What is the purpose of adding fiber in concrete?

Adding fibers to concrete serves several purposes and can enhance the performance and properties of the concrete in various ways:

1. Control of Cracking:

• Fiber reinforcement helps control the formation and propagation of cracks in concrete. The fibers act as micro-reinforcements, bridging across cracks and restraining crack widths, thereby improving the overall durability and serviceability of the concrete.

2. Increased Flexural Strength:

• Fiber reinforcement increases the flexural strength and toughness of concrete, particularly in tension. This is especially beneficial in applications where the concrete is subjected to bending or flexural loads, such as in pavements, floors, and bridge decks.

3. Impact Resistance:

• Fibers improve the impact resistance of concrete by absorbing and redistributing energy upon impact. This property is important in structures prone to impact loads, such as industrial floors, parking decks, and blast-resistant structures.

4. Reduced Shrinkage and Curling:

• Fiber reinforcement helps mitigate shrinkage cracking and reduces the tendency of concrete slabs to curl. By providing internal restraint, fibers minimize the effects of volume changes associated with drying shrinkage, temperature fluctuations, and moisture differentials.

5. Enhanced Toughness and Ductility:

• Fibers improve the toughness and ductility of concrete, allowing it to better withstand sudden loading events and post-cracking deformations. This is beneficial in seismic-resistant structures and in applications requiring enhanced structural integrity.

6. Control of Plastic Shrinkage Cracking:

• Fibers can help control plastic shrinkage cracking by reducing surface water evaporation and providing early-age reinforcement. This is particularly useful in hot or windy conditions where rapid moisture loss from the concrete surface can lead to cracking.

7. Crack Bridging:

• Fibers act as crack-bridging elements, spanning across cracks that may develop due to various factors such as drying shrinkage, thermal gradients, or structural loading. This helps maintain structural integrity and prevents crack propagation.

8. Improved Durability:

• The addition of fibers can enhance the durability of concrete by reducing the ingress of harmful substances such as chlorides, sulfates, and other aggressive agents. This results in increased resistance to corrosion, chemical attack, and freeze-thaw cycles.

9. Control of Plastic Settlement Cracking:

• Fibers help control plastic settlement cracking by providing internal support and reinforcement to the fresh concrete during placement and consolidation. This minimizes settlement differentials and reduces the likelihood of crack formation.

10. Enhancing Fire Resistance:

• Certain types of fibers, such as steel or polypropylene fibers, can enhance the fire resistance of concrete by providing additional reinforcement at elevated temperatures. This is important in fire-rated structures and fireproofing applications.

In summary, adding fibers to concrete offers multiple benefits, including improved crack control, increased flexural strength, enhanced impact resistance, reduced shrinkage and curling, enhanced toughness and ductility, control of plastic shrinkage and settlement cracking, improved durability, and enhanced fire resistance. These benefits make fiber-reinforced concrete suitable for a wide range of structural and non-structural applications in construction.