The Use of Fiber Reinforced Concrete in Resistant and Lighter Architecture

The use of fiber-reinforced concrete to reinforce concrete materials is a well–known concept. It has been practiced since ancient times, with straw mixed into mud bricks and horsehair included in mortars. However, in our modern-day construction practices, we have forgotten the ancient practices to control cracks in concrete. Concrete cracking is normal. Portland cement concrete is considered to be a relatively brittle material and is prone to crack in the plastic as well as the hardened stage. Plastic shrinkage occurs when the evaporation of water from the surface of the concrete is greater than the rising bleed water. As concrete is very weak in tension in its plastic stage, a volume change causes the surface to crack. As it hardens, the water present in the pores of concrete begins to evaporate. This causes the concrete to shrink due to the volume change, which is restrained by the subgrade and reinforcement. This results in tensile stress being developed in hardened concrete, again causing the concrete to crack.

Incorporating Synthetic fibers help to reduce thermal and shrinkage cracks. The addition of steel fibers enhances the ductility performance, post-crack tensile strength, fatigue strength and impact strength of concrete structures. 

What is Fiber Reinforced Concrete (FRC)?

Fiber Reinforced Concrete is Portland cement concrete reinforced with more or less randomly distributed fibers. In Fiber Reinforced Concrete, thousands of small fibers are dispersed and distributed randomly in the concrete during mixing, thus improving concrete properties in all directions. Fibers help to improve the pre-crack tensile strength, post-peak ductility performance, fatigue strength, impact strength and minimize thermal and shrinkage cracks.

Natural fibers, metallic (steel), synthetic (polymers) and mineral ones (carbon or glass) are used to this end. They act as a deterrent of cracks in the concrete due to the plastic retraction and the drying process, also reducing its permeability. When the structure undergoes high tension from external loads, changes in temperature or humidity, the fibers going through it create structural micro-reinforcements preventing fissures from expanding. All in all, fiber reinforced concrete substantially improves the performance of concretes and mortars under traction and shear stress, normally presenting a low resistance to those.

Using a similar fabrication method, the GFRC (Glass Fiber Reinforced Concrete) consists of a mortar made of concrete, sand, alkali-resistant glass fiber and water. Plasticity is one of the main qualities of the material, enabling molding of facade panels precisely following the architectonic design permitting the production of slenderer thus, lighter pieces. 

Some companies have already developed products that take advantage of the properties that fibers have in concrete. Besides facade panels and furniture, the applications of fiber-reinforced concrete strongly associate with works of basic restructuring and transport, such as paving and tunnels, also in rigid soils, industrial floors, hillside containment, and structural reinforcement. It is worth mentioning that despite its integral application; the material requires a rigid laboratory control and accurate technical knowledge for its production.