Polypropylene fibers in concrete role can not be ignored

Modern concrete technology has proven theory, concrete outlook on fine and coarse scale is a porous structure of the transition zone (interface) orthopedics, as well as between the cement paste composition. The porous structure contains native and secondary microcracks, these cracks affect the integrity of the concrete, wear resistance and durability. Under the effect of temperature or force, which cracks easily crack, expand, resulting in decreased bond strength steel, affect the structural properties of concrete and life.

By adding fiber to improve the performance and service life of the material is an effective means mankind has been in use since ancient times. In the 70s of last century, the United States polypropylene fibers as secondary concrete reinforcing ribs effectively suppresses the concrete in the plastic and hardening of the early (WCMC early) due to the segregation of construction, maintenance periods, bleeding, shrinkage cracks and other factors to ensure the continuity of the material medium, so that the structure of the hardened concrete performance has been significantly improved. Especially roads and bridges concrete, due to withstand high loads and repeated impact load native sensitivity to concrete crack number and scale, the effect of improving the concrete with polypropylene fiber is more apparent.

Role of polypropylene fibers in concrete
Polypropylene fibers are fibers made from a hydrocarbon polymer or copolymer made from propylene, specific gravity 0.91, tensile strength of 620MPa ~ 785MPa, elastic modulus greater than 3500 MPa, elongation at break of 8%, non-absorbent, neutral material , and acid-base reaction can not afford.

According to the structure in the form of polypropylene fibers, it can be divided into polypropylene mesh fiber and polypropylene monofilament fiber. Sectional shape of the reticular fibers whose monofilament irregular rectangle. Composed of a number of parallel monofilament fiber aggregate have a number of parallel longitudinal slit cut fiber mesh, forced tearing Serve one filaments. Single wire based surface roughness, good bond strength. Polypropylene monofilament fiber of circular cross-section, from the spinning process processed into a smooth surface, bond strength is better reticular fibers.

Concrete is a brittle composite material, in concrete hardening process, along with a variety of contraction (plastic shrinkage, temperature contraction) increases, resulting in concrete produce many microcracks, microcracks which result in reduced structural properties of concrete is the main the reason. After the incorporation of polypropylene fiber concrete, rely on fiber and concrete bonding interface, together with concrete to withstand all kinds of contraction, reduce microcracks, improve the integrity and structural performance of concrete.

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