Varying Fiber Content Research Articles

Influence of shear strength parameters on loose fine sand treated with coir fiber and microbially induced calcite precipitation

In recent years, there has been an increasing use of Microbially Induced Calcite Precipitation (MICP) technology in ground improvement. Adding fiber to bio-cemented sand leads to significant improvements in its properties. This paper examines how coir fiber and microbially induced calcite precipitation (MICP) might be used to improve the engineering qualities of fine sand. The sand was mixed with Coir fiber at varying Fiber Contents (FC) of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight of sand. Additionally, varied Aspect Ratios (AR) of 45, 90, 136, 182, and 227 were considered. The mixture also included urease-producing bacteria (Sporosarcina Pasteurii), as well as solutions of urea and calcium chloride with 3M molarity. The untreated and treated sand samples were submitted to a Direct Shear Test (DST). The study found that the shear strength parameters, such as the angle of internal friction, increased by 1.1 times compared to standard fine sand. Additionally, the angle of internal friction (ϕ) of fiber-reinforced sand with MICP showed 1.4 times increase, while the cohesion values demonstrated a sixfold increase compared to MICP fine sand. It was determined that the optimal aspect ratio was 182, and the optimal fiber content was 0.3%. Moreover, the Scanning Electron Microscope (SEM) was utilized to examine the calcite formations present in the treated sand samples, and calcite precipitation was observed between the pores of the soils.

Numerical failure modelling of natural fibre composite coupons using X-ray computed tomography based modelling

Natural fibre composites offer versatile applications across industries while being superior in sustainability aspects compared to other composite types. To unlock their full potential, it is essential to understand their complex failure involving fibre failure, matrix cracking, and debonding at the fibre-matrix interface. Efforts to address these challenges focus on advanced numerical models, probing behaviour from micro to macro scales. However, these models face complexities in handling intricate failure modes given the non-uniform nature of natural fibres. To overcome these challenges, image-based modelling using X-ray computed tomography scans is proposed. This work’s novelty lies in integrating detailed microstructure information with a nonlinear calibration procedure to accurately model damage and failure in natural fiber composites. It marks a significant step toward developing a virtual testing model, paving the way for assessing composites with varying fiber content or fiber types.

A study of the effect of coconut fiber on reinforced concrete beams subjected to combined bending and shear

This review paper examines the impact of coconut fiber reinforcement on the behavior of reinforced concrete beams subjected to combined bending and shear. Coconut fibers, also known as coir fibers, are a sustainable and cost-effective alternative to traditional steel reinforcement. The use of coconut fibers in concrete has shown promise in enhancing the ductility, energy absorption capacity, fracture resistance, and durability of concrete structures. The study highlights the mechanical properties and applications of coconut fiber reinforced concrete (CFRC) and investigates the effects of varying fiber content on concrete performance. Factors affecting the properties of fiber-reinforced concrete, such as the relative fiber matrix index, volume of fibers, aspect ratio of fibers, fiber orientation, workability, compaction, size of coarse aggregate, and mixing techniques, are also discussed. Understanding these factors is crucial for designing and constructing durable and sustainable concrete structures.

A comparative study of low cyclic loading effects on plastic strain, nonlinear damping, and strength softening in fiber-reinforced recycled aggregate concrete

The incorporation of fibers significantly enhances the properties and structural performance of recycled aggregate concrete. This study introduces Fiber-Reinforced Recycled Aggregate Concrete (FRAC) by integrating steel fibers (SF) and polypropylene fibers (PPF) into the recycled aggregate concrete (RAC) matrix. A comprehensive series of cyclic loading tests, including reload and unload sequences, were conducted to meticulously analyze the deterioration of strength and energy dissipation capabilities of SF/PPF-reinforced RAC. The research examines the effects of fiber characteristics, volume ratios, lengths, and diameters on strength degradation after the peak stress along the stress-strain curve. Degradation models based on plastic strain were proposed for both SF-reinforced RAC and PPF-reinforced RAC. The study further investigates the fluctuation of strain energy in FRAC under low cyclic loading, revealing the correlation between plastic strain energy and equivalent viscous damping ratio. A nonlinear viscous damping model that accounts for the influence of the reinforcing index (RI) is proposed. This model effectively predicts the degradation of strength, the evolution of plastic strain, and the dynamics of nonlinear viscous damping in composite materials with varying fiber content. Ultimately, this research provides essential technical insights for the practical engineering application of RAC.

Liquefaction behavior and shear strain-based pore pressure model of fiber reinforced calcareous sand

The generation mechanism of pore pressure plays an essential role in understanding the liquefaction behavior of sand under cyclic loading. Extensive undrained simple shear tests were undertaken to study the pore pressure and shear strain development characteristics of calcareous sand reinforced by fibers. The results show that the deformation patterns of the tested calcareous sand gradually shift from brittle to ductile failure as fiber content increases. The mechanism of pore pressure generation in calcareous sand subjected to cyclic loading is quite distinct from that of siliceous sand, exhibiting more pronounced accumulation in the initial stage of cyclic loading. Fiber reinforced calcareous sand exhibits reverse shear contraction behavior when liquefaction is imminent. A remarkable finding is the establishment of a unique correlation between pore pressure ratio and shear strain, irrespective of the fiber reinforcement. Consequently, a shear strain-based pore pressure generation model of reinforced calcareous sand is then developed to predict the pore pressure built-up trend under varying fiber content and length conditions. This model is also applicable to various testing conditions and soil types.

Enhancement effect of kale fiber on physicochemical, rheological and digestive properties of goat yogurt

This study incorporated kale fiber into goat milk as a functional component to investigate its impact on the quality and functional characteristics of set goat yogurt. Kale fiber content ranging from 0% to 1.5% (w/v) was added to 15% (w/v) defatted goat milk powder dissolved in water to form set yogurt. The addition of fiber increased the particle size and absolute potential of the goat yogurt, with a positive correlation observed between yogurt hardness, cohesiveness, and fiber content. Optimal water retention and thermal stability were achieved at a 0.5% fiber concentration. Microscopic analysis confirmed the successful incorporation of kale fiber into the yogurt gel network, resulting in significant differences in gel structure based on varying fiber content. Oscillatory temperature scan results indicated enhanced resistance to temperature changes due to the inclusion of kale fiber. Additionally, thixotropy results showed a 10% to 30% increase in gel structure recovery rate compared to the control group. In vitro digestion studies confirmed that kale fiber significantly improved protein bioavailability and release rate during digestion. Thus, incorporating kale fiber into goat milk as a natural plant-based functional component can enhance its nutritional value and rheological properties.

Dynamic constitutive modeling of steel fiber reinforced concrete considering damage evolution under high strain rate

This study conducted quasi-static compression and splitting tensile tests on steel fiber reinforced concrete (SFRC), as well as dynamic compression tests using the split Hopkinson pressure bar (SHPB). The mechanical properties of SFRC with varying fiber contents and under different loading strain rates were examined separately. Experimental results indicate that the addition of steel fibers effectively enhances the properties of concrete. The dynamic mechanical performance of SFRC specimens (compressive strength, peak toughness, ultimate toughness, and energy absorption capacity) demonstrated a clear strain enhancement effect. The dynamic stress-strain curves of SFRC reveal the material's good viscoelastic properties. Then, a viscoelastic constitutive model for SFRC considering damage under high strain was proposed, with parameter fitting based on SHPB test results. The constitutive model was applied to the numerical simulation by the user-defined material (UMAT) in ABAQUS. The dynamic stress-strain curves and damage patterns obtained by numerical simulation are basically consistent with the test results. This further demonstrates that the proposed constitutive model effectively describes the dynamic characteristics of SFRC.

Optimizing water Absorption’s influence on composite mechanics through response surface methodology

This study systematically examines how different fiber contents—Diss, Sisal, and luffa—affect the mechanical properties of bio-composites at rates of 10%, 15%, and 25%, with a particular focus on water absorption behavior. It investigates the relationship between water absorption and bending behavior, utilizing response surface methodology (RSM) optimization and analysis of variance (ANOVA) to thoroughly analyze input parameters, including a 44-day absorption duration, fiber type, and fiber content. The findings reveal that sisal-reinforced composites demonstrate the highest flexural strength, with an average stress of 31.15 ± 1.82 MPa for a 10% sisal fiber rate. However, an increase in fiber content leads to a decrease in mechanical properties and an increase in water absorption, with water absorption ratios of 2%, 3% and 5% for sisal biocomposites at fiber rates of 10%, 15% and 25%, respectively. The study’s reliability is confirmed by a significant R-squared coefficient of 0.94, indicating strong consistency between predicted and observed results. This comprehensive investigation offers valuable insights into how varying fiber content impacts both mechanical performance and water absorption in fiber-reinforced composites.

Evaluation of long-term properties and life cycle assessment of alkali-activated concrete with varying fiber inclusions

The potential for using alkali-activated concrete (AAC) as a sustainable substitute for Portland cement (PC) concrete is a topic of ongoing research interest. The uncertainties in the raw material composition, the reportedly low tensile strength of AAC, and the lack of relevant standard codes of practice further inhibit wider industrial usage of AACs. Fiber inclusions reportedly enhance the tensile properties of traditional PC concrete. However, there is no long-term data available for fiber-reinforced alkali-activated concrete (FRAAC) mixtures. Hence, the present study is aimed at investigating the long-term mechanical properties of ambient-cured FRAAC with GGBS as the sole precursor. Four different types of fibers, viz., steel (SF), polyvinyl alcohol (PVAF), polypropylene (PPF) and glass (GF) are used in this research as reinforcements in AAC. Tests for compressive strength (fc′), splitting tensile strength (fsp) and flexural strength (fr) are conducted for FRAAC containing varying fiber contents of 0.1–0.3%. The findings demonstrated that fiber additions do not have any noticeable influence on the compressive strength of AAC. However, relative to the plain mix, the fsp and fr of FRAACs were enhanced by up to 32% and 29%, respectively. The formation of the hardened calcium aluminosilicate matrix and evolution of the fiber-matrix bonding over time was evident from the scanning electron microscopy (SEM) images. The related molecular bonds over a period of 7-d to 360-d was identified through mineralogical and chemical analyses. Furthermore, to validate its environmental sustainability, life cycle assessments were conducted. The AACs exhibited at least 43% lesser impacts than PC concrete on the ecosystem. FRAACs had only slightly higher (≤ 7% increase across all fiber types) impacts than plain AAC.

EFFECT OF DUNE SAND AND FLY ASH ON THE MICROSTRUCTURE OF FIBER REINFORCED CONCRETE

The current study investigates the effect of dune sand (DS) and fly ash (FA) on the microstructure of fiber-reinforced concrete (FRC). Concrete is a widely used construction material, and understanding its behavior under different conditions is important for optimizing its performance. The use of alternative materials, like FA and DS, in concrete production has gained attention due to their abundance and potential environmental benefits. The research methodology involved the preparation of FRC mixes with different combinations of FA and DS, along with varying fiber content. The microstructural analysis of the samples was conducted through scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The findings revealed that the addition of FA and DS influenced the microstructure of the FRC. Furthermore, the inclusion of FA contributed to improved pore structure and enhanced the pozzolanic reaction, resulting in a denser microstructure. The incorporation of steel and basalt fibers demonstrated significant effects on the microstructure of the concrete. The results provide valuable insights for optimizing the design and performance of concrete structures in arid regions while considering sustainable materials.

Experimental Investigation on Mechanical and Viscoelastic properties of Kenaf, Basalt and Carbon Fiber reinforced Hybrid Epoxy Polymer Composites

Abstract In this study, a hybrid polymer composite reinforced with natural fibers such as Kenaf and Basalt, as well as carbon fiber was developed and analyzed for mechanical properties of the composite with varying fiber content and orientation. The composites were made using a hand layup process in which the plies were alternately stacked. Further, specimens were cut from the fabricated laminate according to ASTM standards. For the tensile and flexural test was conducted using a Universal Testing Machine (UTM). It is noticed that a hybrid composite made up of both natural fibers and carbon fiber has shown greater strength than a composite made up of only natural fibers with the same volume percentage of fiber. Furthermore, it is observed that the hybrid fiber composite in equal proportion is shown maximized strength.

Grey modeling study on mechanical properties and pore structure of concrete with different basalt fiber contents based on NMR

This paper investigates the correlation between strength and pore characteristics of basalt fiber-reinforced concrete (BFRC) with different fiber contents and establishes a link between meso- and macro-properties. The research focuses on BFRC with differing fiber contents, analyzing compressive strength, flexural strength, and splitting tensile strength across eight admixture levels (ranging from 0 % to 0.35 %). Using the nuclear magnetic resonance (NMR) technique, T2 spectra of BFRC with varying fiber contents are obtained, deriving curves of the pore distribution. Additionally, considering the parameters of different pore size proportions, the paper delves into analyzing the impact of pore structure on BFRC's distinct mechanical properties using grey correlation. Utilizing the optimal pore structure parameters derived from GCA to forecast different strengths, this study establishes GM(1,3) prediction models for three strengths, respectively. The results showed that basalt fibers can enhance concrete strength. And, 0.25 % basalt fibers optimize concrete's the inner structure of BFRC by decreasing harmful pores. The comprehensive correlation between pore parameters and BFRC strength ranges significantly indicating a notable relationship between strength and pore alterations. The compressive strength was most related to the total porosity and the proportion of non-harmful pores, and the splitting tensile and flexural strengths were related to the fractal dimension and porosity of the harmful pores as well as to the total and non-harmful porosity, respectively. A BFRC strength prediction model formula was developed based on the most relevant pore structure parameters derived from GCA. This calculation formula showcases a high accuracy in predicting BFRC strength, establishing a mesoscopic-to-macroscopic quantitative relationship that effectively informs the production and application of BFRC.

Utilization of Alkali-Activated Rice Husk Ash for Sustainable Peat Stabilization

Abstract Peat is formed from organic matter (OM) in wetlands under an anaerobic environment. Peat is considered weak and problematic soil because of high-water retaining capability, high compressibility, and low shear strength. The cement is generally used to stabilize peat, but cement production is energy intensive and contributes 7–8 % of total carbon dioxide to the atmosphere. Nowadays, there is a need to use a potential “greener” alternative that is sustainable in the long term. Therefore, this research assesses the feasibility of rice husk ash (RHA)–based alkali-activated binder (AAB)–stabilized peat with varying fiber content (6–73 %) and OM (21–79 %). The RHA-based AAB was prepared by adding bauxite powder (as alumina source) to RHA in proportion to keep constant silica to alumina ratio (silica/alumina = 3). The samples were prepared using sodium hydroxide (NaOH) of molarities 3, 6, and 9 to activate the binder with percentages 10, 20, and 30 % by weight of dry peat and alkali (A) to binder (B) ratio chosen as 0.5, 0.7, and 0.9. The results illustrate that the factors like pH of pore solution, the molarity of NaOH, binder content, A/B ratio, OM, and curing affect the unconfined compressive strength (UCS) of treated peat. The maximum UCS of 962, 873, and 668 kPa was found at an optimum combination of molarity (6M), binder content (20 %), and A/B ratio (0.7) for sapric, fibric, and hemic peat. It was seen that OM has a negative impact, whereas the curing period positively impacts the UCS of treated peat. Furthermore, the cumulative mass loss of fibric peat (13.6 %) is more than hemic (11.4 %) and sapric (10.6 %) peat. The X-ray diffraction patterns and field emission scanning electron microscopy micrographs confirm the cementitious minerals that fill pore spaces or cavities to form a smooth and dense gel responsible for strength gain.

Impact behaviour of 3D printed fiber reinforced cementitious composite beams

Recent interest has grown in using 3D printing for military and civil defense engineering, particularly for infrastructure resilience against impacts. This study delves into the impact resistance of 3D printed fiber-reinforced cementitious composite (FRCC) beams. By analyzing varying fiber content, impact directions, and 3D printing nozzle sizes, the research found that the total energy dissipation of 3D printed FRCC beams was more than 40% higher and the 3D printed beams exhibited superior impact resistance compared to traditional beams, largely due to the fibers' role. The impact energy dissipation varied with different impact directions for the specimens, and the Z direction was identified as the most resistant, demonstrating anisotropic behavior in impact resistance. Smaller nozzle sizes in printing showed higher total energy dissipation, indicating increased impact resistance. X-ray analysis further revealed that the 3D printing process creates denser beams with better fiber–matrix adhesion and less porosity, improving overall impact resistance.

Effects of PLA-Type and Reinforcement Content on the Mechanical Behavior of Additively Manufactured Continuous Ramie Fiber-Filled Biocomposites

The present work aimed to examine the tensile and flexural behaviors of biocomposites reinforced with continuous plant fibers, utilizing a range of polylactic acid (PLA) matrix materials and varying fiber content. These biocomposites were fabricated using an in situ-impregnated fused filament fabrication (FFF) technique. The study incorporated three different PLA matrix materials, namely PLA, PLA-Matte (PLA-Ma), and PLA-ST, each with distinct mechanical properties. The effect of different linear densities of continuous ramie yarns on the biocomposites was also investigated. The results show that adding continuous ramie yarn significantly enhances both the tensile and flexural strengths, as well as the modulus, of the matrixes. Furthermore, there was a positive correlation between the content of ramie yarn and the increases in strength and modulus. Moreover, the introduction of ramie yarns altered the fracture behavior of the biocomposites, shifting towards brittle fracture. This change significantly impacted the fracture toughness of the matrixes and resulted in a convergence of elongation at the point of breakage.

Utilization of waste face masks to reinforce magnesite mine tailings for sustainable subgrade construction

The disposal of magnesite mine tailings (MMT), a by-product of magnesite mining, raises significant environmental concerns due to its adverse effects on soil, water and air quality. Likewise, the improper disposal of used face masks exacerbates environmental burdens. The innovative use of polypropylene fibres (PPF) derived from disposable face masks to reinforce. This study explores the compaction and strength characteristics of PPF-MMT composites with varying fibre content to develop a sustainable composite for subgrade construction. The findings indicate that the addition of PPF increases optimal moisture content and decreases maximum dry density. Shear strength analysis reveals a linear failure envelope for both MMT and PPF-MMT, with initial angle of internal friction improvement at lower PPF content (0.25% and 0.5%) but a decline at higher contents (0.75% and 1%). Importantly, PPF-MMT consistently exhibits a unique strain-hardening behaviour across all stress levels, distinguishing it from MMT, which only transitions to strain-hardening at higher stresses. Under vertical load, MMT shows contraction, while the PPF-MMT composite initially contracts but later dilates due to increased fibre-MMT interaction during horizontal displacement. Furthermore, California bearing ratio (CBR) tests demonstrate increased dry CBR with PPF, reaching a peak of 33.85% at 0.5% fibre content. The soaked CBR tests affirm the remarkable durability of PPF-MMT, maintaining significantly higher values than MMT even after 60 days of soaking. The study concludes that 0.5% fibre content as optimum dosage.

Experimental Study of the Physical and Mechanical Properties of Cement‐Based Composite Reinforced With Macro‐/Microfibers: Case of Rhecktophyllum camerunense and Triumfetta pentandra

Plant fibers have the ability to bridge crack propagation on a microscopic scale for microfibers and on a macroscopic scale for macrofibers. Therefore, the use of two or more fiber types in an appropriate combination can potentially improve the overall properties of the cement composite as well as promote green construction. The hybrid composite was cast using random orientation with two fibers: Rhecktophyllum camerunense as macrofiber and Triumfetta pentandra as microfiber. Cement mortar matrices were reinforced with a constant microfiber length of 1 mm and three different macrofiber lengths of 1.5, 3, and 6 mm at varying fiber contents of 1%, 1.5%, and 2.5% wt. The physical characteristics of the composite were assessed by porosity, density, and water absorption. Mechanically, three‐point bending tests and single‐edge notch bending (SENB) tests were performed after 7 and 14 days of curing. Mode I fracture behavior (KIC) and modulus of rupture (MOR) were calculated as per formulation. Physical experimental results reveal that there is a correlation between the rate of water absorption, porosity, density, and that of the fiber loading and length in the composite. Mechanically, the developed material presented a multiple cracking behavior under bending. There was a decrease in MOR and fracture toughness values with a decrease in macrofiber content in the hybrid composite. They both presented an increase in value with an increase in fiber content and fiber length. The composites reinforced with both fibers presented higher values of MOR than the unreinforced due to the powerful interfacial bond between the fibers and the cement matrix. The unreinforced composites had the least MOR and fracture toughness values of 0.442 MPa and 694,000 N.m1.5, respectively, showing that they are very reactive to faults at low stress levels.

Flexural Toughening of Hooked-End Steel Fibers Reinforced Mortars

This paper investigated the effect of hooked-end steel fiber at varying fiber content on the flexural toughening of fiber reinforced cement mortars (FRCM) by using three-point bending tests. In particular, to preserve the mortar workability, three low weight fractions (0.3%, 0.5% and 0.7%) and two cement matrices (M10 and M15) were investigated. The results showed that the mechanical bending behavior of the FRCM increases significantly at increasing fiber content and cement plaster matrix. An important aspect that has been addressed is how the flexural toughening is varied at varying fiber content and the type of matrix. Especially, all composite mortars exhibited a toughness index (TI) in the range of 10–45, indicating a suitable strengthening and toughening effect supplied by the hooked-end fiber addition. The best TI value, equal to 44, was experienced for the M10-D7 batch characterized by 0.7 wt.% of hooked-end steel fibers and an M10 cement matrix. Furthermore, unlike unreinforced concrete where brittle and unexpected failure occurs dominated by a sudden and catastrophic propagation of tensile cracks, the FRCM samples exhibited a ductile behavior with a marked residual post-crack resistance even for composites mortars with low metal fiber content.

Effects of polypropylene and basalt fibers on tensile and compressive mechanical properties of fiber-reinforced ice composites

As an environmentally friendly and low-cost construction material, ice has a rich historical usage and has been gaining significance in cold-zone engineering constructions. However, the low tensile strength and brittle damage characteristics limit the potential applications of ice. Incorporating fibers in ice has been recognized as an effective method to improve the mechanical properties. This research aims to investigate the effects of polypropylene fibers (PF) and basalt fibers (BF) on the mechanical properties of fiber-reinforced ice composites. To do so, approximately 200 PF- and/or BF-reinforced ice specimens with varying fiber contents (0 %, 2 %, 4 %, 6 %, 8 %) were produced and subjected to splitting tensile and uniaxial compressive tests at −10 °C. Besides, the synergistic effect of hybrid fiber-reinforced ice on tensile mechanical properties was further investigated. The experimental results demonstrate that the addition of fibers transforms the brittle failure of ice into ductile failure, and both BF and PF improve the tensile and compressive mechanical properties of ice composites in strength and ductility as functions of fiber contents. The tensile mechanical properties of hybrid fiber-reinforced ice exhibit both negative and positive synergistic effects. Furthermore, the research established the tensile and compressive strength formulas of PF- or BF-reinforced ice composites with different fiber contents, and the calculated results correlated well with the tested ones.

Effects of Curing Conditions on Splitting Tensile Behavior and Microstructure of Cemented Aeolian Sand Reinforced with Polypropylene Fiber.

Aeolian sand is widely distributed in the Takramagan Desert, Xinjiang, China, which cannot be directly used as railway subgrade filling. It is beneficial for environmental protection to use fiber and cement-reinforced aeolian sand as railway subgrade filling. The present work is to explore the enhancement of tensile strength in cemented aeolian sand via the incorporation of polypropylene fibers under conditions of elevated temperature and drying curing. The purpose Is to delve into the examination of the temperature's impact on not only the mechanical attributes but also the microstructure of cemented aeolian sand reinforced with polypropylene fiber (CSRPF). For this, a comprehensive set of tests encompassing splitting tensile strength (STS) assessments and nuclear magnetic resonance (NMR) examinations is conducted. A total of 252 CSRPF specimens with varying fiber content (0, 6‱, 8‱, and 10‱) are tested at different curing temperatures (30 °C, 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C). The outcomes of the NMR examinations indicate that elevating the curing temperature induces the expansion of pores within CSRPF, both in size and volume, consequently contributing to heightened internal structural deterioration. STS tests demonstrate that the STS of CSRPF decreases as the curing temperature increases. Meanwhile, the STS of CSRPF increases with fiber content, with optimal fiber content being 8‱. Regression models accurately predict the STS, with the curing temperature exhibiting the greatest influence, followed by the fiber content according to sensitivity analysis. The research results provide a valuable reference for the use of CSRPF as railway subgrade filling under high temperature and drying conditions.