What is the primary purpose of adding fibers to concrete?

What is the primary purpose of adding fibers to concrete?

• A. To control cracking due to plastic shrinkage and drying shrinkage, and to enhance durability and impact resistance.
• B. To speed up curing.
• C. To reduce concrete strength.
• D. To make it heavier.

Answer: (B)

Fibers in concrete mainly serve to control cracking and improve durability. They act as tiny bridges across developing cracks, which helps keep cracks small and distributes stresses more evenly as the concrete dries and as it experiences plastic shrinkage soon after placement. This crack-bridging action reduces crack propagation, lowers permeability, and boosts resistance to impact and abrasion, all of which contribute to longer-term durability and toughness. Curing speed, strength changes, or weight are not the primary reasons fibers are added. Fibers don’t speed up the curing process—curing is governed by moisture, temperature, and the cement hydration chemistry. They also don’t purposefully reduce strength or make the concrete heavier; while they can influence post-crack behavior and slightly affect certain strength aspects, the main goal is crack control and durability, not curing rate, strength reduction, or weight increase.

Fibers in concrete mainly serve to control cracking and improve durability. They act as tiny bridges across developing cracks, which helps keep cracks small and distributes stresses more evenly as the concrete dries and as it experiences plastic shrinkage soon after placement. This crack-bridging action reduces crack propagation, lowers permeability, and boosts resistance to impact and abrasion, all of which contribute to longer-term durability and toughness.

Curing speed, strength changes, or weight are not the primary reasons fibers are added. Fibers don’t speed up the curing process—curing is governed by moisture, temperature, and the cement hydration chemistry. They also don’t purposefully reduce strength or make the concrete heavier; while they can influence post-crack behavior and slightly affect certain strength aspects, the main goal is crack control and durability, not curing rate, strength reduction, or weight increase.