Recycled Polypropylene Fibers Research Articles

Structural performance of fibre reinforced recycled aggregate concrete road kerb sections under monotonic and cyclic loading

In recent years, there has been a notable emphasis on waste reduction and the adoption of recycled materials within the construction industry to reduce the industry’s overall carbon footprint. This study investigates the structural performances of concrete kerb sections prepared with five different concrete mixes containing recycled concrete aggregate, recycled tyre-derived aggregates and recycled polypropylene fibres. Kerb sections were cast at a road site in a suburb of Adelaide, Australia. After the concrete hardened, sections were cut and brought to the laboratory. A large number of monotonic and cyclic load tests were conducted on the kerb sections. The load-carrying capacity, bending moment capacity, cyclic fatigue capacity, durability properties along with deformation tolerance were evaluated. Kerb sections made with concrete containing recycled aggregate and polypropylene fibre could sustain nearly 2000 cycles of loading. Kerb sections prepared with natural aggregate concrete performed comparatively better. The addition of polypropylene fibre significantly improved the post-cracking behaviour of kerb sections and can delay crack propagation and other distress when subjected to cyclic loadings such as excessive soil movement, e.g., in areas with expansive soils or prone to tree root migration. Long-term observation may be required to confirm the mechanical and durability performance improvement in real field conditions.

Polymer-fiber combined effect for improving sand mechanical and micro-damage response

Sand instability is always an intractable problem in geotechnical engineering and its reinforcement using additives is an effective method. This paper introduces the organic polymer reinforcer (OPR) and the recycled polypropylene fiber (RPF) to modify sand. The unconfined compression and corresponding numerical tests were performed to investigate mechanical properties, deformation failure behavior, and microscopic response. Results showed that both materials positively affect the mechanical and deformation properties of modified sand synergistically. Optimized particle structure by the inter-particle polymer membrane linked the loose sand into a whole with fibers as a framework. Strain-softening properties were reduced with less strain localization under loading. This is also clearly related to the improvement of the micro-damage based on numerical results. OPR-RPF reinforcement transformed the bond failure from unidirectional concentration to multilocal dispersion by improving force chain construction, microcrack propagation, and energy allocation. Thus, the failure of modified sand showed a macroscopic progression from shear-faulting via ductile-faulting to ductile flow. Future research lies in further considering the particle shape and pore structure variations to provide new insights for a deeper understanding of sand stabilization mechanisms and engineering applications.

Impact of Recycled Polypropylene Fibers on the Density and Strength of Unreinforced Concrete

Polypropylene (PP) is widely used in the construction industry to produce a variety of materials. Accordingly, a huge amount of waste is produced during or after the construction activity. The PP fiber provides a good alternative solution to enhance concrete properties and more sustainable concrete produced in terms of isolation and weight reduction. In this study, 24 concrete cubic samples are cast by adding different PP fiber content to characterize this fiber effect on concrete density and unconfined compressive strength (UCS). The results demonstrate that using higher fiber content of 2%, 6%, and 10% leads to a mass reduction that equals to 59, 157, and 290 kg compared to normal concrete per one cubic meter. However, at higher PP fiber content, the unconfined compressive strength decreases compared to the controlled samples. The concrete mix with 2% PP fiber revealed a higher value of compressive strength with increment by (10-12)% at age (7-28) days compared to normal concrete. The outcomes imply that using PP fiber contributes to the protection of the environment by reducing the quantity of PP waste from construction materials.

A comprehensive summary on the enhancement of properties of concrete with recycled polypropylene materials

AbstractThe scientific community is currently confronted with critical problems in providing a healthy world for future generations. The study for sustainable plastic recycling methods is difficult for a variety of purposes. Indeed, during the previous century, the widespread usage of plastic materials has resulted in vast amounts of long‐lasting waste that has remained largely unaddressed by effective collection and disposal policies. Packaging materials are responsible for the majority of this waste which also includes polypropylene materials. However, environmental concerns imposed a new trend in the previous decade that brought this research under focus, as seen by the growing number of linked publications. For the recycling of polymeric plastic materials, several chemical and mechanical methodologies have been proposed. Due to the low ultimate tensile strain of concrete, plastic waste fiber materials have been used in concrete in recent times as the reinforced concrete components often function with cracks during the serviceability phase. The bonding strength and stress variation during flexure, toughening effect of a hybrid combination of steel and recycled polypropylene fibers on high‐strength concrete are investigated. Polypropylene's compressive and tensile strength, good dielectric characteristics, and acid and alkali resistance have all been observed in various studies. Hence the current review focus on the past researches on utilization of recycled polypropylene in concrete for the enhancement of its physical and mechanical properties.

The prediction and evaluation of recycled polypropylene fiber and aggregate incorporated foam concrete using Artificial Neural Networks

Reinforcement with recycled fiber is widely investigated to improve the mechanical behavior of foam concrete. In addition, the use of recycled aggregate in concrete provides benefits in terms of sustainability as it reduces the use of raw materials. In this research, 6 mm-long fibers and aggregates obtained from waste polypropylene were utilized in foam concrete production. This study also presents an evaluation of the recycled polypropylene fiber (PppF) and aggregate (PppA) incorporated foam concretes using ANOVA and ANNs. The ANN model was developed to estimate the compressive and flexural strengths, dry density, and thermal conductivity. The results indicated that the use of recycled polypropylene fiber increased the compressive and flexural strengths, however, polypropene aggregates affected the strengths negatively. And mixtures with higher levels of RppA and RppF have lower thermal conductivities. The slump of fresh concrete had an apparent reduction with the increase in RppA quantity. Also, both the ANN and ANOVA approaches were appropriate for optimizing and estimating responses.

The RSM-Based Optimization of Recycled Polypropylene Fiber Reinforced and Ground Calcium Carbonate Incorporated Roller Compacted Concrete for Pavement

The RSM-Based Optimization of Recycled Polypropylene Fiber Reinforced and Ground Calcium Carbonate Incorporated Roller Compacted Concrete for Pavement

Mechanical characterisation and small-scale life-cycle assessment of polypropylene macro-fibre blended recycled cardboard concrete

This paper presents an experimental study and findings on the requalification of waste cardboard as a fine-aggregate replacement in the development of waste-based concrete. The design of eco-efficient and green-star concrete has become a significant focus, driven by the impact of industrial and municipal waste on both the environment and the global economy. The study aimed to utilise materials such as waste cardboard, polypropylene, and ground-granulated blast furnace slag as partial replacements for Ordinary Portland Cement and fine natural aggregate. It specifically focused on developing techniques for processing recycled cardboard into an aggregate suitable for this study. Six concrete batches were cast with incremental dosages of finely processed recycled cardboard and a fixed dosage of recycled polypropylene macro-fibres. An experimental program was conducted to determine fresh and mechanical properties at 7 and 28 days. The results were used to identify an optimal dosage level of waste cardboard suitable for commercial use. Additionally, a small-scale life-cycle assessment was performed to evaluate the environmental impact of the hybrid concrete mix. The processed cardboard exhibited desirable rheological and mechanical properties, making it a suitable fine-aggregate replacement. The addition of recycled polypropylene fibres enhanced flexural and tensile strength, establishing the blend as a suitable concrete mixture design for real-world applications. Furthermore, the life-cycle assessment highlighted the effectiveness of the mixture designs when compared to benchmark concrete mixtures.

Preparation and performance of sugarcane bagasse ash pavement repair mortars

Pavement rehabilitation is typically required to ensure the service life of the road and the safety of road traffic. Due to various environmental and loading factors, pavements can present degradation or failures along their length, such as cracks, fissures, deformations, and disintegration of the wearing course. One way to reapair these defects is by using sealant materials. The objective of this research is to design mortars with sugarcane bagasse ash as a substitute for sand for the repair of cracks in pavements. Compression, tensile, shrinkage, fluidity and adherence tests were carried out on mortar samples that varied their dosage with 0 %, 50 % and 75 % ash content as a substitute for sand. These tests allowed for the evaluation of the physical and mechanical properties of the samples, determining compressive strength values of 16.65 MPa, adhesion of 0.52 MPa, among others. The control mix 5 with a 50 % replacement of ash by sand (M5–50 %), obtained the best results under the criteria of each of the tests performed. This article also evaluates the environmental impact of construction materials using the established procedures, finding that considering sugarcane bagasse ash as waste, using recycled polypropylene fibers, and incorporating zeolite for carbon capture can reduce the carbon footprint of concrete by up to 50 % compared to baseline mixes.

Axial Stress-strain Behavior of Recycled Polypropylene Fiber Ropes-reinforced Polymer-confined Low Strength Circular Concrete

Axial Stress-strain Behavior of Recycled Polypropylene Fiber Ropes-reinforced Polymer-confined Low Strength Circular Concrete

Mechanical properties, microstructural evolution, and environmental impacts of recycled polypropylene fiber stabilized loess

The deterioration of polypropylene fiber (PF) stabilized loess and its environmental performance are crucial factors for assessing the effectiveness of its reinforcement against frequent collapse and spalling induced by drying and wetting (D-W) cycles. For this purpose, the influence and underlying mechanisms of recycled PF content (0%, 0.1%, 0.3%, 0.5%, and 0.7%) and the number of D-W cycles on the strength, ductility, and resistance to deterioration of PF stabilized loess were investigated. Additionally, a life cycle assessment (LCA) was conducted to analyze the environmental impact of PF production. The results demonstrate a significant improvement in the strength, ductility, and resistance to deterioration of the samples upon the addition of PF. Although the initial five D-W cycles led to a decrease in specimen strength, they concurrently enhanced the ductility. Optimal mechanical properties were observed at fiber content of 0.5%, resulting in a remarkable increase in strength by 123.26% and resistance to deterioration by 25.49%. Specimens with 0.5% fiber content exhibited a three-dimensional network structure, contributing to enhanced mechanical properties compared to specimens with lower and higher fiber contents that exhibited dispersed and planar agglomerated structures. The study advocates for the use of industrial recycled PF in loess reinforcement, which exhibits significant advantages in terms of greenhouse gas emissions and energy demand when compared to virgin PF and domestic recycled PF. This innovative investigation provides insights into the durability and environmental impact of PF-stabilized loess and establishes a theoretical foundation for promoting the widespread utilization of PF in the loess foundation reinforcement market.

RECYCLED AGGREGATE CONCRETE (RAC): A viable solution for sustainable construction

Construction activities are booming in and around the cities with development and modernization. As a result of these constructions, natural aggregates are being extracted. Simultaneously, there is a significant amount of construction and demolition waste (CDW) generated due to the demolition of structures either due to the structure attaining service life or fashion and the ongoing trend of reconstruction. Therefore, recycling coarse aggregate from CDW in concrete is one of the sustainable solutions to prevent a serious threat to the environment due to the extraction of virgin aggregates and landfilling. This paper presents the results of a study undertaken to examine the influence of recycled concrete aggregate on the properties of new concrete and its life cycle cost (LCC) analysis. It is clear from the test that the strength of RAC is much lowered than natural aggregate concrete (NAC). In order to achieve the optimum strength, the natural aggregate is replaced by recycled aggregate within a range of 0% to 100%, in intervals of 10%. Additionally, to enhance its strength further, reinforcing RAC with new and recycled polypropylene (PP) fiber is done in percentages ranging from 0.25% to 2% by weight of cement with an interval of 0.25%. For analysis, compression, and split tensile strength tests were performed at the end of 28 days of the curing period. The result revealed that 40% replacement of natural aggregate with recycled aggregate achieves the ideal percentage replacement without compromising the strength. Moreover, incorporating 1.5% of new PP fiber or 1.25% of recycled PP fiber in the RAC provides optimum strength. For LCC analysis, the initial investment cost, operations, and maintenance cost, and salvage cost of all the alternatives are compared. Through this analysis, it was determined that the LCC of concrete manufactured using recycled aggregate as concrete ingredients is the lowest. Consequently, incorporating recycled aggregates in concrete production reduces the LCC compared to using natural aggregates.

Improving nonlinear behavior and tensile and compressive strengths of sustainable lightweight concrete using waste glass powder, nanosilica, and recycled polypropylene fiber

Abstract Concrete is one of the most extensively utilized building materials that can be produced, and has the potential to release a significant quantity of CO2 into the environment. In this research, through studying lightweight (LW) concrete, attempts are made to produce environmentally friendly LW concrete with high strength using nanosilica rather than part of the cement and waste glass powder instead of aggregates. Recycled polypropylene fibers are used to increase the concrete’s compressive strength and nonlinear behavior. The use of glass powder was 20, 25, and 30% of the weight of aggregates, the consumption of nanosilica was 1, 2, and 3% of the weight of cement, and the consumption of recycled fibers (FORTA Ferro-Green) was 0.5, 1, and 1.5% of the weight of cement. Leca is also utilized as a LW aggregate. According to 7- and 28-day experimentation results and field emission scanning electron microscope analysis, the best sample had 1.5% fiber, 3% nanosilica, and 25% waste glass powder, and had a compressive and tensile strengths of roughly 1.7 and 1.6 times, respectively, those of the control specimen after 28 days. Also, using 3% nanosilica instead of cement can reduce greenhouse gas emissions by about 3%.

Sustainable Use of Polypropylene Fibers as a Cement Mortar Reinforcement

Reinforcing cement mortars with fibers is an essential step to enhance their flexural strength. This study compares the fresh properties and mechanical characteristics of cement mortars reinforced with polypropylene fibers and recycled polypropylene fibers. The reinforcing fibers ratio were (0, 0.5,1, and 1.5) % by weight of cement mortar for both types of fibers. The casted samples were tested by means of flow test for fresh mortar, compressive strength, flexural strength, and toughness for hardened mortars. The results from this experimental program showed that both types of fibers caused a reduction in the mortar flow and enhanced its mechanical characteristics. The results were statistically tested to measure the significance of the difference. The cement mortar reinforced with recycled fibers exhibited approximately similar results as compared to the mixtures containing raw polypropylene fibers at 95% confidence level. However, it shows a significant increase in flexural strength when comparing to the mixtures with new polypropylene fibers that may be attributed to the fiber shape and cross section area.

Effect of Polypropylene Fibers on the Shear Strength–Dilation Behavior of Compacted Lateritic Soils

The stress–dilatancy relationship for fiber-reinforced soils has been the focus of recent studies. This relationship can be used as a foundation for the development of constitutive models for fiber-reinforced soils. The present study aims to investigate the effect of recycled polypropylene fibers on the shear strength–dilation behavior of two lateritic soils using the stress–dilatancy relationship for direct shear tests. Results show that fibers improved the shear strength behavior of the composites, observed by increases in the friction angle. Fibers’ orientation at the sheared interface could be observed. The volumetric change during shearing was altered by the presence of fibers in both soils. Overall, results indicate that the stress–dilatancy relationship is affected by inclusions in the soil mix. Results can be used to implement constitutive modeling for fiber-reinforced soils.

Strength and toughness of ambient-cured geopolymer concrete containing virgin and recycled fibres in mono and hybrid combinations

This paper presents an investigation on the workability and mechanical properties of ambient-cured fly ash geopolymer concrete (GPC) containing four different fibres, namely steel (S), polyvinyl alcohol (PVA), polypropylene (PP) and recycled polypropylene (RPP) fibres at 1% volume of concrete. The influences of hybrid S-PVA, S-PP and S-RPP on GPC at 0.5% of each type of fibre were also studied. In the mono fibre reinforced GPC (FRGPC) series, steel fibre showed the most effective role in improving the mechanical properties which were 4.0% in compressive strength, 74.3% in splitting tensile strength and 65.3% in flexural strength. In the hybrid FRGPC series, mixing of steel and RPP fibres was found more effective than the other combinations. The improvements by S-RPP were 15.5% in compressive strength, 48.9% in splitting tensile strength and 60.0% in flexural strength. The highest toughness was achieved for the S-RPP hybrid fibres following by mono steel fibres. A net deflection equal to 1/75 of the span could be regarded as the end deflection point to calculate the total flexural toughness of FRGPC according to quantitative analysis of toughness enhancement. There is a strong positive correlation between the total toughness and stress at the limit of proportionality (LOP) point.

Reinforcing effect of recycled polypropylene fibers on a clayey lateritic soil in different compaction degrees

The present research investigates the reinforcing effect of recycled polypropylene (R-PP) fibers on a compacted clayey lateritic soil in different compaction degrees. R-PP fibers of 12 mm length were mixed with the soil in the contents of 0.1 and 0.25% of soil dry weight. Unconfined compression strength tests (UCS), direct shear tests and indirect tensile strength (ITS) tests were conducted. Fibers addition showed no significate alterations in the optimum compaction parameters. The study evidenced increases in UCS, changing the soil behavior from a brittle failure to a ductile failure, while fiber contribution was most effective for 0.25% R-PP fibers content and 95% compaction degree. The use of fibers improved the shear stress-strain behavior of the composites and soils compacted at different degrees of compaction showed similar shear behavior, which is coherent to the soil water retention curves (SWRC) results. Significant increases in the tensile behavior of soil-mixtures for both fiber contents used were observed, and fibers increase was more significate than increase in soil degree of compaction. The stretching of the fibers and fibers orientation at the sheared interface in direct shear tests and the fiber “bridge” effect in ITS tests could be observed.

Effect of elevated temperature on flexural behavior and fibers-matrix bonding of recycled PP fiber-reinforced cementitious composite

This research aims to study the effects of elevated temperature exposure on the flexural performance of recycled polypropylene (PP) fiber-reinforced cementitious composites. Four mixtures with different percentages of PP fibers (0%, 0.5%, 1%, and 1.5% by volume) were studied. For each mortar, 9 samples of 40 × 40 × 160 mm were cast and cured for 28 days. While 3 samples of each mixture were tested under standard conditions, the other 6 were exposed to high temperature (200 °C) for 2 h and cooled in two different ways before testing (3 were tested hot and 3 were let cool down completely). Flexural strength test, Differential Image Correlation (DIC) and digital microscopy techniques were employed to evaluate the effects of high-temperature exposure and cooling procedures on flexural strength, toughness and bonding. Results showed that the use of recycled PP fibers had a negligible effect on flexural strength in normal conditions. However, fibers provided mortars a residual strength and ductile behavior after peak-load. Besides, flexural strength, post-peak residual strength, secondary strength and secondary toughness were enhanced after exposure to 200 °C and slow cooling, improving the behavior of the composite under flexural stresses. These results, along with the optical microscope images, suggest an improved bonding between the mortar matrix and the PP recycled fibers after exposure to 200 °C (temperature close to the melting point of fibers).

Sürdürülebilir Malzemelerin Büzülen Killerin İyileştirilmesinde Kullanımı

Global warming, pandemics, and poverty are the evidences of human destruction of the planet. Excavating and disposing of fertile soils destructively effect wildlife and nature and causes natural disasters such as fires and flooding leading to economic losses and casualties. This study investigates the effects of mechanical and chemical stabilization agents on the shrinkage of marine deposited clays. Three different sustainable materials such as polypropylene fibers, wood ash, and copper slag were used to reduce cement usage in resisting shrinkage problem of the studied clay. Then, the prepared specimen was brought to a slurry state to produce a mix of adequate workability and erase the structure of clay to better highlight the effect of replacement materials. In a controlled environment, the specimens were subjected to free shrinkage and specimen height, diameter, and mass were measured at regular intervals until the dried condition was reached and no further change was monitored. The measurements were then averaged for each set of mix to calculate axial, radial, and volumetric shrinkage strains as well as weight loss. The obtained data were further statistically assessed by evaluating the individual impact of each controllable factor and second-order interaction of cement and fiber. The results indicated that a mix of 1% fiber and 7% cement performed best for reducing the volumetric shrinkage of the clay. Furthermore, the availability of aluminous elements in clay accelerated the chemical interaction with cement and wood ash particles, forming a densified composite structure. This interaction appears to isolate the available moisture in the particles and restrict weight loss, resulting in reduced volumetric shrinkage of wood ash treated specimens. In addition to the environmental and economic benefits of cement usage reduction, using harmful waste materials such as recycled polypropylene fiber, wood ash, and copper slag enable their safe disposal. Incorporating such materials in-situ requires no specific tools; field application is conventional and straightforward.

Effect of freeze-thaw cycles on the response of roller compacted concrete pavement reinforced by recycled polypropylene fibre under monotonic and cyclic loadings

The present research focused on the effect of freeze-thaw cycles on behaviour of roller-compacted concrete pavement (RCCP) reinforced with recycled polypropylene fibres. RCCP specimens were designed with dry aggregates, four water to cement ratios of 0.3, 0.4, 0.5 and 0.6 and four fibre dosages of 0, 1, 3 and 5 kg/m3. Experiments were performed before and after exposure to freeze-thaw cycles in the presence of de-icing salt. The main experiments included the workability test by measuring the Vebe time, the ultrasonic pulse velocity (UPV), the modulus of rupture and the fatigue resistance with three-point bending method. Based on the results of the UPV test, which was performed before freeze-thaw cycles, and every 60 cycles up to 300 cycles, the specimens designed with water to cement ratios of 0.4 and 0.5 and reinforced with 1 kg/m3 fibre had better performance than other reinforced RCCPs. Modulus of rupture and fatigue tests were conducted after 0, 150 and 300 freeze-thaw cycles. The results of the modulus of rupture tests were largely similar to the UPV test. In contrast, given to the fatigue test results, the specimens containing 1 and 3 kg/m3 fibre exhibited similar behaviour after being exposed to freeze-thaw conditions and had a higher fatigue life than unreinforced specimens and those reinforced with 5 kg/m3 fibre. According to the results of monotonic and cyclic loadings, RCCPs with water to cement ratios of 0.4 and 0.5 and fibre contents of 1 and 3 kg/m3 are recommended to be used in real practice.

Characteristics of Recycled Polypropylene Fibers as an Addition to Concrete Fabrication Based on Portland Cement

High-performance concrete has low tensile strength and brittle failure. In order to improve these properties of unreinforced concrete, the effects of adding recycled polypropylene fibers on the mechanical properties of concrete were investigated. The polypropylene fibers used were made from recycled plastic packaging for environmental reasons (long degradation time). The compressive, flexural and split tensile strengths after 1, 7, 14 and 28 days were tested. Moreover, the initial and final binding times were determined. This experimental work has included three different contents (0.5, 1.0 and 1.5 wt.% of cement) for two types of recycled polypropylene fibers. The addition of fibers improves the properties of concrete. The highest values of mechanical properties were obtained for concrete with 1.0% of polypropylene fibers for each type of fiber. The obtained effect of an increase in mechanical properties with the addition of recycled fibers compared to unreinforced concrete is unexpected and unparalleled for polypropylene fiber-reinforced concrete (69.7% and 39.4% increase in compressive strength for green polypropylene fiber (PPG) and white polypropylene fiber (PPW) respectively, 276.0% and 162.4% increase in flexural strength for PPG and PPW respectively, and 269.4% and 254.2% increase in split tensile strength for PPG and PPW respectively).