amplitude of the bonding compression-shear performance of specimens gradually increases, when the fiber content is from 0.5 % to 1.0 %, the increased amplitude of the bonding compression-shear performance of specimens reaches the maximum, and when the fiber content is from 1.0 % to 1.5 %, the increased amplitude of bonding compression-shear performance of specimens decreases. The simulation results of industrial green fiber-reinforced concrete and old concrete specimens with fiber content of 1.5 % under different compressive stresses are basically in agreement with the experimental results. This study can provide references for the research of bonding compression-shear behavior of steel fiber-reinforced old and new concrete materials and the recycling of steel wire from waste tires.

Effectiveness of Concrete Reinforcement with Recycled Tyre Steel Fibres.

The role of searching for industrial waste management solutions in construction is key for environmental protection. Research in recent years has focused on solutions aimed at reducing the carbon footprint. This paper presents the results of tests conducted on concrete reinforced with treated recycled tyre steel fibres (RTSFs) compared to the same amount of manufactured steel fibres (MSFs). The effectiveness of concrete reinforcement with RTSFs was analysed using the fracture mechanics parameters of cementitious composites. Rheological tests, residual flexural tensile strength tests, work of fracture measurements, toughness indices, examinations of the fibre distribution in the concrete, and SEM observations of the concrete fractures with fibres were performed. Determining the work of fracture and toughness indices was an innovative aspect of this paper. As the amount of RTSFs increased, a decrease in the consistency was observed, although the distribution of fibres in the concrete was uniform, as proven by the results of computer tomography tests. Concrete reinforced with RTSFs that is purified and refined during the recycling process might have better properties than concrete reinforced with the same amount of MSFs. The application of RTSFs in construction has environmental and economic benefits in addition to the strengthening of cementitious composites.

The effect of recycled tyre steel fibers on the properties of concrete

Abstract Steel fibers recovered from recycled tires were considered for use as reinforcement in concrete to improve the tensile properties of concrete as well as being an economically viable and environmentally friendly alternative. This paper investigates the effect of purified and non-purified recycled tire steel fiber in concrete with a constant fiber proportion of 30 kg m−3 to determine properties in fresh and hardened concrete. The results indicate that concrete with purified tire fibers have better tensile properties than those with non-purified tire fibers. Density, strength, and toughness significantly increase but workability tends to decrease when using recycled tire steel fiber as reinforcement in concrete.

Effect of recycled steel fibers on the mechanical strength and impact toughness of precast paving blocks

Owing to high density, concrete paving blocks (CPB) are highly brittle when subjected to occasional impact loads. Fractures in CPB create riding discomfort and increase maintenance costs. This issue demands the engineering design of CPB suitable for occasional dynamic loadings. Therefore, this study explores the effect of eco-friendly and cheap fiber recycled from scrape tire steel on the performance of paving blocks. For this purpose, several CPB batches were prepared and studied with the varying contents of recycled tire steel fiber (RTSF). The studied properties included density, water absorption, ultrasonic pulse velocity (UPV), compressive strength, flexural strength, and impact toughness. It was shown that RTSF caused nominal changes in the compressive strength of CPB. However, it was highly useful in enhancing the flexural strength and impact toughness of CPB. At 0.5% volume fraction RTSF, flexural strength and impact toughness of plain CPB were increased by 42% and 271%, respectively. RTSF incorporation can prolong the life of CPB pavements and can help in preserving riding comfort.

Static and impact mechanical properties of ferrocement slabs produced from green mortar

Ferrocement is a common type of reinforced mortar that can be produced in sections of relatively small thickness. The production of ferrocement as a sustainable building material with good mechanical properties has resulted in many advantages like; saving cement, reducing the consumption of raw materials, reducing the agglomeration of waste materials, and reducing the emission of greenhouse gases. Therefore, this research has focused on the production of sustainable (green) ferrocement slabs.The experimental work was divided into three main phases; the use of supplementary cementitious materials (metakaolin (MK) and slag (GBS)) as a partial replacement of cement was in the first phase. In the second phase, the limestone powder (LSP) was used as a partial substitute of sand by 20% and 30% in the mixes (M5 and M10) that gave the best performance. Moreover, the recycled steel fibers (RSF) were used by 0.3%, 0.6%, and 0.9% for reinforcing the best mix (MS4) obtained in this phase. The last phase has involved the production of ferrocement slabs and testing their properties.The results indicated that using MK, GBS, and LSP gave a good performance of mortar. The ferrocement slabs reinforced with steel wire welded mesh with a diameter "3 mm" showed an increase in modulus of rupture by 75% compared to slabs reinforced with that mesh of diameter "2 mm" and fibers ratio of 0.6%. The slabs reinforced with steel wire welded mesh with a diameter "2 mm" and fibers showed an increase in impact resistance of 18% compared with the slabs reinforced with that mesh of diameter "3 mm".

Development of reactive powder concrete with recycled tyre steel fiber

Reactive Powder Concrete (RPC) is a part of an ultra-high-strength concrete family. It has a dense matrix due to a very low water-cement ratio, which increases its brittleness. Therefore, RPC is produced with a high volume of fiber reinforcement to attain ductility and fire resistance. Unfortunately, new fibers are expensive and yield a high carbon footprint. The rise in the cost and carbon footprint of fiber-reinforced RPC can be controlled by using Recycled Steel Fibers (RSF) derived from scrap tyres. In this study experimental campaign is conducted to compare the mechanical performance of RPC with new steel fiber (NSF) and RSF. Performance of NSF and RSF is compared at 0%, 1%, 2%, 3% and 4% volume fractions. The studied properties are bond strength, compressive strength (CS), splitting-tensile strength (STS), flexural strength (FS), and ultrasonic pulse velocity (UPV). Testing results showed that 3% RSF improves the CS, STS, and FS of plain-RPC by 9%, 23% and 58%, respectively. RSF-RPC performs around 90% potential of equivalent NSF-RPC in all mechanical properties at the same volume of fiber. RSF has implications for a cheap and eco-friendly substitute for NSF. The optimum dosage of NSF and RSF is 2% considering maximum mechanical strength without a significant increase of the self-load.

Two-Stage Cementitious Composites Containing Recycled Steel Fibers

Two-Stage Cementitious Composites Containing Recycled Steel Fibers

Magnetic Alignment of Microsteel Fibers as Strategy for Reinforcing UHPFRC

The objective of this paper is to provide an insight into current basic research at ITE on the manufacturing process of resource-efficient components through the controlled, automated magnetic distribution and alignment of steel fibers in UHPFRC (Ultra-High Performance Fibre-Reinforced Concrete). The method for distributing and aligning steel fibers in UHPFRC is based on the physical phenomenon of magnetism. Since steel fibers are ferromagnetic, magnetic fields can selectively change their position in the fresh concrete and align them according to the force flow and the maxim "form follows force". The magnetic fiber alignment (MFA) process developed on this principle combines the capabilities of digital and automized component manufacturing with the potential of targeted fiber alignment to increase the material efficiency of UHPFRC. It is highlighted at four levels: UHPFRC
 At the material level, studies were conducted on the composite properties of different brand-new and recycled microsteel fibers (MSF), formwork designs suitable for the MFA process were developed, flux densities of different magnets were simulated with special software solutions and measured in practice, and an end effector was fabricated that was implemented on 3- and 6-axis kinematics. At the process level, the interaction of the main parameters of the MFA process was evaluated by visual analysis on transparent glucose syrup-based solutions, and series of specimens were analyzed by micro-CT scans. At the component level, centric tensile tests were performed on a wide variation of dog-bones to provide an assessment of the potential increase in tensile performance of UHPFRC by the MFA process. At an economic and environmental evaluation level, the results from the tensile tests were used to assess and quantify the potential savings from reducing the fiber content and using recycled steel fibers.

Sustainability of Using Recycled Steel Fibers in Concrete

Sustainability of Using Recycled Steel Fibers in Concrete

Retracted] Study on Seismic Performance of Recycled Steel Fibers Locally Reinforced Cruciform Concrete Frame Beam‐Column Joint

At present, concrete frame structures are widely used, and the frame beam‐column joints are the key parts of the whole frame in seismic resistance. In previous studies, recycled steel fiber‐reinforced concrete is a new type of environment‐friendly reinforcement material, which can also be widely used in the construction industry. Therefore, in this paper, MTS electrohydraulic servo loading systems were used to carry out low‐cycle reciprocating cyclic loading tests to study the seismic performance of five 1/2 scale cruciform concrete frame beam‐column joint specimens with plain concrete, normal steel fiber‐reinforced concrete, and three recycled steel fiber‐reinforced concrete with different fiber contents in the joint core area. The results show that the addition of normal steel fibers can improve the bearing capacity, ductility, energy dissipation capacity, and shear strength of concrete frame joint specimens and delay the stiffness degradation of joint specimens, recycled steel fibers can improve the seismic performance of the cruciform concrete frame joints better than normal steel fibers, and the seismic performance increases gradually with the increases of volume ratio of recycled steel fibers. Moreover, with the recycled steel fiber content from 0.5% to 1.0% and then to 1.5%, the increased amplitude of the seismic performance of joint specimens increases. Considering the reinforcing effect of recycled steel fibers on concrete matrix and based on the design formula of shear capacity of reinforced concrete joints, the design formulas of shear capacity of recycled steel fiber‐reinforced concrete beam‐column joints were established by using the statistical analysis method and the baroclinic rod‐truss model, and the calculation results were in good agreement with the test results. This study can provide references for seismic performance research of steel fiber‐reinforced beam‐column joints and the recycling of steel wire from waste tires.

Fundamental Understanding of the Mechanical and Post- Cracking Behaviour of Ultra-High Performance Mortar with Recycled Steel Fibers

Fundamental Understanding of the Mechanical and Post- Cracking Behaviour of Ultra-High Performance Mortar with Recycled Steel Fibers

Performance of Manufactured and Recycled Steel Fibres in Restraining Concrete Plastic Shrinkage Cracks

Performance of Manufactured and Recycled Steel Fibres in Restraining Concrete Plastic Shrinkage Cracks

Mechanical performance of alkali-activatedconcrete reinforced with recycled tire steel fibers

Alkali-activated/geopolymer composites have attracted interest of the research community in recent years. The popularity of alkali-activated composites is backed by the global pressure towards producing environmentally friendly construction materials and contributing to the effort of reducing the carbon dioxide footprint associated with ordinary Portland cement production. Various by-product materials (e.g., slag, fly ash and red mud) or natural resources (e.g., metakaolin) were utilized for producing alkali-activated concrete.Previous research conducted on various alkali-activated composites have shown satisfactory mechanical properties. The addition of manufactured steel fibers (MSF) to alkali-activated concrete mixtures have also been commonly used for improving its mechanical properties. Utilizing recycled tire steel fibers (RSF) from post-consumer tires, instead of MSF, have the potential to reduce costs and positively contribute to sustainability by reducing the CO2 emissions generated from manufacturing industrial steel fibers.Therefore, this research is investigating the role of RSF dosage on alkali-activated concretes mechanical properties. The experimental program included synthesis of metakaolin-fly ash based alkali-activated concrete specimens with various percentages of RSF. The performance of the RSF mixes was also compared against a mix with MSF. The prepared specimens were tested for the compressive stress–strain behavior, bond-slip relationship and residual compressive strength after exposure to elevated temperatures. Although the addition of RSF slightly influenced the compressive strength, it significantly enhanced the strain capacity at peak strength. The addition of RSF also reduced the deterioration in compressive strength after exposure to elevated temperatures.

Enhancing the Static and Dynamic Properties of Fly Ash-Slag Based Strain-Hardening Geopolymer Composites Using Recycled Tyre Steel Fibres

Enhancing the Static and Dynamic Properties of Fly Ash-Slag Based Strain-Hardening Geopolymer Composites Using Recycled Tyre Steel Fibres

Various recycled steel fiber effect on mechanical properties of recycled aggregate concrete

PurposeThe current study mainly focuses on the effect of varying diameter recycled steel fibers (RSF) on mechanical properties of concrete prepared with 25 and 50% of recycled coarse aggregate (RCA) as well as 100% natural aggregate (NA). Two types of RSF with 0.84 mm and 1.24 mm diameter having 30 mm length were incorporated into normal and recycled aggregate concrete (RAC).Design/methodology/approachThe fresh behavior, compressive, splitting tensile, flexural strengths and modulus of elasticity of all the mixes were investigated to evaluate the mechanical properties of RACs. In addition, specimen crack and testing co-relation were analyzed to evaluate fiber response in the RAC.FindingsAccording to the experimental results, it was observed that mechanical properties decreased with the increment replacement of NA by RCA. However, the RSF greatly improves the mechanical properties of both normal concrete and RACs. Moreover, mixes containing 1.24 mm diameter RSF had a more significant positive impact on mechanical properties than mixes containing 0.84 mm diameter RSF. The 0.84 mm and 1.24 mm RSF addition improved the mixes' compressive, splitting tensile and flexural strength by 10%–19%, 19%–30% and 3%–11%, respectively when compared to the null fiber mix. Therefore, based on the mechanical properties, the 1.24 mm diameter of RSF with 25% replacement of RCA was obtained as an optimum solution in terms of performance improvement, environmental benefit and economic cost.Practical implicationsThe practice of RCA in construction is a long-term strategy for reducing natural resource extraction and the negative ecological impact of waste concrete.Originality/valueThis is the first study on the effects of varying size (0.84 mm and 1.24 mm diameter) RSF on the mechanical properties of RAC. Additionally, varying sizes of RSF and silica fume added a new dimension to the RAC.

In-plane cyclic behaviour of RC frames strengthened with composite sandwich panels

This paper presents an experimental study about the development of a sustainable and multifunctional composite sandwich panel for the rehabilitation of reinforced concrete (RC) buildings from the 1960s to the mid-1980s. For this purpose, the cyclic behaviour of representative RC frames was assessed by performing in-plane quasi-static cyclic tests on three different specimens: (i) a bare RC frame (individual behaviour of the frame); (ii) an RC frame with masonry infill wall (representative of target buildings); and (iii) an RC frame strengthened with an innovative sandwich panel formed by outer wythes in recycled steel fibre reinforced micro-concrete and polystyrene core layer. The results show that, in comparison with the traditional masonry infill wall solution, the proposed rehabilitation solution significantly improved the cyclic performance of the RC frame, reaching higher levels of load carrying capacity (395% vs. 349% increase) and energy dissipation (700% vs. 524% increase). Moreover, the sandwich panel has maintained its structural integrity with low level of damage in its internal load-bearing layer for high values of lateral drift (up to 2.1%).

Laboratory Tests of Concrete Beams Reinforced with Recycled Steel Fibres and Steel Bars.

This paper explores the possibility of the partial replacement of the longitudinal reinforcement in reinforced concrete (RC) beams with recycled steel fibres (RSF). Testing was focused on the contribution of two volume ratios of the RSF—0.5%, 1.0%. Basic compression and flexural tensile tests were performed to evaluate the effectiveness of the fibres following current standards. Additionally, the full-scale beams with and without conventional reinforcement were subjected to four-point bending tests. The results indicate that RSF improved the load-bearing capacity of the RC beams. Cooperation of RSF with the steel bars in carrying loads was proved. Findings from the Digital Image Correlation (DIC) revealed no impact on the cracking pattern of the RC beams.

Technical and environmental potentialities of recycled steel fiber reinforced concrete for structural applications

The use of recycled materials and industrial by-products as sustainable constituents of cement-based materials could be an environmentally and technically promising solution for application to structural elements. In the present work, the technical and environmental impact of using recycled steel fibers as an alternative to industrial steel fibers for concrete reinforcement was assessed at material level. Numerical simulations were performed to derive the post-cracking constitutive laws of the developed Recycled Steel Fiber Reinforced Concrete (RSFRC) and Industrial Steel Fiber Reinforced Concrete (ISFRC) by inverse analysis of experimental results obtained from three-point notched beam bending tests (3PNBBT), round panel tests supported in three points (RPT-3ps) and double edge wedge splitting tests (DEWST). These simulations were able of fitting with high accuracy the experimental results and consequently to derive the tensile stress-crack width relationships of RSFRC and ISFRC that was used to numerically simulate the bending response of a T-cross section steel RSFRC beam failing in shear.The environmental impact of the incorporation of RSF in concrete in comparison with ISFRC was evaluated using Life Cycle Assessment methodology. The reduction of the environmental impact of the production of RSFRC compared to ISFRC with the same concrete strength class is demonstrated.