Use Of Fiber Reinforced Concrete Research Articles

ОБ ОПЫТЕ И ПЕРСПЕКТИВАХ ПРИМЕНЕНИЯ ТЕХНОЛОГИЙ ПРОХОЖДЕНИЯ ВЕРТИКАЛЬНЫХ СТВОЛОВ В УКРАИНЕ

Purpose. Analysis of production experience, scientific and technical developments and assessment of the prospects for the application and development of technologies for the construction of vertical shafts in Ukraine in the context of the need to restore the coal mining industry to preserve the energy independence of the state. Methodology. The methods of analysis of the accumulated production experience of shaft sinking in Ukraine, in the post-Soviet space and in the leading mining countries, as well as scientific and technical literature were used. Results. The classification of technologies and methods of vertical shaft sinking is considered and supplemented, technological schemes and equipment used and promising for Ukraine for the construction of shafts by conventional and special methods are analyzed, the production experience of the Donetskshakhtoprokhodka and Spetsshakhtobureniie trusts is generalized from the point of view of applicability in the construction of shafts of block No. 12 of PJSC Shakhtopravlenie Pokrovskoe”. The possibility of using a modified parallel technological scheme of shaft sinking has been substantiated. The prospects of mechanized shaft sinking in Ukraine – by drilling and with the use of shaft-sinking machines – are assessed. The characteristics of the conditions for the construction and operation of shaft lining, the final element of the shaft, as a structure and functional complex are given. Variants of combined lining, including those with the use of fiber-reinforced concrete, are considered. Scientific novelty. The results of the analysis of technological schemes and methods of vertical shafts sinking, accumulated production experience and scientific and technical developments are generalized, trends and prospects for the development of technologies are considered. Practical value. The analysis of technological schemes and methods of sinking vertical shafts was carried out on the basis of domestic and foreign production experience. Key words: vertical shaft, sinking technology, shaft sinking flow chart, drilling and blasting operations, shafts drilling, shaft-sinking machine.

Experimental Investigation on Fibre Reinforced Concrete Using Waste Plastics and Different Mineral Admixtures

Use of Fibre Reinforced Concrete (FRC) is one of the ways of overcoming the low tensile strength of concrete. Both organic and inorganic fibers can be made use in the production of FRC. On the other hand, the use of waste plastic is causing a serious environmental pollution since the plastic don’t deteriorate. Such waste plastic can be reused in the form of fibres to produce waste plastic FRC. Further, flyash, microsilica and redmud are another industrial waste materials adding to environmental pollution. These waste materials are having cementatious properties and can be used along with waste plastic fibres in concrete to reduce their detrimental effect on mother earth. Therefore in this paper an attempt is made to assess the suitability of waste plastic FRC for construction purposes when different percentages of flyash, microsilica and redmud are introduced. Various strength properties such as Compression, Tension, Flexure and Impact are studied along with workability characteristics. Based on the obtained results the industrial wastes such as flyash, microsilica, redmud and also waste plastic fibres can be used in the production waste plastic fibre reinforced concrete composite material.

ФИБРОБЕТОН. ПЕРСПЕКТИВЫ РАЗВИТИЯ И ПРИМЕНЕНИЯ

In the article, the authors present the main features and advantages of using fiber-reinforced concrete in the manufacture of various building structures. The features preventing the wider use of fiber-reinforced concrete are given. An analysis of the influence of various factors in the manufacture of structures on the mechanical properties of fiber-reinforced concrete made it possible to evaluate the differences in its operation in the stretched and compressed zone of structures. Recommendations are given on improving the mechanical characteristics of fiber-reinforced concrete and an analysis of the work of other researchers on this issue.

Application of fibro concrete mixture at construction of bases and coatings automobile roads

Fiber concrete – concrete with the inclusion of fibers (fibers) from inorganic or organic materials (steel, glass, polyethylene, etc.). Fiber concrete reinforced with fibers, has a high resistance to shock loads and abrasion, well perceives tensile stresses. An important issue in the preparation of fiber-reinforced concrete is its mobility. One of the difficulties encountered in practice when working with fiber reinforced concrete, reinforced by steel wire, is its lack of workability. To ensure the required workability of the concrete mixture and to achieve a uniform distribution of wire segments in it, it is necessary, in addition to the wire segments and the core, to control their ratio. Tests of fiber reinforced concrete showed that the larger the aggregate size, the lower the flexural strength. The use of granite crushed stone with a size of 20 mm allows to obtain better results than when using crushed stone from gravel or limestone. While in ordinary concrete, the quality of rubble increases the flexural strength, in fibrous concrete, the flexural strength increases the effectiveness of the fibers. The use of fiber-reinforced concrete in the construction of road pavements is determined by technical and economic efficiency, which is caused by the most complete use of the positive properties of fiber-reinforced concrete as compared to conventional cement concrete. Fiber concrete has several advantages compared to conventional cement concrete: a) increased crack resistance, impact toughness, wear, – frost and fire resistance, thermodynamic resistance, etc.; b) the possibility of use without conventional rod or wire steel reinforcement; c) reducing labor costs for reinforcement works, increasing the degree of mechanization and automation of road and airfield pavement construction. In recent years, the use of concrete (cement concrete) foundations and pavements of highways and industrial sites has begun to revive in road construction. The use of various types of cement concrete and fiber concrete (steel fiber concrete, glass fiber concrete, fiber concrete on synthetic fiber) will increase the durability of road and airfield pavements, increasing resistance to shock loads, abrasion and tensile stresses.

Investigating the Effects of Fiber Reinforced Concrete on the Performance of End-Zone of Pre-Stressed Beams.

This paper presents the results of the behavior of end zone of post-tensioned (PT) beams made of fiber reinforced concrete (FRC). The principal aim of using FRC was to enhance the ductility and post-cracking behavior of end-zone of post-tensioned beams. A stronger and tougher end-zone of PT-beams is necessary when it is subjected to dynamic loading. Post-tensioned (PT) beams are typically used for the construction of bridges and industrial buildings, which are often subjected to vibrations and cyclic loading. Pre-mature cracking of the end zone (EZ) of a PT-beam is considered the type of problem that may cause the structural collapse. In this research program, polyvinyl alcohol (PVA) and copper-coated steel (CCS) fibers were used in concrete for improving the EZ performance of PT-beams. The use of FRC caused a 50% reduction in the shear reinforcement within the end zone of the PT-beam, which also avoided the congestion of steel in the end zone. Hence, the concrete was placed homogeneously, and smooth finished surfaces of the beams were obtained. FRC controlled the bursting of the end zone during the transfer of the full pre-stress force, and approximately 25% increment in the strain energy of the end zone was observed, which was also found efficient in strain diminution along the length of the beam.

Normality of Post-Crack Performance Data for Fiber-Reinforced Concrete

Abstract With the increasing use of fiber-reinforced concrete (FRC) for civil infrastructure projects, challenges have become apparent in quality control (QC) testing for this material. The most common problem is high variability, but a secondary problem is identifying the most appropriate probability distribution function (PDF) for post-crack performance data. This article has examined the second of these challenges. It is widely assumed that the normal PDF most reliably describes the distribution of outcomes for many stochastic processes. Most of the conventions underlying probabilistic modeling of engineering processes are therefore predicated upon a normal distribution of material properties. However, evidence exists that other functions, such as the Weibull, lognormal, or gamma distribution functions, may be more appropriate representations of the distribution of test results for some post-crack performance parameters related to FRC, such as fatigue life. The present investigation has examined a large body of QC data to identify the most reliable function describing the probability distribution of post-crack performance of FRC as obtained from ASTM C1550, Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel), and ASTM C1609/C1609M, Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete (Using Beam with Third-Point Loading). The results demonstrate that the normal and lognormal functions model the distribution of post-crack performance data obtained for FRC equally well. However, the normal function produces the best fit for data assembled from multiple specimen sets, thereby confirming the validity of the central limit theorem. Moreover, a derivative of the normal function also reliably predicts the distribution of variances for data sets comprising a small number of replicate test results.

Seismic damage performance of the steel fiber reinforced face slab in the concrete-faced rockfill dam

Damage and cracks in concrete face slabs threaten the safety of concrete-faced rockfill dams (CFRDs). The use of fiber-reinforced concrete is an effective engineering measure that prevents the formation of cracks in face slabs. However, there is little research regarding steel fiber reinforced CFRDs. In this study, dynamic elasto-plastic finite analyses were performed to investigate the performance of reinforced concrete (RC) and steel fiber reinforced concrete (SFRC) face slabs for a two-dimensional 250 m high CFRD. A widely used plastic damage model was modified to capture the influence of the fiber content on the behavior of concrete. Additionally, the rockfill material was described using a generalized plasticity model. The interfaces between the face slabs and the rockfill were modeled using a three-dimensional state-dependent elasto-plastic model. The damage development and equivalent crack width in RC and SFRC face slabs were investigated under varying intensities of ground motions. The results indicate that the damage to the SFRC face slab is much less than that of the RC face slab. The extent of the damage decreases by 23%, the range of damage decreases by 79%, and the maximum equivalent crack width decreases by 32%. The SFRC can greatly reduce the earthquake-induced damage to the face slab. Thus, SFRC face slabs can be used to improve the anti-seismic capabilities of CFRDs in meizoseismal areas.

Mechanics and failure characteristics of hybrid fiber-reinforced concrete (HyFRC) composites with longitudinal steel reinforcement

While the properties of hybrid fiber-reinforced concrete (HyFRC) have been well-reported in the literature, the behavior of reinforced HyFRC (i.e., HyFRC with embedded steel rebar) is less understood. This paper investigates the mechanics and failure characteristics of reinforced HyFRC under direct tension. Samples with a low longitudinal steel reinforcement ratio were studied to evaluate the feasibility of reducing rebar congestion in structural applications through the use of fiber-reinforced concrete. Although reinforced HyFRC forms multiple cracking sites when loaded, rebar strain and HyFRC crack opening are generally concentrated at a single location under post-yield displacements. The onset of rebar plastic deformation and the exhaustion of fibers’ bridging load capacity are coincident events at a dominant crack. For a cracked reinforced HyFRC section to strengthen, the magnitude of load resistance increase from strain hardening rebar must exceed the magnitude of load resistance decrease from fiber pull-out processes. Comparisons are made with studies reported in the literature to demonstrate how longitudinal reinforcement ratio and fiber type influence cracking behavior and ultimate strain capacity. The research presented herein has far-reaching impacts on the structural design of all types of reinforced fiber-reinforced concrete materials detailed for a ductile response under large displacements.

The effect of age and testing method on the added fracture energy of fibre reinforced concrete

The use of Fibre Reinforced Concrete (FRC) is widely accepted in the tunnelling industry. The generally accepted method to determine the material parameters of FRC is the standard 3-point beam test. The effect of age can be relevant for tunnels, because these structures are usually designed for life cycles over 100 years. In this paper the test results of FRC specimens with different fibres using different testing methods (beam and square panel) at different ages will be presented. FRC changes its properties over time in case of both fibre types. The post crack capacity of steel FRC increases in beam tests, while it decreases in panel tests, which yields the conclusion that steel fibres work better at smaller crack width. This changes only a small amount over time. The energy absorption measured from panel tests reduces in case of steel fibre, but stays at a constant level for synthetic fibre.

Fiber Reinforced Concrete for repairing and strengthening RC structures: some recent advancements

Enhancement of seismic behaviour of existing structures, both masonry or reinforced concrete, is a key issue for future technical activities in many Western Countries, since construction of new buildings has decreased in favour of an increased attention to the structural rehabilitation and re-use of existing buildings. The development of innovative repairing, strengthening, and retrofitting techniques is, therefore, a crucial topic to improve the structural safety of existent constructions. Fibre Reinforced Concrete (FRC) may now be particularly efficient in these cases, due to the high toughness provided by fibres that may reduce or avoid the use of conventional reinforcement.This paper presents the results of two experimental research studies carried out at the University of Brescia, concerning the use of FRC as the principal reinforcing material. The first study aims at assessing the structural response, under cyclic horizontal loads, of a full scale (1:1) Unreinforced Masonry (URM) building retrofitted with Steel Fibre Reinforced Mortar (SFRM) as external plaster. The second study concerns the seismic retrofitting of a scaled (1:4) reinforced concrete bridge pier by means of a High Performance Fibre Reinforced Concrete (HPFRC) jacketing. In both cases, repair material is applied in thin layers, due to the high mechanical properties compared to those of the respective substrates, with the addition of a limited amount of traditional reinforcement, placed only on the most stressed sections.

Application of Fiber-reinforced Concrete in Tram Track Foundation

The use of polymer fiber-reinforced concrete is one of the most promising trends in tram track development. It was first successfully used as tram track foundation in 2010-2011. The analysis of such structures has shown a number of their advantages: reduced construction time, economic benefits in terms of reducing cost and labour, and construction technology simplification. Mathematical modelling of structure strength characteristics and field testing specifying the model parameters are required for the subsequent use of fiber-reinforced concrete as tram track foundation.

Sustainability based-approach to determine the concrete type and reinforcement configuration of TBM tunnels linings. Case study: Extension line to Barcelona Airport T1

Fibre-reinforced concrete (FRC) is a suitable alternative to the traditional reinforced concrete used in the manufacture of precast segments used to line tunnels excavated with a tunnel boring machine (TBM). Moreover, its use as a structural material has been approved by several national codes and by the current fib Model Code (2010). The use of FRC in segmental linings confers several technical and economic advantages, evidenced by the fact that structural fibres have been used to partially or entirely replace reinforcing bars in many TBM tunnels built over the past 20years or currently under construction. FRC could also have been used in other tunnels, which are currently in the planning stage or under construction. However, despite its technical suitability and approval in current codes, the use of FRC was not possible in some cases. The impediment has sometimes been an incomplete understanding of the structural behaviour of the material, but a more general motive has been that comparisons of materials have taken into account only direct material costs and have not considered indirect costs or social and environmental factors. The aim of the present research is to develop a method for analysing the sustainability of different concrete and reinforcement configurations for segmental linings of TBM tunnels using the MIVES method (a multi-criteria decision making approach for assessing sustainability). This MCDM method allows minimising subjectivity in decision making while integrating economic, environmental and social factors. The model has been used to assess the sustainability of different alternatives proposed for manufacturing the segmental tunnel lining for the extension of the rail line of Ferrocarrils de la Generalitat de Catalunya (FGC) to Terminal 1 of El Prat Airport in Barcelona.

Modelling the behaviour of steel fibre reinforced concrete using a discrete strong discontinuity approach

The use of Fibre Reinforced Concrete (FRC) is gradually wide-spreading due to the significant advantages relatively to Normal Concrete (NC). In the case of steel fibres, the quasi-brittle behaviour of plain concrete structures can be modified into an enhanced ductile behaviour as a direct result of this addition. Since the mechanical properties of both FRC and NC can be significantly different, this work aims at developing a finite element formulation to specifically address the simulation of the behaviour of FRC members up to failure. For this purpose, the Conforming Generalised Strong Discontinuity Approach (CGSDA) is adopted with steel fibres explicitly introduced in the finite element mesh. The resulting formulation has the following main characteristics: (i) variational consistency; (ii) fibre elements automatically considered regardless of the presence of cracks; and (iii) no additional degrees of freedom are required. The proposed formulation is validated using experimental results from tests conducted with different dosages of steel fibres.

Concrete-Filled Steel Tube Columns Encased with Thin Precast Concrete

An experimental study was performed to investigate the axial-flexural load-carrying capacity of concrete-filled steel tube columns encased with thin precast concrete (PC). Six eccentrically loaded columns and one concentrically loaded column were tested. To prevent the premature failure of the concrete encasement, various reinforcement details such as studs, steel fiber, welded wire mesh, and cross ties were used. The maximum axial loads of the specimens agreed with the strengths predicted by current design codes, although in some specimens, the load-carrying capacity decreased immediately after the peak strength owing to early spalling of the concrete encasement. On the basis of the test results, the use of fiber-reinforced concrete is recommended to increase the ductility of columns by restraining the spalling of the concrete encasement.

Ductility Enhancement of High Strength RC Columns Using Steel Fiber Reinforced Concrete (SFRC)

The principal aim of this research is to improve the seismic performance of high strength concrete (HSC) reinforced columns using fiber reinforced concrete (FRC) by mixing steel fiber into the concrete. Two reinforced concrete columns 200mm x 300mm in cross-section with a height of 1250 mm were tested under cyclic lateral loading. The first specimen was casted using high strength concrete of 100 MPa and the second specimens were also casted using similar concrete strength but the steel fiber of 0.5% by volume was added to the concrete in the plastic hinge region. Both columns were subjected to lateral cyclic load until the failure occurs. The test results showed that the use of FRC in the plastic hinge region could significantly improve column displacement ductility. The maximum drift at column failure at 4.5% for non-ductile column could increase to 8% in FRC column. It is evident that the cracks in FRC column are much smaller properly spread in the plastic hinge region and hence the plastic hinge could be able to rotate without lateral strength being compromised. In FRC column, concrete spalling was observed in a very high drift (7%) and bar buckling occurred at around 8% drift whilst in HSC column concrete spalling and bar buckling occurred at only 3.5% and 4% drift respectively. It was evident that the use of steel fiber in HSC columns could significantly improve seismic performance of the column.

Seismic Behavior of Synthetic Fiber-Reinforced Circular Columns

Ductile behavior and high energy-dissipation ability are two essential properties for a reinforced concrete column part of a structure in a moderate to high seismic region. Concrete design codes ensure ductile behavior of columns by setting a requirement for a minimum amount of transverse steel reinforcement. Studies have shown, however, that use of fiber-reinforced concrete (FRC) can enhance the post-peak behavior and hence, the ductility and energy dissipation ability of concrete columns subjected to axial force and bending moment. Therefore, the inclusion of macro fibers in the concrete mixture, combined with a reduced amount of lateral reinforcement, can be an alternative to the conventional lateral reinforcement required by the codes. Moreover, the higher resistance to crack growth and the excellent durability of FRC over nonfibrous concrete can result in a higher cost-effective value. In this regard, tests on large-scale circular synthetic fiber-reinforced concrete (SNFRC) columns subjected to a combined constant axial load and reversed cyclic flexure simulating earthquake loading were carried out. The aim of this test program was to examine the influence of adding synthetic fibers to the concrete mixture on the behavior of normal-strength concrete (NSC) columns. The results show that, in terms of ductility and energy dissipation, SNFRC columns outperformed NSC columns. The results also show that the larger the amount of lateral reinforcement the smaller the influence of the fibers on the column's behavior. Based on the test results, the amount of confinement steel required by concrete design codes could be reduced when SNFRC is used.

An Experimental Study on the use of Fiber-Reinforced Concrete in Bridge Approach Slabs

Fiber-reinforced concrete is well known for crack control by bridging cracks in the concrete. Short, discontinuous fibers are added into plain concrete to provide post-cracking ductility to the fiber-reinforced concrete. Although fiber-reinforced concrete has been used in various civil engineering applications, the practical application of fiber-reinforced concrete in bridge approach slabs is rarely found. In this paper, steel fibers, serving as macro-fibers, and polyvinyl alcohol fibers, serving as micro-fibers, were added to the approach slab concrete for crack control purpose. This paper describes flexural tests of four fiber-reinforced concrete beams and loading test of a full scale fiber-reinforced concrete approach slab. Results from the flexural beam test show that the addition of fibers greatly improves the fracture toughness of the concrete. Results from the loading test show that the overall performance of the slab is comparable to conventional reinforced concrete approach slabs, and the surface cracks on the slab due to negative moment can be adequately controlled by the addition of steel and polyvinyl alcohol fibers into concrete, even without top reinforcement mat.

Seismic Performance Enhancement of Non-Ductile RC Columns Using Steel Fiber Reinforced Concrete (SFRC)

The principal aim of this research is to improve the seismic performance of non-ductile reinforced columns using fiber reinforced concrete (FRC) by mixing steel fiber into the concrete. Two reinforced concrete columns 200mm x 300mm in cross-section with a height of 1250 mm were tested under cyclic lateral loading. The first specimen was casted using normal strength concrete of 24 MPa and the second specimens were also casted using similar concrete with similar strength but the steel fiber of 1% was added to the concrete in the plastic hinge region. The axial load for all specimens was 300 kN and kept constant during the test. The test results showed that the use of FRC in the plastic hinge region could significantly improve column displacement ductility. The maximum drift at lateral strength loss at 3.7% for non-ductile column could increase to 6% in FRC column. It is evident that the cracks in FRC column are much smaller and more widely spread in the plastic hinge region and hence the plastic hinge could be able to rotate without lateral strength being compromised. In FRC column, concrete spalling was observed in a very high drift (5%) and bar buckling occurred at around 6% drift whilst in non-ductile column concrete spalling and bar buckling occurred at 2.5% and 3% drift respectively. It was evident that the use of steel fiber in non-ductile columns could significantly improve seismic performance of the column.

Flexural Cracks in Fiber-Reinforced Concrete Beams with Fiber-Reinforced Polymer Reinforcing Bars

The use of fiber-reinforced polymer (FRP) in reinforced concrete results in excessive crack widths under service due to its generally low elastic modulus and poor bond characteristics. This study proposes that fiber-reinforced concrete (FRC) be used with FRP to reduce crack widths. Sixteen beams are tested under four-point bending with either Grade 420 (Grade 60) steel or FRP reinforcing bars, and either plain concrete or FRC. A modified Gergely-Lutz model was applied to the measured crack widths to calculate bond coefficients that were used to quantify the effectiveness of FRC in reducing crack widths. Results showed that FRC significantly reduced maximum crack widths in beams with FRP reinforcing bars. However, FRC was found to have little influence on crack width in beams with steel reinforcing bars. The use of FRC was also found to reduce bond coefficient on the order of 45-75% for FRP-reinforced beams, compared to 1-15% for steel-reinforced beams.

Fibre reinforced concrete: new design perspectives

Although the use of Fibre Reinforced Concrete (FRC) for structural applications is continuously increasing, it is still limited with respect to its potentials, mainly due to the lack of International Building Codes for FRC structural elements. Within fib (Federation Internationale du Beton), the Special Activity Group 5 is preparing a New fib Model Code that aims to update the previous CEB-FIP Model Code 90, published in 1993, that can be considered as the reference document for Eurocode 2. The New Model Code includes several innovations and addresses among other topics, new materials for structural design. In this respect, FRC will be introduced. The Technical Groups fib TG 8.3 “Fibre reinforced concrete” and fib TG 8.6 “Ultra high performance FRC” are preparing some sections of the New Model Code, including regular and high performance FRC. This paper aims to briefly explain the main concepts behind the structural rules for FRC structural design.