scholarly journals Effect of Modified Polyvinyl Alcohol Fibers on the Mechanical Behavior of Engineered Cementitious Composites

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 37 ◽  
Author(s):  
Mian Sun ◽  
Youzhi Chen ◽  
Jiaoqun Zhu ◽  
Tao Sun ◽  
Zhonghe Shui ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Polyvinyl Alcohol ◽  
Performance Improvement ◽  
Fracture Resistance ◽  
Cementitious Composites ◽  
Cementitious Composite ◽  
Engineered Cementitious Composites ◽  
Engineered Cementitious Composite ◽  
Pressure Resistance ◽  
Pva Fiber

：Polyvinyl alcohol (PVA) fiber was proposed to enhance the mechanical performance of engineered cementitious composite in this research. A mixture of engineered cementitious composite with better expected performance was made by adding 2% PVA fiber. Mechanics tests, including pressure resistance, fracture resistance, and ultimate tensile strength, were conducted. They reveal that the engineered cementitious composites not only exhibit good pressure resistance, but they also exhibit excellent fracture resistance and strain capability against tensile stress through mechanics tests, including pressure resistance, fracture resistance, and ultimate tensile resistance. To further improve the engineered composites’ ductility, attempts to modify the performance of the PVA fiber surface have been made by using a vinyl acetate (VAE) emulsion, a butadiene–styrene emulsion, and boric anhydride. Results indicated that the VAE emulsion achieved the best performance improvement. Its use in fiber pre-processing enables the formation of a layer of film with weak acidity, which restrains the hydration of adjacent gel materials, and reduces the strength of transitional areas of the fiber/composite interface, which restricts fiber slippage and pulls out as a result of its growth in age, and reduces hydration levels. Research illustrates that the performance-improvement processing that is studied not only improves the strain of the engineered cementitious composites, but can also reduce the attenuation of the strain against tensile stress.

Compressive behavior of steel spiral confined engineered cementitious composites in circular columns

2020 ◽  
Vol 23 (14) ◽  
pp. 3075-3088
Author(s):  
Wei Hou ◽  
Guan Lin ◽  
Xiaomeng Li ◽  
Pandeng Zheng ◽  
Zixiong Guo
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Uniaxial Tensile ◽  
Cementitious Composites ◽  
Test Results ◽  
Cementitious Composite ◽  
Compression Tests ◽  
Compressive Behavior ◽  
Engineered Cementitious Composites ◽  
Engineered Cementitious Composite

Extensive research has been conducted on the uniaxial tensile and compressive behavior of engineered cementitious composites. Despite the high tensile ductility and high toughness of engineered cementitious composites, transverse steel reinforcement is still necessary for high-performance structural members made of engineered cementitious composites. However, very limited research has been concerned with the compressive behavior of steel-confined engineered cementitious composites. This article presents the results of axial compression tests on a series of circular engineered cementitious composite columns confined with steel spirals. The test variables included the engineered cementitious composite compressive strength, the spiral pitch, and the spiral yield stress. The test results show that steel-confined engineered cementitious composites in the test columns exhibited a very ductile behavior; the steel spiral confinement contributed effectively to the enhancement of both strength and ductility of engineered cementitious composites. The test results were then interpreted by comparing them with the predictions from some existing models. It was found that the existing models previously developed for confined concrete failed to predict the compressive strength of steel-confined engineered cementitious composites with sufficient accuracy. New fitting equations for the compressive properties of steel-confined engineered cementitious composites were then obtained on the basis of the test results of this study as well as those from an existing study.

Mechanical behavior of a novel precast beam-to-column connection with U-shaped bars and engineered cementitious composites

2018 ◽  
Vol 21 (13) ◽  
pp. 1963-1976 ◽  
Author(s):  
Bingqing Dong ◽  
Cong Lu ◽  
Jinlong Pan ◽  
Qifeng Shan ◽  
Wanyun Yin
Keyword(s):  
Energy Dissipation ◽  
Experimental Program ◽  
Cementitious Composites ◽  
Cementitious Composite ◽  
Engineered Cementitious Composites ◽  
Seismic Region ◽  
Engineered Cementitious Composite ◽  
Flexural Failure ◽  
Bonding Performance ◽  
Precast Column

This article investigates a novel precast connection, with U-shaped bars extending from precast column to connect with the longitudinal bars in precast beams. To improve the seismic behavior of the connection, engineered cementitious composites, one kind of highly ductile concrete, were introduced into the core area of the connection, which also act as the cast-in-place material in the beam top and end. Prior to the test, finite element modeling was conducted to determine the proper splice length between U-shaped bars and beam reinforcements and also to evaluate the bonding performance of the proposed connection. The experimental program was then carried out on a monolithic connection, a precast connection with normal concrete as well as a precast connection with engineered cementitious composite, after which the seismic behaviors of the connections including their failure mode, hysteresis characteristic, stiffness degradation, ductility, and energy dissipation were analyzed. All three types of connections underwent typical flexural failure where the joint area remained intact. The negative carrying capacity, ductility, and energy dissipation were slightly lower for the connection with concrete, while the connection with engineered cementitious composite exhibited satisfactory behavior comparable to monolithic specimens. The latter connection with engineered cementitious composite is therefore suggested to be applied in highly seismic region.

Study on Durability of Engineered Cementitious Composites

2011 ◽  
Vol 236-238 ◽  
pp. 2688-2693 ◽  
Author(s):  
Hui Qing Xue ◽  
Zong Cai Deng
Keyword(s):  
Tensile Stress ◽  
Crack Resistance ◽  
Strain Hardening ◽  
Tensile Load ◽  
Strain Curve ◽  
Uniaxial Tensile ◽  
Cementitious Composites ◽  
Stress Strain ◽  
Engineered Cementitious Composites ◽  
Pva Fiber

Engineered cementitious composites (ECC) has good ductility, with its unique strain hardening and multiple cracking characteristics. Through the research of uniaxial direct tension performance and durability tests of ECC blending with polyvinyl alcohol (PVA) fiber, the tensile stress-strain curves, the freeze-thaw resistances and the impermeability of ECC were analyzed. The tensile stress - strain curve results show strain hardening of ECC achieved under the uniaxial tensile load; PVA fiber has good crack resistance toughening effect, can significantly improve crack resistance and deformation capacity of cementitious composites. The maximum tensile strain of the ECC is between 3800με to 8657με (20-50 times that of polypropylene fiber concrete) displays high toughness and large deformation characteristics. The freezing level of the ECC is higher than F300, which is ideal for the maintenance and reinforcement of concrete structures in cold regions. Domestic and imported PVA fiber can significantly improve the impermeability and crack resistance of the ECC.

scholarly journals Behavior Deterioration and Microstructure Change of Polyvinyl Alcohol Fiber-Reinforced Cementitious Composite (PVA-ECC) after Exposure to Elevated Temperatures

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5539
Author(s):  
Qing Wang ◽  
Boyu Yao ◽  
Runze Lu
Keyword(s):  
Polyvinyl Alcohol ◽  
Elevated Temperatures ◽  
Heating Temperature ◽  
Polymer Fibers ◽  
Cementitious Composites ◽  
Cementitious Composite ◽  
Fiber Reinforced ◽  
Explosive Spalling ◽  
Polyvinyl Alcohol Fiber ◽  
Dense Microstructure

In the case of fire, explosive spalling often occurs in cementitious composites due to dense microstructure and high pore-pressure. Polymer fibers were proved to be effective in mitigating such behavior. However, deterioration of these fiber-reinforced cementitious composites inevitably occurs, which is vital for the prediction of structural performance and prevention of catastrophic disaster. This paper concentrates on the behavior and mechanism of the deterioration of polyvinyl alcohol fiber-reinforced engineered cementitious composite (PVA-ECC) after exposure to elevated temperatures. Surface change, cracking, and spalling behavior of the cubic specimens were observed at room temperature, and after exposure to 200 °C, 400 °C, 600 °C, 800 °C, and 1200 °C. Losses in specimen weight and compressive strength were evaluated. Test results indicated that explosive spalling behavior was effectively prevented with 2.0 vol% polyvinyl alcohol fiber although the strength monotonically decreased with heating temperature. X-ray diffraction curves showed that the calcium hydroxide initially decomposed in the range of 400–600 °C, and finished beyond 600 °C, while calcium silicate hydrate began at around 400 °C and completely decomposed at approximately 800 °C. Micrographs implied a reduction in fiber diameter at 200 °C, exhibiting apparent needle-like channels beyond 400 °C. When the temperature was increased to 600 °C and above, the dents were gradually filled with newly produced substance due to the synergistic effect of thermal expansion, volume expansion of chemical reactions, and pore structure coarsening

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