ReinFlex twisted macro synthetic fiber 38 mm
Twisted fiber with a dual action. Holds cracks together and stops shrinkage.
Certificates and compliance
ISO 9001:2015, certificate No. UA.QM.ASCB.057.01-26, valid until February 25, 2029
What is ReinFlex
ReinFlex is a macro fiber in the form of a twisted bundle, 38 mm long, that works like an anchor. The spiral shape creates a mechanical bond with the concrete along the entire length of the fiber. That’s why pulling it out of the matrix takes much more energy than pulling out a straight fiber. The result is tough, crack-resistant concrete that keeps carrying the load after the first cracks appear.
Dual action
During mixing, the bundle gradually opens up. The fine filaments disperse throughout the mix and stop plastic shrinkage in fresh concrete, while the thicker macro fibers reinforce the hardened concrete. That’s why, in floors and slabs on grade, a single product replaces both micro fiber and steel mesh.
Specifications
| Material | polypropylene |
|---|---|
| Shape | twisted bundle |
| Length | 38 mm |
| Diameter | 0.3 mm |
| Tensile strength | 550 MPa |
| Modulus of elasticity | 5.6 GPa |
| Color | gray |
| Density | 0.91 g/cm³ |
| Melting point | ~160 °C |
| Class per EN 14889-2 | II |
Technical data sheet (TDS) and quality certificate available on request.
Benefits
Anchoring bond
The twisted shape doesn't slip out of the concrete, so the fiber works at its full strength.
Two in one
Shrinkage crack protection and structural reinforcement in a single product.
Impact resistance
Higher resistance to impact and fatigue loads. Suitable for floors carrying forklifts and racking.
No corrosion
Lightweight, rust-free, safe for workers and equipment.
Looks good on the surface
The gray color masks any fibers that come up to the surface.
How and where to use ReinFlex
Where to use it
- Floors under dynamic loads: warehouses, logistics centers, auto service shops
- Floor slabs on metal decking (in addition to the rebar required by design)
- Road and airfield pavements, bridges, repair overlays
- Shotcrete
- Precast products exposed to impact: curbs, drainage channels, fences
When not to use it
- Does not replace structural rebar in load-bearing structures without engineering calculations.
We are upfront about the limits of each fiber, so you don't overpay or end up with cracks.
Recommended dosage
| Application | Dosage |
|---|---|
| Slabs and screeds with higher performance requirements | 1.8–3 kg/m³ |
| Industrial floors, roads | 3–5 kg/m³ |
| Shotcrete, precast concrete | 4–7 kg/m³ |
The exact dosage depends on loads, thickness, concrete grade and subbase. We will match it to your project.
How to add it to concrete
- Add the fiber to the drum during or after batching the other components and mix for 4–5 min at operating drum speed.
- At the batching plant: add the fiber together with the aggregates or with the first portion of water.
- In a truck mixer: add the fiber to the drum at the start of loading. If you add it to ready-mixed concrete, mix at maximum drum speed for another 5 min (at least 70 drum revolutions).
- For placing with a concrete pump, fit the pump hopper with a grate made of round bars and a vibrator.
- Workability: compensate with a superplasticizer (PCE), not with water. Recommended slump at discharge: S3 or higher.
- Placing: vibrating screed or laser screed.
- Finishing: use magnesium floats, trowel as late as possible and keep the blades flat.
- Before your first project, make a trial batch.
ReinFlex documentation
Click a document to enlarge it.
Further reading on ReinFlex
-
Fiber vs Steel Mesh: How to Reinforce a Concrete Floor
Can fiber replace steel mesh in a concrete floor? Macro fiber vs steel mesh compared, the declared dosage, and when you still need rebar or mesh. -
CMOD Test to EN 14651: How Concrete Fiber Is Tested
How fiber concrete is tested in bending to EN 14651 and what CMOD, fR1 and fR4 mean, with photos of our ReinStrong and ReinFlex tests at TSÚS in summer 2026. -
Concrete Fiber Dosage: How Much Fiber to Add per m³
How much fiber to add per m³ of concrete: dosage tables for ReinStrong, ReinFlex, ReinLite, ReinGlass and ReinBasalt in floors, screed and plaster.
ReinFlex FAQ
ReinStrong or ReinFlex: which one should I choose?
ReinStrong is the classic macro fiber for most slabs. Choose ReinFlex when you need maximum toughness and impact resistance, or when you want a single product to handle both shrinkage and reinforcement.
Why is the fiber twisted?
The spiral shape creates a mechanical bond with the concrete along the entire length of the fiber. Pulling it out of the matrix takes much more energy than pulling out a straight fiber.
Become a ReinFlex distributor
We are looking for distributor partners in new markets and look forward to your request. Tell us about your company and market, and we will be glad to help with your order, the right fiber range and delivery to your country.
- Our own production
- Export to 15 EU countries
- Help with orders and delivery to your country
Other Reinforce fibers
ReinStrong
Macro fiber for concrete reinforcement. Replaces steel mesh in floors and slabs on grade.
Learn more →
ReinLite
Millions of fine fibers against shrinkage cracks in concrete, screed and plaster.
Learn more →
ReinGlass
Fine glass fiber against shrinkage cracks in screeds, plasters and dry mixes.
Learn more →