Some Effects Of Polypropylene Fiber On Concrete After Hardening

Effects Of Polypropylene Fiber On Concrete After Hardening

The addition of polypropylene fiber to concrete has no obvious effect on the compressive strength and elastic modulus of concrete, but it does increase the tensile strength of concrete. The tensile strength of fly ash concrete is about 9% to 13% of its compressive strength. The addition of polypropylene fibers to concrete can increase the splitting tensile strength by about 20% to 50% .

1. Compressive strength: The compressive strength of concrete is a very important parameter because it determines other parameters such as tensile, bending, etc. The effect of polypropylene fibers on the compressive strength of concrete has been discussed in many literatures, and polypropylene fibers have been observed to reduce or increase the compressive strength of concrete, but in many cases the overall effect is negligible. In fact, the effect of small volume polypropylene fibers on the compressive strength of concrete may be masked by experimental errors.

2. Bending tensile strength: As the volume fraction of the fiber increases, the bending tensile strength increases. As the fiber length-to-diameter ratio increases, the strength of the fiber also increases.

3. Fracture performance: The use of fibers effectively improves the failure performance of high-strength concrete. Typical shear bond breaks due to strain localization can be avoided. Instead, as shown in Figure 7, a large number of longitudinal cracks form across the concrete specimen, mainly in the direction parallel to or subparallel to the external compressive stress.

4. Creep and shrinkage properties of concrete: fibers reduce creep strain, which refers to the time-varying deformation of concrete under constant stress. However, the compressive creep value may be only 10% to 20% of that of ordinary concrete. Concrete shrinkage is also reduced by fibers due to the extraction of water from the concrete during the drying process. The shrinkage, creep and total time-varying deformation of various PFRC mixtures as well as non-fiber concrete mixtures are shown. From many point of view, shrinkage decreases due to the presence of fibers. First of all, the fibers do not show any shrinkage, which reduces the overall shrinkage of the mixture. In addition, the water retention effect of the fiber in the concrete mix ratio reaches a certain limit, which helps to delay shrinkage. Therefore, adding fibers to the concrete mix ratio is conducive to reducing shrinkage deformation.