Which fiber to choose for reinforcing concrete?

Which fiber to choose for reinforcing concrete?

Modern construction has long since departed from classical canons. Today, to obtain strong concrete, it is not necessary to knit kilometers of heavy steel reinforcement or lay a metal mesh that corrodes over the years. Metal has been replaced by polymer technologies, namely fiberglass.
However, at the design stage, a dilemma arises: which fiber to choose? Using the example of the Astra brand line, we will analyze the radical difference between two popular products — Astra ProMicro and Astra PolyexMesh. Despite the similar names, they have completely different tasks, structure, and areas of application.

1. The secret of the name: what is hidden inside?
The main difference between these two materials lies in their geometric parameters and the scale of action in the concrete body.

Astra ProMicro or Protex polypropylene fiber (Microfiber): These are ultra-thin, single fibers of 100% polypropylene, 12 mm long. Their thickness is only 18 microns (thinner than a human hair). One kilogram of such material contains millions of microfibers, which are evenly distributed in the solution.
Astra PolyexMesh (Macrofiber): This is a high-strength structural fiber made from a special blend of copolymer and polypropylene. It is much longer (available in sizes 24, 38 and 54 mm) and thicker (69 microns). The fibers have a special twisted shape (small flagella), which provides maximum adhesion to the concrete.

2. Difference in functions: crack control vs. load holding
The most common mistake beginners make is to assume that all fibers make concrete «stronger» in the same way. This is not true.
Astra ProMicro: Fresh Solution Protection
This fiber starts working in the first minutes after pouring, when the concrete is still «alive», plastic and losing moisture.

Main function: Prevent microcracks from forming during the drying (plastic shrinkage) of concrete in the first 24 hours. When water evaporates, internal stress occurs in the concrete. A dense 3D mesh of millions of microfibers restrains these microcracks.
Result: A perfectly smooth surface without hairline cracks, increased frost resistance and water resistance of the top layer. However, ProMicro is not able to withstand large structural loads on bending or breaking after the concrete hardens.

Astra PolyexMesh: Structural strength frame
This material «turns on» when the concrete has completely hardened and external forces begin to act on it — the weight of the equipment, impacts, temperature fluctuations.

Main function: Structural reinforcement. Due to its high tensile strength (over 620 MPa), PolyexMesh redistributes forces within the slab. It works in the same way as steel fiber or road mesh.
Result: Concrete gains tremendous impact strength, tensile strength when bent, and the ability to withstand heavy machinery without the formation of through cracks.

3. Application areas: where is every fiber king?
The wrong choice of material means either wasted money (overpayment) or a disaster-prone condition of the facility in the future.

  
The choice comes down to a simple rule: what problem are you solving?

If your goal is to make a neat, even household screed, protect plaster from shrinkage, or make a self-leveling floor that does not crack under laminate flooring, Astra ProMicro is your choice.
If you are faced with the task of pouring an industrial floor, a durable slab in the yard under a car, building a blind area around the house, erecting an industrial hangar, or forgetting about rust from metal mesh in a humid environment, you need Astra PolyexMesh, which can replace metal mesh or steel fiber.

In some projects, technologists even combine both types of fiber, obtaining «absolute» protection of concrete at all levels — from microshrinkage to macroimpacts.