Hybrid Fiber Reinforced Concrete Research Articles

Bond performance between hybrid fiber-reinforced concrete and BFRP bars under freeze-thaw cycle.

This study applied the pull-out test to examine the influence of freeze-thaw cycles and hybrid fiber incorporation on the bond performance between BFRP bars and hybrid fiber-reinforced concrete. The bond-slip curves were fitted by the existing bond-slip constitutive model, and then the bond strength was predicted by a BP neural network. The results indicated that the failure mode changed from pull-out to splitting for the BFRP bar ordinary concrete specimens when the freeze-thaw cycles exceeded 50, while only pull-out failure occurred for all BFRP bar hybrid fiber-reinforced concrete specimens. An increasing trend was shown on the peak slip, but a decreasing trend was shown on the bond stiffness and bond strength when freeze-thaw cycles increased. The bond strength could be increased significantly by the incorporation of basalt fiber (BF) and cellulose fiber (CF) under the same freezing and thawing conditions as compared to concrete specimens without fibers. The Malvar model and the Continuous Curve model performed best in fitting the ascending and descending sections of the bond-slip curves, respectively. The BP neural network also accurately predicted the bond strength, with relative errors of predicted bond strengths ranging from 3.75% to 13.7%, and 86% of them being less than 10%.

Performance evaluation of hybrid fiber reinforced concrete on engineering properties and life cycle assessment: A sustainable approach

Conventional concrete in its existing form possesses characteristics like better compressive strength, density, resistance against moisture and enhanced performance under various exposure conditions like elevated temperature and long-term durability etc. However, some of the shortcomings such as reduced ductility, brittleness can be improved by using additives like fibers to improve its properties. The present study highlights the performance evaluation of engineering properties and life cycle assessment (LCA) of hybrid fiber reinforced concrete (HFRC) incorporating with glass and polypropylene fibers in equal proportions (0%, 0.5%, 1.0%, 1.5%, and 2.0%). In addition to these, impact resistance at first crack phase and post cracking phase i.e., at failure have also been investigated to ascertain the effect of HFRC vs conventional concrete mixes. Sorptivity studies also performed to find its effect on HFRC, and control concrete mixes prepared with and without glass and polypropylene fibers. Reduction in workability of concrete was observed with increase in hybrid fiber content. Superior performance in terms of strength and durability properties was observed at 1% hybrid fiber content. Similarly, this study also focuses on studying the impact of HFRC and conventional concrete on environment using LCA approach. For LCA, SimaPro software and EcoInvent database is used to compare environmental impact assessment of HFRC and conventional concrete mixes. Impact on environment and cost comparison on HFRC mixes exhibits satisfactory results when compared to conventional mix. Finally, this research will address the need for HFRC mixes to achieve their adaptability in construction sector to make concrete economic and environmentally friendly.

Fracture performance of fiber reinforced geopolymer: Synergetic perspective

It is well-known the hybridization of different types of fibers exaggerates the contribution of mono fiber reinforcement on the mechanical and/or fresh properties of the concrete. Despite this fact, very few researchers have pointed out the synergetic effect of hybrid fibers on the fracture response of the geopolymer concretes. Hence, the present work seeks to extend the current knowledge of material science to cover the synergetic effect of hybrid fibers. To this end, a total of 15 mixtures, including plain matrix were manufactured. Steel, carbon, and glass fibers were incorporated into the mixtures at varying ratios. For the fracture evaluations, the rectangular prisms with the central notches were exposed to a three-point static bending test. Crack formations on the specimen surfaces were recorded through the 2D digital image correlation (DIC) method. Test results were examined in terms of some mechanical and fracture properties of geopolymer composites. Accordingly, the compressive strength, Young's modulus, flexural strength, limit of proportionality, and residual strengths were evaluated as the mechanical properties, while the fracture energy, characteristic length, effective crack length, initial stress intensity factor, and unstable stress intensity factor were considered as the fracture properties. Based on the experimental results, carbon fiber was found to be capable of increasing pre-peak mechanical response, while the steel and glass fibers were useful in improving the post-peak fracture properties of geopolymer concretes. In most cases, similar results were also attained for the hybrid fiber-reinforced concretes.

Research on Mechanical Properties of Steel-Polypropylene Fiber-Reinforced Concrete after High-Temperature Treatments

A mechanical property experiment was carried out on steel-polypropylene fiber-reinforced concrete after elevated temperatures by using a 50 mm diameter SHPB apparatus. The regulations of compressive strength, elastic modulus, Poisson’s ratio, and other mechanical properties under six heating temperature levels (normal temperature, 100 °C, 200 °C, 400 °C, 600 °C, and 800 °C) and three impact pressures (0.3 MPa, 0.4 MPa, 0.5 MPa) were studied. Using ANSYS/LS-DYNA 19.0 numerical simulation software and LS-PrePost post-processing software, numerical simulation analysis was conducted on the dynamic Hopkinson uniaxial impact compression and uniaxial dynamic impact splitting mechanical experiments of C40 plain concrete and steel-polypropylene hybrid fiber concrete. The results show that the dynamic compressive strength of hybrid fiber concrete with the optimal dosage reaches its maximum at a temperature group of 200 °C, and the dynamic compressive strength of hybrid fiber concrete with the optimal dosage increases by 97.1% compared to C40 plain concrete at a temperature group of 800 °C. The impact waveform and stress-strain curve results of the numerical simulation are very similar to the experimental results. The errors in calculating the peak stress and peak strain are within 6%, which can truly and accurately simulate the static mechanical properties and failure process of hybrid fiber-reinforced concrete.

Hybrid Fiber Influence on the Crack Permeability of Cracked Concrete Exposed to Freeze-Thaw Cycles.

This paper describes hybrid fiber's influence on the crack permeability of cracked concrete exposed to freeze-thaw cycles. A permeability setup and a laser-scanning setup have been designed to measure the crack permeability and the fractured surface roughness of cracked hybrid fiber-reinforced concrete, containing polypropylene fiber and steel fiber, under a splitting tensile load. The results show that, when the effective crack width of the specimens is less than 25 μm, the rough crack surface significantly reduces the concrete's crack permeability. As the crack width increases, the effect of the concrete crack surface on crack permeability gradually decreases, and the crack permeability of the concrete is closer to the Poiseuille flow model. The permeability parameter α derived from the Poiseuille flow model is effective for assessing the crack permeability of concrete. Compared to the modified factor ξ of crack permeability, the permeability parameter α can effectively evaluate and quantify the development trend of crack permeability within a certain range of crack widths. The permeability parameter α of SF20PP2.3, subjected to the same freeze-thaw cycles, decreases by 16.3-94.8% compared to PP4.6 and SF40, and SF20PP2.3 demonstrates a positive synergistic effect on the crack impermeability of cracked concrete. The crack impermeability of SF40PP2.3, subjected to the same freeze-thaw cycles, lies between that of PP6.9 and SF60. The roughness of crack surface (X) and the crack permeability (Y) are highly correlated and follow an exponential curve (Y = 1.0415 × 107·e-6.025·X) in concrete. This demonstrates that hybrid fibers enhance crack impermeability by increasing the crack surface roughness. Furthermore, the combination of polypropylene fiber and steel fiber effectively promotes the formation of micro-cracks and facilitates the propagation of multiple cracks in the concrete matrix. This combination increases the head loss of water flow through the concrete and decreases the crack permeability.

A Comparative Study of the Experimental Investigation of different types of fibres used in Concrete

Different types of fibres used in concrete have received much attention in civil engineering in recent years, mainly because they improve the low tensile strength and shrinkage cracks of concrete. However, there are still many problems in the research results on different types of Fibers. For example, there is still debate about the performance-enhancing or detrimental effects of different types of fibres in concrete. There is also a dispute about the influence of the size, strength, elastic modulus and other characteristic parameters of each fibre on the properties of the substrate. Research on fibre mixing rules of hybrid fibre reinforced concrete (HFRC) is incomplete. There is controversy regarding the choice of fibres for hybrid yarns as well as the characterization of the hybrid effect. In summary, it is necessary to review, synthesize and compare current research on FRC. Based on the major research achievements on FRC in recent years, this article synthesizes and evaluates existing research in experimental research and theoretical research on different types of fibre materials, aiming to create Reference conditions for researchers in the same field. Finally, combined with research experience in related fields, new perspectives and proposals on FRC's research are proposed for research and application. This research paper is mainly focus on the different fibres (glass, cotton, steel). KEYWORDS:- GLASS FIBRE, COTTON FIBRE, STEEL FIBRE, TENSILE STRENGTH, COMPRESSIVE STRENGTH,

Predictive modeling of rheological, mechanical and durability characteristics of hybrid fiber-reinforced self-compacting concrete

Predictive modeling of rheological, mechanical and durability characteristics of hybrid fiber-reinforced self-compacting concrete

Investigation of the bond properties between hybrid fiberreinforced concrete and BFRP bars after exposure to high temperature

This research investigated the bond properties at high temperatures and with hybrid fiber addition between basalt fiber reinforced polymer (BFRP) bars and hybrid fiber-reinforced concrete (HFRC). The tensile strength and appearance morphology of BFRP bars were analyzed. Used scanning electron microscopy (SEM) to examine the microscopic morphology and used the bond-slip constitutive model to fit the bond-slip curves. When BFRP bars after exposed to 300 °C, their tensile strength dropped by 42%. With the increasing temperature, the bond strength and stiffness of normal concrete (NC) specimens decreased by 27.3 % and 67.5 %, respectively, while HFRC specimens decreased by 20.8 % and 55 %, respectively. Hybrid fibers increased the bond strength and stiffness of HFRC specimens by 27.1 % and 49.1 %, respectively. The best fitting models were the Malvar model and the Continuous Curve model.

Effect of elevated temperature exposure on the flexural behavior of steel–polypropylene hybrid fiber-reinforced concrete

Effect of elevated temperature exposure on the flexural behavior of steel–polypropylene hybrid fiber-reinforced concrete

Predictive models for mechanical properties of hybrid fibres reinforced concrete containing bamboo and basalt fibres

The aim of this study was to investigate hybrid fibre reinforced concrete containing natural Bamboo and basalt fibres and forecasting the effect of these fibres on Mechanical properties. The contents of Basalt fibres were (0%, 0.25%, 0.50%, 0.75% and 1.00%). The mechanical performance of the hybrid fibre-reinforced concrete was studied in terms of compressive, splitting tensile and flexural strengths. All the samples were tested at the ages of 7, 14, and 28 days. The results showed that an increase in fibre percentages led to a reduction in the concrete slump. It was also found that 0.75% Basalt fibres with 1% bamboo fibres resulted in the optimum performance of the mechanical properties of the concrete. Based on regression models, it was found that bamboo fibres have negative impact on the compressive and splitting tensile strength while basalt fibres enhanced this strength, however, the negative effect of bamboo fibres reduces with the age of concrete. While the effect of bamboo fibres on flexural strength was positive and basalt fibres have negative impact on it. It was concluded that the bamboo and basalt fibre have good relation in overall improving the mechanical properties of hybrid fibre reinforced concrete.

Investigating the applicability of deep learning and machine learning models in predicting the structural performance of V-shaped RC folded plates

Reinforced concrete folded plates (RC-FPs), which are a special class of shell structures, have recently become very popular in modern architectural and engineering applications because of the need for lightweight and aesthetic structures to cover large areas. However, it is known that studies on the structural performance of RC-FPs are insufficient. Therefore, this article presents a study on the development and comparison of different deep learning (DL) and machine learning (ML) models for the prediction of the structural performance of full-scale V-shaped RC-FPs produced from hybrid fiber-reinforced self-consolidating concrete (HFR-SCC) having different plate thicknesses (50, 60, 70, and 80 mm), fiber volumes (1.00% and 1.25%), and combinations (single, binary, and ternary). While vanilla long short-term memory (VLSTM) and bidirectional long short-term memory (BILSTM) are used as DL models, random forest (RF), extremely randomized trees (ERT), and adaptive boosting (AdaBoost) are preferred for ML models. To construct the models, the structural performance results of a total of 44 full-scale V-shaped RC-FPs subjected to four-point bending loading were adopted as the database. In addition to all these, the AdaBoost model is used to determine the relative feature importance of the input parameters. Based on the results, among the DL models, the BILSTM has the best ability to predict the structural performance values of V-shaped RC-FPs (such as R-squared values for maximum load-bearing capacity, cracking load, toughness, and deflection ductility are 0.934, 0.987, 0.972, and 0.812, respectively), while in ML models, this is valid for the ERT (such as R-square values are 0.917 for maximum load-bearing capacity, 0.936 for cracking load, 0.947 for toughness and 0.825 for deflection ductility). On the other hand, DL models predicted all other structural performance values better than ML models, except for deflection ductility. Besides, the most relative important input features for maximum load-bearing capacity and toughness values is plate thickness, whereas for cracking load and deflection ductility values compressive strength is important. In conclusion, it can be emphasized that the use of DL models can provide significant advantages in engineering applications, such as predicting the structural performance of V-shaped RC-FPs.

Study on high temperature dynamic characteristics and mesoscopic simulation of HFRC under dynamic and static combined loading

The Φ50mm SHPB system was used to carry out three-dimensional dynamic and static combined loading tests on hybrid fiber reinforced concrete (HFRC) treated at different temperatures (25 °C, 200 °C, 400 °C) under different confining pressure ratios (0, 0.1, 0.2, 0.3). The temperature effect, confining pressure effect and failure characteristics of HFRC under impact load were studied. The effect of fiber was equivalently treated in mortar, and the meso-aggregate model of HFRC considering aggregate, mortar and interfacial transition zone (ITZ) was established. The simulation results were compared with the experimental results. The results showed that the higher the confining pressure ratio, the more significant the temperature effect of peak stress is. The higher the temperature is, the less obvious the enhancement effect of confining pressure on peak stress is. Compared with the influence of confining pressure on dynamic peak strain, the influence of temperature effect on dynamic peak strain is higher. The established three-dimensional meso-aggregate model and calculation method can accurately reflect the dynamic response characteristics of HFRC at different temperatures and confining pressure ratios. Prestress will affect the internal stress distribution of the specimen, thus affecting the compression failure characteristics of the specimen. The confining pressure can constrain the damage course of the specimen and has a good protective effect on the specimen.

Concrete canals lining with modern materials: A Review of hybrid fiber reinforced concrete

Water losses in irrigation canals occur during the process of water transportation, with seepage loss being the main contributor to total water loss in irrigation conveyance. Cracks and settlement are the most problematic factors affecting canal lining structures, leading to reduced performance of irrigation canals due to issues such as sediment deposition, waterlogging, and leakage. Seepage losses typically range from 20 % - 30 %, but this can be reduced to 15 % - 20 % with the use of canal lining. However, the concrete lining structure, being a thin plate, is prone to high rates of cracking, which weakens the performance of canals. Therefore, it is crucial to enhance the flexure and splitting-tensile strengths of concrete to control the rate of cracking in the canal lining. The splitting-tensile strength of concrete is particularly important in crack control. Hybridization of fibers, such as combining polypropylene and jute fibers, can efficiently enhance flexural toughness, flexural strength, and fracture energy more than using a single type of fiber. The overall aim of this review is to summarize the literature on the use of modern materials to reduce water losses in concrete canal lining. Initially, hybrid fibers (one natural fiber and one artificial fiber) are selected to explain the behavior of hybrid fiber reinforced concrete (HFRC). The crack arresting mechanism of HFRC can help reduce losses in concrete canal lining. The findings of this review will be valuable as a reference for both industry practitioners and academic researchers interested in the development of hybrid fiber reinforced concrete materials, particularly for canal lining applications.

Tests and modeling of hybrid fiber-reinforced geopolymer concrete elements having BFRP helix: An application for sustainable built environment

Due to the high quantity of carbon emissions from the cement industry, sustainable development for the built environment applications is required by utilizing geopolymers in concrete construction. Considering this problem, the structural efficiency of hybrid fiber-reinforced geopolymer concrete (HFGC) compressive elements made of basalt fiber-reinforced polymer (BFRP) bars is not well understood through experiments or numerical modeling in the literature. By conducting experiments and using finite element analysis (FEA) modeling, the primary goal of current research is to examine and compare the structural performance of BFRP-reinforced HFGC compressive elements (GHC) and steel-reinforced HFGC compressive elements (SHC), both of which are subjected to either concentric and or eccentric loading. The HFGC was created using a combination of steel and polypropylene fibers. Twelve circular compressive elements with a cross-sectional dimension of 300 mm and a height of 1200 mm were created i.e., six GHC and six SHC compressive elements. A parametric study was carried out using the proposed FEA model. The findings of the current research showed that the axial strength of GHC compressive elements was on average 91.8 % that of SHC compressive elements. Both types of elements depicted similar amounts of reduction in the axial strength when subjected to eccentric loads, for instance, 38.5 % and 144.2 % reductions were observed for GHC elements having helix spacing of 38 mm compared with the concentrically loaded counterparts. The recommended analytical relationship based on the database also performed well. The comparative study, which considers the axial involvement of main BFRP bars and the confinement effect of transverse BFRP helix, firmly supports the validity and applicability of the newly developed analytical and FEA models for capturing the axial strength of GHC compressive elements.

Effects of steel fiber type and ratio on the one-way bending behavior of hybrid fiber reinforced concrete thin panels

Performance of hybrid fiber reinforced concrete (HyFRC) determined through standardized material tests usually correlates well with the structural performance. However, for thin panels, this correlation may be disturbed due to the fiber orientation and small crack surfaces, and more detailed investigations are required. In this study, effects of steel fiber type and ratio on the one-way bending behavior of HyFRC thin panels was investigated through concrete mixes obtained by using three different steel fiber types and polyvinyl alcohol (PVA) fibers. 45 dog bone shaped, notched specimens were cast and tested under direct tension to investigate the direct tension behavior of used HyFRC. Nine panels of 2500 × 500 × 50 mm in dimension were tested under three-point bending, and nine panels of 1240 × 500 × 50 mm in dimension were tested under four-point bending. An inverse analysis to obtain crack width-stress variation in three- and four-point bending specimens was also performed and behavior of steel fiber reinforced concrete specimens with and without PVA addition were compared. It was found that steel fiber type and ratio was consistently the dominant factor for all types of tests on HyFRC specimens. Addition of PVA fibers in HyFRC specimens either resulted in a similar or worse behavior for direct tension and three-point bending compared to their steel fiber only counterparts. Adverse effect of PVA fibers was more pronounced in three-point bending tests. On the other hand, PVA addition had a more positive effect in four-point bending tests. Inverse analyses performed on three-point bending tests revealed that stress levels develop between crack surfaces in these thin panels were significantly lower compared to direct tension stress levels. However, under four-point bending, these tensile stresses were closer to direct tension stresses, especially for specimens with shorter steel fibers. Loading conditions were found to be an effective factor in the behavior of HyFRC thin panels.

The Effects of Hybrid Steel/Basalt Fibers on the Durability of Concrete Pavement against Freeze-Thaw Cycles.

Freeze-thaw (F-T) is one of the principal perils afflicting concrete pavements. A remedial strategy used during construction encompasses the integration of hybrid fibers into the concrete matrix. An extant research gap persists in elucidating the damage mechanism inherent in hybrid steel fiber (SF)- and basalt fiber (BF)-reinforced concrete subjected to F-T conditions. This paper empirically investigated the durability performance of hybrid fiber-reinforced concrete (HFRC) subjected to F-T cycles. The impact of SF/BF hybridization on mass loss, abrasion resistance, compressive strength, flexural strength, damaged layer thickness, and the relative dynamic modulus of elasticity (RDME) was examined. The damage mechanism was explored using micro-hardness and SEM analysis. The results indicate that incorporating hybrid SF/BF effectively enhances the F-T resistance of concrete and prolongs the service life of concrete pavement. The mechanisms underlying these trends can be traced back to robust bonding at the fiber/matrix interface. Randomly dispersed SFs and BFs contribute to forming a three-dimensional spatial structure within the concrete matrix, suppressing the expansion of internal cracks caused by accumulated hydrostatic pressure during the F-T cycle. This research outcome establishes a theoretical foundation for the application of HFRC to concrete pavements in cold regions.

Adhesion and Sliding Constitutive Relationship between Basalt–Polypropylene Hybrid Fiber-Reinforced Concrete and Steel Bars

The extreme marine environment of the South China Sea Islands, which features high temperatures, high humidity levels and high salt levels, seriously affects the safety of building structures. The durability of concrete can be significantly improved by adding a basalt–polypropylene hybrid fiber, but its bonding mechanism with deformed bars is complicated. Therefore, the bonding performance of hybrid basalt–polypropylene fiber-reinforced concrete and deformed bars was studied by combining experiments and a theoretical analysis. We designed 38 groups of different concrete strengths, different thicknesses of concrete covers, different anchor lengths and different diameters of rebars. The bond strengths, bond–sliding curves and failure forms of each pull specimen were compared and analyzed. The results showed that the failure forms and bond–slip curves of the basalt–polypropylene hybrid fiber-reinforced concrete specimens and the ordinary concrete specimens were essentially the same. Based on the results of the axial tensile tests, an ultimate bond strength prediction model was developed, and a bond–sliding constitutive model for hybrid fiber-reinforced concrete and steel bars was also established.

Flexural Performance of Hybrid Fiber-Reinforced Ultrahigh-Performance Concrete with Locally Available Materials

Flexural Performance of Hybrid Fiber-Reinforced Ultrahigh-Performance Concrete with Locally Available Materials

Relationship between Compressive Strength and Pore Structure of Hybrid Fiber-Reinforced Concrete Subjected to Carbonation

Relationship between Compressive Strength and Pore Structure of Hybrid Fiber-Reinforced Concrete Subjected to Carbonation

The Efficacy of Electromechanical Impedance Monitoring of Embedded Piezoelectric Ceramic Lead Zirconium Titanate Sensors in Different Orientations for Hybrid Fiber-Reinforced Concrete Structures Hydration

Abstract In this study, the influence of the orientation of embedded piezoelectric ceramic lead zirconium titanate (PZT) on the mechanical performance of hybrid fiber-reinforced (polypropylene and glass fiber) concrete beams was evaluated. The performance of concrete was evaluated under self-weight, followed by assessing the mechanical property using the electromechanical impedance (EMI) technique after optimization of M30 grade concrete with polypropylene fiber and glass fiber. PZT patches are embedded at different orientations, i.e., 0 deg, 45 deg, and 90 deg, with the axis of the structure for monitoring the hydration of the RC beam. The change in stiffness due to heat hydration in the concrete structure after 5, 7, 14, 21, and 28 days was observed by curing hybrid concrete beams and examining them after 5, 7, 14, 21, and 28 days. On the fifth day, beams were simply supported and allowed to deflect under their weight, and measurements of heat hydration in terms of conductance at frequencies ranging between 1 and 1000 kHz were done. Similarly, days 7, 14, 21, and 28 were done. Day 5 was considered the baseline. It is noted that the PZT sensor placed at an angle of 45 deg is the least effective in recording the incremental changes in hydration that occurred in the concrete beam. The highest quality results were obtained at 90 deg, which is further demonstrated by statistically quantifying the changes using the root-mean-square deviation (RMSD) percentage method and proves to be the most optimized orientation to obtain the stiffness of the hybrid reinforced beam in terms of conductance.