Polyolefin Fibers Research Articles

Durability and Compressive Strength of Composite Polyolefin Fiber-Reinforced Recycled Aggregate Concrete: An Experimental Study

This study investigates of using recycled concrete aggregates along with the reinforcement of polyolefin fibers to augment both the compressive strength and durability of concrete, in alignment with the principles of sustainable development. This study experimentally investigated the compressive strengths and durability of composite polyolefin fiber-reinforced recycled aggregate concrete (PFRRAC) exposed to chloride and acidic environments. For this purpose, 150 cubic samples of 100 × 100 × 100 concrete with various combinations of recycled aggregates and polyolefin fibers were made and subjected to axial compressive loading. The results show that the addition of fibers significantly enhances the compressive strength of concrete, with an increase of up to 34.36% at 5% fiber content. However, increasing the proportion of recycled aggregates reduces the compressive strength, with reductions ranging from 21.12% to 43.85% as the recycled aggregate content rises to 70%. Moreover, the combination of fibers and recycled aggregates demonstrates potential for improving the sustainability and durability of concrete under challenging environmental conditions, particularly in chloride and acidic environments. In acidic environments, the inclusion of fibers significantly enhances the resistance to strength reduction. Furthermore, the study uncovers that a higher concentration of recycled aggregates exacerbates the reduction in strength in chloride-rich settings, emphasizing the imperative nature of meticulous mix design and material selection. The findings for the integration of even minor quantities of polyolefin fibers to amplify the performance and sustainability of concrete mixtures, especially when utilizing recycled aggregates, thus promoting eco-friendly construction practices.

The influence of polyolefin and steel fibres on flexural performance of reinforced concrete beams under cyclic loads

The influence of polyolefin and steel fibres on flexural performance of reinforced concrete beams under cyclic loads

Effect of acid soak treatment of the precursor on the structure and properties of polypropylene-based carbon fibers

Polyolefin fibers have received wide attention as the precursor for low-cost carbon fiber, and cross-linking of linear polyolefin by strong acid has been proven to be an effective way to stabilize the precursor fiber prior to carbonization. However, the conventional temperature used in sulfonation process is too high and could result in severe decomposition of the linear chain of the polymer, which further deteriorated the mechanical properties of the as-prepared carbon fiber. Thus, reducing the duration of sulfonation process operated at high temperature may alleviate the degradation behavior, conferring the polyolefin-based carbon fibers with better performance. In this paper, polypropylene (PP) fibers were soaked in sulfuric acid at 50 °C–90 °C, before the conventional preparation protocol of PP-based carbon fiber. The structural evolution from PP to carbon fiber were characterized by Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The mechanical and conductive properties of carbonized fibers where further measured. The results showed that the soak in sulfuric acid resulted in swelling of PP fibers in diameter direction, as well as reducing the crystallinity of the fibers, both of which were physical transformation, and could be easily controlled by soak temperature. The subsequent sulfonation at conventional temperature was fastened for the soaked PP fibers, and the duration of sufficient sulfonation were almost reduced by half. The obtained carbon fibers exhibited better thermal conductivity and mechanical properties, which were enhanced by 25 % and 40 %, respectively, compared with that without soak pretreatment.

Tension Lap Splices in Recycled-Aggregate Concrete Strengthened with Steel–Polyolefin Fibers

The bond strength of tension lap splices in recycled-coarse-aggregate-reinforced concrete strengthened with hybrid (steel–polyolefin) fibers was experimentally investigated. This study was conducted with the help of twelve lap-spliced beam specimens. The replacement level of coarse natural aggregates with recycled concrete aggregate (RCA) was 100%. The following variables were investigated: various ranges of steel–polyolefin fibers—100–0%, 75–25%, 50–50%, 25–75%, and 0–100%—in which the total volume fraction of fibers (Vf) remains constant at 1%; and two lengths of lap splices for rebars of 16 mm diameter (db): 10 db and 15 db. The test results showed that the best range of steel–polyolefin fibers that gave the highest bond strength was 50–50%. The ductility of the fiber-reinforced recycled-aggregate (FR-RA) concrete was significantly improved for all the cases of various relative ratios of steel and polyolefin fibers. The bond strength was also predicted using three empirical equations proposed by Orangun et al., Darwin et al., and Harajli. This study showed that the Harajli equation gave a more accurate estimation of the bond strength of reinforcing bars embedded in FR-RA concrete than those proposed by Orangun et al. and Darwin et al.

Exploring the acoustic activity in brittle materials in terms of the position of the acoustic sources and the power of the acoustic signals - Part II: Applications

The present study is the continuation of a previously published one (Part I), in which the D- (three-dimensional distance between the sources of any two successive acoustic events) and P-functions (the rate of the energy of the acoustic signals) were introduced for the analysis of the acoustic activity developed in marble specimens under uniaxial tension. The concepts introduced in Part I and the analysis procedure analytically described there, are here employed to analyze the acoustic emissions data gathered from additional experimental protocols in order to support and validate the conclusions drawn in Part I. In this direction, the acoustic activity generated in marble and concrete (either plain or reinforced with short polyolefin fibers) specimens under uniaxial compression or three-point bending, respectively, is studied in the direction of detecting characteristics of the temporal evolution of the D- and P-functions that could provide early hints warning about upcoming fracture. The evolution of the D- and P-functions is considered in juxtaposition to that of the F-function, which is in fact a convenient and flexible mean for the quantification of the average frequency of generation of the acoustic events. The conclusions drawn here are in excellent agreement with the respective ones drawn in Part I, suggesting that the D- and P-functions can indeed be a valuable tool in hands of engineers working in the field of Structural Health Monitoring of structures made of brittle building materials.

Low-Density and High-Performance Fiber-Reinforced PP/POE Composite Foam via Irradiation Crosslinking.

This study addresses the challenge of achieving foam with a high expansion ratio and poor mechanical properties, caused by the low melt viscosity of semi-crystalline polypropylene (PP). We systematically employ a modification approach involving blending PP with polyolefin elastomers (POE), irradiation crosslinking, and fiber reinforcement to prepare fiber-reinforced crosslinked PP/POE composite foam. Through optimization and characterization of material composition and processing conditions, the obtained fiber-reinforced crosslinked PP/POE composite foam exhibits both low density and high performance. Specifically, at a crosslinking degree of 12%, the expansion ratio reaches 16 times its original value, and a foam density of 0.057 g/cm3 is reduced by 36% compared to the non-crosslinked PP/POE system with a density of 0.089 g/cm3. The density of the short-carbon-fiber-reinforced crosslinked sCF/PP/POE composite foam is comparable to that of the crosslinked PP/POE system, but the tensile strength reaches 0.69 MPa, representing a 200% increase over the crosslinked PP/POE system and a 41% increase over the non-crosslinked PP/POE system. Simultaneously, it exhibits excellent impact strength, tear resistance, and low heat shrinkage. Irradiation crosslinking is beneficial for enhancing the melt strength and resistance to high temperature thermal shrinkage of PP/POE foam, while fiber reinforcement contributes significantly to improving mechanical properties. These achieve a good complementary effect in low-density and high-performance PP foam modification.

Torsional behavior of polyolefin fiber reinforced concrete Beams of different strength levels

Torsional behavior of polyolefin fiber reinforced concrete Beams of different strength levels

Experimental and Numerical Study of Torsional Solid and Hollow Section of Polyolefin Fiber-Reinforced Concrete Beams

An experimental and theoretical program was undertaken to enhance comprehension regarding how variations in fiber ratio impact the structural performance of both solid and hollow reinforced concrete beams when subjected to pure torsion. Polyolefin fiber was utilized in this study. To achieve this objective, a total of sixteen specimens of fiber-reinforced concrete beams were manufactured. Among these, eight were solid beams, while the remaining eight were hollow beams, all featuring rectangular cross-sections. These specimens were constructed employing polyolefin fiber. The findings indicated that incorporating polyolefin fiber into the concrete mixture led to improved mechanical properties in the cured concrete. The most significant enhancements were observed in the splitting tensile strength and flexural strength tests conducted on the specimens. Both solid and hollow beams exhibited notable enhancements in their torsional performance. These enhancements occurred as the polyolefin fiber percentage increased from zero to 1.5%, while the transverse and longitudinal reinforcement ratios remained constant. Furthermore, the reduction ratio of torsional strength becomes more noticeable when comparing solid and hollow sections in high-strength beams, as opposed to normal-strength beams.

Effect of macro-synthetic and hybrid fibres on the behaviour of square concrete columns reinforced with GFRP rebars under eccentric compression

GFRP rebars have emerged as a suitable alternative for steel rebars to tackle corrosion-related issues. However, the abrupt failure of GFRP-reinforced concrete (RC) elements due to the brittle behaviour of GFRP rebars is a significant concern. Fibre reinforced concrete (FRC) reduces brittleness by providing pseudo-ductility to GFRP RC members failing in compression. Moreover, fibre addition helps reduce crack widths by bridging them when subjected to tensile stresses. The current study aims to understand the influence of adding macro-synthetic Polyolefin (PO) and a hybrid mix of steel and PO fibres (HB) on the behaviour of GFRP-RC columns. Twenty-six square columns reinforced with GFRP rebars and discrete fibres are tested. A low-eccentricity to-width ratio (e/d of 0.2) and a high-eccentricity to-width ratio (e/d of 0.4) are chosen as loading parameters. The test matrix includes the following specimens: i) control with no fibres, ii) only PO fibres, and iii) a hybrid mix of steel and PO fibres. Test results show that specimens reinforced with hybrid fibres outperformed macro-synthetic fibres in energy absorption and strength improvement. They also had better post-peak behaviour under eccentric compression. Fibre addition increased the load resistance contribution of GFRP rebars and prevented the complete spalling of concrete cover. It also improved the deformabilty factors when compared to control columns with no fibres under eccentric compression.

Experimental study on flexural toughness of fiber reinforced concrete beams: Effects of cellulose, polyvinyl alcohol and polyolefin fibers

Flexural toughnesses of concrete reinforced by cellulose fibers (CTFs), polyvinyl alcohol fibers (PFs) and polyolefin fibers (VSs) are studied through notched beam tests. Flexural strength, ultimate strength, residual flexural and tensile strength, fracture energy, the relationship between crack mouth opening displacement and deflection, as well as the synergistic effect of hybrid fibers are investigated. The results show the following. (1) With the increase of fiber dosage, CTFs enhance the flexural strength and ultimate strength of concrete, while high dosages of PFs and VSs weaken the flexural and ultimate strengths. (2) CTF-PF hybrid fibers have a positive synergistic effect on the flexural strength and ultimate strength of concrete. (3) With the increase of fiber dosage, CTFs firstly strengthen and then weaken the fracture energy of concrete, while PFs weaken and then strengthen the fracture energy, and VSs strengthen the fracture energy. CTF1.2PF2.0VS2.0 is considered the optimal combination of hybrid fibers. (4) It is significant that there is a three-stage linear functional relationship between the crack mouth opening displacement and deflection of fiber reinforced concrete.

Durability and Mechanical Properties of Granulated Blast Furnace Slag Based Geopolymer Concrete Containing Polyolefin Fibers and Nano Silica

In the current study, the improvement of granulated blast furnace slag (GBFS) based geopolymer concrete (GPC) applying 0 – 2% polyolefin fibers (POFs) and 0 – 8% nano-silica (NS) is investigated. After curing the specimens, they are subjected to compressive strength, tensile strength, elastic modulus, Ultrasonic Pulse Velocity (UPV), and impact resistance tests to evaluate their mechanical properties and durability. Moreover, the permeability of specimens is also assessed using water absorption. The compressive strength, tensile strength, and elastic modulus of the concrete increase by up to 22%, 14%, and 24%, respectively. The addition of the POFs to the GPC significantly increases the tensile strength (by up to 9%) and the absorbed energy due to the impact. By adding NS to the GPC composition, the results of the permeability and water capillary absorption test were improved. These results are evaluated through microstructure analysis, along with ultrasonic, X-Ray diffraction (XRD), X-Ray fluorescence (XRF), and scanning electron microscope (SEM) tests.

Mechanical properties of polyolefin and polypropylene fibers-reinforced concrete–An experimental study

Concrete, a widely used construction material, exhibits inherent brittleness and limited tensile strength. To address these shortcomings, the incorporation of fibers has gained prominence, with polyolefin and polypropylene fibers emerging as promising reinforcements. This study experimentally conducted and examined the mechanical characteristics of polyolefin and polypropylene fibers-reinforced concrete. The study involved conducting compressive strength tests and durability tests, including sulfate resistance, acid resistance, chloride ion penetration resistance, and abrasion tests. The results demonstrated a notable enhancement in the compressive strength of both cubic and cylindrical specimens with varying dimensions, owing to the inclusion of polyolefin fibers. Polyolefin fibers exhibited a greater reinforcing effect compared to polypropylene fibers, especially in larger cubic specimens and cylindrical specimens. The quantitative results show that specimens with polypropylene fibers exhibited a 9.67 % improvement in compressive strength, while those with polyolefin fibers showed a 30.47 % enhancement compared to specimens without fibers. The acid resistance test revealed that both types of fiber-reinforced specimens exhibited higher compressive strength in acidic environments compared to plain concrete specimens. In the chloride ion penetration resistance test, the polyolefin fiber-reinforced specimen demonstrated the highest resistance to degradation, while the plain concrete specimen exhibited the lowest resistance. Polyolefin demonstrated superior reinforcement compared to polypropylene, with a 35 % increase in acid resistance and better chloride ion resistance. In contrast, specimens without fibers weakened by 35.36 % in a chloride environment. The sulfate resistance test showed that the polyolefin fiber-reinforced specimen had the highest compressive strength in a sulfate environment, while the plain concrete specimen had the lowest. In sulfate and abrasion tests, polyolefin-fiber-reinforced specimens displayed the highest resistance and the lowest abrasion rate of 34.6 %. These findings highlight the potential of polyolefin fiber-reinforced concrete for enhancing mechanical properties and durability in various applications.

Effect of Macro Polyolefin Fibers on Bond Strength of Tension Lap Splices in RC Beams

The effect of macro synthetic polyolefin fibers on the bond strength of tension lap splices in reinforced concrete (RC) beams is investigated in this study. The bond between the reinforcement and concrete plays a vital role in the strength of RC beams. The presence of polyolefin fibers in the lap splice zone confines the concrete and enhances the bond strength of the steel bars. The use of synthetic fibers is preferable to steel ones since steel suffers from corrosion over time. Tests were conducted on 12 full-scale beam specimens to determine the effect of fiber volume fraction (Vf), bar diameter (db) and concrete cover-to-bar diameter (c/db) on the response. Four volume fractions (Vf = 0, 0.5, 1 and 1.5%) of polyolefin fibers and three bar sizes (db = 16, 20 and 25 mm) with the corresponding (c/db = 2.31, 1.75 and 1.30) were considered to evaluate the bond strength. The test results demonstrated that the polyolefin fibers noticeably enhanced the bond strength and ductility of spliced tension bars. Experimental results were compared with those obtained from two theoretical methods including ACI Committee 318 design provisions. The results showed that the equation proposed by the ACI Committee overestimates the bond strength.

Numerical Simulation of PFRC Fracture Subjected to High Temperature by Means of a Trilinear Softening Diagram.

Fibre-reinforced concrete (FRC) has been used for decades in certain applications in the construction industry, such as tunnel linings and precast elements, but has experienced important progress in recent times, boosted by the inclusion of guidelines for its use in some national and international standards. Traditional steel fibres have been studied in depth and their performance is well-known, although in recent years new materials have been proposed as possible alternatives. Polyolefin macro-fibres, for instance, have been proven to enhance the mechanical properties of concrete and the parameters that define their behaviour (fibre length, fibre proportion or casting method, for instance) have been identified. These fibres overcome certain traditional problems related to steel fibres, such as corrosion or their interaction with magnetic fields, which can limit the use of steel in some applications. The behaviour of polyolefin fibre-reinforced concrete (PFRC) has been numerically reproduced with success through an embedded cohesive crack formulation that uses a trilinear softening diagram to describe the fracture behaviour of the material. Furthermore, concrete behaves well under high temperatures or fire events, especially when it is compared with other construction materials, but the behaviour of PFRC must be analysed if the use of these fibres is to be extended. To this end, the degradation of PFRC fracture properties has been recently experimentally analysed under a temperature range between 20 °C and 200 °C. As temperature increases, polyolefin fibres modify their mechanical properties and their shape, which reduce their performance as reinforcements of concrete. In this work, those experimental results, which include results of low (3 kg/m3) and high (10 kg/m3) proportion PFRC specimens, are used as reference to study the fracture behaviour of PFRC exposed to high temperatures from a numerical point of view. The experimental load-deflection diagrams are reproduced by modifying the trilinear diagram used in the cohesive model, which helps to understand how the trilinear diagram parameters are affected by high temperature exposure. Finally, some expressions are proposed to adapt the initial trilinear diagram (obtained with specimens not exposed to high temperature) in order to numerically reproduce the fracture behaviour of PFRC affected by high temperature exposure.

Investigating the Mechanical and Durability Properties of Geopolymer Concrete Based on Granulated Blast Furnace Slag as Green Concrete

Geopolymer concretes (GPCs) are known as green, environmentally friendly, sustainable concretes in the development of the structural industry with superior mechanical performance and durability compared to ordinary Portland cement concrete (OPCC). This type of concrete emits less CO2 than OPCC and aims for efficient waste management while reducing environmental impacts. In this experimental research, 5 mixed designs were made of GPC based on granulated blast furnace slag (GBFS), which contains 0-8% Nano silica (NS) and 1-2% polyolefin fibers (POFs). A mixed design was also made of OPCC to compare with GPC. The tests of compressive strength, tensile strength, drop weight impact (DWI), Ultrasonic Pulse Velocity (UPV), water permeability and microstructural examination by scanning electron microscope (SEM) images and X-ray fluorescence (XRF) spectroscopy were performed on concrete samples and the results were analyzed and compared. The results obtained in this laboratory research, while overlapping with each other, indicate the superiority of mechanical properties and durability of GPC compared to OPCC.

Microcrack monitoring and fracture evolution of polyolefin and steel fibre concrete beams using integrated acoustic emission and digital image correlation techniques

The use of polymer and steel fibres in plain concrete appears to be an excellent solution for limiting crack propagation and improving the post-ductility performance of concrete structures. Based on this premise, this study investigated the fracture evolution of polyolefin fibre-reinforced concrete (PFRC) and steel fibre-reinforced concrete (SFRC) specimens through the integrated application of two diagnostic techniques, acoustic emission (AE) and digital image correlation (DIC), under three-point bending tests. Based on the processing of AE signals, different AE statistical parameters such as the cumulative number of hits, amplitude distribution, and some representative analysis methods including the b-value method, Ib-value method, and AE intensity analysis methods were selected to analyse the early detection of cracking and post-cracking behaviour in PFRC vs SFRC specimens during mechanical degradation. Simultaneously, the DIC technique was used to validate the fracture evolution of the AE results. Furthermore, to verify the reliability of the AE and DIC results, the damage localisation and fracture evolution of the PFRC versus SFRC specimens were confirmed by integrating the AE fracture energies and DIC outcomes. The tests and analysed results showed that the addition of steel fibres to plain concrete significantly improved the ability to restrict crack propagation and provided higher post-cracking resistance compared to PFRC specimens owing to their stronger fibre–matrix bonding, effective fibre bridging, and crack-arresting mechanism. The present study indicates that the combined AE and DIC techniques are highly effective for the early detection of damage and ductility performance in fibre-reinforced concrete structures.

Evaluation of Mechanical Properties and Microstructure of Pozzolanic Geopolymer Concrete Reinforced with Polymer Fiber

In recent decades, Geopolymer concrete (GPC) is a new material in the construction industry, which has favorable performance and workability and contains aluminosilicate materials full of silicate (Si), aluminum (Al), and alkaline solution as a binder. The advantages of using geopolymer materials instead of cement in concrete are not limited to high mechanical and microstructural properties. It also has a remarkable effect in reducing greenhouse gas emissions. In the current study, Granulated Blast Furnace Slag (GBFS) GPC was used with 0-2% polyolefin fibers (POFs) and 0-8% nano-silica (NS) to improve its structure. After curing the specimens under dry conditions at a temperature of 60 °C in an oven, they were subjected to compressive strength, tensile strength, elastic modulus, ultrasonic pulse velocity (UPV) and impact resistance tests to evaluate their mechanical properties. The addition of NS enhanced the whole properties of the GBFS geopolymer concrete. The compressive strength, tensile strength, and elastic modulus of the concrete increased by up to 22%, 14%, and 24%, respectively. Besides, it leads to ultrasonic wave velocity enhancement to 12% in the room temperature. The addition of the fibers to the GPC significantly increased the tensile strength (by up to 9%) and the energy absorbed due to the impact. Moreover, compared to Concrete containing ordinary portland cement (OPC), the GPC demonstrated much better mechanical and microstructural properties. Besides, the presence of POFs in the GPC compound substantially affects tensile strength and resistance against an impact. Accordingly, the sample’s tensile strength had an improvement by 8.4% in the room temperature. In the following, by conducting the X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), and Scanning electron microscope (SEM) tests, a microstructure investigation was carried out on the concrete samples. In addition to their overlapping with each other, the results indicate the GPC superiority over the regular concrete.

Experimental study on bio fiber reinforced composites

Biofibers are an economical, environmentally friendly, and lightweight alternative to traditional materials. Different types of fibers have different properties, and each plays a key role in composites. Screw Pine (Pandanus Odoratissimus) is abundant and strong. This research made and tested NaOH- and Acetic Acid-treated random fiber composites. This research shows the mechanical properties of Pandanus Odoratissimus composite. The stem of the screw pine plant, Pandanus Odoratissimus, contained several interesting fibers (PO fibers). This research will investigate the effect of fibre concentration and alkali treatments on the mechanical properties of unsaturated polyester matrix composites. Similarly, soaking times will vary for alkali treatments. Individual PO fibres exhibit modifications in their cross-sectional area and water absorption prior to and after treatment with NaOH solution and acetic acid for varying durations of time. These modifications are observable prior to and after treatment. As a result of extended therapy, the cross-sectional area of PO fibres gradually decreases. Compared to other fibre types, PO fibres that were submerged in water for the longest period of time exhibited the most structural degradation. There is a considerable effect on the improvement of polyester composites' tensile strength and tensile modulus when PO fibre is soaked in different concentrations of NaOH and acetic acid for roughly 90 min. This influence is significant. This investigation will also shed light on how the composition of polyolefin (PO) fibres influences the mechanical properties of composite materials. Maximum tensile strength of a composite material is proportional to the fraction of fibres present in the material. After calculating tensile, compressive, shear, and other stresses, materials (components) are manufactured.

The Effect of Type of Fiber in Density and Splitting Tensile Strength of SIFCON

SIFCON is characterized as a construction material of high ductility and very high strength. It is suitable for concrete structures used for special applications. However, the density of SIFCON is much higher than that of Fiber Reinforced Concrete (FRC) due to the need for a large amount of high-density steel fibers. This work examines the split tensile behavior of modified weight slurry infiltrated fiber concrete utilizing a mixture of two types of fibers, steel fiber, and polyolefin fiber. For the investigation, 30 cylinders and 15 cubes were poured. The used volume fraction (V.F) is (6 %) and the use of five series once as each type separately and once a hybrid in proportions of 2/3 polyolefin with 1/3 steel fiber and vice versa. The splitting tensile strength and the unit weight of SIFCON resulting from tests were studied. The results indicate that SIFCON produced from a mixture of 1/3 hook-end steel fibers with 2/3 polyolefin fibers achieved good results in reducing density while maintaining a high split tensile strength. It significantly decreased density by 140 kg per cubic meter and improved splitting tensile strength by 494%.

Comparative Study of Concrete Reinforced with Polyolefin Fiber

This research aims to analyze the mechanical behavior of concrete reinforced with polyolefin fibers. The intention is to evaluate the possibility of using concrete as a structural material without steel bars in its interior. For this purpose, specimens with different dosages of polyolefin fibers were prepared, and bending and compression tests were carried out. The results show no significant increase in mechanical strengths, especially in bending, but it is interesting in the mechanical behavior after the first cracking. Controlling cracking is considered beneficial for sustainability.