Glass Fiber Reinforced Concrete Research Articles

An experimental study on mechanical and fracture characteristics of hybrid fibre reinforced concrete

This research investigates the impact of polypropylene and glass fibres on the mechanical and fracture properties of concrete. Prepared specimens consisted of plain concrete (PC), polypropylene fibre-reinforced concrete (PPFC), glass fibre-reinforced concrete (GFC), and polypropylene-glass hybrid fibre-reinforced concrete (HFC). The specimens were evaluated for their mechanical and fracture properties. PPFC indicated a little drop in compressive strength and GFC demonstrated a moderate gain; HFC, as a result of synergistic effect of polypropylene fibre and glass fibre, demonstrated a marginal increase in compressive strength. The substantial increase in flexural and split tensile strength was observed in all the fibre reinforced concrete specimens, compared to plain concrete. The incorporation of polypropylene fibre yields the greatest improvement in concrete's split tensile strength, whereas the incorporation of glass fibres results in the highest improvement in concrete's flexural strength. The fracture characteristics also showed significant improvement in fibre incorporated concrete. The coaction of polypropylene and glass fibre in HFC resulted in 30.1 % increase in first crack strength and a threefold rise in flexural toughness compared to plain concrete. Compared to plain concrete, the critical crack tip opening displacement of PPFC, GFC, and HFC increased by 43.90 %, 26.25 %, and 39.02 %, while the critical stress intensity factor increased by 15.73 %, 13.10 %, and 14.22 %. Subsequently, it was determined that the fracture energies of PPFC, GFC, and HFC were 3.35, 1.78, and 2.50 times those of PC, respectively. In addition, the synergistic effect of polypropylene and glass fibres in concrete was studied, and it was found that when used together, the fibres have better fracture characteristics than when used alone, without compromising mechanical strength. Subsequently, different bilinear softening curves were used to predict fracture parameters, and it was seen that the computed values agreed with the experimental values.

Investigation of the Engineering Properties of Glass Fiber Reinforced Concrete (GRC) Cured with Internal Resistance

In this study, it was aimed to produce glass fiber reinforced concrete (GRC) samples cured with internal resistance by placing resistance wires at different distances within the concrete molds and applying electric current at various voltages, while the mold surfaces were covered with stretch film. The engineering properties of these samples were then investigated. Previous studies have shown that the mechanical properties of conventional concrete, which were subjected to different curing methods, improved compared to samples that did not undergo any curing process. This study aimed to enhance both the engineering properties of the concrete samples and to accelerate the curing process. Glass fiber reinforced concrete (GRC) with dimensions of 50×50×4 cm was produced, and 25, 35, and 45V resistances were applied to three different molds with wire spacing of 5cm, 6cm, and 7cm. With this application, the GRC samples were subjected to internal resistance curing for the first 24 hours. By applying three different voltages to molds with three different wire spacings, 9 concrete samples were produced, along with 1 reference sample that did not contain any resistance wires and was not subjected to any curing process, making a total of 10 different concrete samples. After curing, the concrete samples were cut into 16cm×4cm×4cm GRC mechanical test specimens. The obtained specimens were tested for 7, 14, and 28 day compressive strength, flexural strength, unit weight, and ultrasonic pulse velocity. To examine the microstructure of the GRC samples, Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FT-IR) analyses were conducted. These analyses investigated the physical and chemical development processes of the samples, mass losses, products formed after hydration, and structural behaviors. As a result, it was observed that the early-age strength properties of GRC samples cured with internal resistance showed a partial increase compared to the reference sample that was not internally cured, especially in the 7-day samples. In the 14 and 28-day strength comparisons, it was observed that the cured samples showed improvement in flexural strength. According to the data obtained, the samples subjected to 35 volts of electric current yielded better results, especially in the early ages, compared to the reference sample.

Experimental investigation of mechanical and physical properties of glass fiber reinforced concretes produced with different magnetized waters

Magnetized water may act as a thickener in cementitious mixtures due to its slippery effect. Therefore, it can be beneficial for the mixture to settle easily and to improve its strength. This study investigated the effects of magnetized water passing through pipes with magnetic field intensity (MFI) 8 and 10 on glass fiber reinforced concrete (GFRC). Three different mixtures, the GFRC mixture produced with regular tap water, were obtained, and the properties of the produced GFRC samples, such as 7, 14, and 28 days H-Leeb hardness, density, Ultrasonic pulse velocity (UPV), flexural strength, compressive strength, and fracture mechanics were investigated. In addition, SEM, EDS, FTIR, and TGA analyses were carried out to investigate the change in surface tension in the internal structures of GFRCs produced with magnetized water. Overall, the results were promising. Results showed a proportional H-Leep hardness increase with curing time and density variations. Magnetized water reduced air voids, enhancing sound transmission speeds. Flexural and compressive strength improved with magnetic water. The study suggests significant contributions to energy savings and reduced production costs, highlighting the efficient use of energy resources.

Effects of Glass Fiber on a Mechanical Properties of Concrete

The purpose of the study is to find out how adding glass fiber to concrete can improve its mechanical qualities. It assesses qualities including compressive strength, flexural strength, and strength and contrasts glass fiber-reinforced concrete (GFRC) with regular concrete. Tests on concrete samples with different glass fiber contents reveal that higher fiber content enhances ductility and flexural strength. Environmental pressures like chemical attacks and freeze-thaw cycles are not able to break down GFRC. Tests are enhanced by finite element analysis (FEA), which shows the distribution of stress and strain in the composite. In general, the research advances our knowledge of how GFRC may fortify concrete constructions, perhaps leading to the development of more robust building frameworks.

Implementation of Large-Format 3D Façade Components Using Glass Fibre Reinforced Concrete:ČSOB Hradec Králové, C&A Zürich, Illuster Uster

Glassfibre reinforced concrete (GRC) is a close-grained concrete material reinforced with glass fibres that allows architects complete freedom in designing rear-ventilated façades. It can be shaped, coloured, surface-treated or otherwise tailored to the specific needs of their projects without significant limitations. The main properties of GRC material include its long life-time and sustainability. The results are visually appealing façade panels that can withstand adverse weather conditions for decades. The characteristic high strength and durability is achieved by dispersing glass fibres within the base mixture of Portland cement, sand, water and further refining additives. Fine-grained particles in the composite structure ensure low water absorbency and high frost resistance. This article is an overview of the technical solution and process of GRC façade design. It deals with the design possibilities for anchoring large-format and 3D shaped façade panels. The article further presents all of the above-mentioned characteristics and process details as they are used on three specific structures. The first presented project is the ČSOB Central Office in Hradec Králové, with its typical distinct ledges combined with glazed surfaces. The cascading entrance portal is a significant element of its façade. The next implementation chosen is the renovation of the C&A department store building in Zürich, Switzerland. This building’s façade is comprised of structured large-area panels with distinctive frames. The article concludes with the creatively implemented renovation of the Illuster shopping centre in Switzerland, with its kaleidoscopic façade made up of glassfibre reinforced concrete panels.

Glass Fibre Reinforced Concrete (GFRC) Materials and Its Applications

In the 1940’s, potential of glass as a construction material was realized and improvement continued with the addition of zirconium dioxide in 1960's for harsh alkali conditions. The development of new glass fibre generations is focused on improving the process of material durability. In order to meet various needs, glass fibre reinforced concrete, or GFRC, was thus introduced into production. Research and experiments conducted on GFRC have demonstrated that the material quality and production precision have an impact on the material's mechanical and physical characteristics. GFRC can be applied anywhere an impermeable, weather-resistant, fire-resistant, light-weight, and robust material is required. With the development of technology, it may be possible to construct sophisticated freeform structures and entire buildings at a reasonable cost. Recently, research has been done on the impact of glass fibres in hybrid mixtures for high-performance concrete (HPC), a newly developed technology that is gaining popularity in the building sector.

Numerical and Experimental Studies on Crack Resistance of Ultra-High-Performance Concrete Decorative Panels for Bridges

This study develops a new type of decorative bridge panel by ultra-high-performance concrete (UHPC) based on the project of the Guangyangwan Bridge. First, the numerical analysis was carried out using MIDAS and ABAQUS to find the critical position of the bridge and decorative panels. The numerical results showed that the last concrete cantilever segment had the greatest vertical deflection, and the corresponding panel had the greatest stress response. Based on the numerical results, this study conducted a series of full-scale, self-balanced bending tests to examine the crack resistance of six UHPC panels and six glass fiber-reinforced concrete (GRC) panels with varying curved section thicknesses (from 25 to 40 mm). The experimental results indicate that, due to the high strength of the UHPC matrix and the wall effect of steel fiber distribution, the crack resistance of UHPC panels is significantly superior to that of GRC panels. UHPC panels possessed superior stiffness and ductility, while GRC panels showed brittle fracture when the curved section thickness reached 34 mm. The uniaxial tensile cracking strength of UHPC with a steel fiber volume fraction of 1.6% was 14.7% greater than that of GRC with a glass fiber volume fraction of 5%. At the same curved section thicknesses, UHPC decorative panels exhibit cracking loads and ultimate loads that are 64.3% to 123.0% and 29.2% to 115.0% greater than GRC panels, respectively. Hence, UHPC is more suitable to produce ultra-thin decorative panels for bridges that are subjected to severe environmental action and external forces.

Effects of utilizing various types of facade material on the Embodied and operational energy; a case study of apartment building in Indonesia

ABSTRACT This study investigates the impact of using prefabricated facade materials on the embodied energy (EE) and operational energy (OE) consumption of apartment buildings. To analyze the total EE, a life cycle assessment (LCA) was conducted, which calculated the EE from cradle-to-use each of the products employed. In addition, a building energy simulation was performed for the case study building using various prefabricated facade materials to assess its OE. The findings reveal that the selection of facade wall materials with low energy intensity must be favored to optimize building energy and that layered materials, such as insulated panels, can reduce the cooling energy load due to their higher thermal resistance (r- values). Furthermore, the LCA results showed that solid precast concrete materials with thicknesses of 120 and 150 mm have EE and greenhouse gas emissions that are more than twice the average of all materials tested. In contrast, uninsulated Glass-Fiber Reinforced Concrete (GRC) removable walls (disassembly panels) exhibited the lowest EE, corresponding to 50% of the average. Finally, the results of the OE simulations using EnergyPlus software indicate that insulated GRC removable walls with a thickness of 120 mm can reduce the cooling energy load by 29.5% compared to precast concrete facades.

Numerical analysis of 3d truss bridge using ANSYS

Trusses are typically lighter and more cost-effective than alternative structural support systems and are used in a variety of structures including vehicle frames, mechanical equipment, buildings, bridges, and towers. A truss structure takes advantage of the inherent geometric stability of the triangle to evenly distribute weight and to handle changing tension and compression. This project deals with the analysis of a 3D truss bridge which is proposed to be constructed connecting the two platforms of the Tripunithura railway station, with three different deck materials glass fibre reinforced concrete (GFRC), concrete and steel. Analysis and design of the proposed structure is carried out using ANSYS (Workbench) 2022 R2 software. ANSYS is an analysing software that is used for mechanical product designs and civil structure designs. It uses computer based numerical techniques to solve problems. This software helps to engineer and design complex, highly nonlinear and large models. It enables to design and manage 3D structures in steel, concrete and glass fibre reinforced concrete (GFRC). Structural performance of 3D truss bridges with three different deck material in terms of axial force, shear stress and deformation are compared in order to find which combination of materials will give better performances. Dynamic analysis is performed to examine the frequency and modes of vibrations caused by the movement of trains.

Electrical and microstructural characterization of carbon nanotube-carbon fiber added cementitious conductive surface coating

In contrast to the traditional methods of directly adding conductive fillers to the cement matrix in the development of heatable conductive concrete, radiation shielding and smart sensing cementitious materials, this study proposes a more efficient approach by covering the non-conductive glass fiber reinforced concrete (GRC) surface with a thin conductive layer. Single-walled carbon fiber (SWCNT) and carbon fiber (CF) were used as conductive additives in the mixture of electrically conductive surface coating. Dosages of 0.1%, 0.2%, and 0.3% (wt) for SWCNT and 0.2%, 0.4%, 0.6%, 0.8%, and 1% (Vol) for CF were preferred. According to these ratios, a total of 15 different conductive cement coatings were carried out. White Portland cement and fine silica sand were used as binder and filler material, respectively. The conductive cement-based coating with a thickness of approximately 3 mm shows good adhesion and integration properties, since it is placed in the mold gradually at the same time as the GRC, which acts as the substrate. Resistivity, impedance, heatability (electrothermal), TGA-DTA and microstructure characterization were performed to investigate the electrical, thermal and microstructural properties of the coatings.The impedance/resistance properties of the cement-based composite samples containing CF showed superior performance compared to the other samples. In TGA/DTA analyses, the amount of CF in the cement mixture did not affect the thermal weightlossmuch. The lowest resistivity values were measured as 20 and 80 Ω.cm for the CF1.0 and CF0.8 samples, respectively, and the electrothermal test results showed that the temperature reached 45.5 and 28 °C from 23 °C, respectively, by applying 24 V voltage within 1 h with a power consumption of 750 W/m2 and 232 W/m2.

Behavior of Square Footings Reinforced with Glass Fiber Bristles and Biaxial Geogrid

This study investigates the influence of biaxial geogrids on the flexural behavior of square footing foundations reinforced with glass fiber reinforced concrete (GFRC). Experimental research is conducted, involving the testing of five reinforced concrete square footings under area loading until failure. The variables considered are the number of geogrid layers and the percentage of longitudinal reinforcement. Various parameters including deflection, loads at each stage, stiffness, ductility, energy absorption, crack patterns, as well as strains in steel, concrete, and geogrid, are analyzed and compared. The results reveal that incorporating geogrid layers as a reinforcement technique with GFRC significantly enhances the flexural behavior of the footings and improves cracking patterns. The number of geogrid layers used in the footings substantially increases the loads at each stage. Furthermore, an empirical equation is developed to establish a correlation between the moment acting on the footings and the tensile strength of geogrid reinforcement. The empirical evidence demonstrates a substantial improvement in the strength resistance of geogrid-reinforced footings with GFRC, surpassing those reinforced with steel and normal concrete mix. This research contributes valuable insights for the design and construction of earth structures, highlighting the advantages of biaxial geogrids in reinforcing GFRC footings with enhanced flexural performance.

Several machine learning models to estimate the effect of an acid environment on the effective fracture toughness of normal and reinforced concrete

Crack extension and subsequent concrete fracture are regulated by the concrete's fracture toughness, making it an essential feature. Concrete, made from the most common and inexpensive building components, is the material of choice in civil engineering. Therefore, fractures and cracks may cause significant damage that may be impossible to repair. Furthermore, concrete constructions lose mechanical strength when encountering an acidic environment. This has led to the development of fiber-reinforced concrete, which addresses the issues. Therefore, studying the mechanical properties of concrete under different environmental conditions is of particular importance and should be considered in designs. For this purpose, in this study, the effect of an acid environment (PH = 5) on the effective fracture toughness (Keff) of three types of concrete, including conventional concrete (CC), glass fiber-reinforced concrete (GFC), and glass fiber/microsilica-reinforced concrete (GFMSC), was investigated using the central straight notched Brazilian disc (CSNBD) test. Also, since conducting laboratory tests to obtain the Keff of concrete samples is time-consuming and costly, it is necessary to provide tools to estimate this concrete property with high accuracy in a short period and without the need for such a high cost. Using machine learning (ML)-based models was a suitable option to address such problems. For this purpose, twelve ML-based models were presented using 420 datasets generated from the CSNBD test to estimate the Keff of different concrete samples. The behavior of the ML models compared to the CSNBD test was investigated, and the correct and acceptable performance of each of them in estimating the Keff of concrete was confirmed. The CSNBD and ML results showed that an acid environment (PH = 5) has a more destructive effect on the concrete’s Keff than a neutral environment (PH = 7). Also, reinforced concrete (GFC and GFMSC) is always more resistant to acid environments than normal concrete (CC). To further aid in the estimation of the concrete's Keff for engineering challenges, a graphical user interface (GUI) for the ML-based models was developed.

Experimental study on strength comparison of the glass fiber reinforced concrete (GFRC) and conventional concrete (M30 grade)

This is a comparatively recent advancement in construction technology. This saves money in the construction process because it is light weight. The use of glass fiber to replace steel in reinforced concrete structures helps reduce corrosion and structural damage. Many alternatives have been investigated to increase concrete’s strength, durability, shrinkage characteristics, and serviceability while considering global environmental factors. As a consequence, glass fiber has been employed as an additive, and trials with various percentages of 1%, 2 %, and 3% cement have been carried out. When considering this material, concepts such as glass fiber, light weight, cost-effective, ecologically friendly, and compressive strength must be considered. GFRC is a cement matrix made up of cement, sand, water and admixtures, and contains short glass fibers. Facade panels, pipes and channels are examples of non-structural elements that have been extensively used. Light weight (which lowers dead load), fire resistance, an attractive appearance, and tensile strength are just a few of the benefits of GFRC. Trial tests for concrete with and without glass fiber are conducted using cubes, beams, and cylinders to measure the differences in compressive strength, flexural strength, and split tensile strength. Because glass fiber may be molded and sculpted in a number of ways, its demand is growing in India due to rising building activity and other causes. Compared to other reinforcing materials, it is a more affordable and cost-effective solution.

Feasibility Study on the Effect of FRP Shear Reinforcements on the Behaviour of FRP-Reinforced Concrete Deep Beams

Unlike steel reinforcements in concrete, Fiber Reinforced Polymer (FRP) materials are light and free from corrosion. Therefore, FRP materials are increasingly being used in structural engineering as a replacement for steel reinforcements. While the use of FRP bars as longitudinal reinforcements in concrete deep beams has been studied somewhat widely, their use and effectiveness as web reinforcements are not well studied. In this study, the effect of the FRP web reinforcements on the behaviour and strength of FRP-reinforced concrete deep beams were investigated in an experimental study. Four glass fiber-reinforced concrete (RC) simply supported deep beam specimens were tested under a concentrated load with different shear span-to-depth ratios and web reinforcement ratios. The behaviour of the deep beams was described in terms of load–deflection behaviour, crack developments, strain in FRP reinforcements, and failure modes. The experimental investigation emphasized the significance of web reinforcements in determining the reinforced concrete deep beam behaviour, such as mid-span deflection, crack breadth, failure modes, and ultimate strengths. Furthermore, to predict the behavior of deep beams, numerical Finite Element models using Abaqus software were created. The present test results were compared to those predicted using the Finite Element models. This investigation shows that web reinforcement is quite important for FRP-RC deep beams to achieve a robust behaviour by enhancing its capacity and deformability.

Numerical Investigations of GFRC beams strengthened in shear with innovative techniques

This paper discusses the Finite Element analysis (FE) conducted to predict the behavior of Glass Fiber Reinforced Concrete (GFRC) beams without shear reinforcement (stirrups) and strengthen them with proposed techniques to increase their shear strength. for this study, A total of eighteen (18) (120 * 300 * 2200 mm) specimens were modeled using Ansys™ mechanical. The main variables were the percentage of discrete glass fiber in the concrete (0.0, 0.6, and 1.2%), the type of main reinforcing bars (steel or GFRP), the shear strengthening material (GFRP or steel) links, the strengthening systems (side near-surface mounted (SNSM) bars, externally bonded (EB) sheet, or both), various NSM GFRP bars configurations (side bonded links, full wrapped stirrups, side C-shaped stirrups, and side bent bars), the link spacing, the link inclination angle, and the number of bent bars. Each model had a free span of 2000 mm with a constant shear span-to-depth ratio (a/d) of 2.0. The numerical models were verified against experimental results presented in the earlier publication. These results were analyzed to investigate the effect of main variables on shear strength. Increasing the ratio of discrete glass fiber in the R.C beam to 0.6 and 1.2% enhanced the ductility and increase the shear strength by 24% and 32% for steel reinforcement and by 16% and 29% for GFRP reinforcement, respectively. The use of GFRP bars instead of steel bars as the main reinforcement slightly enhanced the shear strength and ductility but decreased the stiffness. the use of various strengthening systems enhanced the shear capacity by a ratio of up to 115%. A new strengthening technique (SNSM bent bars with strips) produced better improvements in terms of shear capacity, ductility, and crack propagation compared to other strengthening techniques. The results of Numerical analyses and the experimental results for eighteen beams were considered, the ratio between them is equivalent by a factor of 0.96 to 1.04.

Mechanical and Durability Performances of Alkali-resistant Glass Fiber-reinforced Concrete

Concrete, being the most widely used construction material in the world, lacks strength in direct tension and flexure. Attempts to reinforce concrete in tension include the use of steel rebars to strengthen the tensile side of concrete as well as the use of discrete fibers as a reinforcing medium. The study conducted in this manuscript details the effects of including alkali-resistant glass fibers in concrete. Mechanical strength, such as strength in compression and flexure, chord modulus of elasticity and bond pull-out strength, have been measured along with porosity and resistance to accelerated carbonation. Five different water to binder ratios in a range of 0.4 to 0.6 had been used to prepare the design mix proportions. The optimum fiber dosage was found to be 1.5% by weight of cement used. The same had been adopted in the design mix proportions. The average increase in compressive strength and flexural strength was 13% and 28%, respectively. Alkali-resistant glass fiber concrete showed less resistance to carbonation when compared to control mix. Results indicate that glass fibers play a predominant role in providing flexural strength to concrete. The pull-out strength of fiber was added to extra post-cracking flexural strength. The inclusion of alkali-resistant glass fibers imparted a maximum addition of 44% increase in the flexural strength compared to control concrete. The inclusion of alkali-resistant glass fibers in concrete paves the way for a leaner mix and eradicates the possibility of congestion of steel reinforcement for certain structures. KEYWORDS: Alkali-resistant glass fibers, Accelerated carbonation, Bond strength, Compressive strength, Flexural strength.

Effects of glass fiber usage on fracture energy and mechanical behavior of concrete: An experimental approach

In this study, the fracture and mechanical behavior of glass fiber reinforced concrete (GFRC) are investigated comparatively. For this purpose, three-point bending tests were carried out on notched beams produced using GFRC with 1, 2, and 3 kg/m3 fiber contents and the dimension of 6, 12, and 24 mm to determine the fracture energy. Fracture energy values of the GFRC specimens were calculated by analyzing load versus crack mouth opening displacement (CMOD) curves. Compressive strength was determined using cube samples with the dimension of 150x150mm. Tensile strength and Modulus of elasticity were determined using notched beams with the dimensions of 48010050 mm. Also, notched beams were produced and tested in accordance with RILEM recommendations. In addition, microstructural analyses were performed based on Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations. The results showed that the effects of fiber contents on fracture energy were very significant. However, the effect of fiber addition on the compressive strength and modulus of elasticity values was not significant.

Use of Corrosion Inhibitors in Stainless Steel Anchors Used In Glass Fiber Reinforced Concrete (GRC) Precast Facade Elements

Corrosion is the process of losing the physico-mechanical properties of the metallic material over time as a result of chemical or electrochemical reactions. It is one of the most fundamental problems encountered in the construction industry; according to the latest research despite all the precautions taken corrosion causes an economic loss of approximately 546 million pounds per year. In addition to financial consequences, numerous dramatic damage events are directly or indirectly attributed to the corrosion process. Revealing the corrosion risk at the architectural design stage, taking into account the compatibility of the materials to be used, will contribute significantly to the steps to be taken regarding the monitoring and prevention of corrosion. In this study; the benefit of preventing the corrosion that occurs over time in the stainless steel anchors used in glass fiber reinforced concrete (GRC) precast facade elements by using corrosion inhibitor before mounted to the GRC was investigated. Creating a protective layer on the metal surface by using a patented chemical solution containing a corrosion inhibitor was used for the first time in the GRC sector in this study. After washing with corrosion inhibitor solution, stainless steel anchor elements were immersed in 5%(w/v) NaCl solution. After 30 days, the metal surfaces were examined by visually and were investigated by surface imaging methods (Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS)) and Atomic Force Microscopy (AFM). The findings show that washing with a solution containing corrosion inhibitor, especially after welding; increases the strength of the oxide film formed on the stainless steel surface and protects it against corrosion.

Macro-micro mechanical properties and reinforcement mechanism of alkali-resistant glass fiber-reinforced concrete under alkaline environments

As a reinforced composite material, alkali-resistant glass fiber-reinforced concrete (AR-GFRC) has been extensively applied in large-scale projects due to its advantages such as strong corrosion resistance, high tensile and impact resistance, high elastic modulus and low cost. However, the mechanical properties and optimal ratio of AR-GFRC in complex environments such as strong alkaline along with their meso-damage and failure mechanism have not yet been fully understood. In order to investigate damage deformation and fiber reinforcement mechanisms of AR-GFRC under alkaline environments, the tensile performance of concretes with different fiber contents were investigated through splitting tensile tests, scanning electron microscopy (SEM) and numerical simulations. First, orthogonal design and splitting tensile tests were conducted to determine the optimum combination and ratio of each fiber content, while the effect on concrete strength was clarified. Second, the internal microstructure of AR-GFRC was evaluated using concrete SEM images, and the interaction of microstructure and macro-properties as well as the strengthening mechanism and crack resistance of AR-GFRC were determined. Third, a randomly distributed fiber-reinforced concrete model was developed and a calculation method was proposed based on finite element numerical simulation results and the variations of AR-GFRC tensile damage was clarified. The obtained results could provide guidance and reference for safe engineering constructions and further application of concrete in alkaline environments.

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.