Polyvinyl Alcohol Fiber Content Research Articles

Durability and Mechanical Properties of Nano-SiO2 and Polyvinyl Alcohol Fiber-Reinforced Cementitious Composites Subjected to Saline Freeze–Thaw Cycles

To investigate the effects of nano-SiO2 (NS) and polyvinyl alcohol (PVA) fibers on the durability and mechanical properties of cementitious composites subjected to saline freeze–thaw cycling, a series of PVA fiber-reinforced cementitious composite (PFRCC) specimens were prepared using various fiber contents, and a series of NS and PVA fiber-reinforced cementitious composite (NPFRCC) specimens were prepared using various combinations of NS and fiber contents. Durability and fracture toughness tests were subsequently conducted on the specimens after different numbers of saline freeze–thaw cycles. The results indicate that the degradation of material properties can be divided into slow and accelerated damage stages before/after 50 freeze–thaw cycles. The durability and fracture toughness of the specimen series tended to increase, then decrease with increasing NS and PVA contents, suggesting optimum levels. When the PVA fiber content was 0.5%, PFRCC specimens had the best durability after saline freeze–thaw cycles; when the NS and PVA fiber contents were 1.0% and 0.5%, respectively, NPFRCC specimens had the best durability and fracture properties, and the initiation toughness, destabilization toughness, and fracture energy after 100 saline freeze–thaw cycles were 120.69%, 160.02%, and 451.31%, respectively. The results of this study may guide future exploration of the durability and mechanical properties of concrete subjected to freeze–thaw action.

Development of low-cost engineered cementitious composites using Yellow River silt and unoiled PVA fiber

One of the main problems for restricting the extensive practical application of Engineered Cementitious Composite (ECC) is its expensive price due to the incorporation of high-price fine quartz sand and polyvinyl alcohol (PVA) fibers. To address this defect, the replacement with solid waste fine aggregate and locally produced PVA fiber has been proved to be a good choice. This work aims to develop low-cost green ECC using Yellow River silt as fine aggregate and locally produced unoiled PVA fiber. The effects of water-binder ratio, sand-binder ratio, and PVA fiber content on the mechanical characteristics of as-prepared ECC were evaluated by a comparative experiment. It has been indicated that the mechanical characteristics of as-prepared low-cost ECC are significantly affected by water-binder ratio, sand-binder ratio, and PVA fiber content. As the water-binder ratio rises, the tensile ductility of as-prepared low-cost ECC gradually increases, but the tensile strength, compressive strength, and flexural strength all decrease. The compressive strength and flexural strength exhibit a positive correlation with the sand-binder ratio, albeit with a minimal impact. Too low or high sand-binder ratio leads to a decrease in strain-hardening ability. Moreover, the as-prepared ECC exhibits a comparatively reduced tensile strain capacity when using locally produced unoiled PVA fiber as opposed to imported oiled PVA fiber. Finally, the environmental impact and economic benefits of the as-prepared low-cost ECC and Typical ECC are compared. The as-prepared low-cost ECC has good strain-hardening ability and low cost, indicating a potential application in real engineering.

Fiber Synergy of Polyvinyl Alcohol and Steel Fibers on the Bond Behavior of a Hybrid Fiber-Reinforced Cementitious Composite.

Based on multi-scale characteristics inherent in the cracking process of cementitious composites, fibers with different geometric dimensions are simultaneously used to restrain the formation and development of cracks at different scales. Accordingly, hybrid fiber-reinforced cementitious composites (HyFRCCs) exhibit excellent bond behavior and deformation capacity in terms of tension and compression, accompanied by higher damage tolerance. Using these benefits of the mechanical properties of HyFRCCs, the structural performance of HyFRCC structures under complex loading conditions can be improved. To objectively evaluate the contributions of all fibers to the mechanical properties of HyFRCCs, steel macro-fibers, and polyvinyl alcohol (PVA) micro-fibers were used to design several reinforced cementitious composites. Four of the specimens were mono-fibrous cementitious composites, three specimens were cementitious composites reinforced with hybrid fibers, and one was a non-fibrous cementitious composite. The synergy effect of the steel and PVA fibers was analyzed using various fiber combinations. The results indicated a significant enhancement of the bonding properties of HyFRCCs through the incorporation of PVA and steel fibers. Specifically, the peak bond strength, peak slip displacement, and residual bond strength exhibited increments ranging from 31.0% to 41.7%, 60.6% to 118.4%, and 34.6% to 391.3%, respectively, in comparison to the reference test block. Notably, the combined presence of the PVA and steel fibers consistently demonstrated a positive confounding effect on the residual bond strength. However, negative confounding effects were observed in terms of the peak bond strength and peak slip displacement, particularly with 1.0% steel fiber content and 0.5% PVA fiber content.

Compressive behavior of polyvinyl alcohol engineered cementitious composites incorporating steel slag as aggregate

Disposal of the steel by-product steel slag (SS) negatively impacts the environment. The use of SS as an aggregate in engineered cementitious composites (ECC) can prevent pollution and mitigate natural aggregate depletion. In this study, river sand (RS) was replaced by SS with maximum size of 4750 µm, and the properties of ECC with varying contents of SS and polyvinyl alcohol (PVA) fiber were investigated. SS changed the hydration product composition and enhanced the bond stress between the fiber and cementitious matrix, increased the bulk specific density and compressive strength, and reduced the porosity. ECC containing only SS and with high PVA fiber content exhibited superior performance. A 25% SS replacement ratio and 2% PVA fiber content improved the compressive strength, ductility index, and toughness index to 47.5 MPa, 1.45, and 2.60, respectively.

Influence of PVA fibers on the durability of cementitious composites under the wet–heat–salt coupling environment

Abstract To investigate the effects of wet–heat–salt coupling environment (WHSCE) and the content of polyvinyl alcohol (PVA) fibers on the durability of cementitious composites (CC), a series of durability tests were carried out. In this study, the salt concentration in the WHSCE was set to 5%, the temperature at 50°C, and the relative humidity at 100%. Six different contents of PVA fibers were set up in the test for exploring their effects on the durability (impermeability, chloride ion penetration resistance, freeze–thaw resistance, and chloride salt erosion resistance under dry and wet cycle conditions) of CC. The results showed that durability of CC under the WHSCE was enhanced regardless of the content of PVA fibers added. At the PVA fiber amount of 1.2%, the impermeability pressure, electric flux, mass loss rate, compressive strength loss rate, and compressive strength corrosion resistance coefficient under the WHSCE reached the optimal values. This indicated that the durability of CC was most favorable when the amount of PVA fibers was 1.2% since many engineering structures are subject to erosion by various factors in the ocean, which can inevitably affect the service life of the purchase. In this study, the effect of PVA fiber content on the durability of CC in complex environment is studied, which provides experimental data and analytical ideas for improving engineering located in the ocean, hoping to provide a theoretical basis for their subsequent application in practical engineering.

Effect of PVA fibers on durability of nano-SiO2-reinforced cement-based composites subjected to wet-thermal and chloride salt-coupled environment

Abstract Marine engineering structures are often faced with complex environmental factors. It is the focus of current research to modify cement-based composites (CBCs) to achieve their high durability in complex environments such as seawater. In this study, the effect of polyvinyl alcohol (PVA) fibers on durability of nano-SiO2 (NS)-reinforced cement-based composites was investigated by simulating seawater environment and taking PVA fiber content as variable. In addition, based on the Weibull probability distribution model, the damage degree of NS and PVA fiber-reinforced cement-based composites (NFRCCs) subjected to wet-thermal and chloride salt-coupled environment (WTCSE) after 300 freeze–thawing cycles (FTCs) was predicted. The test results demonstrated that the NFRCC exhibited the most excellent durability subjected to WTCSE when the content of PVA fibers was 1.2%. Compared with the reference group only doped with NS subjected to WTCSE, its impermeability pressure increased by 150%, the chloride ion electric flux decreased by 31.71%, the compressive strength loss rate decreased by 19.00% after 125 FTC, and the compressive strength corrosion resistance coefficient of chloride salt erosion increased by 9.15% after 25 wetting–drying cycles. The predicted results of the Weibull probability distribution model indicated that the damage degree of NFRCC subjected to WTCSE after 300 FTC would not exceed 0.35. The microscopic test analysis showed that the incorporation of PVA fibers reduced the proportion of large pores and the overall porosity of NFRCC subjected to WTCSE. PVA fibers bridged microcracks while adsorbing NS and its hydration products, thus enhancing the adhesion of the substrate. This study provides a reference for the research of high-performance CBC in complex environment.

The early-age shrinkage cracking and late-age fracture properties of fiber-reinforced cementitious composites

In this research, the shrinkage cracking and fracture properties of fiber-reinforced cementitious composites (FRCC) are investigated using eccentric ring test and three-point bending test. In the eccentric ring test, the concept of the equivalent crack width (weq) is proposed based on the morphology and number of cracks of FRCC. A function considering curing time and fiber volume fraction is established to calculate the equivalent crack width of FRCC. The initial and complete-through cracking times of FRCC were measured to explain the effect of the fibers. In the three-point bending test, the crack initiation in FRCC is determined based on the average transverse force. The initial and unstable fracture toughnesses, as well as the fracture energy, have been calculated. The experimental results indicate that an increase in polyvinyl alcohol (PVA) fiber content can reduce the crack width and prolong the initial and complete-through cracking times induced by shrinkage. The unstable fracture toughness and fracture energy increase with the increase in the PVA fiber content. The results of the eccentric ring test and three-point bending test demonstrate that the primary role of PVA fibers is to extend the intermediate stage of cementitious materials from initial cracking to unstable cracking. Additionally, PVA fibers delay the energy release rate during the failure process.

Performance optimization of geopolymer mortar blending in nano-SiO2 and PVA fiber based on set pair analysis

Abstract The method of set pair analysis was used to evaluate the comprehensive performance of geopolymer mortar (GM) based on metakaolin and fly ash modified by nano-SiO2 (NS) and polyvinyl alcohol (PVA) fiber, and the design of mix proportion for GM was optimized. According to the experimental results, the addition of the NS and PVA fiber can improve the comprehensive properties of GM. The properties of GM are better when the NS content is 1.5% and PVA fiber content is 0.6%. The comprehensive performance of GM included workability, mechanical properties, fracture properties, and durability, and the typical performance parameters were selected as slump flow, compressive strength, bending strength, fracture energy, loss ratio of compressive strength after cycles of freezing-thawing, and electric flux values. The results show that the weights of each indicator derived from the method of set pair analysis have reduced subjective arbitrariness, improved the evaluation accuracy, and made the conclusions obtained from the set pair analysis method more scientific and reasonable. The method of set pair analysis combines the mechanical properties, durability, and workability of GM blending in PVA fiber and NS to achieve a comprehensive qualitative and quantitative evaluation, which can provide a new method for assessing the comprehensive performance of the GM composites blending in PVA fiber and NS in the future.

Effect of waste colemanite and PVA fibers on GBFS-Metakaolin based high early strength geopolymer composites (HESGC): Mechanical, microstructure and carbon footprint characteristics

This study investigated the effects of polyvinyl alcohol (PVA) fiber and colemanite on the physical, mechanical and transport characteristics of GBFS-metakaolin-based geopolymer composites with high early-age strength (HESGC). The microstructure was intensified using 100, 150 and 200 kg/m3 colemanite instead of quartz powder. In addition, 0.25% and 0.50% PVA fiber were added to the blend to prevent the permeability problem in the condensed microstructure. HESGCs were cured in 3 different environments: ambient, 60 and 80 °C. The binder dosage (GBFS + Metakaolin) in HESGCs is 750 kg/m3. The alkali solution ratio is approximately 75% (according to binder amount. While the apparent porosity exceeds 10% in HESGCs subject to ambient cure, the porosity % in heat-cured HESGCs) In addition, the porosity and water absorption decrease when colemanite is used in heat cured HESGCs. Adding 0.25% PVA fiber to HESGCs creates a micro-aggregate effect, reducing porosity and water absorption relatively. It varies between 2393 kg/m3. The compressive strength (fc) of HESGCs subjected to ambient cure varies between 27.5 and 43.8, and the fc of HESGCs heat cured at 80 °C varies between 77.4 and 95.6 MPa. The flexural strength (ff) of HESGCs varies between 3.6 and 13.3 MPa. As the PVA fiber content and curing temperature increase, the ff increases. If 0.5% PVA fiber is used, the ff of HESGCs is increased between 8.3% and 89.6%0.200 kg/m3 colemanite is used in heat-cured HESGCs fc can increase up to 20%. While 0.25% PVA fiber ratio is the most suitable ratio in fc, 0.5% PVA fiber ratio is more suitable in ff. The capillary water absorption of HESGCs varies between 0.27–2.67 kg/m2. In the case of heat curing of HESGCs at 80 °C instead of ambient curing, capillary water absorption can be reduced up to 88%. Using colemanite instead of fine aggregate in microstructure investigations intensified the microstructure, but using 0.5% PVA fiber increased the porosity relatively. As a result, it has been observed that heat curing must be used in colemanite-containing HESGCs. When a heat cure is applied to HESGCs containing 0.25% PVA fiber and 200 kg/m3 colemanite, a fc of more than 12 MPa can be obtained.

Development of strain hardening cement based composite for concrete retrofitting purposes

The ever-increasing population in earthquake-prone areas necessitates the modification of both the current buildings and those that have already been damaged. Installing earthquake-resistant parts is required for this. In order to fulfill the continually expanding need for retrofitting materials that are both efficient and economical, civil engineers are under great pressure to develop novel new materials. A recent development in the construction sector is cement composites that harden under stress. Small particles and fibers are both used to make these composites. The chemical may enter the creep of the damaged structure without causing any vibrations. In order to restore the structure's original virgin strength, the mechanical and durability properties of the cement-based composite with strain hardening have yielded positive results. These qualities contributed to the success. The SHCC has also been used to connect deck slabs since the addition of fibers boosts the material's potential for abrasion resistance. These characteristics are provided through the incorporation of fibres. The combination of glass-fiber-reinforced polystyrene, (Ground Granulated Blast furnace Slag) and polyvinyl alcohol (PVA) fibers impacts the characteristics of a strain-hardening cement-based composite material has been investigated via experimentation, study, and analysis. A Ground Granulated Blast furnace Slag (GGBS) composition that varies from 10 to 30 percent has taken the place of the prior level of fly ash. PVA fibers with content levels of 2.0 and 3.0 percent, each measuring 12 mm in length, were employed in the experiment. These tests examined the compressive strength, tensile strength, and durability of a wide range of materials. The test findings reveal that although tensile strength and durability characteristics of the strain-hardened cement-based composite rose with a higher percentage of Ground Granulated Blast Furnace Slag (GBBS) content, compressive strength did not change significantly. It has been shown that better outcomes are obtained when PVA fiber content is greater. This is valid for both the mechanical strength and durability characteristics that different combinations have.

Shear properties of engineered cementitious composites using polyvinyl alcohol fiber

The utilization of Polyvinyl Alcohol (PVA) fibers in Engineering Cementitious Composites (ECC) has garnered significant attention in the realm of construction materials. This composite, formed from cement and ultra-ductile fibers, demonstrates exceptional properties, including high strength, resistance to elevated temperatures and corrosion, making it indispensable in structural engineering. Notably effective in seismic-resistant infrastructure and enduring structures subjected to harsh environmental conditions, ECC with PVA fibers stands out for its ductility and strainhardening capabilities. This study delves into ECC by incorporating various materials like cement, fly ash, sand, PVA fibers, and superplasticizer. PVA fibers, despite being costly, significantly augment ECC's ductility, strain-hardening behavior, and energy absorption properties. The inclusion of these fibers bolsters both shear and compression strength, elevating overall structural performance. Unlike conventional concrete, ECC showcases a remarkable tensile strain capacity of 3- 7%, contributing to its distinct characteristics. The literature review consolidates studies investigating PVA fiber's impact on ECC's mechanical properties, emphasizing enhancements in strength, toughness, and crack control. Factors such as fiber types, density, and additives are explored, showcasing how ECC with PVA fibers can augment performance and sustainability in construction materials. Findings reveal an increase in compressive strength at 7 days with added PVA fibers, albeit with some variations at 28 days. Similarly, shear strength escalates with increased PVA fiber content up to 1.5%, enhancing bonding and load-bearing capacity. However, higher fiber content at 2% causes increased water consumption, reducing load-carrying capacity. ECC fortified with PVA fibers demonstrates superior strength and durability compared to traditional concrete, overcoming brittleness and crack susceptibility. The research highlights the influence of fiber content on enhancing bonding and shear strength, establishing the potential for ECC with PVA fibers to revolutionize construction materials and practices.

Gray correlation analysis of factors influencing compressive strength and durability of nano-SiO2 and PVA fiber reinforced geopolymer mortar

Abstract To investigate the mechanical properties and durability of nano-SiO2, polyvinyl alcohol (PVA) fiber-modified fly ash (FA), and metakaolin (MK)-based geopolymer mortar (FMGM), tests of compressive strength, electrical flux, freeze–thaw cycles, and sulfate dry and wet cycles were conducted. Based on the experimental results, combined with Dunn’s gray correlation theory analysis method, a mathematical analysis of the effect sensitivity of the contents of the four mixtures on the mechanical properties and durability of FMGM was carried out. The method of gray correlation analysis can solve the mathematical problem with partial unclear and uncertain information, and the method requires less data and less computation compared with other mathematical analysis method. The results showed that the gray correlation degree between the content of MK and the electric flux value is higher than the that of other comparison sequence and each reference sequence, while the gray correlation degree between the PVA fiber dosage and the loss rate of compressive strength is lower than that of other comparison sequence and each reference sequence. The influence of the four mixture contents on the compressive strength and mass loss rate was in the following decreasing order: MK and FA, PVA fiber, and nano-SiO2. In addition, the influence of the four material mixture contents on the electric flux value and compressive strength loss rate was consistent in the following decreasing order: MK and FA, nano-SiO2, and PVA fiber. Furthermore, the mechanical properties and durability reached the optimum when the PVA fiber content was 0.6% and the dosage of nano-SiO2 was 1.0%. The results of this study can provide a new method for the analysis and evaluation of mechanical properties and durability of nano-SiO2 and PVA fiber-reinforced FMGM in future.

Fracture behavior of multi-scale nano-SiO2 and polyvinyl alcohol fiber reinforced cementitious composites under the complex environments

This paper aims to investigate the fracture properties and microscopic mechanisms of multi-scale nano-SiO2 (NS) and polyvinyl alcohol (PVA) fiber-reinforced cementitious composites (MNFRCC) in complex environments. The complex environment was the coupling effect of wet-thermal and chloride salt environments (CEWTSE) simulated by an environmental simulation test chamber. And the parameters of temperature, relative humidity (RH), mass fraction of NaCl solution, and action time were determined as 50 °C, 100 %, 5 %, and 30 d, respectively. The Double-K Fracture model (DKFM), boundary effect fracture model (BEM), and work fracture method (WFM) were used to reveal that PVA fiber and NS improved the fracture properties of MNFRCC under the CEWTSE. And when the contents of PVA fiber and NS were 1.2 % and 0.5 %, respectively, the fracture parameters were significantly improved. Based on the comparative analysis of DKFM and BEM, the reasonable fracture parameters could be obtained by linking them through the crack propagation length. Moreover, the fictitious crack growth lengths and characteristic cracks increased with the increase of PVA fiber contents. On the microscopic level, PVA fiber and NS improved pores, microcracks and interfacial transition zone in the MNFRCC.

Effect of Single and Synergistic Reinforcement of PVA Fiber and Nano-SiO2 on Workability and Compressive Strength of Geopolymer Composites.

Geopolymer composites can be used as a proper substitute for ordinary Portland cement, which can reduce carbon dioxide (CO2) emissions and make rational use of industrial waste. In this study, an investigation of the workability and compressive strength of geopolymer composites was carried out through a series of experiments, such as slump flow test, consistency meter test and compressive strength test, to clarify the interaction mechanism among superplasticizer (SP), polyvinyl alcohol (PVA) fiber, Nano-SiO2 (NS) and geopolymer composites, thereby improving the properties of engineered composites. The results showed that with the increase in PVA fiber content, the flowability of geopolymer composites decreased, while the thixotropy increased. With the increase in the NS content, the flowability of geopolymer composites first increased and then decreased, reaching its best at 1.0%, while the thixotropy was the opposite. With the increase in the SP content, the flowability of geopolymer composites increased, while the thixotropy decreased. A significant correlation between thixotropy and flowability of geopolymer composites was found (R2 > 0.85). In addition, the incorporation of single PVA fiber or NS significantly improved the compressive strength of geopolymer composites. Specifically, the compressive strength of geopolymer composites with 0.8% content PVA fiber (60.3 MPa) was 33.4% higher than that without PVA fiber (45.2 MPa), and the compressive strength of geopolymer composites with 1.5% content NS (52.6 MPa) was 16.4% higher than that without NS (45.2 MPa). Considering the synergistic effect, it is found that the compressive strength of geopolymer composites (58.5–63.3 MPa) was significantly higher than that without PVA fiber (45.2–52.6 MPa). However, the flowability and compressive strength of geopolymer composites were only slightly improved compared to that without NS. With the increase in the SP content, the compressive strength of geopolymer composites showed a trend of a slight decrease on the whole. Consequently, the results of this study may be useful for further research in the field of repair and prevention of the delamination of composite structures.

Mechanical properties and damage constitutive of recycled aggregate concrete with polyvinyl alcohol fiber under compression and shear

This paper researched the mechanical properties and damage constitutive of polyvinyl alcohol (PVA) fiber recycled aggregate concrete (RAC) under compression and shear. A total of 102 cube specimens were performed considering the effects of PVA fiber volume content, replacement ratios of recycled coarse aggregate, and normal stress. The shear strength, peak shear displacement and shear force-displacement relation of RAC were analyzed. The test results show that the shear strength increases with increasing normal stress and decreases with increasing replacement ratios of recycled coarse aggregate. The maximal shear strength generally appears at a PVA fiber content between 0.05 % and 0.1 % when identical to the normal stress and replacement ratios of recycled coarse aggregate. The peak shear displacement increases with increasing normal stress and PVA fiber volume content. The optimal PVA fiber content was 0.1 % considering the shear strength and shear displacement. It is suggested that a damage constitutive model be used to explain the shear force-displacement relationship of PVA fiber RAC in a compression-shear composite stress condition. The test findings and calculation results showed good consistency, proving that the damage constitutive model suggested in this research is applicable to PVA fiber RAC.

High-temperature behavior of polyvinyl alcohol fiber-reinforced metakaolin/fly ash-based geopolymer mortar

Polyvinyl alcohol (PVA) fiber-reinforced geopolymer mortar is an eco-friendly construction material with excellent mechanical properties and durability. Visual observation, mass loss measurement, cubic and prism compressive tests, flexural tests, thermogravimetric and differential thermal analysis, scanning electron microscopy, and bubble parameter tests were conducted to evaluate the effect of PVA fiber and exposure temperature on the behavior of PVA fiber-reinforced geopolymer mortar after exposure to high temperatures. The PVA fiber contents were selected as 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, and 1.2%, and the target temperatures were 25 °C, 200 °C, 400 °C, 600 °C and 800 °C. The results indicate that significant mass loss of the geopolymer mortar could be observed when the exposure temperature increased from 25 °C to 250 °C, whereas slight mass loss occurred from 250 °C to 700 °C, and no mass loss was detected from 700 °C to 800 °C. As the temperature increased, the geopolymer mortar gradually densified, while the geopolymer mortar continuously developed more cracks and pores. The compressive and flexural strengths of the geopolymer mortar improved as the temperature increased from 25 °C to 200 °C, but it decreased significantly as the temperature further increased to 800 °C. In addition, on exposure to 200 °C, the presence of PVA fibers significantly improved the cubic and prism compressive strengths and flexural strength by 50.5%, 29.4%, and 66.3%, respectively, compared with the geopolymer mortar without fibers. As the temperature increased above 200 °C, although the PVA fiber decomposed, the defects left by the melt fibers slightly influenced the strength of the geopolymer mortar.

Characterization of PVA Fiber-Reinforced Pervious Concrete with Blended Recycled Ceramic Aggregates and Natural Aggregate

Effective industrial waste management is one of the important challenges facing modern society. Ceramic wastes occupy an important proportion of industrial waste. The utilization of waste of ceramics is becoming more and more attractive for many researchers to alleviate the environmental impact of industrial waste. As a low-impact development method, pervious concrete (PC) received more and more attention from researchers in recent years. However, the relatively low strength compared with ordinary concrete restricts the application of pervious concrete. This research used recycled ceramic coarse aggregates (RCCA) to partially replace natural coarse aggregates (NCA) to prepare recycled ceramic coarse aggregate pervious concrete (RCCAPC) and fiber-reinforced RCCAPC incorporating polyvinyl alcohol (PVA) fibers, and the effect of the replacement rate of RCCA and the amount of PVA fiber on the mechanical properties and permeability was investigated. The results show that RCCA can improve the mechanical properties of PC at a low substitution rate, as well as PVA fiber, and when the PVA content is about 0.3%, the enhancement effect is the best. Both RCCA replacement rate and PVA fiber content have little effect on the permeability coefficient of PC. Based on described studies, using RCCA to partially replace NCA at a low substitution rate is suitable for the preparation of PC, and PVA fibers can enhance the strength of PC, which may help to broaden the application scenarios of PC.

Discussion of “Fiber-Reinforced Cement-Stabilized Macadam with Various Polyvinyl Alcohol Fiber Contents and Lengths” by Chunhua Zhao, Naixing Liang, Xiaolong Zhu, Lingqing Yuan, and Bo Zhou

Discussion of “Fiber-Reinforced Cement-Stabilized Macadam with Various Polyvinyl Alcohol Fiber Contents and Lengths” by Chunhua Zhao, Naixing Liang, Xiaolong Zhu, Lingqing Yuan, and Bo Zhou

Carbonation Model and Prediction of Polyvinyl Alcohol Fiber Concrete with Fiber Length and Content Effects

Durability is an important aspect of reliability of concrete structures. In order to establish the carbonation model of polyvinyl alcohol (PVA) fiber concrete including the influences of PVA fiber length and volume content, a series of accelerated carbonation experiments were carried out on the normal concrete specimens and PVA fiber concrete specimens with fiber lengths of 3 mm, 6 mm, 12 mm and 18 mm and fiber volume contents of 0.1%, 0.3%, 0.5%, 0.75%, 1.0% and 1.5%, respectively. The experimental conditions remained at temperature of 20 ℃, humidity of 70%, and carbon dioxide concentration of 20%. It was found that the addition of PVA fibers could improve the carbonation resistance of concrete considerably. Within the investigated range of fiber length and content, the carbonation resistance of concrete is first strengthened and then weakened with increasing PVA fiber length or content. The quadratic carbonation depth prediction model could characterize the influences of PVA fiber length and content better than the linear model. The carbon dioxide diffusion equation was established by introducing a PVA fiber influence factor and its parameters were determined from the carbonation depth prediction model. The carbonation process of PVA fiber concrete under the accelerated carbonation experiment condition was simulated. Both the model and the numerical method were validated by comparison between the experimental and numerical results. Finally, the influences of added PVA fibers on the carbonation life and durability of reinforced concrete components were further studied numerically. The results showed that compared with the normal concrete component, the durability of PVA fiber concrete components is significantly improved.

Interfacial properties of geopolymer mortar and concrete substrate: Effect of polyvinyl alcohol fiber and nano-SiO2 contents

Geopolymer mortar, which is a new type of green cementitious material, can be used as an alternative to traditional cement mortar in the repair and reinforcement of defective structures, and the addition of polyvinyl alcohol (PVA) fiber and nano-SiO2 (NS) can improve the interfacial properties of geopolymer mortar and concrete substrate. In this study, the influence of PVA fiber and NS on the shear characteristics of geopolymer mortar and concrete substrate was studied through a double-interfaced shear experiment. Based on the results of this experiment, surface-based cohesive contact was utilized to analyze the shear behavior of the PVA fiber and NS-reinforced geopolymer mortar and concrete substrate, and a shear toughness evaluation method was proposed to further evaluate the shear behavior. The results indicated that the optimal bond strength was achieved when the geopolymer mortar was mixed with 0.8% PVA fiber and 2.0% NS; compared with geopolymer mortar without PVA fiber and NS, the bond strength increased by 34.76% and 13.78% respectively. The numerical modeling results were consistent with the mechanical mechanism and damage mode of the experimental results, which indicated that surface-based cohesive contact could accurately describe the shear characteristics of a double-interfaced shear specimen. Using the proposed shear toughness evaluation method, it was found that when the PVA fiber content was 0.8%, feq, γp and Tp reached their respective maximum values with increment of 0.69, 0.61 and 1.66, respectively, indicating that the toughening effect of geopolymer mortar was optimal. The shear toughness of geopolymer mortar first rose and then declined with the increase of NS content. The PVA fiber and NS had a positive synergistic effect on the shear toughness of geopolymer mortar and concrete substrate.