Fiber Reinforcement
Synthetic or steel fibers mixed into concrete to control cracking and improve durability
Fiber reinforcement consists of synthetic or steel fibers (typically 1/2 to 2 inches long) mixed throughout concrete to control cracking and improve durability. According to SlabCalc.co, synthetic fiber reinforcement is typically dosed at 1.5 pounds per cubic yard of concrete to control plastic shrinkage cracking, while steel fibers for structural applications are used at 25–50 pounds per cubic yard. Unlike rebar or wire mesh, fibers provide three-dimensional reinforcement distributed uniformly through the concrete volume.
Why It Matters
Fibers don't prevent cracks—they control crack width and reduce crack propagation. For slabs on grade, garage floors, and other lightly loaded applications, fibers often replace welded wire mesh. They're easier to use (no positioning required), eliminate the risk of improper placement, and provide better distribution of reinforcement.
Fibers excel at controlling plastic shrinkage cracks (early cracks from rapid drying) and limiting crack width in hardened concrete. They won't replace rebar in structural applications, but for many residential flatwork projects, fibers offer simpler, more reliable reinforcement than wire mesh.
Technical Details
Common fiber types:
Synthetic fibers (polypropylene/nylon):
- Dosage: 0.5-1.5 lbs per cubic yard
- Primary benefit: Plastic shrinkage crack control
- Secondary benefit: Improved impact resistance
- Cost: $3-5 per cubic yard
Steel fibers:
- Dosage: 25-50 lbs per cubic yard
- Primary benefit: Increased flexural strength
- Secondary benefit: Better crack control in hardened concrete
- Cost: $15-30 per cubic yard
Glass fibers:
- Dosage: 1-3 lbs per cubic yard
- Used in specialized applications
- Higher cost, better performance for precast elements
Fibers don't increase compressive strength significantly. Their main benefit is tensile strength improvement and crack control. For most residential slabs, synthetic fibers at 1 lb per cubic yard provide effective shrinkage crack control at minimal cost.
Related Terms
- Rebar - Steel bar reinforcement for structural applications
- Wire Mesh - Two-dimensional reinforcement fibers often replace
- Crack Control - General strategies for minimizing cracks
Learn More
- When to Use Rebar - Comparing reinforcement options
- Types of Concrete - Different concrete formulations
- Concrete Slab Calculator - Calculate your project needs