Fiber-reinforced Concrete Composites Research Articles

Ultra-High-Performance Fiber-Reinforced Concrete Composites Incorporating Hybridized Polymer Fibers: Resistance to Static and Impact Loads

Ultra-High-Performance Fiber-Reinforced Concrete Composites Incorporating Hybridized Polymer Fibers: Resistance to Static and Impact Loads

Effect of Fiber Treatments on the Mechanical Properties of Sisal Fiber-Reinforced Concrete Composites

The mechanical behavior of fiber-cement composites is significantly influenced by the interfacial bonding between the fiber and the cement matrix. However, natural fibers are less chemically compatible with the cement matrix. As a result, it is essential to modify the surface of natural fibers to achieve good fiber-matrix interfacial bonds. In the current study, sisal fibers intended for use as a reinforcement in concrete matrices were alkali treated with NaOH solutions (2%, 5%, and 10%) for 12 hrs, 24 hrs, and 48 hrs. Water absorption, tensile strength, and surface morphological changes in fibers were studied. The effect of fiber treatment on the concrete was also assessed by measuring its slump, compressive strength, flexural strength, and toughness. Alkali treatment was discovered to reduce the water absorption capacity of sisal fiber. On the contrary, fiber surface morphology and mechanical properties improved up to a point and then gradually declined. The addition of treated sisal fiber considerably increases concrete’s flexural strength and toughness. However, an insignificant change in compressive strength was observed.

Optimization of Fresh and Mechanical Characteristics of Carbon Fiber-Reinforced Concrete Composites Using Response Surface Technique

As a top construction material worldwide, concrete has core weakness relating to low tensile resistance without reinforcement. It is the reason that a variety of innovative materials are being used on concrete to overcome its weaknesses and make it more reliable and sustainable. Further, the embodied carbon of concrete is high because of cement being used as the integral binder. Latest research trends indicate significant potential for carbon fiber as an innovative material for improving concrete mechanical strength. Although significant literature is available on the use of carbon fiber in concrete, a limited number of studies have focused on the utilization of carbon fiber for concrete mechanical strength improvement and the reduction of embodied carbon. Following the gap in research, this study aimed to investigate and optimize the use of carbon fiber for its mechanical characteristics and embodied carbon improvements. The use of carbon fiber in self-compacting concrete lowers sagging. The greatest quantity of carbon fiber is that it reduces the blockage ratio, forcing the concrete to solidify as clumps develop. With time, carbon fiber improves the durability of concrete. Self-compacting concrete with no carbon fiber has a poor tensile strength. Experiments were conducted by adding carbon fiber at 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% by weight. Fresh concrete tests including slump test and L-box test, hardened concrete tests involving compressive strength and splitting tensile strength, and durability tests involving water absorption and acid attack test were conducted. Embodied carbon ratios were calculated for all of the mix ratios and decreasing impact, in the form of eco-strength efficiency, is observed with changes in the addition of carbon fiber in concrete. From the testing results, it is evident that 0.6% carbon fiber is the ideal proportion for increasing compressive strength and split tensile strength by 20.93% and 59%, respectively, over the control mix. Response Surface Methodology (RSM) is then applied to develop a model based on results of extensive experimentation. Optimization of the model is performed and final modelled equations are provided in terms of calculating the impact of addition of carbon fiber in concrete. Positive implications are devised for the development of concrete in the future involving carbon fiber.

Fracture characteristics of various concrete composites containing polypropylene fibers through five fracture mechanics methods

Abstract This paper investigates and compares the experimental results of fracture characteristics in various polypropylene fiber-reinforced concretes (high strength concrete, lightweight concrete, and engineered cementitious composite) on 90 three-point bend (notched and un-notched) beams. Five widely used fracture mechanics testing methods, such as work of fracture method, stress-displacement curve method, size effect method, J integral method, and ASTM E399, were used to investigate the fracture behavior. Results have demonstrated that fracture energy and fracture toughness improved as the dosage of polypropylene fibers increased in concretes. However, this improvement was different in concretes owing to various results of fracture mechanics testing methods and different properties of each concrete. Aggregates played significant role in the performance of polypropylene fibers on the fracture behavior of concretes. Among testing methods, the ASTM E399 showed the lowest values for the fracture toughness of concretes. Both work of fracture and stress-displacement curve methods exhibited appropriate results for the fracture energy of polypropylene fiber-reinforced concrete composites. The accuracy of size effect method was acceptable for determining size-independent fracture parameters of plain high strength and lightweight concretes. Furthermore, the J integral method showed more relevant results for the fracture toughness of polypropylene fiber-reinforced engineered cementitious composite.

Finite Element Modelling and Analysis of Fiber Reinforced Concrete under Tensile and Flexural Loading

Concrete is a material exhibiting high compressive strength but about tenfold lower tensile strength. Its brittle property also prohibits the transmission of stresses after cracking. Thus, steel, polymer, polypropylene, glass, carbon, and other fibers are added to concrete to form fiber-reinforced concretes (FRC) having enhanced mechanical properties. The utilization of fiber-reinforced concrete is widespread. Identifying the mechanical properties of fiber-reinforced cement composites under dynamic loading, establishing relationships between their composition, structure, and properties, justifying the correct mathematical model, and determining its parameters are challenging. Utilizing finite elemental modeling and analysis to comprehend the mechanical characteristics of the FRC addition to concrete bricks has shown considerable benefit. In the present study, polypropylene microfibers are included in fiber-reinforced concrete composites, and their performance is compared to that of unreinforced concrete bricks. Under FEA analysis, three-point bending and uniaxial tensile tests were conducted. The results indicate that using fiber reinforcements increases the tensile strength and endurance of the brick.

Finite Element Modelling and Analysis of Fiber Reinforced Concrete under Tensile and Flexural Loading

Concrete is a material exhibiting high compressive strength but about tenfold lower tensile strength. Its brittle property also prohibits the transmission of stresses after cracking. Thus, steel, polymer, polypropylene, glass, carbon, and other fibers are added to concrete to form fiber-reinforced concretes (FRC) having enhanced mechanical properties. The utilization of fiber-reinforced concrete is widespread. Identifying the mechanical properties of fiber-reinforced cement composites under dynamic loading, establishing relationships between their composition, structure, and properties, justifying the correct mathematical model, and determining its parameters are challenging. Utilizing finite elemental modeling and analysis to comprehend the mechanical characteristics of the FRC addition to concrete bricks has shown considerable benefit. In the present study, polypropylene microfibers are included in fiber-reinforced concrete composites, and their performance is compared to that of unreinforced concrete bricks. Under FEA analysis, three-point bending and uniaxial tensile tests were conducted. The results indicate that using fiber reinforcements increases the tensile strength and endurance of the brick.

Assessment of frictional-bond strength at the interface of single SSF in cementitious composite and prediction of accompanying pressure of surrounding matrix

ABSTRACT This paper deals with the study of bond in fiber-reinforced concrete composites and the effect of fiber/concrete interfacial friction on the fiber bond capacity. The paper presents the results of an experimental campaign including direct pull-out test of straight steel fiber-SSF embedded in concrete matrix, aimed at investigating the effect of some parameters, such as bonded length, yielding strength of steel fiber, fiber/concrete roughness, surrounding pressure of concrete matrix, and Poisson’s ratio of concrete. Two analytical models based on the experimental results were proposed. Groups of single fiber embedded in concrete were prepared using different values of bonded length. The results showed that the frictional-bond strength, during fiber-slip stage, can be considered as constant despite changing the fiber embedment length. Furthermore, the SSF/concrete system can be considered as an elastic system, whereas the stress–displacement relation is semilinear. Finally, the results showed good improvements in the efficiency of frictional-bond strength when using fresh concrete with higher self-compacting, greater roughness at the interface of SSF/hardened-concrete, and fiber with lower yield strength. While no significant effect of Poisson’s ratio on the frictional-bond strength was noticed.

Effect of Steel Fiber Volume Fraction on the Mechanical Behavior of Ultra-high Performance Concrete Composites

In order to investigate the effect of fiber volume fraction on the mechanical behavior of ultra-high performance concrete composites (UHPCC), five different volume fractions of macro steel fibers (Vf = 0.5, 1, 1.5, 2 and 2.5%) are used within identical mortar matrix. Ultra-high performance fiber reinforced concrete (UHPFRC) mix was designed to achieve a compressive strength of 155 MPa based on the particle packing method. For 12 series of UHPCC mixes, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity at 28 days are determined. Test results showed a significant improvement in splitting tensile and flexural strengths of UHPFRC with the addition of steel fibers. The maximum values of compressive, splitting tensile and flexural strengths were 155.39, 17.76, and 32.50 MPa, respectively. Stress-strain behavior of fiber-reinforced concrete composites is studied and elastic modulus values evaluated are in the range of 39.52-47.99 GPa. Empirical expressions are developed based on the test results in terms of fiber volume fraction to predict the 28-day strengths of UHPFRC. Comparing the experimental values of earlier researchers to the ones predicted by empirical equations, the average absolute error (AAE) value obtained is within 5%. The proposed model's predictions are in good agreement with the experimental values. Relationship between compressive and flexure strengths of UHPFRC isdeveloped with R2=0.99 and validated.

Deformation and Strength Characteristics for the Calculation of Structures Based on Fiber-Reinforced Concrete Composites

Currently, there is a steady increase in the production of reinforced concrete structures in factory and construction site conditions for various types of modern buildings with higher operational requirements for them. These structures are pre-calculated according to complex design schemes of loading which also leads to increased requirements for the materials used. One of the ways to solve a number of these problems is the use of fiber-reinforced concretes, but for this it is necessary to experimentally identify the deformation and strength characteristics of dispersed reinforced concretes and take it into account when calculating structures. A scientific team of the Institute of New Materials and Technologies of the Ural Federal University is engaged in solving of this research task, which will expand a number of construction opportunities while maintaining economic feasibility in the future.

Geopolymers and Fiber-Reinforced Concrete Composites in Civil Engineering.

This paper discusses the influence of fiber reinforcement on the properties of geopolymer concrete composites, based on fly ash, ground granulated blast furnace slag and metakaolin. Traditional concrete composites are brittle in nature due to low tensile strength. The inclusion of fibrous material alters brittle behavior of concrete along with a significant improvement in mechanical properties i.e., toughness, strain and flexural strength. Ordinary Portland cement (OPC) is mainly used as a binding agent in concrete composites. However, current environmental awareness promotes the use of alternative binders i.e., geopolymers, to replace OPC because in OPC production, significant quantity of CO2 is released that creates environmental pollution. Geopolymer concrete composites have been characterized using a wide range of analytical tools including scanning electron microscopy (SEM) and elemental detection X-ray spectroscopy (EDX). Insight into the physicochemical behavior of geopolymers, their constituents and reinforcement with natural polymeric fibers for the making of concrete composites has been gained. Focus has been given to the use of sisal, jute, basalt and glass fibers.

Study of the fracture surface of concretes reinforced with basalt fiber coated with titanium and zirconium dioxides. Fiber-reinforced concrete composites

It is impossible to imagine the development of modern technologies without the use of efficient and affordable fibrous materials based on minerals, glass, and other fibers. The intensive development of the production of fibers and materials based on them worldwide determines the formulation of significant scientific and technical problems of obtaining them with a given set of properties and high-quality indicators, optimization of processing, and rational use. However, the possibility of modifying the composition of the rock with other components that could significantly improve the physical and chemical properties of the fibers is not always taken into account. For the first time, a study was conducted to research the coating of basalt fibers, such as TiO2, ZrO2 and their effect on the physical and chemical characteristics of aluminosilicate melts made from rocks, fiber formation processes, structure, and physical and chemical properties of fibers. Studies have shown that fibers modified with oxides of TiO2 and ZrO2 have higher chemical resistance in aggressive environments compared with unmodified fibers obtained from melts of similar component groups.

Soft computing approaches for comparative prediction of the mechanical properties of jute fiber reinforced concrete

The fibers in concrete is necessary to enhance its engineering properties. Different types of fibers are used as a reinforcing material. Due to low cost, availability, and environmentally friendly, in recent years, the use of natural fibers in concrete has increased attention widely. Among all the natural fibers, jute fibers are very cheap and available in tropical countries. This study assesses different soft computing approaches: RSM (Response Surface Methodology), ANN (Artificial Neural Networks) and SVR (Support Vector Regression) for development of nonlinear empirical models that predict the mechanical properties (compressive and tensile strengths) of Jute Fiber Reinforced Concrete Composites (JFRCC). These properties are mainly dependent on water-cement (W/C) ratio, length and volume of jute fiber. The codes for ANN and SVR were written in MATLAB (R-2019a), while Minitab® 18 statistical software was used for generating experimental design matrix via Box-Behnken design (an experimental design for RSM). The data for the properties of JFRCC were obtained based on this design matrix and these data were utilized to develop, compare and evaluate the suggested models. The results indicate that SVR model performs much better than ANN and RSM models with respect to various performance measuring parameters (e.g., correlation coefficient, residual, relative error, mean absolute error, root mean squared error, and fractional bias) for predicting both compressive and tensile strengths.

Stress-Strain Constitutive Material Models for Hybrid Steel Fiber Reinforced Concrete

Recent advancements in fiber reinforced concrete (FRC) technology has led to the development of fibrous concrete composites, comprised of fibers with different material and/or geometry, commonly known as hybrid FRC. In one type of hybrid FRC composites, advantageous behaviors of fibers of the same material but with different geometries are gathered in a single FRC mix. The aim of this paper is to develop and validate stress-strain relationships for hybrid steel FRC composites. Six different steel FRC mixes are produced and characterization tests are conducted. Cube, cylindrical and beam specimens are produced for each characterization test corresponding to each of the Steel FRC (SFRC) composites. In this regard, an experimental program is performed to determine the basic engineering properties of SFRC composites using standard compressive, splitting tensile and three-point bending tests. The prescribed procedure of the RILEM guideline, originally developed for non-hybrid FRC, is followed using the obtained experimental results to develop stress-strain behavior models for the SFRC mixes. To validate results for the hybrid SFRC composites, numerical simulations of the 3-point bending tests were performed and compared to that of corresponding experimental results. The results indicated that the proposed stress-strain relationships yield acceptable results for characterizing the behavior of hybrid SFRC composites.

An experimental investigation and modeling approach of response surface methodology coupled with crow search algorithm for optimizing the properties of jute fiber reinforced concrete

The natural jute fiber can be the effective material to reinforce concrete strength. This study investigates the effect of jute fiber on the compressive and tensile strengths of Jute Fiber Reinforced Concrete Composites (JFRCC). A Response Surface Methodology (RSM) articulated with crow search algorithm (CSA)-based platform was developed for predicting and optimizing the variables that affect JFRCC properties. For this, cylinders and cubes of standard dimensions have been made with varying three independent factors, such as water-cement (W/C) ratio, length and volume of jute fiber. Initially, the RSM-based on Box-Behnken Design (BBD) was utilized for finding the second order polynomial models for both compressive and tensile strengths of JFRCC. Later, a platform integrated RSM with crow search algorithm (CSA) was applied to find the global optimal solution. The predicted maximum compressive and tensile strengths of 35.1 N/mm2 and 3.5 N/mm2 (after 28 days of curing), respectively, were found with an optimal set as fiber length of 6 mm, fiber volume of 0.2% and water-cement (W/C) ratio of 0.55. The predicted optimal conditions were validated experimentally and it was found that the experimental strengths using the optimum values were varied by around 5% from the predicted values.

Flexural performance of hybrid polypropylene–polyolefin FRC composites

The objectives of the present study are to conduct experimental studies and determine the flexural strength and ductility of fiber-reinforced concrete (FRC) by adding two types of fibers, namely the polypropylene (PO) and polyolefin (PP) fibers in mono and hybrid forms, and assess the flexural toughness of fiber-reinforced concrete (FRC). The reinforced concrete (RC) beams of size 150 mm × 200 mm × 1000 mm were cast by adding discontinuous fibers of volume fraction (Vf) of 1% of PP (100%), PO (100%) and PP–PO (50–50%) in concrete. The flexural toughness of FRC beams with PP-1%, PO-1% and hybrid-1% (PP–PO) was evaluated from the area under the load–deflection curve and compared with control specimens (CS) (without fibers). The flexural strength and ductility were higher for FRC beam specimens reinforced with hybrid fibers (PP-Vf = 0.5% + PO-Vf = 0.5%) than beam specimens cast with mono PP fibers of Vf = 1% and PO fibers of Vf = 1%, and CS. The flexural toughness (FT) at beam deflection, L/150 (L = span length) and flexural toughness ratio (FTR) were found to be higher for FRC-hybrid PP–PO beam specimens than the specimens reinforced with PP and PO and control specimens (CS). The first-crack width and ultimate crack width of beam specimens were comparatively lesser for hybrid PP–PO than PP, PO fibers and CS.

A Comparative Study of the Mechanical Properties of Jute Fiber and Yarn Reinforced Concrete Composites

ABSTRACTA relatively better performance of jute fiber and yarn reinforced concrete composites can open up a wide access to application of natural resources in concrete strengthening. In order to achieve this goal, an experimental investigation on the flexural, compressive and tensile strengths of Jute Fiber Reinforced Concrete Composites (JFRCC) and Jute Yarn Reinforced Concrete Composites (JYRCC) has been conducted. To draw a specific conclusion, the mix ratios of 1:1.5:3 and 1:2:4 (by volume) of concrete have been maintained with incorporation of jute fiber and yarn in concrete mortar having different cut lengths with distinct volumetric ratios. Finally, a comparison of the JFRCC and JYRCC strength increments with respect to the plain concrete has been investigated. A significant increment of compressive, flexural and tensile strength was observed only for a short cut length having a low volumetric ratio, where JYRCC increment value was always found progressive. A far more regular arrangement and adequate mixture of JYRCC was also visualized compare to JFRCC in concrete mortar. All the principal increment values were found only in case of JYRCC with a mix ratio of 1:1.5:3. So, it can be concluded that the presence of jute yarn and more cement content can strengthen the concrete to a great extent.

Low impact fiber reinforced material composite

Low impact fiber reinforced material compositeABSTRACTThis article investigates the mechanical behavior of fiber-reinforced cementitious composites using moderate to high contents of fly ash (FA) as a replacement for cement; the goal is to create primary building elements with low environmental impact. The experimental results showed that the compressive strength, modulus of elasticity, and post-cracking flexural strength for specimens with w/cm = 0.60 and 20% FA substitution increased with respect to the control. Moreover, the specimens with high FA substitutions had significantly lower mechanical strength values and elastic modulus values. The results indicate that it is feasible to use fiber-reinforced concrete composites as an alternative for low-environmental impact primary construction.Keywords: fiber; cementitous; composites; fly ash, impact material.

Scope of using jute fiber for the reinforcement of concrete material

The natural jute fiber can be the effective material to reinforce concrete strength which will not only explore a way to improve the properties of concrete, it will also explore the use of jute and restrict the utilization of polymer which is environmentally detrimental. In Bangladesh, jute is locally available and, hence, less expensive. To achieve this goal, an experimental investigation of the compressive, flexural, and tensile strengths of Jute Fiber Reinforced Concrete Composites (JFRCC) has been conducted. Cylinders, prisms, and cubes of standard dimensions have been made to introduce jute fiber varying the mix ratio of the ingredients in concrete, water-cement ratio, and length and volume of fiber to know the effect of parameters as mentioned. Flexural, compressive, and tensile strength tests have been conducted on the prepared samples by appropriate testing apparatus according to standard specifications. The results of JFRCC were also compared to the plain concrete. The large cut length and higher content of reinforcing materials (jute fiber) result to the unfortunate tendency of balling formation and high porosity of composites followed by the degrading of mechanical properties of JFRCC in reference to plain concrete. But in the incorporation of short and low fiber content, an intact structure develops which enhances the mechanical properties of the same composite. It was also noted that all the remarkable increment values were found mostly in the presence of higher cement content. So it can be concluded that the presence of jute fiber with more cement content strengthens the concrete in greater extent.

Multi-Scale Characterization of Corrosion Initiation of Preloaded Hybrid Fiber-Reinforced Concrete Composites

Many reinforced concrete structures susceptible to corrosion damage are subjected to externally applied loads, causing cracking. These cracks increase the permeability of the material, accelerating the ingress of corrosion-inducing deleterious agents. In this paper, the effect of multiple microcracking and macrocrack formation on corrosion initiation was investigated. A hybrid fiber-reinforced concrete (HyFRC), which forms ductile, distributed microcracking prior to dominant crack localization due to multiple tiers of fiber reinforcement, is being studied for its performance against corrosion damage. The effect of matrix cracking on corrosion initiation was studied with beam specimens preloaded in flexure prior to long-term corrosion exposure. Reinforced HyFRC composites were found to have a delayed corrosion initiation response due to reductions in crack widths and suppression of splitting cracks, compared to conventional reinforced concrete. The influence of microcracks on corrosion is studied using X-ray micro-computed tomography (μCT) on reinforced fiber-reinforced cementitious composites and reinforced mortar preloaded in tension.

Self-consolidating hybrid fiber reinforced concrete: Development, properties and composite behavior

The workability of an existing Hybrid Fiber-Reinforced Concrete (HyFRC) composite is improved though the incorporation of concepts from the field of Self-Consolidating Concrete (SCC). The resulting composite, achieved through a described parametric study, allows for easier placement within areas of high reinforcement congestion while maintaining the desired mechanical performance benefits inherent to high performance hybrid fiber-reinforced concrete composites. Retention of the strengthening and ductility enhancement, characteristic of the original HyFRC, is gauged by material response to direct tension and four point bending tests. The designated goal of the SC-HyFRC mix is to provide an optimal structural material for construction in which concrete might be expected to face tension, compression and bending as part of a common service load and must be designed to withstand high levels of deformation under maximum credible earthquake or similar design scenarios. The ductility response of Self Consolidating Hybrid Fiber Reinforced Concrete (SC-HyFRC) to severe loading is then investigated through a comparison with conventional concrete by conducting reinforced compression and tensile tests. In both scenarios the presence of hybrid fiber reinforcement is shown to provide an improvement to the phenomena of internal confinement and tension stiffening, for compression and tension loading respectively, which allow for a significantly improved post cracking response.