Efficiency of polypropylene fiber in fine-grained concrete
The introduction of cement based polypropylene fiber based mixtures is one of the most effective methods of improving their performance. Polypropylene fibers are recommended to be introduced into the formulation of masonry, plaster, assembly, porous solutions, as they contribute to the improvement of the following parameters:
- frost resistance;
- water tightness;
- fracture resistance;
- impact resistance;
- corrosion resistance.
Although the effectiveness of polypropylene fiber in fine-grained concrete is undeniable, in Ukraine this technology is not as widespread as in Europe and the Americas. This may be due to the inertia and conservatism of the Ministry of Construction, which is responsible for harmonizing Ukrainian standards with European ones. As such standards will be the basis for design and construction organizations to make extensive use of the useful qualities of polypropylene fiber in concrete.
How the effect of fiber on fine-grained concrete is investigated
Creation of a mixture with the entry of fiber must meet the standards of GOST and DSTU. Fine-grained concrete with a ratio of cement and other occurrences of 1: 3 is used for the study .
Before beginning the study on the effectiveness of polypropylene fiber in fine-grained concrete, it is necessary to prepare a homogeneous mixture of cement and sand with the addition of water. Further, with constant stirring, the fiber is introduced into the resulting mass. The resulting mixture is divided into samples with parameters 40x40x160 mm. They are involved in determining the level of compressive strength and tensile strength. Part of the mixture is allocated to create samples of cylindrical shape – they are used to determine the impact resistance.
As a result of the research on compressive strength, there is a slight increase in performance, when using the dosage of polypropylene microfiber in concrete in the amount of 0.035 – 0.05% by weight of concrete. The fiber compacts the location of the particles of the cement-sand mixture, thereby making the concrete stronger. Polypropylene microfiber creates millions of microlinks: fiber + cement clinker + sand grain, thus making the mixture more dense and homogeneous. This is achieved with a dosage of only 0.6-0.9kg / m3.
When using microfibers in flexural tensile tests, the increase in performance was very small, as this type of fiber is not intended to improve these parameters of concrete.
With regard to compressive strength, high dosage has a negative effect on this indicator. But for such a criterion as impact resistance, water permeability, frost resistance, abrasion, standard dosage of 0.9 kg / m3 gives a significant improvement in these necessary characteristics of concrete.