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Types of Concrete Cracks

Concrete is broadly known as an extremely versatile, cost-effective construction material. Yet it is also affected with some disadvantages that are inherent to its composition.  By generally accepted engineering standards, concrete is relatively brittle and lacks ductility.  Intertwined with these problems is concrete’s propensity to crack in both its plastic (early-age) and hardened (long-term) state.  Early-age cracks are microscopic fissures caused by the intrinsic stresses created when the concrete settles and shrinks over the first 24 hours after being placed.  Long-term cracking is in part caused by the drying shrinkage that transpires over time.  In either case, these cracks can risk the overall integrity of the concrete and not allow it to uphold or possibly ever achieve its maximum performance capability.

Severe Road Cracking Forta
Severe cracking from years of heavy truck traffic            

Crack on Slab Forta
Slab-on-ground crack          

Why Use Reinforcement in Concrete?

This is the basic reason why reinforcement in concrete is essential.  Irregular cracks are unattractive and hard to maintain although generally do not affect the concrete’s integrity.  Joints in concrete slabs are simply pre-planned cracks that are created by forming, sawing, or tooling. Concrete slabs that are designed for serviceability typically use reinforcement such as deformed reinforcing steel bars (rebar) or welded wire fabric (WWF) to hold cracks tight.  The primary function for the reinforcement is to maintain aggregate interlock for load transfer and improve joint strength.  Rebar and WWF do not inhibit the formation of cracks, but if properly positioned provide reinforcement once a crack has developed.

Fiber reinforcement provides the similar function, is mixed throughout the concrete and distributes the stresses attributed to shrinkage throughout the concrete panel making the joints much more stable. This distribution of fibers offers a complete reinforced cross-section of concrete and changes the way the concrete works.

Synthetic and steel fibers have been applied in concrete for over 30 years to improve concrete’s plastic (early-age) and hardened properties.  Micro-synthetic fibers have been used to control random plastic-shrinkage cracking.  Steel fiber and Macro-synthetic fibers have been used to provide crack width control in concrete after it reaches a hardened state.  Combining both products gives advantages in both plastic and hardened state.  The concrete applications that fiber reinforcement is used in includes, but not limited to, slabs-on-ground, composite metal deck slabs, topping slabs over precast panels, precast, and shotcrete.

Fiber reinforcement makes good concrete better because fiber reduces cracking and adds long-term durability to a wide variety of concrete applications.  Fiber reinforcement offers an alternative construction method to traditional welded wire fabric and rebar reinforcement and provides additional benefits, including guaranteed 3-dimensional reinforcement, safer installation and more cost-effective.

Warehouse floor forta ferroBike path
Utilize of FORTA fibers to reinforce multiple slab applications of warehouse and bike path, increasing the load capacity of the slab and the fatigue performance.

 

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July 27, 2018