PVA Fibers Research Articles

Experimental Study on the Flexural Performance of Steel-Polyvinyl Alcohol Hybrid Fiber-Reinforced Concrete.

This paper explores the impact of steel-PVA hybrid fibers (S-PVA HF) on the flexural performance of panel concrete via three-point bending tests. Crack development in the concrete is analyzed through Digital Image Correlation (DIC) and Scanning Electron Microscope (SEM) experiments, unveiling the underlying mechanisms. The evolution of cracks in concrete is quantitatively analyzed based on fractal theory, and a predictive model for flexural strength (PMFS) is established. The results show that the S-PVA HF exhibits a synergistic effect in enhancing and toughening the concrete at multi-scale. The crack area of steel-PVA hybrid fiber concrete (S-PVA HFRC) is linearly correlated with deflection (δ), and it further reduces the crack development rate and crack area compared to steel fiber-reinforced concrete (SFRC). The S-PVA HF improves the proportional ultimate strength (fL) and residual flexural strength (fR,j) of concrete, and the optimal flexural performance of concrete is achieved when the steel fiber dosage is 1.0% and the PVA fiber dosage is 0.2%. The established PMFS of hybrid fiber-reinforced concrete (HFRC) can effectively predict the flexural strength of concrete.

Mechanical properties, micro-mechanisms, and constitutive models of seawater sea-sand engineered cementitious composites

Three mixing proportions of engineered cementitious composites (ECCs) were prepared using seawater, sea-sand, and PVA fibers, corresponding to three strength grades of C30, C40, and C50, respectively. The mechanical properties of these three kinds of seawater sea-sand engineered cementitious composites (SS-ECCs), including compressive strength, tensile strength, flexural strength, elastic modulus, ultimate elongation, uniaxial compressive and tensile stress-strain relationship, and so on, were analyzed by compressive, tensile, and flexural tests. The tensile and flexural strength of SS-ECCs are influenced by their ductility. The SS-ECC with C40 strength grade exhibited the best ductility, with an average ultimate tensile strain reaching 3.42 %, and possessed the highest tensile and flexural strength. The C50 specimen had the worst ductility, but its tensile strength and flexural strength came in second place. As the strength grade increased, the elastic modulus gradually increased, while the Poisson's ratio decreased. Uniaxial compressive and tensile constitutive models for SS-ECCs were established. The uniaxial compressive constitutive model was divided into a nonlinear ascending stage and a bilinear descending stage. XRD and TGA results revealed that the improvement in the strength of SS-ECCs was mainly attributed to the increased content of Ca(OH)2 in the reaction products. Additionally, the gypsum content in the raw materials decreased with the increasing strength grade, resulting in a reduction in the generation of ettringite (AFt).

Rice straw-based cellulose nanofiber reinforcing polyvinyl alcohol antibacterial film through electrospinning

TEMPO-cellulose nanofibers (T-CNF) were prepared from rice straw through 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation method. Subsequently, T-CNF reinforced polyvinyl alcohol fiber films (T-CNF/PVA) were fabricated by electrospinning. SEM images revealed that the introduction of T-CNF into PVA resulted in a slight decrease in fiber diameter within the T-CNF/PVA films. The tensile strength and elastic modulus of the T-CNF/PVA-2 fiber film were 44.59 MPa and 20.75 MPa, respectively, with T-CNF content of 1.64 wt%. The tensile strength of T-CNF/PVA-2 being approximately 9 times greater than that of pure PVA fiber film. Molecular dynamics (MD) simulation showed that the intermolecular forces between T-CNF and PVA were stronger than those within pure PVA. Additionally, the T-CNF/PVA-2 fiber film exhibited excellent antibacterial properties, achieving an inhibition rate of 99.99 % against S. aureus.

Synergetic effect of multiwalled carbon nanotubes on mechanical and deformation properties of engineered cementitious composites: RSM modelling and optimization

Engineered cementitious composites (ECC) have outstanding energy absorption and ductility, but their primary drawbacks continue to be their poor elastic modulus and severe drying shrinkage. Therefore, the incorporation of multiwalled carbon nanotubes (MWCNTs) to mitigate the stated drawbacks and also the influence of MWCNTs on the mechanical characteristics of ECC has been examined. However, the primary goal of this research investigation is to apply the response surface methodology (RSM) modelling for optimizing multiple objectives, effectively handling variable interactions, and achieving significant improvements. A total of thirteen mixtures were produced through RSM modelling using two input factors including different concentrations of MWCNTs at 0.05 %, 0.065 %, and 0.08 %, as well as varying concentrations of PVA fiber at 1 %, 1.5 %, and 2 %. The central composite design (CCD) technique of RSM modelling was used in the production of these mixtures. The results demonstrated that the incorporation of 0.05 % MWCNTs and 1 to 1.5 % PVA fiber together considerably enhanced all of the characteristics of the ECC. The optimum compressive strength, flexural strength, tensile strength, and modulus of elasticity of the ECC were recorded by 74.28 MPa, 14.14 MPa, 5.51 MPa, and 31.10 GPa at 0.05 % MWCNTs at 28 days correspondingly. Furthermore, the drying shrinkage is getting decreased as the extent of MWCNTs increases in ECC. It has been concluded that the use of 0.05 % of MWCNTs and 1 % to 1.5 % of PVA fiber provided good outcomes for construction purposes.

Effect of fibers and boron carbide on the radiation shielding properties of limestone and magnetite aggregate concrete

Research on new composite materials in the field of radiation shielding materials requires adequate means and meticulousness in their manufacture and characterization. In this study, concretes that use elements that theoretically improve their shielding properties are developed, such as fibers and boron-rich additions. Both magnetite and limestone concrete have been manufactured, incorporating steel fibers to improve the linear attenuation coefficient and polyvinyl alcohol to increase neutron scattering cross section. The incorporation of boron carbide is intended to increase the neutron absorption cross section. 5 mixes have been manufactured that have been tested with several gamma radiation sources (570–1280 keV) and with an Am–Be neutron source (111 GBq). The experimental results have been used to validate simulations carried out with MAVRIC® and have led to the modelling of a simplified spent nuclear fuel cask. Boron carbide produces a decrease of more than 50% on the neutron dose rate in contact with the cask. Incorporating PVA fibers supposes gain in neutron attenuation capacity of up to 13%, while fibers have a negligible effect on the photon dose rate.

Experimental study on the flexural fatigue performance of slag/fly ash geopolymer concrete reinforced with modified basalt and PVA hybrid fibers

Geopolymer, owing to its inherent low-carbon emission advantages, emerges as a potential substitute to diminish reliance on high-carbon-emitting Portland cement. Nonetheless, similar to ordinary Portland cement concrete, geopolymer concrete tends to exhibit brittle fracture under cyclic bending loads. To improve its flexural fatigue performance, this paper incorporated the modified basalt (MB) fiber and PVA fiber in hybrid form into the geopolymer concrete. The flexural fatigue behavior of hybrid fibers reinforced geopolymer concrete was investigated, with a focus on the influence of varying hybrid fibers volume fractions. Digital Image Correlation technology was utilized to accurately track the evolution of crack length and the local strain field during the fatigue failure process. The results revealed that the incorporation of both MB and PVA fibers effectively delayed the initiation and propagation of cracks, leading to a more complex path of fatigue cracks. The PVA fiber demonstrated significant efficacy in inhibiting microcracks, while the MB fiber played a crucial role in controlling the expansion of macroscopic cracks. When the proportion of MB fiber was predominant in the hybrid mix, the crack development pattern mirrored that of samples containing MB fiber alone, exhibiting a greater extent of crack length. At a volume fraction of 0.9% for MB fiber and 0.2% for PVA fiber, a significant improvement in the fatigue life of the concrete was observed, resulting in a remarkable 136.23% increase compared to the control. This study has developed geopolymer concrete featuring enhanced crack resistance and superior flexural fatigue endurance under cyclic loading, promoting the application of environmentally friendly building materials in practical engineering.

Experimental investigation on bond-slip performance and damage evolution mechanism of deformed reinforcing bar embedded in steel polyvinyl-alcohol hybrid fiber high performance concrete after high temperature

Hybrid Fiber High Performance Concrete (HFHPC) utilizes the synergistic effects of macro and micro fibers at different stages, which can effectively improve its mechanical properties, fracture toughness, ductility, and impact resistance after high temperature. The bonding between steel bars and hybrid concrete is a fundamental prerequisite for ensuring that these two materials with completely different mechanical properties work together. In order to study on bond-slip performance and damage evolution mechanism of deformed reinforcing bar embedded in steel-polyvinyl-alcohol (S-PVA) hybrid fiber high performance concrete (HFHPC) after high temperature, a total of 75 specimens were designed and manufactured by selecting volume fraction of steel fiber and PVA fiber and dosing of slag powder as the orthogonal test factors, and the central pull-out test were completed after exposure to room temperature, 200℃, 400℃, 600℃, and 800℃. The experimental results indicate that the bonding failure mode of HFHPC specimens all showed steel bar pull-out failure after high temperature, and the bond stress-slip curve can be divided into 4 stages: elastic rise stage, nonlinear rise stage, plastic degradation stage, and residual stage. As the temperature increases, the bonding strength of HFHPC specimens gradually decreases and the peak slip gradually increases. The addition of hybrid fibers can significantly improve the bonding ductility and energy dissipation capacity of deformed reinforcing bar embedded in S-PVA HFHPC after high temperature. When the temperature is below 200℃, the bonding strength damage rate of S-PVA HFHPC specimens is relatively slow; when the temperature exceeds 200℃, the bonding strength damage rate of S-PVA HFHPC specimens increases.

Structuration and yield strength characterization of hybrid alkali-activated cement composites (HACC) for ultra-rapid 3D construction printing

This study investigates the critical time-dependent rheological properties, including structuration rate and yield stress, of hybrid alkali-activated cement composites (HACC). HACC, a blend of geopolymer and cement paste, is examined to evaluate its suitability for ultra-rapid 3D construction printing (3DCP), which refers to a material’s ability to attain rapid structuration and buildability within 5–10 min after mixing, essential for additive manufacturing of 3D structures. The investigation extends to the impact of filler materials like silica sand and PVA fibers on HACC’s rapid structuration. Vicat needle, fast- and slow-penetration resistance measurements indicate that setting time increases with decreasing the Silicon/Aluminum (S/A) molar ratio and the addition of silica sand. Conversely, the addition of fibers reduces setting time while enhancing yield strength. Specifically, HACC mixtures with 0.5% and 1% PVA fiber additions, alongside combined sand (30%, 40%) and fiber (0.5%) mixtures, demonstrate ultra-rapid setting behavior within 3–5 min. Notably, mixtures with 40% silica sand and 0.5% PVA fiber exhibit highest yield strength development, i.e., 14 MPa at 12 min. Remarkably, incorporating 1% fibers into the HACC mixture yields the highest 28-day compressive strength (∼80 MPa) and flexural strength (∼11 MPa). The synergistic interplay between geopolymer and cement facilitates rapid setting time and high early-age strength development in HACC mixtures. The varying effects of silica sand and PVA fiber on setting time and yield strength provide opportunities for designing suitable structuration profiles. These findings underscore the exceptional rapid setting, structuration, and mechanical properties of HACC, positioning it as a promising material for ultra-rapid 3D construction printing.

An Investigation into PVA Fiber Modified with SiO2 for Improving Mechanical Properties of Oil-Well Cements.

In this paper, we conduct a comprehensive investigation into PVA fiber modified with SiO2 to improve the mechanical properties of oil-well cements. Specifically, SiO2 was coated onto the surface of polyvinyl alcohol fiber (PVAF) as its silicon source via a sol-gel process by using tetraethyl orthosilicate (TEOS), while hydrochloric acid and ammonia were respectively used as the catalyst in the sol (hydrolysis) and the gel (condensation) processes. The PVAF microstructure was then characterized with the scanning electron microscope (SEM), while the effects of the modified PVAF on both mechanical and rheological properties of oil-well cements were examined. Due to the fact that SiO2 can be uniformly coated onto the PVAF surface, such modified PVAF can slightly improve the rheology of the cement slurry, while the raw PVAF exhibits poor dispersion at a high dosage. Compared with those of cement stone without PVAF after curing for 28 days at 60 °C, the flexural strength, compressive strength, and elastic modulus of the cement stone incorporated with the modified PVAFs were enhanced by 37.7%, 66.1%, and 50.0%, respectively. The SEM test (EDX) test, XRD test, and thermogravimetric test prove that the SiO2 coating on the PVAF surface can promote the hydration of cement clinker and can react with Ca(OH)2 to generate CSH gel. The SiO2 grafted onto the surface of PVAFs can improve the bond strength at the fiber/cement matrix interface, thus improving the mechanical properties of cement stone.

Synergistic effect and reinforcement mechanism of porous inorganic polymers via the fiber addition and carbonation curing

Porous inorganic polymers with good compressive strength can be applied in various applications. In order to obtain porous inorganic polymers with good compressive strength, fibers addition and carbonation curing was employed in porous inorganic polymers producing process. With the addition of 6 mm 2 wt% PVA fibers and 12 hours’ carbonation curing, the inorganic porous polymers with 2.0 MPa compressive strength and 540 kg/m3 density were successfully produced. X-ray diffraction, thermogravimetric analysis, fourier transform infrared spectroscopy and scanning electron microscope - energy dispersive X-ray spectroscopy were applied to explore the reinforcement mechanism of porous inorganic polymers. It suggested that the synergistic compressive strength reinforcement mechanism involved in both physical and chemical changes. Physically, fiber addition promoted bridging effect, restricted crack expansion and accelerated carbonation process. Chemically, the formation of CaCO3 through carbonation reaction filled in the voids of the matrix and facilitated network structural, enhancing densification and overall strength.

Study of the shear bond behavior of a hybrid fiber-reinforced concrete (HyFRC) composite slab

In this study, a new composite slab consisting of a prefabricated hybrid fiber-reinforced concrete (HyFRC) formwork and a cast-in-place ordinary concrete (OC) topping was proposed. The HyFRC was comprised of steel and PVA fibers. The compressive strength and bending strength of the HyFRC were 111.4 MPa and 15.6 MPa, respectively, and the toughness coefficient was 12.1 MPa. Seven full-scale composite slabs including six simply-supported slabs and one two-span continuous slab were tested under four-point bending to study the shear bond behavior. Three different contact surface conditions were considered for the simply supported slabs. Despite the different interface conditions, results showed that the interfacial bond strength between the HyFRC formwork and the OC topping was sufficient to achieve flexural failure. Numerical simulation was used to analyze the interfacial force transfer mechanism and was validated by the experimental data. The validated numerical model was used to study the influence of concrete topping depth and amount of reinforcement on the load-carrying capacity and longitudinal shear stress at the joint surface. The numerical results identified a critical condition of positive effect between reinforcement ratio and OC topping thickness. The peak load of a properly designed composite slab was almost two times that of the corresponding slab with ordinary concrete only, and the deformation capability was also larger. A procedure for calculating the flexural capacity of the composite slab was proposed.

Preparation and Properties of Temperature Resistant and Salt Resistant Lotion Fracturing Fluid Thickener

In order to prepare fracturing fluid with excellent solubility, temperature resistance, salt resistance and shear resistance, acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and acryloylmorpholine (ACMO) were copolymerized, and anionic cellulose was introduced to synthesize a new type of polyacrylamide copolymer p (AM/AMPS/ACMO) through inverse emulsion polymerization. The structure and morphology were characterized by infrared spectroscopy and scanning electron microscope. The results showed that in 0, 5, 10, 20, 50, 100, 150 and 200 g/L NaCl, CaCl2, and MgCl2 solutions, the viscosity of p (AM/AMPS/ACMO) solution modified by PVA fiber was always higher than that of conventional PAM solution, and the polymer modified by PVA fiber had better salt resistance. The anionic cellulose modified thickener was sheared at 120 ℃ and 150 ℃ for 1 h at 170 s－1, and the viscosity after shearing is 89.92 mPa·s and 80.10 mPa·s, respectively, which is much higher than the viscosity required by the general technical conditions of fracturing fluid more than 50 mPa·s, indicating that anionic cellulose modified p (AM/AMPS/ACMO) has good temperature and shear resistance.

Assessing the desiccation crack propagation performance of cemented soil reinforced by modified polyvinyl alcohol fiber

The increasing application of fiber reinforcement to mitigate desiccation cracks induced by evaporation during backfill curing addresses the dispersion challenge associated with high fiber addition. This study aims to enhance the interfacial strength between fibers and cement-soil mixtures through chemical modification methods (NaOH, HCl, and Silane Coupling Agent). By conducting a single fiber pull-out test and microstructures observation, the outcomes reveal that modified PVA fibers exhibit a notable increase in shear strength and pull-out energy compared to unmodified ones, thereby necessitating a reduced fiber dosage for desiccation crack reduction. Furthermore, this investigation delves into the Digital Image Correlation (DIC) feasibility of employing the Digital Image Correlation (DIC) method to monitor the desiccation crack pattern of cement-soil slurry during the initial hydration stages. The findings indicate that NaOH and HCl treatment notably diminishes stress concentration under drying conditions, consequently reducing crack width and area.

Study on Cyclic Mechanical Behavior and Damage Constitutive of PVA Fiber Recycled Aggregate Concrete

Study on Cyclic Mechanical Behavior and Damage Constitutive of PVA Fiber Recycled Aggregate Concrete

Quantum Sensing and Light Guiding with Fluorescent Nanodiamond‐Doped PVA Fibers (Advanced Optical Materials 14/2024)

Quantum Sensing and Light Guiding with Fluorescent Nanodiamond‐Doped PVA Fibers (Advanced Optical Materials 14/2024)

HIGH TEMPERATURE HEAT RESISTANCE OF CONCRETE CONFINED WITH CFRP USING FIBER REINFORCED GEOPOLYMER BONDING AGENT

Rehabilitation and improvement of concrete structures by strengthening is an environmentally sustainable option compared to demolition and building of new structures. Epoxy resin is typically used as the bonding agent to strengthen concrete structures by using FRP. However, a major drawback of epoxy resin is that it loses bond strength by melting at high temperatures. Geopolymer is an alternative binder that possesses high resistance to elevated temperatures. This paper presents the results of CFRP confined concrete cylinders using 0.2% short PVA fiber reinforced geopolymer paste as the bonding agent. Concrete cylinders of 45 MPa were wrapped with one or two layers of CFRP and exposed to temperatures of 200, 400 and 800°C for 90 minutes and then tested for compressive strength. The specimens exhibited failure by tearing the CFRP fabric. The percentage of increase of strength by the CFRP wrapping at 800°C was 86% for one layer with fiber, 51% for one layer without fiber, 65% for two layers with fiber, and 73% for two layers without fiber. While strength of the cylinders increased with the increase of CFRP layers, the addition of PVA fiber did not have an obvious benefit to the strength enhancement. No melting, though cracks were observed in fiber reinforced geopolymer due to high temperature exposures.

HIGH TEMPERATURE HEAT RESISTANCE OF CONCRETE CONFINED WITH CFRP USING FIBER REINFORCED GEOPOLYMER BONDING AGENT

Rehabilitation and improvement of concrete structures by strengthening is an environmentally sustainable option compared to demolition and building of new structures. Epoxy resin is typically used as the bonding agent to strengthen concrete structures by using FRP. However, a major drawback of epoxy resin is that it loses bond strength by melting at high temperatures. Geopolymer is an alternative binder that possesses high resistance to elevated temperatures. This paper presents the results of CFRP confined concrete cylinders using 0.2% short PVA fiber reinforced geopolymer paste as the bonding agent. Concrete cylinders of 45 MPa were wrapped with one or two layers of CFRP and exposed to temperatures of 200, 400 and 800°C for 90 minutes and then tested for compressive strength. The specimens exhibited failure by tearing the CFRP fabric. The percentage of increase of strength by the CFRP wrapping at 800°C was 86% for one layer with fiber, 51% for one layer without fiber, 65% for two layers with fiber, and 73% for two layers without fiber. While strength of the cylinders increased with the increase of CFRP layers, the addition of PVA fiber did not have an obvious benefit to the strength enhancement. No melting, though cracks were observed in fiber reinforced geopolymer due to high temperature exposures.

Experimental and simulation study on seismic performance of steel‐PVA hybrid fiber cementitious composites‐encased CFST

AbstractSix hybrid steel and PVA fiber cementitious composite (S&PFCC)‐encased concrete‐filled steel tube (CFST) columns were designed and fabricated, and the effects of axial compression ratio, core concrete strength grade and steel tube thickness on the seismic performance of composite columns were studied. The test results show that the increase of core concrete strength can obviously improve the bearing capacity and energy dissipation capacity of composite column and can restrain the strain growth rate of steel tube after yielding. Low axial compression ratio and thicker steel tube thickness can improve the overall seismic performance of composite columns. Three calculation methods are modified, and the modified An method can predict the lateral bearing capacity of composite column well. Finally, based on the OpenSees finite element software, the seismic performance of the CFST column wrapped in S&PFCC is simulated to verify the test, and the numerical study shows that the seismic performance of the composite column can be optimized by increasing the steel fiber content, while PVA fiber has a weak effect in the elastic stage, and can effectively improve the ductility of the composite column in the plastic stage.

Numerical simulation investigation on the seismic performance of high-strength concrete columns reinforced with PVA fibers and HTRB630 steel bars

Numerical simulation investigation on the seismic performance of high-strength concrete columns reinforced with PVA fibers and HTRB630 steel bars

Construction of interfacial interlocking structure in epoxy composites with enhanced mechanical performance and ultraviolet resistance

Replacing carbon fibers with organic fibers to reinforce the polymer matrix has become a promising development direction in the preparation of structural composites owing to its low density and cost, but the mechanical performance of organic fibers restricts their further application. Herein, poly(vinyl alcohol) (PVA) fibers were utilized to reinforce the epoxy resin (EP) through the incorporation of zinc oxide nanoparticles (ZnO NPs) in PVA solution (PVAS), and high-strength composite for 122.3 MPa with interfacial interlocking structure was successfully fabricated via vacuum assisted resin transfer molding (VARTM). ZnO NPs were coated on the PVA fibers and enhanced the surface roughness, which improved the mechanical performance of the composite. In comparison with untreated composites, the interlaminar shear strength (ILSS) of composites displayed a significant increase, from 99.4 MPa to 122.3 MPa, resulting from improved interfacial bonding and reduced interfacial gap. Simultaneously, the incorporation of ZnO NPs efficiently enhanced the ultraviolet (UV) resistance.