Papers by Keyword: PVA Fiber

Abstract: This study aims to analyzes the shear behavior, crack patterns, and failure modes of reinforced concrete beams strengthened with geopolymer mortar panels (GMP) which consisted PVA fibers and wire mesh with varying bolts spacing. Shear behavior is discussed based on load-deflection behavior, maximum load, steel load strain, and concrete load strain. The research stages were divided into two, namely compressive strength of geopolymer mortar and shear test of reinforced concrete beams. The geopolymer mortar compressive strength test used 50x50x50 mm cube samples, tested at 3, 7, and 28 days. The geopolymer mortar was produced from fly ash as the base material and activators, such as sodium hydroxide and sodium silicate. Meanwhile, the beam shear test have cross section of 150x300 mm with a length of 2300 mm. There were four variation, namely CB, GM-W-200, GM-W-300, and GM-NW-200 beams. The results showed that adding reinforcement panels with geopolymer mortar material which consisted PVA fibers and wire mesh with distance of 200 mm (GM-W-200) affected the behavior of reinforced concrete beams to become more ductile and no longer occur shear collapse. Meanwhile, GM-W-300 and GM-NW-200 beams have not improved the bending behavior of the beams, and shear failure still occur as in CB beams.

Abstract: Using cement as the primary material for making concrete, around 7%-15%, requires a significant amount of energy and generates abundant waste, thus significantly impacting the environmental conditions. Innovative materials are needed as alternatives to cement. Fly ash, as an environmentally friendly material, can be a solution to minimize the use of cement. The selected fiber is Poly-Vinyl Alcohol (PVA) fiber due to its high tensile strength, which can effectively inhibit the rate of crack development occurring in the beams. The research process was divided into two stages: geopolymer mortar compressive strength testing and beams flexural testing. Compressive strength testing of geopolymer mortar was conducted on 50x50x50 mm cube samples, tested at ages of 3, 7, and 28 days using both air curing and moist curing methods. Geopolymer mortar was created using fly ash as the base material, along with activators such as Sodium Hydroxide (NaOH) and Sodium Silicate (Na₂SiO₃). Meanwhile, flexural beams were tested in 5 samples of 150x200 mm beams with a length of 3300 mm each. The samples consisted of a control beam, a beam reinforced with commercial grouting mortar, a beam reinforced with commercial grouting mortar and PVA geopolymer fibers, a beam reinforced with geopolymer mortar, and a beam reinforced with geopolymer mortar and PVA fibers. The research results indicated that adding PVA fibers to geopolymer mortar could enhance the maximum load-bearing capacity and stiffness of the beams. Regarding failure modes, beams reinforced with PVA-free geopolymer mortar experienced delamination failure, whereas beams reinforced with PVA-containing geopolymer mortar encountered debonding failure.

Abstract: In the comparative study of single mixed PVA fiber (0,1%, 2%, 3%) and basalt fiber (0,0.1%, 0.2%, 0.3%) on the polymer mortar fluidity and mechanical properties, the results show that: PVA fiber and basalt fiber under the appropriate amount can improve mortar water retention, basically will not appear water phenomenon, which makes the construction more convenient. When the basalt and PVA fibers were 0.2%, the 28-d folding resistance was 5.60 MPa and 5.72 MPa, respectively. The results of the compressive strength test showed the same pattern as the folding strength. When the amount of PVA and basalt fiber was 0.2%, the 28-d folding strength was the greatest, which is 44.91 MPa and 41.92 MPa, respectively.

Abstract: To evaluate the suitability of domestic polyvinyl alcohol (PVA) fiber for preparing high ductility cementitious composites (HDCC), single PVA fiber pullout tests were conducted. The tests were carried out with four matrices having a water-to-cement ratio of 0.25 or 0.30, and fly ash replacement level 60% or 80%. The micromechanical behavior of single PVA fiber pullout from the matrix was monitored using a fiber tensile testing machine. Micromorphology of the pulled fiber was subsequently investigated using scanning electron microscopy (SEM). The results indicated that the slip-hardening coefficient is greater than zero and that the fiber therefore meets the micromechanical requirements for preparing HDCC. The chemical bonding energy and frictional bond strength were determined to decrease with the increasing fly ash content and/or water-to--cement ratio. SEM images indicate a significant number hydration products attached to the fiber surface, associated with an increase friction force during fiber pullout. After the pullout test, a complete tunnel containing fiber fragments was observed in the matrix, indicative of matrix cutting.

Abstract: In order to study the flexural toughness of PVA fiber reinforced concrete, employ the volume mixing ratio is 0.2%, 0.1%, 0.08%, polyvinyl alcohol (PVA) will be mixed with ordinary C40 concrete to form PVA fibers reinforced concrete. Its flexural toughness properties were tested and the load-deflection curve of all beams is obtained. Based on the ASTM method, the flexural toughness of PVA fiber reinforced concrete is analyzed. The experimental results indicate that the PVA fiber can improve the flexural toughness and the deformation ability of concrete beams remarkably. When the fiber volume ratio is 0.1%, the flexural toughness index I₅ and I₁₀ of concrete with PVA fiber are 3.73 and 6.23 times higher than that of the plain concrete respectively. The failure mode of PVA fiber concrete is changed from brittle to ductile fracture.

Abstract: The preparation of polyvinyl alcohol fibers mainly consists of three steps: 1. The polymerization of vinyl acetate. Need the preparation of vinyl acetate and polymerization of vinyl acetate. The polymerization of vinyl acetate uses acetylene method and ethylene method.2. Preparation of PVA. Mainly to let the polyvinyl acetate taking alcoholysis reaction to the effect of methanol or sodium hydroxide. 3. Preparation of polyvinyl alcohol fiber. Complete dope preparation through washing and dehydration, dissolving, mixing, filtering and deaeration, and uses the dry, wet two methods to form the spinning. Finally, through the follow-up processing, to accomplish the preparation of polyvinyl alcohol fiber. Water soluble and high concentration polyvinyl alcohol fiber ‘s performances are fine and is application widely.

Abstract: This article prepared a new type PVA fiber with large diameter by plasticizing melt spinning method, which instead of traditional wet-spinning or gel-spinning method. The mechanical properties and microstructure of fiber were characterized by tensile instrument respectively and SEM. Then, the PVA fiber was used in cementitious composites after surface sizing. The test result shown that: the melt-spinning PVA fiber could achieve stress-strain hardening in ECC system, and appeared multi-cracking phenomenon, the flexural deflection and strength is not worse than the Japan Kurary PVA fiber. Finally, the PVA has an advantage in price.

Abstract: Polyvinyl Alcohol (PVA) fiber reinforced mortars (FRM) have been shown to increase the ductility of unreinforced masonry walls thus improving their out-of-plane flexural capacities. As these mortars become increasingly popular, their durability under freeze-thaw conditions requires further scrutiny. Previously, the durability of PVA FRM has been evaluated as mortar components only and not in combination with masonry units. The freeze-thaw testing of masonry mortars requires a complex analysis to duplicate in-situ conditions. Accelerated testing conditions are desired to represent the weathering that a structure would endure over time. This is done by simulating an aggressive weathering pattern on a test specimen in order for the analysis of the durability of the mortar and brick to be obtained within a timely manner. Currently, the standard freeze-thaw durability testing method for cementitious materials utilized in the United States of America, ASTM C666/C666M-03, is characterized by two methods: rapid freezing in water and thawing in water; and rapid freezing in air and thawing in water. This testing method provides a durability rating for specimens created and contained within a laboratory, but does not accurately represent all of the environmental factors that influence the durability of a mortar/brick structure. In this study, in order to replicate in-situ conditions, PVA FRM test specimens are constructed and subjected to freezing in water on only one side and are enclosed in a plastic bag to remedy the effect of the dry, frozen air reducing the moisture content of the mortar. Furthermore, the test specimens are frozen and thawed in a controlled environmental chamber where the relative humidity is controlled to prevent moisture change within the specimen. This enables rapid thawing of the specimen while controlling the relative humidity to better represent the in situ characteristics of masonry structures. The specimens are then subjected to 300 freeze-thaw cycles and evaluated to determine their degradation over that time. Results of the testing show limited reduction in material volume and weight of the PVA FRM compared to control samples that do not include PVA fibers.

Abstract: PVA fiber reinforced cement-based composite is a new high-performance cement-based composite material, which usually manufactured with PVA short fibers (does not exceed 2.5% vol.) and cement-based matrix. It has a significant strain-hardening characteristic and excellent crack controlling ability. Its ultimate tensile strain is up to 3% and crack width is not exceed 100μm. PVA fiber reinforced cement-based composite can be utilized to fabricated high energy absorption opponents, such as protective shield, seismic joint, impact-resistant site, etc. In this paper, the basic mechanical properties of PVA fiber reinforced cement-based composite has been tested and verified first. Then the impact resistance of PVA reinforced cement-based composite has been investigated via drop weight impact test, and compared with ones of plain concrete and steel fiber reinforced concrete with the same strength grade. Through analyzing the test results, it is concluded that PVA reinforced cement-based composite’s impact energy absorption is 48 times than plain concrete, and 9 times than steel fiber reinforced concrete respectively. The impact numbers of PVA reinforced cement-based composite is slightly lower than steel fiber reinforced concrete, but its impact absorption energy after initial cracking is 15 times than steel fiber reinforced concrete. In conclusion, PVA reinforced cement-based composite is an excellent impact material.

Abstract: The aim of the research is to develop engineered cementitious composite mixtures satisfying the self-compacting concrete requirements and to evaluate the hardened properties of self-compacted ECC mixtures. To enhance the concrete performance, PVA is used. The PVA improved some characteristics and properties of the concrete. Ten mixes with different Polyvinyl Alcohol (PVA) fiber contents (0.0%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5% and 5.0%) have been prepared. Three cubes (100mm x 100mm x 100mm), three beams (100mm x 100mm x 500mm) and three cylinders (150mm diameter and 300mm height) have been cast for each mix and tested at the age of 7 and 28 days for compressive strength and at age of 28 days for splitting and flexural strength. The V-funnel, L-box and slump test also have been conducted to access the fresh properties like workability and flowability of the concrete. The results indicated the increase in the strength of the concrete and the formulas for predicting the compressive, splitting and flexural strength from PVA (%) has been developed.