Forum 

Bearing in mind all the building materials, concrete is one of the most used materials in that regards. It is a brittle material which has low tensile strength and strain capacities. Brittle materials are prone to cracking. Presence of cracks reduce not only the load carrying capacity but also durability of the structure. Adding fibers of some kind can help to overcome these problems. Fiber and brittle matrix compose a composite material which is commonly called Fiber Reinforced Concrete (FRC). There has been a steady increase in the use of FRC over the past 50 years. The fibers are not added to improve the strength, though modest increases in strength may occur. Fibers can alter the behavior of the matrix by bridging across the crack which leads to ductile failure instead of brittle one. Steady growth of research on this material brought us new generation of FRC materials called “Ultra-High-Performance Fiber Reinforced Concrete (UHPFRC), which exhibit multiple cracking and strain hardening beyond the point of first cracking, with a concomitant increase in energy absorption capacity. Tensile strength over 10MPa is achievable.

Depending on loading conditions, fibers in hardened concrete may have at least three important effects:

• Improve strength from insignificant to substantial (several times the strength of the parent matrix).
• Improve ductility of the inherently brittle cementitious matrix.
• Reduce crack width and crack spacing.

During last few decades, numerous researches has been conducted on properties of harden SFRC. Various efforts have resulted in an increasing number of applications over the past years. SFRC has been successfully  used in industrial pavements, harbor and airport pavements, shotcrete linings, tunnel segments, precast sewer pipes, retaining structures, foundation slabs, slabs on piles and elevated slabs supported on columns because it gains advantages from the redundancy of these structures and allows significant reinforcement optimizations in terms of casting simplification, performance increase such as depth reduction, quality of the casting and durability due to crack opening control.

Q. Why is it important to use fibers in concrete?

A. Concrete is a brittle material. Concrete cracked due to shrinkage during hydration process. By using fiber of some kind, crack can be reduced at the early stage. So, use of fiber in concrete mainly reduced cracking as well as gain tensile strength.