Types Of Fiber-reinforced Concrete Research Articles

Mechanical properties of steel fiber RPC, basalt fiber RPC, and hybrid fiber RPC: A review of research progress

AbstractBased on an analysis of the literature on fiber‐reinforced concrete (FRC), especially the development and formation of various types of FRC combined with reactive powder concrete (RPC) in recent years, this paper systematically expounds the research progress, particularly the mechanical properties, of steel fiber RPC, basalt fiber RPC and hybrid fiber RPC. This paper concludes the improvement in the mechanical properties of RPC under common curing methods, elaborates on the influence of steel fiber on the compressive, tensile, and flexural strength of RPC, and outlines the principle of fiber enhancing the mechanical properties of RPC. Additionally, it discusses the research progress in basalt FRC, and further examines the impact of basalt fiber on the mechanical properties of RPC. Referring to the research on single fiber reinforced RPC, the mechanical properties of hybrid fiber RPC are analyzed and summarized; based on the characteristics of steel fiber and basalt fiber, research on steel‐basalt hybrid fiber RPC is proposed.

Experimental Study of Innovative FRC Dome-Shaped Structures with Industrial, Recycled, and Alternative Reinforcing under Compressive Load

Arc concrete structures are aesthetic and suitable for buildings with large spans. Within the framework of this research, fiber-reinforced concrete (FRC) dome-shaped structures were studied in a lab, analyzing mechanical performance via strength, deformation, and failure mode. The studied FRC was elaborated with industrial, recycled, and alternative fibers. The mold used for producing the dome specimens was made up of two parts in order to favor extraction. This study considered 21 dome samples reinforced with fibers and one control, with replication for those with atypical behavior. The results show that the load-displacement behavior of dome-shaped elements increases with the incorporation of fibers, which depends on the fiber dose and the material. Moreover, the efficiency analysis proved that specimens with low fiber content (20 and 2 kg/m3) have the best strength-reinforcement relation. The recycled and alternative fibers exhibit good mechanical performance and ductility. The main contribution of this research is a study of the scope and limitations of different types of FRC as the only reinforcement in arched structures.

Explainable machine learning model for predicting punching shear strength of FRC flat slabs

Reinforced concrete slabs are vulnerable to punching shear failure at the slab-column joint, which can initiate catastrophic progressive collapse. The addition of steel fibers in the concrete matrix has emerged as an effective strategy to mitigate such progressive failure. However, the effects of the diverse mixture proportions of the concrete matrix with different types and dosages of fibers have made the accurate prediction of the punching shear strength (PSS) of the fiber-reinforced concrete (FRC) flat slabs a complex task, where the existing mechanical models have several limitations. Therefore, this study proposes an explainable XGBoost model for predicting PSS of flat slabs made with different types of FRC based on a newly established comprehensive database of 251 flat slabs including normal strength FRC slabs, high-performance FRC slabs, and ultra-high-performance FRC slabs. A customized procedure was proposed to establish the XGBoost model considering data preparation, feature selection, hyperparameter tuning and model validation. The performance of the XGBoost model was then compared with that of existing mechanical models. Finally, sensitivity analysis and SHapley Additive exPlanations (SHAP) analysis were applied to identify the most influential parameters on the prediction of PSS. Results show that the proposed feature selection method is effective in identifying six influential parameters from the eleven parameters related to the PSS of FRC flat slabs. The developed XGBoost model yielded highest prediction accuracy and lowest variation, which outperformed the other mechanical models. Sensitivity analysis also indicated similar trends of parameters in both the XGBoost model and the mechanical models. The PSS of FRC flat slabs can be improved by increasing the concrete compressive strength, reinforcement ratio, and fiber volume, and by decreasing the column width-to-depth ratio, water-to-binder ratio, and aggregate size ratio. The proposed XGBoost model could enhance the understanding of PSS of FRC flat slabs and guide future pertinent design code provisions.

Comparing Mechanical Characterization of Carbon, Kevlar, and Hybrid-Fiber-Reinforced Concrete under Quasistatic and Dynamic Loadings

Concrete is a brittle material due to its poor tensile strength; consequently, concrete tends to crack or peel under an applied external load. Previous studies have investigated the effect of incorporating fiber into concrete, which can improve its tensile strength. In this study, the static and dynamic mechanical characteristics of three types of fiber-reinforced concrete (FRC) were examined: carbon-fiber-reinforced concrete (CFRC); Kevlar-fiber-reinforced concrete (KFRC); and a combination of both, known as carbon/Kevlar-hybrid-fiber-reinforced concrete (HFRC). This study created concrete specimens by pneumatically dispersing carbon and Kevlar fibers and mixing them with cement to comprise 1% of the weight. The mixture was then combined with aggregates and water to form the concrete specimens. When compared with the benchmark concrete specimens, it was found that the compressive strength of the CFRC, KFRC, and HFRC specimens increased by about 19% to 50%, the bending strength increase by about 8% to 32%, and the splitting strength increased by about 4% to 36%. Specifically, the HFRC made with the 24 mm carbon and Kevlar fibers displayed the most significant mechanical strength in a static state. Furthermore, the HFRC showed superior resistance to impact compared to the benchmark concrete specimens across various impact energies, with the 24 mm carbon and Kevlar fiber HFRC showing the highest resistance. The inclusion of fibers in the split Hopkinson pressure bar (SHPB) test demonstrated a notable increase in the maximum strength, particularly in the case of the 12 mm carbon fiber combined with the 24 mm Kevlar fiber in the HFRC specimen.

Fresh, mechanical, and durability properties of basalt fiber-reinforced concrete (BFRC): A review

Basalt fiber-reinforced concrete (BFRC) is relatively a new type of fiber-reinforced concrete, which has demonstrated good mechanical performance. Several types of fibers such as steel, glass, and carbon fibers, are used to improve the performance of plain concrete. However, basalt fibers (BF) are being considered superior to these because of their comparable mechanical strength, higher durability than glass fibers, lesser cost than carbon fibers, sustainability due to abundant raw material, and environment-friendly production process. Hence, the number of studies on BFRC are increasing over the years. This review paper covers the properties of BF and BFRC. The effects of BF length and dosage are discussed in detail in term of fresh, hardened, and durability properties of BFRC, followed by highlighting some areas for future research. It is concluded that BF can potentially replace the other conventional fibers which are being used in the industry.

Experimental Investigation on the Axial Compressive Behaviour of Cold-Formed Steel-Concrete Composite Columns Infilled with Various Types of Fibre-Reinforced Concrete

The exceptional structural strength and low cost of steel-concrete composite columns make them a popular choice for civil engineering structures. Numerous forms of composite columns, including steel tubes filled with concrete, have been produced recently in response to various construction situations. Cold-formed steel tubular columns with concrete filling have higher strength and ductility due to their capacity to withstand inner buckling and postpone outward buckling. The objective of this research is to determine the ductile and strength performance of composite columns containing various forms of fibre-reinforced concrete when subjected to axial compression. Several different kinds of fibre-reinforced concrete (FRC) are employed as additives in hollow steel columns, including steel FRC, carbon FRC, glass FRC, coir FRC, jute FRC, and sisal FRC. Axial compression tests were performed on 24 columns, including three hollow steel columns and 21 composite columns. Three distinct slenderness ratios were developed and used. Axial bearing capacity, compressive stress-strain curves, ductility, peak strain, axial shortening, and toughness were among the topics covered by the axial compression test. Experimental findings demonstrated that all conventional composite columns experienced failure through overall buckling, Local buckling and crushing of concrete infill, which was transformed into more ductile failure using fibre-reinforced concrete infills. The test results revealed that fibre-reinforced concrete-infilled steel columns outperformed conventional composite columns in terms of strength, ductility, and energy absorption capacity. The percentage increase in load-carrying capacity was observed as 203.88%, 193.48% and 190.03% when compared to hollow cold-formed steel tubular columns in medium, short and stub columns, respectively. Under assessment of stub, short, and medium columns, the load-strain plots demonstrated that the steel fibre-reinforced concrete in-filled columns performed well in terms of ductility. Localized buckling and crushing of the concrete infill caused the composite columns with low slenderness ratios to fail. In contrast, concrete-filled steel tube columns with higher slenderness ratios showed column failure through the overall buckling of the composite column.

Numerical Simulation of the Fracture Behavior of High-Performance Fiber-Reinforced Concrete by Using a Cohesive Crack-Based Inverse Analysis

Fiber-reinforced concrete (FRC) has become an alternative for structural applications due its outstanding mechanical properties. The appearance of new types of fibres and the fibre cocktails that can be configured by mixing them has created FRC that clearly exceeds the minimum mechanical properties required in the standards. Consequently, in order to take full advantage of the contribution of the fibres in construction projects, it is of interest to have constitutive models that simulate the behaviour of the materials. This study aimed to simulate the fracture behaviour of five types of FRC, three with steel fibres, one with a combination of two types of steel fibers, and one with a combination of polyolefin fibres and two types of steel fibres, by means of an inverse analysis based on the cohesive crack approach. The results of the numerical simulations defined the softening functions of each FRC formulation and have pointed out the synergies that are created through use of fibre cocktails. The information supplied can be of help to engineers in designing structures with high-performance FRC.

Assessment of the Post-Cracking Fatigue Behavior of Steel and Polyolefin Fiber-Reinforced Concrete.

Some types of fiber-reinforced concrete (FRC) such as steel fiber-reinforced concrete (SFRC) or polyolefin fiber-reinforced concrete (PFRC) are suitable for structural uses but there is still scarce knowledge regarding their flexural fatigue behavior. This study aimed to provide some insight into the matter by carrying out flexural fatigue tests in pre-cracked notched specimens that previously reached the Service Limit State (SLS) or the Ultimate Limit State (ULS). The fatigue cycles applied between 30% and 70% of the pre-crack load at 5 Hz until the collapse of the material or until 1,000,000 cycles were reached. The results showed that the fatigue life of PFRC both at SLS or ULS was remarkably higher than the correspondent of SFRC. The fracture surface analysis carried out found a linear relation between the fibers present in the fracture surface and the number of cycles that both SFRC and PFRC could bear.

A Comparison on Strength Parameters of Different Types of Fibre Reinforced Concrete

A Comparison on Strength Parameters of Different Types of Fibre Reinforced Concrete

Experimental investigation on chloride-ion penetration resistance of slag containing fiber-reinforced concrete under drying-wetting cycles

The corrosion of reinforcing steel is a major problem of concrete structures, particularly those exposed to chloride environment. In this study, slag was incorporated as cement replacement in various types of fiber-reinforced concrete, and the chloride penetration resistance of the concrete was investigated. The specimens were exposed to drying-wetting conditions and the chloride ion content was determined via potentiometric titration. The results show that the apparent chloride diffusion coefficient decreases with an increase in exposure time, following an exponential relationship. Slag has a positive effect on the chloride penetration resistance of the concrete, and an optimal dosage of slag exists. The effect of macrofibers on the resistance of concrete to chloride ion penetration depends on the macrofiber material; steel fibers can improve the chloride ion penetration resistance of concrete, whereas macrofibers made of polypropylene exacerbate chloride ion penetration. The effects of microfibers are related to its type and volume fraction: A lower volume fraction is favorable, whereas a higher volume fraction weakens the resistance of concrete against chloride-ion penetration.

New Procedure to Evaluate the Post-Crack Behavior of Fiber-Reinforced Concrete

This study attempted to identify the challenges in testing and characterization of the post-crack behavior of structural fiber-reinforced concrete (FRC) for use in pavements. The benefits and challenges associated with three different FRC testing methods, ASTM C1550, C1399, and C1609 were discussed and compared. Two new parameters, post-crack toughness, and post-crack performance (PCP) index were proposed to characterize the post-crack behavior of FRC. These parameters are a function of the fibers’ contribution and are minimally influenced by the properties of the non-fiber ingredients of concrete such as aggregates, cement, and water. A laboratory study conducted on 10 different types of FRCs validated the applicability of the two proposed new parameters. Transportation agencies can use the PCP index to shortlist effective fibers and post-crack toughness to determine fiber dosage. The study found that fibers with irregular cross-section or geometry and high lateral stiffness provide a high post-crack contribution.

Прочностные и теплофизические свойства бетона с полипропиленовой фиброй в условиях температурного режима стандартного пожара

The paper discusses the problems of protection of reinforced concrete tunnel structures from brittle (explosive) destruction of concrete tubbing lining of the tunnel. The relevance of the research is attributed to increasing pace of construction of deep-level tunnels. Fires in such facilities could be catastrophic, often resulting in massive loss of life and great material losses, and their suppression requires involvement of considerable forces and assets. During the construction and operation of road and subway tunnels, the protecting structures - reinforced concrete lining blocks have a higher moisture content, which in the event of fire in the early stages can lead to brittle failure of concrete tubing and the premature loss of their load-bearing capacity. To reduce the effects of brittle fracture of concrete in the protective layer of concrete structures anti-spall mesh is installed, or fire retardant coating is used which reduces the intensity of heating of concrete during fire. However, recent studies have shown that the most effective way of protecting against brittle fracture of concrete from the point of view of labor and material cost is the use of additives in the concrete mixture in the form of polypropylene fibers. Earlier, experiments were carried out in VNIIPO to determine the actual limits of fire resistance of tunnel tubing and the influence of polypropylene fibers additives in concrete mix on the likelihood of brittle fracture of concrete. However it seems impossible to assess the fire resistance of similar structures using numerical methods due to the lack of baseline data on the strength and thermo-physical properties of concrete with polypropylene fibers. To achieve this goal, studies were conducted of concrete strength under axial compression with the addition of polypropylene fibers in the amount of 1 kg/m 3 and experimental data of thermal characteristics of fiber-reinforced concrete at high temperatures were obtained. The paper presents the results of experiments on the samples of fiber concrete under axial compression when exposed to temperature in the range 20-800 °C. Graphics show the process of the strength change of concrete with and without additives during heating. Analytical dependencies for determination of strength of concrete under compression were obtained with two types of polypropylene fibers at high temperatures.A comparison of the strength properties of the investigated concrete mixtures was carried out. It was established experimentally that when using the polypropylene fibers, the strength characteristics of fiber-concrete are reduced on average by 16 %, compared to the concrete without fiber additives, both at normal and high temperatures. As a result of processing of the experimental data by regression analysis the analytical dependencies were obtained for determination of strength characteristics of concrete under axial compression with the addition of domestic and imported fibers when exposed to high temperatures. Experiments to determine the thermal properties of concrete with the addition of polypropylene fibers, were conducted during one-sided heating of board samples on the temperature regime of “standard fire”. In the presence of experimental data, by solving the inverse heat conduction problem using the previously developed computer program, the thermophysical characteristics (thermal conductivity and heat capacity) of fiber-reinforced concrete at elevated temperatures were defined. With increasing temperature, the thermal conductivity decrease is more intensive in concrete with added polypropylene fibers than that of concrete without additives. At the same time, the addition of fiber does not affect the intensity of increase of the heat capacity of concrete. The obtained dependences of thermophysical properties of concrete with domestic and imported polypropylene fibers on temperature increase make it possible to carry out calculations of heating of concrete structures with selected additives on a temperature regime of “standard fire”. The conducted studies on the effect of temperature on the strength and thermal properties of concrete with addition of polypropylene fiber reinforcement can be used in calculation of the fire resistance of load-bearing and enclosing structures made of this type of fiber-reinforced concrete.

Fibre Reinforced Concrete Class Control via Fib Model Code 2010 Approach

Fibre reinforced concrete (FRC) has wide spectrum of advantages in tunnelling. Post-cracking behaviour of FRC wasn’t taken into account by Russian engineers while structural design led to underestimation of material abilities. New approach is based on fib Model Code 2010, which provides residual tensile strength Class of FRC. Research Center “FRC” (http://rcfrc.com/) carried out tests with specimens of different types of FRC, which supported by Russian Foundation for Basic Research. Research involved different specimens – plain concrete and FRC with macro-synthetic fibre of different dosage and types. The results showed the efficiency of each type of fibre. The Class of FRC was defined for each specimen series according to results.

Investigation into the mechanical properties of structural lightweight concrete reinforced with waste steel wires

The study of concrete incorporating different waste fibres has started to increase rapidly due to economic reasons and positive environmental effects. In the study reported here, waste steel wires from steel reinforcement and used formworks were blended with structural lightweight concrete, with the aim of replacing commercial steel fibres of controlled quality with recycled fibres. Compression, tensile, flexural and impact tests were performed to assess the mechanical properties of 28 d old concrete specimens reinforced with mixed waste steel wires, mixed steel fibres as well as plain concrete. The percentages of fibres examined in the fibre reinforced concrete (FRC) specimens were 0·25%, 0·50% and 0·75% (volume fraction of the concrete). With varying fibre contents, similar trends were observed in all the types of FRCs studied. It was thus concluded that waste steel wires could be used as a suitable alternative to industrial steel fibres for structural lightweight concrete applications.

Development and Application of High Performance Green Hybrid Fiber-Reinforced Concrete (HP-G-HyFRC) for Sustainable and Energy-Efficient Buildings

The synergy of hybrid fibers allows for an enhanced concrete composite performance at a lower fiber volume fraction as compared to other types of fiber-reinforced concrete. This paper outlines the development process and properties of a new concrete composite termed high-performance green hybrid fiber-reinforced concrete (HP-G-HyFRC). Steel and polyvinyl alcohol (PVA) fibers were used as discontinuous reinforcement of the composite. Up to 60% of cement by mass was replaced by industrial wastes comprising slag and fly ash. At water-binder ratio of 0.25 and with the presence of coarse aggregates, careful proportioning of the mix constituents allows for a composite that is highly flowable. At a combined fiber volume fraction of only 1.65%, the composite also exhibits a deflection hardening behavior which is known to be beneficial for both serviceability and durability of structures. The composite was proposed to be used in an innovative double skin façade (DSF) system consisting of 30 mm air gap in between two thin HP-G-HyFRC skins with no main reinforcing rebars. It was shown that the DSF system alone allows for about 7.6% reduction of cooling energy in buildings.

Effect of the loading frequency on the compressive fatigue behavior of plain and fiber reinforced concrete

This paper presents the recent experimental results aimed at disclosing the loading frequency effect on the fatigue behavior of a plain concrete and two types of fiber-reinforced concrete, using polypropylene and steel fibers. Compressive fatigue tests were conducted on 123 cubic specimens (100mm in edge length). Four different loading frequencies, 4Hz, 1Hz, 1/4Hz and 1/16Hz, were employed. Themaximum stress applied on the specimen was 85% of its compressive strength and the stress ratio was kept constant as 0.3. The results show that the loading frequency effect on the fatigue behavior of the plain concrete is pronounced. The fatigue life (the number of cycles to failure) at lower frequencies is less than that at higher frequencies. However, the fibers do improve the fatigue behavior significantly under low loading frequencies. Such trend can be attributed to the effectiveness of the fibers in bridging cracks, and thus inhibiting the crack extension under cyclic loads.

NEW ANALYTICAL MODEL TO GENERALIZE THE BARCELONA TEST USING AXIAL DISPLACEMENT

The Barcelona Test has proved to be very suitable for the systematic control of the tensile properties of Fibre Reinforced Concrete (FRC). Nevertheless, the need to measure the total circumferential opening displacement (TCOD) of the specimen entails the use of an expensive circumferential extensometer. In order to simplify the test, studies from the literature propose the use of the axial displacement of the press (δ) instead of the TCOD, obtaining empirical equations to correlate the energy estimated with both measurements. However, these equations are only valid for δ ranging from 1 to 4 mm and were adjusted based on the test results of just a few types of FRC. The verification of this formulation for other types of FRC shows an average error of 51.1%, thus limiting the simplification proposed for the test. In this paper, a new analytical model to convert the δ into the TCOD is developed and validated for a wide range of FRC. Besides being applicable to the whole range of δ, the new model provides a clear physical understanding of the main mechanism observed during the test and shows an average error of only 6.7%, making it possible to simplify the Barcelona test.

Acoustic Emission Monitoring of Fracture of Fiber-Reinforced Concrete in Tension

An attempt was made to experimentally investigate the fracture behavior of fiber-reinforced concrete (FRC) by acoustic emission (AE) characterization during direct uniaxial tensile loading. A previous investigation indicated that conventional concrete incorporating short fibers can produce FRC showing a strain-softening response or a strain-hardening response in tension. These two types of FRCs were further investigated using AE techniques, and the results are reported in this paper. A recently developed uniaxial direct tensile test technique was used to conduct tensile test on specimens without notches. AE monitoring was performed during the entire course of each tensile test. Analyses of AE activities and source locations of AE events were performed to study the damage initiation and propagation in the materials. Results show that nucleation of microcracks can be clearly observed for the FRC that shows a nonhardening response similar to concrete without reinforcement. For FRC showing a hardening response, this phenomenon cannot be observed, which indicates that the fibers were effective in blunting the microcrack nucleation.