Steel Fiber Reinforced Concrete
Steel Fiber Concrete is a type of reinforced concrete. Steel fiber reinforced concrete (SFRC) as the name suggests that is made up of composite materials such as cement, sand, aggregate, water, gravel, steel fiber, and admixture. In this concrete fiber, steel fiber is an additional ingredient.
Fiber is added into the concrete is 0.3 to 2.5% by its volume of plain cement concrete. The diameter of steel fiber is used in concrete is 0.25 mm to 0.75 mm. commonly round shape of steel fiber is used.
In steel fiber reinforced concrete adding steel fibers in the concrete mixer and transfer green concrete into the molds or cubes and then after compacting the concrete, lastly cure the cubes by any conventional method of curing.
During the mixing of ingredients and during compacting the cubes are getting a high chance of segregation, balling of steel fiber, and bleeding of the concrete. Segregation is avoided by adding a uniform rate of fibers. Also, it is more permeable.
Higher efficiency is required for mixing the ingredients, placing, compacting, conveying, and finishing steel-reinforced concrete.
The main objective of adding steel fibers are into the concrete is to improve the mechanical properties and structural properties, particularly flexural strength and tensile strength, ductility, wear and tear, post cracking strength of SFRC is higher than any type of concrete.
For field experiments, steel fiber reinforced concrete is used for runway slabs and that is reduced one-half thickness of plain concrete slab just adding 2% of steel fiber.
Using steel fiber reinforced concrete developed manhole cover in India by the structural Engineering Research center, Chennai.
The Cement Research Institute of India is demonstrated the Steel fiber reinforced concrete for jet bays at Delhi airport.
Steel fiber reinforced concrete is used for garage parking slabs at the Heathrow airport in London.
Various Types of Fibers Are Used for Making Reinforced Concrete
- Steel fibers
- Glass fibers
- Synthetic fibers (Nylon fibers and Polypropylene fibers)
- Natural fibers (Sugar cane, jute, rice husk, bamboo, wood )
Types of Steel Fiber for Reinforced Concrete
- Straight fiber
- Crimped steel fiber
- Hooked steel fiber
- Button end steel fiber
- Twisted steel fiber
Steel Fiber Reinforced Concrete Is A Versatile Concrete Such As,
- Deck of bridge
- Manhole cover
- Highway lining
- Tunnel lining
- Window and doors frame
- For staircase
- Breakwater structure
- Foundation block
- Storage bins
- Lightweight Structure
- For the construction of the workshop
- Industrial Flooring
- For Military Structure
- For pre–fabricated elements
- For commercial structure
- For High resistance
- For the construction of a spillway
- For the construction of Dam
- For Stabilization of rock slope
- For explosion restive structure
- For cavitation work
Benefits For Users
- To minimize the risk of cracking.
- To reduce joint spalling.
- To make high–impact resistance concrete.
- To make stronger and more durable joints.
- To increase the utility period of the structure.
- To decrease the cost of maintenance.
Advantages of Steel Fiber Reinforced Concrete
- Steel reinforced fibers concrete is more durable, high in strength as compared to plain concrete.
- It is good in impact resistance.
- It provides good resistance in torsion, shear force, and compression.
- It is improved surface resistance to abrasion and erosion.
- It is high in flexural strength and tensile strength.
- It is economical.
- In steel fiber reinforce concrete many verities of precast concrete units are available.
- SFRC also helps to reduce the cross–sectional area of the structure and make it a lighter structure. Also, it saves the material.
- To increase the speed of construction. So that saves time.
- To reduce shrinkage of concrete.
- Steel fiber can reduce the slab thickness by up to 50%.
Disadvantages of Steel Fiber Reinforced Concrete
- During rain–damaged slabs, allow both fibers and aggregate to be exposed.
- It is aesthetically not good.
- It adversely affects the work-ability of concrete.
- It is heavy as compared to non–fiber concrete.
- Improper mixing can lead to balling of fiber.
- The use of Steel fiber is crucial to determine the amount of fiber, type, length of the fiber, etc.
- Using Steel fiber for fiber concrete is costly.
- Steel fiber leads to a corrosion effect.
Mix Design of Steel Fiber Reinforced Concrete
- The mix proportion of SFRC is depend upon the various factor such as required strength, work-ability, particular job, cross sectional area etc.
- Many different types of procedures are there for proportioning of SFRC mix. This emphasizes the workability’s of the concrete mix.
- Commonly mixes the higher cement contents and higher ration of fine aggregate to coarse aggregate is required.
- So that the conventional type of concrete mix design is not applicable to steel fiber concrete. Generally to reduce the cement quantity, used fly ash up to 35% of the cement.
- In addition to improve work-ability of concrete admixtures are used such as super plasticizers, water reducing admixture etc.
The proportion range of normal weight steel fiber concrete is given below,
|Property||Mortar||9.5 mm Max. aggregate Size||19 mm Max. aggregate size|
|Cement||415 – 710||355 – 590||300- 535|
|Water cement ratio||0.3 to 0.45||0.35 – 0.45||0.4 – 0.5|
|Fine aggregate / Coarse aggregate||100||45 – 60||45 – 55|
|Entrained air||7 – 10||4 – 7||4 – 6|
|Fiber content by volume Smooth steel||1 – 2||0.9 – 1.8||0.8 – 1.6|
|Deformed steel||0.5 – 1||0.4 – 0.9||0.3 – 0.|
The empirically derived mix design proportion is used for shotcrete work. Typical mix design for fiber shotcrete is given below,
|Property||Fine aggregate mixture||9.5 mm aggregate mixture|
|Cement||446 – 559||445|
|Blended Sand||1438 – 1679||697 – 880|
|9.5 mm aggregate||700 – 875|
|Steel Fiber||35 – 157||39 – 150|
|Water cement ratio||0.40 – 0.45||0.40– 0.45|
Applications of Steel Fiber Reinforce Concrete
The use of steel fiber concrete is widely used for a few years. So that it is difficult to categorize them, the most commonly used in pavement, slab casting, slab repairs, silica fume, and runway so on.
Recently experimental works have been completed on roller compacted concrete (RCC) reinforced with steel fibers.
The steel fiber is relatively expensive like 1% of additions of steel fiber will approximately double the cost of material so that steel fiber reinforced concrete is used in special applications.
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