A Review of the Use of PVA in Cementitious Composites

This study investigates the effects of various fibers and their combinations on the mechanical properties of fiber-reinforced cementitious composites (FRCC). Sixteen distinct mix designs were prepared, each incorporating different types and proportions of fibers, Polyvinyl Alcohol (PVA), Polypropylene (PP), Basalt, and Banana fibers, while maintaining a consistent cement-to-sand ratio of 25% to 75%. The objective was to evaluate how these fibers influence the compressive, flexural, and tensile strengths of the FRCC. The results revealed significant variations in mechanical properties based on fiber type and content. Mixes containing PVA and Basalt fibers demonstrated superior compressive strength, flexural strength, and tensile strength compared to those with other fibers. Notably, hybrid fiber combinations, such as PVA and Basalt or PVA and PP, showed enhanced mechanical performance, indicating the synergistic benefits of combining different fiber types. In contrast, Banana fibers alone were less effective in improving mechanical properties but contributed positively when combined with synthetic fibers. The study highlights the potential of fiber hybridization in optimizing the performance of cementitious composites. The strategic use of PVA and Basalt fibers, both individually and in combination, provides a promising approach for developing high-strength for diverse construction applications. These findings offer valuable insights for future research and the development of advanced composite materials with tailored mechanical properties.Graphical

Recycled concrete aggregate (RCA) is traditionally limited to nonstructural applications. Although the crushing process results in weak mortar particles and surface cracks throughout the RCA, RCA concrete can be employed as rigid pavement materials after its mechanical strength has been improved. This research evaluated the novel use of polyvinyl alcohol (PVA) and fly ash (FA) for the improvement of mechanical strengths of RCA concrete. The influence of PVA to binder (p/b) and FA/cement (FA/c) ratios on the mechanical strength of RCA-PVA-FA concrete was assessed by compressive, split tensile, and flexural strength tests. The mechanisms controlling the improvement of mechanical strengths were discussed based on the results of microstructural analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) methods. The results of this research indicate that the addition of PVA resulted in a reduction of the compressive strength of RCA concrete in both the short and the long term. However, with an optimum p/b of 1%, both the flexural and tensile strengths increased significantly. At the optimal p/b, the PVA films infiltrated into cementitious matrixes and enhanced the reinforcing ability within the matrixes. However, excess p/b retarded the hydration process and caused reductions in the cementitious tensile bonding. The long-term mechanical strength (>28 days) was remarkably improved by FA addition at optimum FA/c of 20:80, and the presence of cementitious products on the FA grains and in the voids was clearly observed. The highest long-term flexural and tensile strengths were found at p/b=1% and FA/c=20∶80, whereby the 28-day flexural strength was higher than the requirement specified by the US Army and the US Air Force. The 28-day compressive strengths were also higher than the requirements specified by Department of Highways, Thailand. The outcome of this research will result in the promotion of using wastes, namely RCA and FA, in rigid pavement application, which is practical and preferred from engineering, economic, and environmental perspectives.

One of the promising applications of nickel hydroxide is electrochemical electrochromic devices. To significantly improve the characteristics, the role of polyvinyl alcohol (PVA) in the synthesis and structure of composite Ni(OH)2-PVA films was investigated by studying the effect of its concentration (30, 40, 50 g/l) and polymerization degree (17-99, 24-99, 30-99 types). Adhesion was investigated visually, and electrochemical and electrochromic properties – by cyclic voltammetry with simultaneous recording of optical characteristics. It was shown that at a concentration of 30 g/l, the film peeled off and had weak electrochemical and electrochromic properties. The presence of two cathodic peaks (E=500–510 mV and E=560 mV) on the cyclic voltammetry showed the presence of nickel hydroxide in the PVA matrix and nickel hydroxide with adsorbed PVA. This indicates the dual role of PVA as a surfactant and as a template. At low concentrations, the role of PVA as a surfactant prevailed. Increasing the concentration led to an increase in the film characteristics by strengthening the role of PVA as a template: at 50 g/l, the film did not peel off and has good electrochemical and electrochromic characteristics. It is shown that at a low degree of polymerization, PVA (17-99 type) mainly played the role of a surfactant but was also a template. The film cracked and had mediocre characteristics. The use of medium polymerization PVA (24-99 type) gave a film with high adhesion, electrochemical and electrochromic characteristics. It is shown that in this case, PVA performed the function of a template, there was only one cathodic peak on the voltammogram at E=500–510 mV. It was found that the use of PVA with a high degree of polymerization (30-99 type) led to a significant deterioration of the characteristics, including complete peeling of the film. This is probably due to the loss of PVA in the film

Recycled geopolymer aggregates as coarse aggregates for Portland cement concrete and geopolymer concrete: Effects on mechanical properties

This paper investigates the effect of high temperatures on the compressive strength, flexural strength, and splitting tensile strength of ultra-high-performance concrete (UHPC), and ultra-high-performance, fiber-reinforced concrete (UHPFRC). The experimental variables in this study were fiber type, fiber content, and high-temperature exposure levels. Three different types of fibers were evaluated, including steel fibers, polypropylene (PP), and polyvinyl alcohol (PVA) fibers. Six concrete mixes were prepared with and without different combinations of fibers. One mix was made with no fibers. Others were made with either steel fibers alone; a hybrid of steel fibers and PVA; and a hybrid system of steel, PP, and PVA fibers. These mixes were tested under a range of temperatures and compared for strength. The UHPC and UHPFRC were exposed to high temperatures at 100°C, 300°C, 400°C, and 500°C for 3 hours. The results showed that UHPFRC did not exhibit any significant degradation when exposed to 100°C. However, reductions of approximately 18% to 25%, 12% to 22%, and 14% to 25% in the compressive strength, splitting tensile strength, and flexural strength were observed when the UHPFRC was exposed to 400°C. UHPFRC made of steel fibers showed higher mechanical properties after exposure to 400°C compared to UHPFRC made of PP and PVA fibers. The results also demonstrate the use of PVA and/or PP fibers, along with steel fiber, to withstand the effects of highly elevated temperature and prevent spalling of UHPC after exposure to elevated temperature. The observed spalling was a direct result of the melting and evaporation of PVA and/or PP fibers when exposed to high temperature, an effect that was confirmed using scanning electron microscopy.

The study focuses on the development of cementitious composites using 3D printing and plastic waste as a sustainable aggregate substitute. This study involves experimenting with various percentages of plastic waste as a partial substitute for ground granulated blast furnace slag (GGBFS) in a control mix. The study examines the anisotropy of the 3D printing process, comparing it with properties of mold-cast samples. In addition, it assesses the fire resistance and mechanical properties of samples at elevated temperatures (100 °C, 300 °C, and 600 °C). Key mechanical properties, including 28-day compressive stress and flexural strength, are determined through experimental testing using a standard compression test and three-point bending test. The study also considers the modulus of elasticity (MOE) in compressive tests to evaluate a sample’s ability to deform elastically and the flexural toughness index to assess energy absorption and crack resistance of flexural samples. Following the experimental testing, the study’s key findings suggest that significant mass loss occurred at 300 °C and above, with plastic samples demonstrating increased mass loss at 600 °C. At 600 °C, plastic degradation led to the formation of voids and cracks within samples due to heightened internal pressure. Anisotropy was evident in 3D-printed samples, with loads parallel to the layer direction resulting in greater compressive strength and MOE. Furthermore, layer direction parallel to the longitudinal axis of flexural samples yielded higher flexural strength and flexural toughness. Mold-cast samples displayed superior compressive strength and stiffer behavior, with higher MOE compared to 3D-printed samples. However, 3D-printed plastic samples exhibited superior flexural strength compared to mold-cast samples, attributed to the alignment of plastic within the samples. The study also observed a reduction in compressive strength with the addition of plastic, explained by the poor bonding of plastic with cement due to its hydrophobic nature. Despite this, flexural strength generally improved with plastic addition, except at 600 °C, where plastic samples showed significant degradation in both compressive and flexural strength due to plastic degradation within the samples.

Cement based composites i.e. paste, mortar and concrete are the most utilized materials in the construction industry all over the world. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to their low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses) etc. These cracks developed at the nanoscale may grow rapidly due to the applied stresses and join together to form micro and macro cracks. The growth of cracks from nanoscale to micro and macro scale is very rapid and may lead to sudden failure of the cement composites. Therefore, it is necessary to develop such types of cement composites possessing higher resistance to crack growth, enhanced flexural strength and ductility. The development of new technologies and materials has revolutionized every field of science by opening new horizons in production and manufacturing. In construction materials, especially in cement and concrete composites, the use of nano/micro particles and fibers in the mix design of these composites has opened new ways from improved mechanical properties to enhanced functionalities. Generally, the production or manufacturing processes of the nano/micro sized particles and fibers are energy intensive and expensive. Therefore, it is very important to explore new methods and procedures to develop less energy intensive, low cost and eco-friendly inert nano/micro sized particles for utilization in the cement composites to obtain better performance in terms of strength and ductility. The main theme of the present research work was to develop a family of new type of cementitious composites possessing superior performance characteristics in terms of strength, ductility, fracture energy and crack growth pattern by incorporating micro sized inert carbonized particles in the mix design of cementitious composites. To achieve these objectives the micro sized inert carbonized particles were prepared from organic waste materials, namely: Bamboo, coconut shell and hemp hurds. For comparison purposes and performance optimization needs, another inorganic waste material named as carbon soot was also investigated in the present research. The experimental investigations for the present study was carried out in two phases; In the first phase of research work, a methodology was developed for the synthesis of the micro sized inert carbonized particles from the above mentioned organic raw materials. In the second phase of research, various mix proportions of the cementitious composites were prepared incorporating the synthesized micro sized inert carbonized particles. For micro sized inert carbonized particles obtained from bamboo and coconut shell three wt.% additions i.e. 0.05, 0.08, 0.20 were investigated and for particles synthesized from hemp hurds 0.08, 0.20, 1.00 and 3.00 wt.% additions were explored. The cement composites were characterized by third-point bending tests and their fracture parameters were evaluated. The mechanical characterization of specimens suggested that 0.08 wt.% addition of micro sized inert carbonized bamboo particles enhances the flexural strength and toughness of cement composites up to 66% and 103% respectively. The toughness indices I5, I10 and total toughness of the cement composites were also enhanced. The carbonized particles synthesized from coconut shell resulted in improved toughness and ductility without any increase in the modulus of rupture of the cement composite specimens. Maximum enhancements in I5 and I10 were observed for 0.08% addition of both carbonized and carbonized-annealed particles. For the carbonized hemp hurds cement composites the results indicate that the micro sized inert carbonized particles additions enhanced the flexural strength, compressive strength and the fracture energy of the cement composites. The microstructure of the cement composites was also studied with the help of field emission scanning electron microscope (FESEM) by observing small chunks of cement composite paste samples. The FESEM observations indicated that the micro sized inert carbonized particles utilized in the mix design of these mixes were well dispersed in the cement matrix. It was also observed that the fracture paths followed by the cracks were tortures and irregular due the presence of micro particles in the matrix. The cracks during their growth often contoured around the inert particle inclusions and resulted in enhanced energy absorption capacity of the cement composites. The study was further enhanced to the cement mortar composites and their performances were studied. The results indicated that the energy absorption behavior of the composites was enhanced for all the cement composites containing micro carbonized particles. Finally, it is concluded that the ductility and toughness properties of the cement composites can be enhanced by incorporating the micro sized inert carbonized particles in the cement matrix. The fracture energy, ductility and toughness properties enhancement of the cement composites greatly depends upon the source and synthesis procedure followed for the production of micro sized inert carbonized particles

Use of hollow glass microspheres and hybrid fibres to improve the mechanical properties of engineered cementitious composite

In relation to the use of retrofit materials on damaged constructions, application on earthquake-resistant buildings, and for the strengthening and rehabilitation on weakened regions, there is a need for a more superior material than concrete. Application sites include beam-column joints, corbels, link-slabs, deep beams, support regions and dapped-end areas. Fiber reinforced engineered cementitious composites (FR-ECC) can address this issue, because FR-ECC is one of the composite materials that has high strength, ductility and durability. In order to develop FR-ECC, this study was done to investigate the effect of adding quartz powder on the compressive strength capacity and properties of FR-ECC through the use of polyvinyl alcohol (PVA) and steel fibers. The volume fraction of fiber was set to 0%–2%. To support the friendly environment, FR-ECC uses by-product materials such as fly ash and silica fume, with a cement content less than 600 kg/m3. In terms of the experimental investigation on FR-ECC, this work conducted the fresh property tests showing that PVA fibers have quite an influence on ECC workability, due to their hydrophilic behavior. By adjusting the superplasticizer (SP) content, the consistency and high workability of the ECC mixes have been achieved and maintained. The test results indicated that the PVA and steel fibers-based ECC mixes can be classified as self-compacting composites and high early compressive strength composites. Significantly, addition of quartz powder into the ECC mixes increased the compressive strength ratio of the ECC samples up to 1.0747. Furthermore, the steel fiber-based ECC samples exhibited greater compressive strength than the PVA fibers-based ECC samples with the strength ratio of 1.1760. Due to effect of the pozzolanic reaction, the fibers dispersion and orientation in the fresh ECC mixes, so that the cementitious matrices provided the high strength on the FR-ECC samples. During the compression loading, the bulging effect always occurred before the failures of the fibers-based ECC samples. No spalling occurred at the time of rupture and the collapse occurred slowly. Thus, FR-ECC has provided unique characteristics, which will reduce the high cost of maintenance.

This paper presents the effects of various cooling methods on residual mechanical properties of geopolymer concrete and fiber reinforced geopolymer concretes (FRGC) after exposure to 200, 400, 600, and 800°C temperatures. Three types of cooling methods are considered namely, ambient air cooling, water spray cooling and rapid water cooling. Results show that irrespective of cooling methods, the compressive strength of geopolymer concrete decreases significantly after exposure to 400, 600, and 800°C temperatures compared to 200°C where only 10–15% reduction is observed. Among the three cooling methods, the compressive strength loss is slightly higher in rapid cooling and water spray cooling than the ambient air cooling at 400 to 800°C. However, at 200°C that loss is about 20–25%. In the case of indirect tensile strength, however, at 200°C no reduction in strength is observed due to rapid cooling and water spray cooling compared to ambient air cooling. Significant reduction in indirect tensile strength is observed in those two cooling methods at 400, 600, and 800°C. Strong correlations between indirect tensile strength and compressive strength of geopolymer concretes at all cooling methods are also observed. Rapid cooling and water spray cooling methods do not cause any significant cracking in geopolymer concretes at 200 and 400°C, followed by minor and significant cracking at 600 and 800°C, respectively. However, at 800°C the rapid cooling caused more cracking than those two cooling methods. Rapid cooling also showed higher reduction in compressive strength than ambient air cooling in both steel fiber reinforced geopolymer concrete (steel‐FRGC) and polyvinyl alcohol fiber reinforced geopolymer concrete (PVA‐FRGC) after exposure to 400 and 600°C temperatures. PVA‐FRGC exhibited more brittle failure behavior in compression than steel‐FRGC irrespective of cooling methods. The existing Eurocode overestimates the residual compressive and indirect tensile strengths of geopolymer concrete at 400 and 600°C temperatures compared to other temperatures. The same is also true in PVA‐FRGC. However, in steel‐FRGC the Eurocode 4 overestimates at 400°C but underestimates at 600 and 800°C.

Due to growing populations, approximately one billion scrap tires are generated annually worldwide. This is a problem particularly in more developed countries where the per-head share of scrape tires is much higher than the global average. The adverse environmental impacts associated with landfilling scrap tires made it imperative to promote eco-friendly solutions such as utilizing them in civil engineering applications. This paper explores the use of tire-derived aggregates (TDAs) with large particle sizes that require less energy to produce as a substitute for traditional aggregates in concrete production. A comprehensive experimental program was conducted to study the effects of the TDA content on the density, compressive strength, elastic modulus, strain at failure, splitting tensile strength, and flexural strength of rubberized concrete at 28 days. Furthermore, with the aim of improving the tensile and flexural properties of rubberized concrete, the use of polyvinyl alcohol (PVA) fibers was also investigated in this study. A total of 126 specimens, half of them containing PVA fibers, were prepared from fourteen different concrete mixtures with varying percentages of TDAs replacing coarse aggregates. Results indicate that a reasonable TDA content of less than 20% can be used to produce concrete with comparable or even superior properties for specific applications requiring moderate strength and higher deformability while reducing waste tires in landfills. In addition, adding 1% PVA fibers to the mixtures was found to enhance the specimens’ compressive, tensile, and flexural strengths and reduce the observed loss of strength rate in rubberized concrete, especially at higher TDA contents. Overall, this research suggests that TDAs can be a sustainable and cost-effective solution for applications that do not require great concrete compressive strength but a more accommodating plastic behavior.

This paper examined how cooperating recycled aggregates into geopolymer concrete affected its compressive strength under various curing conditions. Both recycled coarse and fine aggregates were produced by crushing demolition waste concrete. Total 8 test series of cube specimens were experienced under compressive test. Replacement ratio of recycled coarse aggregate was maintained at 100% while that of recycled fine aggregate varied from 0%, 25%, 50%, 75%, and 100%. The specimens were cured in two different conditions: dry cabinet with temperature of 80 °C for 24 h and mobile dryer with temperature of 120 °C for 8 h. The results showed that the replacement of recycled coarse aggregates had no significant effect on the compressive strength whereas that of recycled fine aggregates exhibited negative effects and the higher replacement ratio led to the more reduction in compressive strength. Specifically, the replacement of 100% recycled coarse aggregate and 25% recycled fine aggregate did not produce any significant negative impact on the compressive strength of geopolymer concrete. On the other hand, specimens cured by mobile dryer produced slightly higher compressive strength than those cured in dry cabinet.

Chapter 11 - Mechanical properties of recycled polyethylene terephthalate (PET) fiber-reinforced fly ash geopolymer and fly ash-slag-blended geopolymer composites

Improvements on energy density of loose biomass such as sugarcane feedstock is crucial in the technology of biomass energy conversion and generation. South Africa is one of the producers and refiners of sugarcane. High energy density of sugarcane bagasse biomass through separation and briquetting is imperative in developing adequate streams and quality energy generation from sugarcane upstream milling processes. Unseparated bagasse and separated fractions of fiber and pith possess energy contents of about: 16.14 MJ/kg, 17.73 MJ/kg and 15.74 MJ/kg respectively. Fiber fractions have high energy content than bagasse and pith which demonstrates that pith fraction from bagasse lowers energy density. However, the use of starch and PVA (Polyvinyl Alcohol) as binders during briquetting contributed no significant difference in the overall energy density of the biomass briquettes produced. In the same vein, the addition of 50% charcoal as the hybrid component significantly improves the energy density and the physical properties of briquettes, biomass fractions of bagasse, fiber and pith to: 19.43 MJ/kg, 19.57 MJ/kg and 18.37 MJ/kg respectively. Fiber fraction remains the biomass fraction with highest energy content as compared to other fractions. After briquetting and drying of briquettes to moisture content below 12%, there was a significant improvement on the burning rate, briquetting, binder, hybridization which does improve the biomass briquettes characteristics. Separation of bagasse is crucial under certain conditions since there are no significance differences in the energy density of bagasse fractions. However, the use of PVA and charcoal does pose the necessity of bagasse separation from its fractions for briquetting.

This study reports on the use of polyvinyl alcohol–based needle punched nonwoven fabrics in cement-based composites as a low-cost reinforcement. In this study, a nonwoven reinforcement using crimped polyvinyl alcohol fibers for cement-based composites was developed. The incorporation of nonwoven fabric in composites improved tensile and flexural properties compared to a discrete polyvinyl alcohol fiber-reinforced composite. Formation of multiple fine cracks, crimped fibers and mechanical interlocking of fibers in the nonwoven fabric structure resulted in superior mechanical performance. The failure mode was due to a single macro-crack for the discrete fiber reinforced composite as opposed to a number of fine cracks for the nonwoven reinforced composite.