Macro Polypropylene Fiber Research Articles

Performance evaluation of indented macro synthetic polypropylene fibers in high strength self-compacting concrete (SCC)

Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0–1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread.

Analysis of synergistic effect of bending energy absorption capacity of fiber reinforced concrete based on fiber distribution characteristic

Macro fibers could contribute to absorb energy through fiber sliding, which significantly enhance the energy absorption capacity of concrete beams. In this research, the synergistic effect of macro steel fibers and polypropylene (PP) fibers on the energy absorption capacity of concrete under bending is under investigated. The three-point bending test is adopted to compared the residual flexural strength and energy absorption capacity of fiber reinforced concrete (FRC) beams. Besides traditional Load-deflection curves, the energy absorption-crack mouth opening displacement (CMOD) curves are adopted to reflect the toughness of FRC beams. The synergistic effect of steel fibers and PP fibers on the residual flexural strength and energy absorption capacity is evaluated. A linear function is proposed to describe the relationship between energy absorption and CMOD for FRC beams. In addition, fiber distribution on cracking surface of FRC beams is analyzed through fiber distribution density and fiber spacing to explain the synergistic effect. Experimental results indicate that the behaviors of FRC beams, that is, residual flexural strength and energy absorption, are improved by adding macro fibers, in particular macro steel fibers. Besides, the relationship between energy absorption and CMOD of FRC beams can be fitted very well by the linear function. The slope of the energy absorption and CMOD relationship is adopted to analyze the contribution of macro fibers to energy absorption. The uniformity of fiber distribution is improved by increasing of fiber dosage for SFRC and PFRC beams. The hybrid use of macro steel fibers and PP fibers demonstrates a positive synergistic effect on the energy absorption capacity and flexural strength of concrete. The improved fiber spacing and fiber distribution density of hybrid fiber on cracking surface contribute to the positive synergistic effect observed in hybrid fiber reinforced concrete (HyFRC) beams.

Yield line-based design of fibre reinforced concrete: assessment of suitability of material models

The present research is intended to address the adequacy of flexural toughness-based material models such as equivalent and residual flexural strength, and the deflection limits at which these parameters are estimated for design of fibre reinforced concrete (FRC), for various applications such as slabs-on-grade/pavements. The work is an experimental study using FRC concrete mixes with individual and hybrid combinations of hooked-end steel (SF) and macro polypropylene fibres (PF). The experimental investigation consisted of toughness testing unnotched and notched prisms and square slabs, prepared with a typical grade of concrete used for FRC pavement applications. To validate the material models, a comparison was made between the theoretical moment/load calculated based on material flexural toughness parameters and the actual moment obtained from slabs using actual yield line formed during testing. From the study it is observed that overall, both equivalent (from unnotched prism test) and residual (from notched prism test) flexural strength, are suitable for designing FRC slabs, however the equivalent strength parameter shows better correlation to the slab response. The results also indicate that the hybrid mixes of PF and SF, with a higher volume fraction of 0.6% Vf, shows a marginal increase in flexural performance, in comparison to the mixes with lower volume fraction but no or minimal synergy due to hybridisation.

QUALITY IMPROVEMENT EFFECTIVENESS OF ROAD SLABS PRODUCED USING MICROSILICA AND FIBER

Here we present the results of testing the concrete physical and mechanical properties for road slabs reinforced with bulk fiber, including polypropylene macro- and microfibers. We have analyzed the effect of the use of macrofibers and microfibers in the concrete composition. There was established the impact of low-modulus synthetic fibers on the characteristics of strength, density, water resistance and frost resistance of concrete for road pavement. It was established that polypropylene macrofibers impact on the physical and technical characteristics of concrete, increase compressive and bending strength, and polypropylene microfibers improve the structure of the cement component of concrete, optimize the pore space, increase the frost resistance and water resistance of concrete. It has been experimentally proved that owing to the combined use of various sized fiber fibers, it is possible to produce concrete that has good characteristics in strength, density and frost resistance. It was established that with the combined concrete fiber reinforcement with microsilica addition, we get the possibility of increasing bending strength up to 35%, frost resistance up to F375 and water resistance up to W14. The research results make it possible to recommend multi-dimensional polypropylene fibers for volumetric reinforcement and microsilica to create additional crystallization centers and reduce the pore space in the concrete body at road slabs manufacture.

Research on Tensile Softening Constitutive Relation of Macro Polypropylene Fiber Reinforced Concrete

Research on Tensile Softening Constitutive Relation of Macro Polypropylene Fiber Reinforced Concrete

Effect of Graphene Oxide Surface Deposition Process on Synthetic Macrofibers and Its Results on the Microstructure of Fiber-Reinforced Concrete.

The improvement of the mechanical properties of concrete can be achieved with the use of synthetic macrofibers. However, this fiber-matrix interaction will be sufficiently efficient for tensile efforts only when there is a binding agent that associates the characteristics of the paste with the characteristics of the surface of the reinforcing material. As already identified, in a first phase of this research using synthetic microfibers, a better fiber-matrix interaction can be achieved with the surface treatment of synthetic fibers with graphene oxide. In this way, we sought to evaluate the surface treatment with graphene oxide on two synthetic polypropylene macrofibers (macrofiber "A" and macrofiber "B") and its contribution to the concrete transition zone. The surface deposition on the macrofiber was carried out using the ultrasonication method; then, the macrofiber with the best deposition for creating reinforced concrete mixtures was identified. To evaluate the quality of GO deposition, scanning electron microscopy (SEM-FEG) and energy-dispersive spectroscopy (EDS) tests were carried out; the same technique was used to evaluate the macrofiber-matrix transition zone. The SEM-FEG images indicated that macrofiber "B" obtained greater homogeneity in surface deposition and it presented a 13% greater deposition of C in the EDS spectra. The SEM-FEG micrographs for reinforced concrete indicated a reduction in voids in the macrofiber-matrix transition zone for concretes that used macrofibers treated with GO.

Damage constitutive model of polypropylene-fibre-reinforced recycled aggregate concrete

Adding polypropylene fibre (PPF) to recycled aggregate concrete (RAC) not only improves performance but also has economic benefits. The effects of single-blend and double-blend micro- and macro-PPFs in RAC specimens were studied. Micro- and macro-PPFs were used to design and produce 30 groups of PPF-reinforced RAC specimens with 0%, 25% and 50% coarse aggregate (CA) substitution rates. Controlling the fibre mixing proportions, the stress–strain curve, elastic modulus, peak strength, peak strain and acoustic emission amplitude–frequency extremum (AFE) of each group of specimens were obtained. The elastic modulus and peak stress of specimens without PPFs decreases gradually with an increase of the CA substitution rate. However, there was a certain increase in elastic modulus and peak stress when PPFs were added. A damage constitutive model for PPF-reinforced RAC was established. By fitting this model, it was found that although the elastic modulus and peak stress of the RAC specimens increased by a certain extent, the fitting parameters of RAC were greater than those of ordinary concrete and the RAC post-peak strength was lower. The evolution law of acoustic emission AFE of PPF-reinforced RAC was studied. It was found that the cumulative AFE of RAC with PPF was larger, indicating that the PPFs limited crack propagation and increased the fracture energy.

Durability Properties of Macro-Polypropylene Fiber Reinforced Self-Compacting Concrete.

Concrete is one of the most commonly used construction materials; however, its durability plays a pivotal role in areas where the concrete is exposed to severe environmental conditions, which initiate cracks inside and disintegrate it. Randomly distributed short fibers arrest the initiation and propagation of micro-cracks in the concrete and maintain its integrity. Traditional polypropylene fibers are thin and encounter the problem of balling effects during concrete mixing, leading to uneven fiber distribution. Thus, a new polypropylene fiber is developed by gluing thin ones together, forming macro-polypropylene fibers. Thus, different amounts of fibers, 0-1.5% v/f with an increment of 0.5% v/f, are used in different grades of concrete to study their impact on durability properties, including resistance to freezing and thawing cycles, sulfate, and acid attacks. A total of 432 cube samples were tested at 28, 56, and 92 days. The results reveal that the maximum durability, in terms of compressive strength loss, is noted with a fiber content of 1% with improved resistance of 72%, 54%, and 24% against freeze-thaw cycles, sulfate attack, and hydrochloric acid attack, respectively, at 92 days. Thus, the resulting fiber-reinforced concrete may be effective in areas where these extreme exposure conditions are expected.

Fin Sandy Concrete Reinforced with Macro Polypropylene Fiber for Rural And Desert Housing

Fin Sandy Concrete Reinforced with Macro Polypropylene Fiber for Rural And Desert Housing

Comparative performance analysis of ground slabs and beams reinforced with macro polypropylene fibre, steel fibre, and steel mesh

This study examines the structural performance of concrete slabs and beams reinforced with various types of reinforcement under centrally concentrated loading until failure. Three types of reinforcement were studied, including steel meshes (A142), steel fibers (30 kg/m3), and macro polypropylene (PP) fibers (6 kg/m3). The study discusses the fracture behavior of ground slabs and the enhancement in performance resulting from the inclusion of PP and steel fibers in terms of load–strain and load–deflection responses, deflection profiles, and crack patterns. In addition, the study compared the flexural behavior of fiber-reinforced concrete beams to determine the effectiveness of using various fibers in beams and slabs. The results revealed a significant increase in the flexural strength of steel fiber or steel mesh reinforced slabs on the ground as compared to the reference specimen while slabs reinforced with PP fibers showed favorable results in post-cracking performance and energy absorption compared to steel fibers. The use of PP fibers, steel fibers, and steel meshes can improve the flexural cracking strength of concrete slabs by 28%, 47%, and 79%, respectively. However, predictions based on the beam tests and physical properties of steel mesh overestimated the flexural strength of ground slabs by 12%, while the corresponding predictions of PP fiber-reinforced slabs and steel fiber-reinforced slabs were 45% and 24% higher than the experimental results. This study provides insights into the performance of different types of reinforcements in concrete slabs and beams, which can be valuable in designing and constructing reinforced concrete structures.

Mechanical behaviour of wollastonite-based cement composites incorporating fibres and recycled rubber aggregates

Calcium phosphate cement (CPC) is a wollastonite-based inorganic cement that hardens at room temperature to a brittle cementitious material with low fracture behaviour. Recycled rubber aggregates from end-of-life tyres were incorporated up to 17.5 wt% into the CPC matrix to produce high-strength composites with improved strain capacities for structural repair purposes. Furthermore, the effects of 0.75% and 1.5% volume fibre content (Vf) of macro polypropylene, amorphous metallic and recycled carbon fibres on the flexural behaviour of CPC were studied. The synergy between the rubber aggregates and the selected corrosion-resistant fibres in improving the fracture properties of the plain CPC was investigated. The changes in other mechanical properties of CPC such as modulus of rupture, compressive and splitting tensile strength due to the inert inclusions (i.e. rubber aggregates and/or fibres) were determined. It was found that increasing the quantity of inert inclusions in the cement matrix improved the fracture energy of the plain CPC. Incorporating 1.5% Vf of macro polypropylene, amorphous metallic, and recycled carbon fibres into the CPC matrix produced cementitious composites with fracture energies that were 11.8 times, 63.4 times, and 75.8 times that of plain cement, respectively. For the rubberised fibre-reinforced CPC composites, a positive synergistic relationship was observed between rubber aggregates and macro polypropylene fibres while a negative synergistic relationship was found between rubber aggregates and the other fibres (amorphous metallic and recycled carbon fibres). The rubber aggregates decreased the flexural, compressive and splitting tensile strengths of the plain CPC, while the fibre inclusions improved these properties.

The effects of steel, polypropylene, and high-performance macro polypropylene fibers on mechanical properties and durability of high-strength concrete

Present study aimed to compare the properties of high-strength and ordinary concrete containing polypropylene fibers (PPFs), high-performance synthetic macro polypropylene (HPP) fibers, and steel fibers (SF) under standard and sulfate curing conditions. The high-strength concrete with water-to-cement ratios of 0.38, 0.33, and 0.28 were tested. The addition of PPF and SF reduced the workability of these mixtures containing supplementary cementitious material. The highest compressive strength belongs to the mixture containing 1% of SF and 0.2% of PPF. The highest tensile strength belongs to the mixture containing 0.5% of HPP fibers with 1% of SF and 0.2% of PPF. The highest flexural strength of the mixture containing 0.5% of HPP fibers with 1% of SF. Fiber- reinforced concretes have less 30-minute water absorption than non-fiber samples. The minimum absorption belongs to the sample containing 0.5% of PPF with 20% of silica fume in the amount of 0.53%.

Improved simplified constitutive tensile model for fiber‐reinforced concrete

AbstractDue to the low strain capacity and the weak crack resistance of concrete, fibers are commonly added to concrete to increase its tensile resistance. The most recent standardized constitutive tensile model is given in the fib Model code 2010, which is based on a simplified stress profile at serviceability limit state (SLS) and ultimate limit state (ULS). However, in current research, an improved stress profile at ULS is proposed. Consequently, three new constitutive tensile models, which are valued for a specific FRC class, are developed. Those models are constructed with the test data of fiber‐reinforced concrete with natural aggregates (FR‐NAC) and three types of recycled aggregates (FR‐RAC). In addition, macro glass fibers and macro polypropylene fibers are used. The test data indicate that the lower concrete Young's modulus of FR‐RAC, as well as the crack growth resistance due to plastic work of the recycled concrete mixtures, result in an increased residual tensile strength at SLS and ULS. The residual tensile strength at 2.5 mm CMOD () of the normal recycled aggregate concrete (nRAC) mixture with 0.75 V% glass fibers is 0.95 MPa, while the FR‐NAC mixture with the same fiber content only indicates a ‐value of 0.43 MPa. Consequently, higher linear postcracking stresses are observed for the FR‐RAC mixtures, especially for the FR‐RAC mixtures with 0.75 V% glass fibers and the lower quality of recycled aggregates.

Influence of Synthetic Fibers on the Flexural Properties of Concrete: Prediction of Toughness as a Function of Volume, Slenderness Ratio and Elastic Modulus of Fibers.

The construction industry requires concrete with adequate post-cracking behavior for applications such as tunnels, bridges, and pavements. For this reason, polypropylene macrofibers are used, which are synthetic fibers that fulfill the function of providing residual strength to concrete. In this study, an experimental plan is carried out to evaluate the bending behavior of concrete reinforced with polypropylene fibers using the four-point bending test according to ASTM C1609. Three fiber dosages (3.6, 7.2 and 10.8 kg/m3) and three fiber lengths (40, 50, and 60 mm) were used. The use of macro polypropylene fibers increased the post-cracking behavior of concrete. In addition, based on the experimentally obtained results and available literature data, a multivariable equation was developed to predict the concrete toughness as a function of the volume, slenderness, and modulus of elasticity of the fibers. A Pearson's correlation coefficient, r of 0.90, showed a strong correlation between the developed equation and the experimental data. From this equation, it was possible to determine the participation of the following parameters in calculating toughness. The participation or weight of the fiber's modulus of elasticity on the concrete's tenacity is 26%, the volume of the fiber is 39%, the slenderness is 19%, and the reinforcement index is 16%.

Experimental Study on Impact Behavior of Concrete Panel with and without Polypropylene Macrofibers

Macrofibers have often been used to increase the tensile strength, durability, crack resistance, spalling, impact resistance, and toughness of concrete. However, the impact behavior of fiber-reinforced concrete (FRC) structures is quite different from their static behavior, and the effectiveness of macrofibers in improving impact resistance should be carefully evaluated. In this study, the impact behavior of FRC with polypropylene (PP) macrofibers was studied through a series of drop-weight impact tests. First, the material characteristics of the FRC with PP fibers under static conditions were evaluated. Test specimens were constructed and drop-weight impact tests were performed. The main parameters were the presence or absence of PP fibers and the drop height, which is related to the magnitude of the impact energy. From the results, it can be found that the crack width of the FRC specimen was smaller than the normal concrete specimen for a similar residual deflection after the impact test due to the bridging effect of the macrofibers. However, the effect of PP fibers on the impact resistance was not significant, even though there was a considerable increase in tensile and flexural performance under static conditions, since the hardening effect after the sharp reduction in strength shown in the static test of FRC is not effective in the impact test.

Flexural Behavior of High Strength RC Beams Incorporating Nano-Silica and Macro-Polypropylene Fiber

This paper investigates the flexural behavior of high-strength RC beams experimentally to assess the effect of Nano-silica (NS) and Macro-Synthetic High Strength Polypropylene Fiber (MPF). Ordinary Portland cement was partially replaced by the NS and MPF with different proportions to produce four concrete mixtures. Tests were conducted on the full-scale high-strength RC beams, including first crack load, failure load, deflection, concrete strain, steel strain, and mode failure, which were examined and compared. In addition, the tests on the mechanical properties of high-strength concrete mixtures were also conducted at the ages of 28 and 56 days. The test results concluded that the addition of NS and MPF significantly improved the first-cracking and failure loads and decreased deflection at levels of cracking and failure loads. Additionally, an increase in NS content resulted in a minor increase in the ultimate strain related to the failure loads. Furthermore, the mix of 3% NS with 0.5% MPF was found to lead to the highest mechanical characteristics of concrete. The improvements were the concrete compressive strength by 33.6%, split tensile strength by up to 54.1%, and flexural strength by up to 28.3% compared with control specimens.

Experimental Study on Dynamic Tensile Properties of Macro-Polypropylene Fiber Reinforced Cementitious Composites

Using a high-speed photography system and a split Hopkinson pressure bar, macro-polypropylene fiber reinforced cementitious composites are tested to reveal the effects of the macro-polypropylene fiber volume fraction and loading rate on the dynamic tensile strength and failure mode. We also analyze the functional relationship between the dynamic tensile strength, loading rate, and fiber volume fraction, and study the splitting failure process using digital image correlation technology. The evolution law of the strain and displacement fields of the specimens is obtained, and the effect of the fiber volume fraction on the crack initiation strain value is quantitatively studied. The results show that the appropriate fiber content (1.5–2%) can significantly improve the dynamic tensile strength, while a higher fiber content (2.5%) leads to deterioration of the specimen. Adding macro-polypropylene fiber prevents the specimen from undergoing central tensile fracturing under dynamic loading, and distributes the impact load more evenly, thus improving the ability of the specimen to resist cracking.

Experimental Volume Incidence Study and the Relationship of Polypropylene Macrofiber Slenderness to the Mechanical Strengths of Fiber-Reinforced Concretes

An experimental study was conducted to examine the mechanical strengths of concretes with straight high-strength knurled polypropylene macrofibers. Incidences of concrete mechanical strengths were determined for three different fiber dosages and lengths. In addition, compressive, indirect-splitting-test tensile, and flexural strengths were determined through testing. The results showed no statistically significant correlation between the volume and length of fibers with the compressive strength of polypropylene fiber-reinforced concrete (PPFRC). However, there was a statistically significant correlation between the split tensile strength, the volume, and the length of the fibers when the volume was greater than 0.80%, and the length of the fibers was greater than 50 mm. Furthermore, the modulus of rupture increased when the volume of fibers was greater than 0.80% and the length of the fibers was 60 mm. Finally, equations were proposed to determine the tensile strength by split test and the modulus of rupture as a function of the mixture’s resistance without fibers, the fibers’ volume and length.

Interfacial bond characteristics of polypropylene fiber in steel/polypropylene blended fiber reinforced cementitious composite

This paper investigates for the first time the interfacial bond characteristics of polypropylene fiber in blended hybrid steel-polypropylene fiber reinforced concrete, which contributes to improving the polypropylene fiber utilization efficiency and then promoting the overall performance of the composite. Single-sided fiber pullout tests were performed on 21 groups of macro polypropylene fiber pullout specimens. The complete fiber pullout load-slip responses were captured, and the fiber interfacial properties were analyzed for different hybrid fiber dosage, fiber embedded length and matrix length. Results show that partial fiber rupture with a non-zero residual pullout load is the dominant failure mode. Increasingly severe abrasion at the PF surface is observed during the pullout process, resulting in a strain hardening behavior after a bent-over point is reached in a typical pullout load-slip curve. An appropriate polypropylene fiber addition in the concrete matrix can effectively improve the maximum pullout load, residual pullout load, the pullout energy, and the contribution of polypropylene fibers is more critical than that of steel fibers. Besides, the reinforcement of polypropylene fibers on the toughness and cracks resistance is proven to be more pronounced in plain concrete than that in high-strength concrete. Finally, theoretical analyses were performed on the polypropylene fiber direct pullout problem and the frictional bond stress vs. slippage relation is obtained with hybrid fiber content taken into account. The research provides a base for an optimized hybrid fiber reinforced concrete with high fiber efficiency and less cement consumption.

Concrete by Preplaced Aggregate Method Using Silica Fume and Polypropylene Fibres.

Preplaced aggregate concrete (PAC) is prepared in two steps, with the coarse aggregate being initially laid down in the formwork, after which a specialised grout is injected into it. To enhance the properties of concrete and to reduce the emission of CO2 produced during the production of cement, supplementary cementitious materials (SCMs) are used to partially substitute ordinary Portland cement (OPC). In this study, 100 mm × 200 mm (diameter x height) PAC cylinders were cast with 10 per cent of cement being substituted with silica fume; along with that, 1.5% dosage of Macro polypropylene fibres were also introduced into the coarse aggregate matrix. Compressive strength test, splitting tensile strength test, mass loss at 250 °C, and compressive strength at 250 °C were performed on the samples. PAC samples with 10% of cement replaced with Silica Fume (SPAC) were used as control samples. The primary objective of this study was to observe the effect of the addition of Polypropylene fibres to PAC having Silica fume as SCM (FRPAC). The aforementioned tests showed that FRPAC had a lower compressive strength than that of the control mix (SPAC). FRPAC had greater tensile strength than that of NPAC and SPAC. Mass loss at 250 °C was greater in SPAC compared to FRPAC. The compressive strength loss at 250 °C was significantly greater in FRPAC compared to SPAC. FRPAC exhibited a greater strain for the applied stress, and their stress-strain curve showed that FRPAC was more ductile than SPAC.