In recent years, polypropylene fibers have been used in concrete applications with high crack resistance requirements. The excellent anti-cracking effect of polypropylene fibers has been confirmed by experimental engineering, but the impact on other properties of concrete, especially long-term performance and durability, has become a concern of researchers and users. This article analyzes the general mechanical properties, long-term properties, and durability properties of polypropylene fiber concrete.
1. Inhibit the shrinkage
The addition of polypropylene fibers can effectively inhibit the shrinkage of concrete. Taking 90d as an example, adding 0.3kg/m3-0.9kg/m3 polypropylene fiber, the dry shrinkage of concrete is reduced by 8% to 15% compared with the benchmark concrete, which is mainly due to the presence of polypropylene fibers in the concrete surface material. It is more difficult to make the concrete surface lose water and moisture so that the tension formed by shrinkage is reduced, thus effectively inhibiting the shrinkage.
2. Anti-chloride ion penetration
Although the enhancement effect of polypropylene fiber on the permeability of concrete against chloride ions is not as significant as that of impermeability, it still shows that with the increase of the content of polypropylene fiber, the diffusion coefficient of chloride ions in concrete decreases, indicating that polypropylene fiber concrete can more effectively resist the erosion of external chloride ions.
The reinforcement in the polypropylene fiber-incorporated concrete is in good condition, showing the ability of the polypropylene fiber concrete to resist chloride ion attack and protect the internal reinforcement.
Polypropylene fiber can effectively inhibit the generation and development of early drying shrinkage micro-cracks and segregation cracks of concrete, effectively reducing the generation of connected cracks, and thereby improving its impermeability performance.
5. Freeze resistance
The addition of polypropylene fibers can significantly reduce the freeze-thaw cycles of concrete after the surface spalling phenomenon, and maintain the integrity of the concrete appearance. Through the experimental research on the conventional mechanical properties, long-term properties,s and durability of polypropylene fiber concrete, it is found that polypropylene fiber can enhance the early crack resistance of concrete, and can also effectively inhibit the shrinkage and creep of concrete, enhance the resistance of concrete. It can resist the corrosion of external chloride ions, protect steel bars and prevent corrosion. To sum up, the fiber content is 0.9kg/m3 polypropylene fiber mixed Concrete exhibits superior general mechanical properties, long-term properties, durability permanent performance.