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Research and application of fiber reinforced concrete building

Time : 2022-01-03 Hits : 20

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Fiber reinforced concrete refers to cement - based material with fiber or fabric as reinforcement material. Traditional Steel reinforced concrete (SRC) has high compressive strength, but it has some problems such as low tensile strength, poor impact resistance, easy cracking and poor durability. Textile materials are light in weight, soft, excellent in corrosion resistance, toughening and cracking resistance. They are used in many large, complex structures or special protective buildings, and are the research focus of modern building materials.

At present, the fibers commonly used to strengthen concrete are metal fibers (steel fibers), inorganic fibers, synthetic fibers and plant fibers.

With the maturity of production technology, synthetic fiber has become the most used building reinforcement fiber material for its excellent physical and chemical properties. Commonly used synthetic fibers are polyvinyl alcohol (PVA) fiber, polypropylene (PP) fiber, polyacrylonitrile (PAN) fiber and so on. The following focuses on the research of synthetic fiber reinforced concrete materials.

PVA fiber

Compared with other synthetic fibers such as PP fiber and PAN fiber, the tensile strength of high strength and high modulus PVA fiber can reach 1 500 MPa, which is equivalent to the tensile strength of low carbon steel fiber (1 000 ~ 2 000 MPa). Besides, the modified PVA fiber has good corrosion resistance and high strength when combined with cement matrix. It can improve the ductility and toughness of concrete and reduce cracks. Its application in architecture is based on the KURALON? K- ⅱ (new PVA fiber) fiber is the representative. In the practice of construction engineering in China, there have been cases of adding appropriate amount of high strength and high modulus PVA fiber into concrete. In each cubic meter of concrete mixed with 1 kg high-strength and high-modulus PVA fiber, 20 days of continuous pouring to complete the workshop floor area of 33 000m2, effectively solve the shrinkage crack problem caused by the early shrinkage of concrete.

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Image credit: Kuraray

PP fiber

PP fiber is light and cheap, high tensile strength, excellent impact resistance and corrosion resistance, so it is often used in bridge DAMS and windproof structures to prevent the formation of cracks and inhibit the development of cracks, improve the freezing resistance and impermeability of the building. The research shows that PP fiber can improve the mechanical properties and durability of concrete, has a good application value, and domestic PP fiber excellent performance, low price, so it can be popularized in practical engineering application. At present, PP fiber has been used in Chang-Jiu expressway, Beijing-Fu-Sanming expressway, Hebei Qing-Yin Expressway and basement engineering in Guangzhou area, showing good permeability and crack resistance.

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PAN fiber

PAN fiber, elastic modulus, high chemical stability, resistance to climate in synthetic fibre, used in concrete can improve its crack resistance, frost resistance and corrosion resistance, so the PAN fiber is becoming a new type of construction engineering with reinforced fiber, which can be widely used in roads and Bridges and other surface structure, the water conservancy project and cold region engineering building roads.

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POM fiber

POM fiber is a kind of high performance synthetic fiber with excellent comprehensive properties. POM resin is spun and stretched to obtain POM fiber. The POM fiber has excellent impact resistance, abrasion resistance and scratch resistance. There are a lot of ether bonds in its molecular structure, which has good compatibility with cement-based materials and high binding strength, and has great potential in improving the performance of concrete materials. However, its production process is monopolized by foreign countries at present. China should strengthen the research on the production and preparation process of POM fiber to meet the demand of concrete market.

Other fiber

Steel fiber is the first fiber used to strengthen concrete and is also the most commonly used fiber in ultra high performance concrete. The tensile strength of steel fiber can reach 2 500 MPa, which can significantly improve the tensile strength and crack resistance of concrete. However, the combination degree of steel fiber and cement matrix is poor, adding too much steel fiber is easy to cause uneven fiber dispersion problem, reduce the fluidity of concrete, so the incorporation amount of steel fiber is about 2%.

Carbon fiber is inorganic high-performance fiber, carbon content in more than 90%, outstanding mechanical properties, tensile performance is 1 ~ 2 times of steel fiber, tensile strength up to 3 000 ~ 4 000 MPa, than steel fiber is more resistant to high temperature, corrosion resistance, is the development of aerospace, national defense necessary materials. Carbon fiber can also improve the compressive strength and impact resistance of concrete and is an excellent seismic material. However, the high cost of carbon fiber limits its application in civil buildings. Currently, carbon fiber is mostly used for repairing and reinforcing old buildings and water conservancy projects. In the aqueduct restoration project of Sichuan Hydraulic Research Institute in sichuan province, the old aqueduct was repaired and strengthened in situ by using carbon fiber, which improved the anti-crack, anti-impact and anti-wear properties of the aqueduct and extended its service life.

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