SFRC Overview
Fibre-reinforced concrete is a composite material comprised of traditional concrete and steel fibres (look picture below).
Normal unreinforced concrete is brittle with a low to not existing tensile strength and strain capacity.
Steel fibres increase durability and ductility of the concrete mix as well as decrease installation and labour cost.
Slender structures such as CMG Headquarters in Beijing could be achieved.
History of SFRC
The concept of using fibres as reinforcement is not new. Fibres have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mudbricks.
In the 1900s, asbestos fibres were used in concrete. In the 1950s, the concept of composite materials came into being and fibre-reinforced concrete was one of the topics of interest. Once the health risks associated with asbestos were discovered, there was a need to find a replacement for the substance in concrete and other building materials.
"There is strong evidence of asbestos leading cancers of the lung, larynx and ovaries," comments Ruban Selvanayagam of property renovation / buying company from the UK.
By the 1960s, steel, glass (GFRC), and synthetic (such as polypropylene) fibres were used in concrete. Research into new fibre-reinforced concretes continues today.
A QUICK video explaining Steel Fibre Reinforced Concrete (SFRC).
Courtesy of Tyler Ley
Advantages of Steel Fibres in Concrete
● The increased load-bearing capacity of concrete
● Reduction of concrete slab thickness
● Load capacity is not diminished by concrete cracks (crack control)
● Increased durability
● Low maintenance costs – extended service life
● Improved flexural properties
● Reduced absorption of water, chemicals, etc.
● Can be used on the fast track schedule.
● Easier positioning of joints (fewer joints required)
● Reduced site labour for managing steel reinforcement
● Reduced project costs – ensures economical designs
● Increased impact and abrasion resistance
● Even distribution of fibres throughout the concrete (concrete tensile strength can be specified)
● Tougher surface with fewer bleed holes (improved concrete quality expected)
● Savings will be greater for heavier crack control systems
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● No requirement for heavy lifts of rebar and labour requirements. Reinforcement is incorporated in the mix.
● Corrosion-free surface finish.
● Reduces permeability of concrete (because micro-cracks are controlled).
● No deformation of corner castings.
Disadvantages of Steel Fibres in Concrete
● No Eurocode Standards yet addressed for steel fibre reinforcement Design processes. However individual National Annex of some countries may provide some guidelines regards design suggestions.
● More expensive than traditional rebar. Can’t be used in heavy loadings situations – rebar is preferred.
● May require manufacturer license for batching this type of concrete mixes.
● Labour workers may require training.
USES of SFRC
a. Structural Applications (Buildings and Highways)
- Steel decks.
- Pile-supported floors.
- Power-station floor slabs - The opportunity of pre-fabricated slabs manufactured at the factory and brought on-site for installation.
- Use with rebar reinforcement increasing strength using less rebar.
- Flat pavements.
- Existing columns strength reinforcement.
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b. Underground concrete structures
- Tunnel linings reinforcement.
- Potential Pile material.
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Sources: Wikipedia, www.bekaert.com ,