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How to Choose PVA Fibers for Concrete and Its Function

wallpapers Environment 2020-04-07 >

In foam concrete products, we always add fibers to many products. Some manufacturers who are new to foam concrete do not know why they should add fibers and how to choose concrete fibers.

Foamed concrete is the hydration reaction between cement and water during the hardening process, causing the concrete volume to shrink. In the later period, the dry reduction is caused by the evaporation of swimming water in the concrete. These shrinkage stresses will exceed the tensile strength of the cement matrix and will be located inside the concrete. About 70% of micro-crack development is completed in the 3-7D gel period when the concrete's tensile strength is less than 1MPa. After the concrete PVA fiber is added to the concrete, the fiber can be easily and quickly dispersed uniformly in the concrete to form a chaotic support system, disperse the directional stress of the concrete, prevent the occurrence and development of the original cracks in the concrete, and eliminate or reduce the initial microcrack. The quantity and size of concrete significantly improve the concrete's ability to prevent cracks and leakage and increase the toughness of concrete, thereby extending the service life of the concrete. In addition, because the fiber itself has individual strength, the concrete fiber is evenly dispersed in the concrete, forming an anchoring effect, which can absorb a certain amount of damage energy in an instant.

At present, we have three main options for foam concrete: glass fiber, PP fiber, and PVA fiber. Glass fiber has excellent corrosion resistance and high mechanical strength, but the disadvantages are brittleness and weak wear resistance. Due to its characteristics, it cannot be effectively and evenly distributed in concrete. Because it is relatively brittle, it cannot exert excellent tensile effects, cannot achieve crack resistance results, and cannot increase bending strength. Polypropylene fibers and polyvinyl alcohol fibers have good strength and excellent toughness. PP fiber and PVA fiber have become the mainstream fiber of foam concrete.

Polypropylene fiber can effectively control the micro-cracks caused by plastic/shrinkage, dry shrinkage, temperature changes and other factors of concrete/mortar, prevent and inhibit the formation and development of primary cracks in concrete, and greatly improve the anti-cracking and impermeability and impact resistance of concrete/mortar Grinding performance, increase the toughness of concrete, thereby improving the service life of the concrete.

Polypropylene fiber undergoes special anti-static and anti-ultraviolet treatment to make the fiber evenly dispersed in the concrete and can exert its effect for a long time; the polypropylene fiber "Y" cross-section increases the fiber surface area; the fiber is chemically and physically modified to rough Porous, greatly improving the binding force of fiber and cement-based aggregates.

Polypropylene fiber improves the performance of concrete by reducing the occurrence and number of primary cracks in concrete, and will not have any conflict and chemical reaction with concrete aggregates, admixtures, admixtures, cement, so it has good adaptability with concrete materials.

In summary, the role of polypropylene fiber in concrete can be summarized as follows:

1. Improve crack resistance;

2. Improve impermeability;

3. Improve impact resistance and wear resistance;

4. Improve frost resistance;

5. Improve toughness;

6. Increase the fire resistance of concrete and improve the anti-explosion function;

7. Improve the quality of concrete products.

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