Polyvinyl Alcohol Fibers Research Articles

Experimental study on mechanical and durability properties of concrete incorporating various polyvinyl alcohol fiber lengths and dosages

To inquire about the properties of concrete reinforced with polyvinyl alcohol (PVA) fiber (various fiber lengths and dosages), different experimental tests including mechanical property, cracking resistance, and chloride resistance were investigated. The overall performance of PVA fiber-reinforced concrete (FRC) was innovatively analyzed integrating mechanical indicators and crack resistance parameters. Furthermore, nuclear magnetic resonance (NMR) and scanning electron microscope (SEM) were selected to analyze the causes and mechanisms underlying the alterations in the performance of PVA-FRC. The experimental results demonstrate that the flexural strength, the crack resistance characteristic and chloride ion penetration resistance of PVA-FRC are significantly improved compared to ordinary concrete. Increasing fiber length plays a key role in flexural strength, compared with fiber dosage. Considering both mechanical properties and durability, PVA-FRC containing 0.25% volume fraction of 12 mm PVA fibers (F12-0.25) demonstrated optimal performance.

Cyclic Performance of Reinforced Concrete Columns Strengthened with Basalt-Fibre-Reinforced Cementitious Matrix (BFRCM)

The purpose of this experimental investigation was to confirm whether the Basalt-Fibre-Reinforced Cement Matrix (BFRCM) effectively enhances the cyclic performance of columns made of reinforced concrete (RC). The BFRCM system, which comprises basalt fabric mesh reinforced with a cementitious matrix containing polyvinyl alcohol (PVA) fibre, has significant practical implications. In the testing phase, concrete and steel reinforcement were used to create RC column specimens, which were then strengthened with three, four, and five layers of BFRCM. The horizontal cyclic and constant axial loads were applied and tested to evaluate the performance of RC columns with and without strengthening. By improving the energy dissipation by approximately 9 to 32% and increasing stiffness by roughly 24 to 44%, the column specimen with three, four, and five layers of BFRCM performed better than the control specimen. Furthermore, incorporating short fibre into the matrix effectively improved the tensile properties of the FRCM systems and decreased the shrinkage-induced cracks. The increased stiffness indicates that the column with BFRCM has better structural strength because it can sustain higher loads with less deflection. The thorough comparative analyses examined the RC column specimens’ failure modes, hysteretic responses, stiffness degradation, and energy dissipation, providing a reliable basis for the conclusions. The test results confirmed that the BFRCM effectively enhanced the seismic capabilities and has been promised a way to strengthen RC elements, providing valuable insights for civil engineering and materials science.

Review of Recent Developments in Tensile Properties of Engineered Geopolymer Composites

Engineered Cementitious Composite (ECC) is a type of highly ductile cementitious material. However, due to its characteristics of high energy consumption and high carbon emissions, it is necessary to seek a new type of low-carbon and environmentally friendly substitute. Engineered Geopolymer Composite (EGC), as a promising construction material for replacing ECC, has broad application prospects. Through visual analysis of the relevant literature in Web of Science, it was discovered that the research on EGC mainly concentrates on aspects such as the types of precursors, the chemical composition of the alkali-activated solution, and the related parameters of fibers. This paper mainly combines the relevant experimental research data on the tensile properties of EGC conducted by scholars at home and abroad, and focuses on analyzing the influence of precursor types, the chemical composition of the alkaline activator, and fibers on the tensile properties of EGC. The statistical results indicate that fly ash and ground granulated blast-furnace slag (GGBFS) are the most commonly used precursor materials. Replacing an appropriate amount of fly ash in the precursor with GGBFS can significantly enhance the tensile strength of EGC. The type of alkaline activator and its molarity have a relatively obvious influence on the tensile properties of EGC. An increase in the molarity of NaOH within a certain range can enhance the tensile strength of EGC. Furthermore, the incorporation of fibers, especially synthetic fibers such as polypropylene (PP) and polyvinyl alcohol (PVA) fibers, as well as inorganic fibers such as glass fibers (GF) and carbon fibers (CF), can effectively enhance the tensile strength and tensile strain capacity of EGC. The use of hybrid fibers may further improve the tensile properties.

Mechanism and Performance Evaluation of a Strain Sensor Made from a Composite Hydrogel Containing Conductive Fibers of Thermoplastic Polyurethane and Polyvinyl Alcohol

Mechanism and Performance Evaluation of a Strain Sensor Made from a Composite Hydrogel Containing Conductive Fibers of Thermoplastic Polyurethane and Polyvinyl Alcohol

Mechanism of interface performance enhancement of nano-SiO2 modified polyvinyl alcohol fiber reinforced geopolymer concrete: Experiments, microscopic characterization, and molecular simulation

This study proposes a method utilizing nano-SiO2 modified polyvinyl alcohol fibers to enhance the interface properties of geopolymer concrete. The surface properties of modified polyvinyl alcohol fibers were analyzed through microscopic characterization. The influence of different dosages of modified polyvinyl alcohol fibers on the mechanical properties of geopolymer concrete was investigated. Molecular dynamics simulations revealed the interfacial toughening mechanism between modified polyvinyl alcohol fibers and geopolymer concrete. Results showed that nano-SiO2 modified polyvinyl alcohol fibers increased surface roughness, thereby enhancing interfacial adhesion and mechanical interlocking between fibers and geopolymer concrete, significantly improving compressive, splitting tensile, and flexural strengths of geopolymer concrete with an optimal fiber dosage of 0.2 %. Relative to unmodified PVA fibers, the modified fibers enhance the compressive, splitting tensile, flexural strength, and elastic modulus by 20.19 %, 15.72 %, 22.34 %, and 30.58 % respectively. KH560 serves as an intermediate medium for nano-SiO2 modified polyvinyl alcohol fibers, generating numerous hydrogen bonds at the interface and tightly adhering nano-SiO2 to the surface of polyvinyl alcohol fibers. Additionally, nano-SiO2 can form ionic bonds and stable Si-O-Si bonds with the hydrated sodium aluminosilicate gel.

Splitting behavior of polyvinyl alcohol fiber reinforced iron ore tailings concrete

To promote solid waste reutilization and reduce natural river sand consumption, iron ore tailings (IOT) are expected to be used in concrete production as a potential substitute for river sand under the premise of comparable material properties with ordinary concrete. In this study an IOT concrete reinforced by Polyvinyl Alcohol (PVA) fiber has been proposed and the slump and splitting behavior under various IOT substitution rates and PVA fiber contents has been experimentally investigated. Slump tests reveal that the optimal PVA fiber content is 0.1 % and IOT substitution rate is 60 % from the view of workability. Splitting tensile tests show a monotonous strength growth with PVA fiber content increase. The incorporation of IOT has increased concrete splitting tensile strength but the strength is smaller than that of normal concrete as soon as IOT substitution rates exceed 50 %. A regression model and Back Propagation (BP) neural network model have been adopted to establish splitting tensile strength prediction model. Compared to regression model, the BP model has exhibited better accuracy which is suitable to predict the splitting tensile strength of PVA-IOT concrete with PVA content less than 0.3 %.

The Influence and Mechanism of Polyvinyl Alcohol Fiber on the Mechanical Properties and Durability of High-Performance Shotcrete

This study investigates the impact of polyvinyl alcohol (PVA) fibers on the mechanical properties and durability of high-performance shotcrete (HPS). Results demonstrate that PVA fibers have a dual impact on the performance of HPS. Positively, PVA fibers enhance the tensile strength and toughness of shotcrete due to their intrinsic high tensile strength and fiber-bridging effect, which significantly improves the material’s splitting tensile strength, deformation resistance, and toughness, and the splitting tensile strength and peak strain have been found to be increased by up to 30.77% and 31.51%, respectively. On the other hand, the random distribution and potential agglomeration of PVA fibers within the HPS matrix can lead to increased air-void formations. This phenomenon raises the volume content of large bubbles and increases the average bubble area and diameter, thereby elevating the pore volume fraction within the 500–1200 μm and >1200 μm ranges. Therefore, these microstructural changes reduce the compactness of the HPS matrix, resulting in a decrease in compressive strength and elastic modulus. The compressive strength exhibited a reduction ranging from 10.44% to 15.11%, while the elastic modulus showed a decrease of between 8.09% and 12.67%. Overall, the PVA-HPS mixtures with different mix proportions demonstrated excellent frost resistance, chloride ion penetration resistance, and carbonation resistance. The electrical charge passed ranged from 133 to 370 C, and the carbonation depth varied between 2.04 and 6.12 mm. Although the incorporation of PVA fibers reduced the permeability and carbonation resistance of shotcrete, it significantly mitigated the loss of tensile strength during freeze–thaw cycles. The findings offer insights into optimizing the use of PVA fibers in HPS applications, balancing enhancements in tensile properties with potential impacts on compressive performance.

Development of sustainable alkali activated composite incorporated with sugarcane bagasse ash and polyvinyl alcohol fibers.

The infrastructure boom has driven up cement demand to 30 billion tons annually. To address this and promote sustainable construction, researchers are developing solutions for carbon-neutral building practices, aiming to transform industrial waste into an eco-friendly alternative. This study aims to develop and enhance the mechanical and durability properties of alkali-activated composites (AACs) by incorporating varying amounts (5, 10, 15, and 20%) of finely ground bagasse ash (GBA) and polyvinyl alcohol (PVA) fibers. Results indicate that higher GBA content initially reduces the 7th and 14th-day strength but results in increased strength at later ages. The optimum 28-day strength is achieved with a 10% GBA content, leading to a 10% increase in compressive strength, 8% increase in tensile strength, and 12% increase in flexural strength. Additionally, the incorporation of GBA enhanced the resistance of the composite to chloride ingress, thus reducing its conductance and increasing the overall durability. This study demonstrated the potential of GBA as an eco-friendly material, emphasizing the significance of tailored AACs formulations for durable and sustainable construction practices.

Influence of Steel and Poly Vinyl Alcohol Fibers on the Development of High-Strength Geopolymer Concrete

The present study focuses on the mechanical performance of steel and polyvinyl alcohol fibers embedded in the geopolymer matrix. A high-strength geopolymer concrete with fly ash, slag and silica fume as precursors and sodium hydroxide and sodium silicate solutions as activators has been tested for its strength in compression and flexure. The influence of fibers on flowability, long-term shrinkage and sulphuric acid attack on the geopolymer concrete has also been studied. The dosage of fibers was maintained at 1%, 2% and 3% by volume, and fibers of length 13 mm have been used in the study. Results indicate that slag with 3% steel fibers by volume had a predominant influence on the strength development of steel fiber-reinforced geopolymer concrete, yielding a compressive strength of 107 MPa after 28 days. Blast furnace slag resulted in increasing the shrinkage of concrete due to rapid gel formation owing to the presence of calcium ions, although the fibers helped reduce the shrinkage to some extent. The strength of steel fiber geopolymer concrete was superior to PVA fiber geopolymer concrete; however, after an acid attack, the strength of steel fiber geopolymer concrete was reduced more than PVA fiber geopolymer concrete due to the enhanced corrosion resistance of PVA fibers.

Experimental and simulation study on seismic performance of seawater sea-sand PVA cementitious composite columns with GFRP bars

The seismic properties of seven seawater sea-sand (SWSS) PVA cementitious composite columns with Glass Fiber Reinforced Polymer (GFRP) bars were studied. The effects of four parameters, namely polyvinyl alcohol (PVA) fiber content, axial compression ratio, cementitious composite strength and stirrup spacing, on the seismic performance of composite columns were analyzed. The failure of the specimen was observed, and the hysteresis curve, skeleton curve, stiffness degradation, energy dissipation capacity, ductility and strain of the specimen were analyzed. The test results show that the large chip-based spalling will occur when the specimen without fiber incorporation is damaged, and the incorporation of PVA fiber, the reduction of stirrup spacing and the reduction of axial compression ratio will delay the rate of crack formation and development. In addition, through cross-section analysis and considering the reinforcement effect of PVA fibers, a proposed formula for calculating the horizontal bearing capacity of composite columns is proposed. Finally, the finite element model of SWSS PVA cementitious composite columns with GFRP bars is established, and it is found that increasing the strength grade of cementitious materials can greatly improve the seismic performance of composite columns. The conclusions could be references for the engineering application. In the context of the global emphasis on green development and environmental protection, seawater and sea-sand cementitious composites and components with fiber reinforcement will have a wide range of application prospects in the construction of coastal areas.

Mechanical behavior and microscopic damage mechanism of hybrid fiber-reinforced geopolymer concrete at elevated temperature

Geopolymer concrete (GPC) that is prepared from eco-friendly materials exhibits much more excellent resistance on high temperature compared with ordinary Portland cement concrete. In this study, hybrid fibers containing varying proportions of steel fiber (0.5%-2.0%) and polyvinyl alcohol (PVA) fiber (0.2%-0.8%) were incorporated in GPC. The hybrid fiber-reinforced geopolymer concrete (HFRGC) was subjected to temperatures ranging from 200 °C to 800 °C. The physical properties tests, mechanical properties tests, and microstructure tests of HFRGC were carried out at elevated temperatures, while the environmental impact and cost-effectiveness of HFRGC were assessed. The results of physical properties tests showed that the appearance and mass loss of the HFRGC were mainly affected by temperature, while hybrid fibers had a negligible effect on both. The appearance of HFRGC gradually transformed from gray to brick red with increasing temperature, and the mass loss of HFRGC at 800 °C was as high as 9.4%. The mechanical performance test results indicated that the mechanical strength of HFRGC increased at 200 °C and then decreased with elevated temperature. At 200 °C, the compressive strength, splitting tensile strength, and flexural strength of HFRGC containing 1.5% steel fibers and 0.6% PVA fibers were respectively increased by 13.1%, 14.7%, and 4.4% as compared with ambient conditions. The microstructure test results showed that further geopolymerization at 200 °C promoted the densification of the matrix. The matrix was damaged at higher temperatures violently while the porosity of HFRGC was dramatically increased from 13.35% at 25 °C to 27.83% at 800 °C. Based on the thermal behavior, environmental impact, and cost-effectiveness of HFRGC, a reference for future research in the fire prevention of GPC was provided.

Effects of aggregates and fibers on the strength and permeability of concrete exposed to low vacuum environment

The performance and regulation of concrete in low vacuum environments are receiving increasing attention. This study investigates the effects of aggregates and fibers on the strength and permeability of concrete in a low vacuum environment, using varying gradients of sand ratios (37.5 %, 40 %, and 42 %) and aggregate-to-binder ratios (3.27, 3.92, and 4.14). Three types of non-metallic fibers are utilized: polyethylene (PE), polyvinyl alcohol (PVA), and glass fibers. Evaluations focus on concrete strength, mass loss, gas permeability, capillary water absorption, and porosity. Results indicate that higher sand and aggregate-to-binder ratios enhance both flexural and compressive strength. Fiber incorporation improves flexural and compressive toughness, with PE fibers showing the most significant toughening effect. The low vacuum environment increases the strength of the concrete but reduces its axial compression toughness ratio and increases brittleness, while fiber incorporation helps improve the compression toughness of the concrete. Higher sand and aggregate-to-binder ratios reduce mass loss and accelerate drying equilibrium, while fibers increase mass loss and prolong drying equilibrium, with PVA fibers causing greater mass loss. The pattern of concrete mass loss can be explained by the tortuosity of the moisture diffusion path. Additionally, low vacuum significantly increases the gas permeability of concrete. Enhancing the sand and aggregate-to-binder ratios reduces permeability both before and after low vacuum treatment. Although fibers increase the gas permeability, they help mitigate this increase under low vacuum condition. Capillary water absorption tests reveal that concrete under low vacuum condition has a significantly higher water absorption rate compared to air-drying condition. Increasing sand and aggregate-to-binder ratios reduces water absorption and capillary water content, whereas fibers have the opposite effect. Porosity tests show that moisture migration in a low vacuum environment is mainly related to permeable porosity, while total porosity is more closely related to compressive strength.

Hyperthermia and biological investigation of a novel magnetic nanobiocomposite based on acacia gum-silk fibroin hydrogel embedded with poly vinyl alcohol

The design and synthesis of biocompatible nanostructures for biomedical applications are considered vital challenges. Herein, a nanobiocomposite based on acacia hydrogel, natural silk fibroin protein, and synthetic protein fibers of polyvinyl alcohol was fabricated and magnetized with iron oxide nanoparticles (Fe3O4 MNPs). The structural properties of the hybrid nanobiocomposite were investigated by essential analyses such as Fourier Transform Infrared Spectrometer (FTIR), Field emission scanning electron microscopy (FE-SEM), and X-ray powder diffraction)XRD(analyses, Thermogravimetric and Differential thermogravimetric analysis (TGA-DTG), Vibrating-sample magnetometry (VSM), and Energy Dispersive X-Ray Analysis (EDX). The biological activities and functional properties of the prepared magnetic nanobiocomposite were studied. Results proved that this nanobiocomposite is non-toxic to the healthy HEK293T cell line. In addition, the synthesized nanobiocomposite showed an approximately 22 % reduction in cell viability of BT549 cells after 72 h. All results confirmed the anti-cancer properties of nanobiocomposite against breast cancer cell lines. Therefore, the prepared nanobiocomposite is an excellent material that can use for in-vivo application. Finally, the hyperthermia application was evaluated for this nanobiocomposite. The SAR was measured 93.08 (W/g) at 100 kHz.

Improvement of aerogel-incorporated concrete by incorporating polyvinyl alcohol fiber: Mechanical strength and thermal insulation

Aerogel incorporated concrete (AIC) effectively improves its thermal insulation performance. However, the potential mechanical strength degradation in AIC limits its further promotion and application. Fiber reinforcement is an effective means for improving the properties of cement-based materials. However, there is currently a lack research on enhancement mechanisms involved in fiber-reinforced AIC. In this study, polyvinyl alcohol (PVA) fibers with high strength and low thermal conductivity are introduced. The influence on the properties of AIC with various lengths (6–12 mm) and proportions (0–1.2 wt%) of PVA fiber was analyzed, and the mechanism of AIC enhancement was discussed based on microscopic test. The enhancing mechanism of PVA fiber on AIC was studied at microscopic scale to establish new solutions to the development of cementitious materials with both excellent load-bearing capacity and thermal insulation performance. The results revealed a synergistic effect of hydrophobic aerogel and PVA fiber on the fluidity of the mix due to the improvement of particle dispersibility and distribution uniformity. Additionally, the PVA fibers crossed aerogel particles around could inhibit crack expansion caused by aerogel fractures, thus effectively mitigating the loss of strength heat transfer with aerogel incorporation. At the same time, PVA fiber also plays a role in thermal resistance. Specifically, the incorporation of 0.6 wt% 9-mm fibers yielded the best overall reinforcement results, with an increase of 31.4 % and 15.5 % in flexural and compressive strengths, respectively, and a 28.5 % decrease in thermal conductivity. The microstructural tests indicated that incorporating PVA fibers at 0–0.6 wt% could optimize the pore structure, reduce the porosity, and increase the water resistance of AIC. The hydration degree of the cement matrix increased due to Ca2+ adsorption by PVA fibers. This study provides an optimized design strategy incorporating PVA fibers to enhance both the physical properties, mechanical strength, and thermal insulation properties of AIC.

Tailoring the size and shape of PbWO4 particles in highly filled polymer fibers for γ‐rays shielding

AbstractHighly filled polymer fibers offer huge promise for radiation protection safety and wear comfort of personal protective equipment (PPE) in radiation environments. However, it usually sacrifices mechanical properties that directly related to practical usability. Here, as high as 75 wt% PbWO4 (PWO) particles have been filled in polyvinyl alcohol (PVA) fiber via tailoring their size and shape for enhanced γ‐rays shielding and good mechanical properties. Clearly shown that 0 dimensional (0‐D) PWO exhibits better dispersion and compatibility between the interfaces than 1‐D PWO in highly filled PVA fibers. In addition, 70 wt% 0‐D PWO/PVA fibers display better mechanical properties than 70 wt% 1‐D PWO/PVA fibers. Note that 75 wt% 0‐D PWO/PVA fibers show 1.02 cN/dtex of tensile strength. However, 75 wt% 1‐D PWO/PVA fibers fail to be fabricated smoothly. Importantly, the overlapped fabrics with 75 wt% 0‐D PWO/PVA fibers display 43.05% of γ‐ray shielding (105 keV) meanwhile it offers good air and water vapor permeability for wear comfort. The superior γ‐ray shielding ascribes the polymer fibers with the higher filling in comparison with its counterpart, which provides a practical means to design radiation protection safety and wear comfort of articles.Highlights This work breaks the upper limit of filling in polymer fibers Filler structure can weigh the integrated properties of polymer fibers. 0‐D PWO particles promote interfacial compatibility in highly filled fibers. Radiation protection safety and wear comfort of articles tend to be designed.

Size effect on tensile bonding strength between new and old concrete

The interface between new and old concrete plays a significant role in reinforced concrete engineering due to its size effect and weak strength. To investigate the size effect of tensile strength in new-to-old concrete, splitting tensile tests and computed tomography (CT) scans on composite specimens were conducted. Specimen size, interface roughness, volume fraction of polyvinyl alcohol fiber and adhesive were considered. The tensile bonding strength initially increases and then decreases with interface roughness and fiber content, while size effect on the strength shows a downward trend before rising. The adhesive notably enhances the tensile bonding strength and weakens its size effect. The interface roughness, polyvinyl alcohol fibers and interface agents influence the size effect by modifying the bonding area, specimen uniformity, and characteristic structure of the interface region. At an interface roughness of 5.5 mm and a polyvinyl alcohol fiber content of 0.5 %, the maximum strength was achieved and the maximum attenuation of size effect occurred. The size effect laws of tensile bonding performance were presented based on the Weibull statistical theory, Bažant energy theory and Carpinteri multi-fractal theory. The experimental values exhibit good consistency with the predictions from the size effect models.

Effect of hybrid lead-PVA fibers on microstructure and radiation shielding properties of high-performance concrete

With the widespread application of nuclear technology in the medical and energy fields, the demand for efficient radiation shielding materials is increasing. Employing only lead or polyvinyl alcohol (PVA) fiber reinforcement cannot achieve improvements in the brittleness of high-performance concrete (HPC) while also enhancing radiation shielding efficiency and mechanical properties. This study develops a novel HPC for radiation attenuation, incorporating magnetite as the aggregate and reinforced with hybrid lead-PVA fibers (RSHPC). The synergistic effects of various proportions of hybrid lead-PVA fibers on the mechanical properties, three-dimensional microstructure, pore structure, and interfacial transition zone (ITZ) were investigated. In addition, the radiation attenuation capacities of RSHPC with different hybrid lead-PVA fiber proportions were evaluated through experimental and simulation analysis. The results show that hybrid lead-PVA fibers notably improve the air-void structure of RSHPC. The incorporation of PVA fibers, by improving the ITZ of matrix, effectively mitigates the negative impact of lead fibers on mechanical performance. The refinement of pore structure and the introduction of light and heavy nuclides lead to a significant enhancement in the gamma-ray and neutron radiation attenuation capabilities of RSHPC. Utilizing X-ray computed tomography (X-CT) for three-dimensional reconstruction further indicates the optimization impact of hybrid lead-PVA fibers on the microstructure, notably in the improvement of pore distribution and fiber dispersion, thus enhancing the overall properties and radiation attenuation performance of RSHPC.

PVA fiber reinforced red mud-based geopolymer for 3D printing: Printability, mechanical properties and microanalysis

Red mud-based geopolymers are an efficient alternative to resolve the high cement consumption in 3D printed concrete (3DPC). From a materials perspective, good printability and mechanical properties are critical to adopting red mud-based geopolymers in 3DPC. In this study, we selected bauxite tailings-red mud and blast furnace slag to prepare geopolymers. Polyvinyl alcohol (PVA) fibers with 0, 0.3 %, 0.6 %, 0.9 %, and 1.2 % volume fractions were used to reinforce 3D printed red mud-based geopolymers. To evaluate the influence of PVA fiber on the printability and mechanical properties of 3D printed red mud-based geopolymer. We tested the workability, extrudability, structural build-up ability, shape stability, and mechanical properties of the red mud-based geopolymer containing different volume fraction PVA fibers, and a microstructural analysis was performed to reveal the interface bond between the fibers and the geopolymer matrix. The results showed that adding PVA fibers impaired the workability of the red mud-based geopolymer mortar. The red mud-based geopolymer mortar showed a more than threefold increase in extrusion pressure compared to the control mixture (P0) when adding 1.2 % vol fiber. For all other mixtures, the increase was less than twice that of the control mixture. The PVA fiber had a significant positive impact on the structural build-up ability and shape stability of the 3D printable red mud-based geopolymer. In addition, PVA fibers promoted the bending strength of the hardened geopolymer specimens better than the compression strength, and the geopolymer gel on the fibers indicated the good interfacial bonding ability of the PVA fiber. This study demonstrates the feasibility of 3D printed red mud-based geopolymer and the reinforcement of 3D printed red mud-based geopolymer by PVA fibers, providing a material perspective to increase the range of red mud applications in 3D printed concrete.

Enhancing toughness in cement-based composites: Unraveling the composite effect mechanisms of polymers and fibers through physic testing and molecular dynamics simulations

To reveal the toughening mechanism of polymers and fibers in composite applications, a combination of physical tests (uniaxial compression, flexural fracture, single fiber pull-out, scanning electron microscopy, and X-ray diffraction (XRD)) and molecular dynamics simulations have been carried out. Three polymers, i.e. ethylene-vinyl acetate copolymer (EVA), styrene-acrylate copolymer (SAE), and styrene-butadiene copolymer (SB), and two fibers, i.e. polypropylene fiber (PP) and polyvinyl alcohol fiber (PVA) are considered. Their composite effect mechanisms are explained in the viewpoint of three scales. At the macro-scale, the pull-out tests of single fiber show that the polymer increased the equivalent bond strength between the fiber and the mortar matrix. At micro-scale, it was observed from the SEM experiments that the fiber and polymer film inhibited the crack extension at different scales, besides the polymer could absorb on the fiber surface to improve the interfacial transition zone (ITZ) density around the fiber and increase the roughness of the fiber surface. At nano-scale, MD simulations demonstrate that three polymers facilitated the bond strength between PP fiber and C–S–H at the nano-scale, mainly because of the formation of Ca–O coordination bond and H-bonds between the polymers and C–S–H, and the presence of van der Waals forces between the polymers and PP fiber. However, SAE facilitated the bonding between the PVA fibers and the C–S–H, which originated from the coordination bonds formed between Ca ions on the surface of SAE and O atoms in PVA. In addition, the large number of H-bonds formed between SAE and PVA.

Structural performance of hybrid reinforced concrete beams containing polyvinyl alcohol fibers under thermal loads

This study focused on the efficiency of concrete beams containing polyvinyl alcohol fibers (PVA) under thermal loads. The eighteen concrete beams were reinforced with hybrid bars or a combination of GFRP bars and steel reinforcement bars (hybrid scheme). The main experimental variables were the level of temperature (25o, 300o, and 600o C), PVA fiber volume (0 %, 0.50 %, and 1.0 %), and the flexural reinforcement bars. The experimental test results are discussed in terms of the first crack load, flexural capacity, and load-deflection curves. Moreover, the initial and post-crack stiffness, ductility factor, and failure modes are discussed. The test results demonstrated a significant increase in the capacity of PVA concrete beams reinforced with hybrid reinforcement bars. At a temperature of 300o C, the inclusion of 0.50 % and 1.0 % PVA ratios improved the flexural capacities by 11 % and 24 %, respectively. Furthermore, the addition of PVA fibers enhanced the toughness by 34 % and 67 %, respectively, when compared to normal concrete beams. The results also demonstrate that using PVA fibers prevents the spalling of concrete beams after exposure to elevated temperatures. At 600 °C, beams containing 0.50 % and 1.0 % PVA fibers exhibited flexural capacities that were 9 % and 6 % higher, respectively, compared to normal concrete beams. Additionally, the inclusion of PVA fibers increased the toughness by 27 % and 21 % for the respective fiber ratios. Finally, a nonlinear finite element analysis (NLFEA) simulation was performed to verify the experimental test results and supplement experiments by predicting the results that are difficult to accomplish through experiments. With an average ratio of 1.02 between experimental and NLFEA ultimate capacity, the numerical results were an exact match of the patterns observed in the experimental results.