Steel Fibres - Advantages And Disadvantages

As a rule of thumb, small fibres tend to be used where control of crack propagation is the most important design consideration. High fibre count (number of fibres per kg) permits finer distribution of steel fibre reinforcement throughout the matrix ' and consequently, greater crack control during drying process. On the other hand, because they exhibit better matrix anchorage at high deformations and large crack widths, longer, heavily deformed fibres afford better post-crack "strength". However, unlike shorter fibres, the dramatically reduced fibre count of longer product yields correspondingly less control of initial crack propagation.

You will get efficient and thoughtful service from well.

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Properties of reinforcement

When steel fibres are added to mortar, Portland cement concrete or refractory concrete, the flexural strength of the composite is increased from 25% to 100% - depending on the proportion of fibres added and the mix design. Steel fibre technology actually transforms a brittle material into a more ductile one. Catastrophic failure of concrete is virtually eliminated because the fibres continue supporting the load after cracking occurs. And while measured rates of improvement vary, Steel fibre reinforced concrete exhibits higher post-crack flexural strength, better crack resistance, improved fatigue strength, higher resistance to spalling, and higher first crack strength, Figure 2 shows concrete flexural strengths when reinforced at various fibre proportions. Additionally, deformed fibres provide a positive mechanical bond within the concrete matrix to resist pull-out. Steel fibres are available in lengths from 38 mm to 50 mm and aspect ratios between 40 and 60. The fibres are manufactured either deformed or hook end, and conform to ASTM A-820.

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Steel fibre reinforced concrete (SFRC) Floor slabs.

Conventional practice usually concentrates welded wire fabric reinforcement within a single plane of a floor slab. Fabric does very little to reinforced the outer zones, which is why spalling is common at the joints and edges. The primary function of welded wire fabric is to hold the floor slab together after the first small hairline cracks have propagate to larger fractures. This serves to maintain some degree of "structural integrity". Conventional wisdom's approach to floor slabs is to maintain "material integrity" through SFRC mix designs. This integrity is accomplished by:

• Increasing the initial first crack strength.
• Large numbers of fibres intercepting the micro-cracks and preventing propagation by controlling tensile strength.
• Unlike rebar and welded wire fabric, fibres are dispersed throughout the slab to reinforce isotropically, so there is no weak plane for a crack to follow.
• Increases in flexural strength can make it possible to use a thinner slab and eliminate the cumbersome welded wire fabric.
• Whether it is for lighter duty commercial service or for heavy manufacturing, SFRC slabs are capable of withstanding any load. The only variable is the addition rate of fibre, which could be as low as 12.5kg/m3 to as high as 100 kg/m3.

'

How they save time and money

COMPLETELY ELIMINATE STEEL FABRIC REINFORCEMENT, SAVING ON BOTH MATERIALS AND LABOUR

• Reduce slab thickness giving savings in concrete and placement costs.
• Possibilities of wider joint spacing. Save on joint forming costs and joint maintenance
• Simplicity of construction. Simpler joints and no more errors in steel fabric positioning
• Increase speed of construction. Save time and reduce costs.

'

Technical and user benefits

• Significantly reduced risk of cracking.
• Reduced spalling joint edges.
• Stronger joints.
• High impact resistance.
• Greater fatigue endurance.
• Reduced maintenance costs.
• Longer useful working life

'

Typical areas of applications include

Industrial Ground Floor Slabs ' Warehouses, Factories, Aircraft Hangers, Roads, Bridge Decks, Parking Areas, Runways, Aprons and Taxiways, Commercial and Residential Slabs, Piling, Shotcrete, Tunnels, Dams and stabilisation.

'

Improved strength and durability

Steel fibre reinforced concrete is a castable or sprayable composite material of hydraulic cements, fine, or fine and coarse aggregates with discrete steel fibres of rectangular cross-section randomly dispersed throughout the matrix. Steel fibres strengthen concrete by resisting tensile cracking. Fibre reinforced concrete has a higher flexural strength than that of unreinforced concrete and concrete reinforced with welded wire fabric. But unlike conventional reinforcement ' which strengthens in one or possibly two directions ' Steel fibres reinforce iso tropically, greatly improving the concrete's resistance to cracking, fragmentation, spalling and fatigue. When an unreinforced concrete beam is stressed by bending, its deflection increases in proportion with the load to a point at which failure occurs and the beam breaks apart. This is shown in Figure 1. Note that the unreinforced beam fails at point A and a deflection of B. A Steel fibre reinforced beam will sustain a greater load before the fist crack occurs (point C). It will also undergo considerably more deflection before the beam breaks apart (point D). The increased deflection from point B to point D represents the toughness imparted by fibre reinforcement. The load at which the first crack occurs is called the "first crack strength". The first crack strength is generally proportional to the amount of fibre in the mix and the concrete mix design.

Two theories have been proposed to explain the strengthening mechanism. The first proposes that as the spacing between individual fibres become closer, the fibres are better able to arrest the propagation of micro cracks in the matrix. The second theory holds that the strengthening mechanism of fibre reinforcement relates to the bond between the fibres and the cement. It has been shown that micro cracking of the cement matrix occurs at very small loads. Steel fibres, then service as small reinforcing bars extending across the cracks. So as long as the bond between the fibres and cement matrix remains intact the Steel fibres can carry the tensile load. The surface area of the fibre is also a factor in bond strength. Bond strength can also be enhanced with the use of deformed fibres, which are available in a variety of sizes.

'

Product mix designs

The proportions of Steel fibres in mix designs usually range from 0.2% to 2.0% (15 to 150 kg/m3 ) of the composite's volume. Key factors to consider largely depend on the application under consideration and/or the physical properties desired in the finished project. Mix designs with fibre proportions above 60kg/m3 are usually adjusted to accommodate the presence of millions of steel fibre reinforcing elements. The adjustments are an increase in the cement factor, a reduction in the top size of the coarse aggregate and the addition of a super plasticiser. Prototype testing is recommended to determine the optimum design for each application.

'

Advantages

• Reinforcing concrete with Steel fibres results in durable concrete with a high flexural and fatigue flexural strength, improved abrasion, spalling and impact resistance.
• The elimination of conventional reinforcement, and in some cases the reduction in section thickness can contribute to some significant productivity improvements. Steel fibres can deliver significant cost savings, together with reduced material volume, more rapid construction and reduced labour costs.
• The random distribution of Steel fibres in concrete ensures that crack free stress accommodation occurs throughout the concrete. Thus micro cracks are intercepted before they develop and impair the performance of the concrete.
• Steel fibres are a far more economical design alternative.

Disadvantages

• Steel fibres will not float on the surface of a properly finished slab, however, rain damaged slabs allow both aggregate and fibres to be exposed and will present as aesthetically poor whilst maintaining structural soundness.
• Fibres are capable of substituting reinforcement in all structural elements (including primary reinforcement), however, within each element there will be a point where the fibre alternative's cost saving and design economies are diminished.
• Strict control of concrete wastage must be monitored in order to keep it at a minimum. Wasted concrete means wasted fibres.

'

DESCRIPCIÓN
STEEL MACRO-FIBER
DESCRIPTION
 
PSI CRIMPED STEEL FIBER are low carbon, cold drawn steel wire bers designed to provide concrete with temperature and shrinkage crack control, enhanced exural reinforcement, improved shear strength and increase the crack resistance of concrete. PSI Crimped Steel Fiber complies with ASTM C, Standard Speci cation for Fiber Reinforced Concrete and Shotcrete and ASTM A820, Type I, Standard Speci cation for Steel Fibers for Fiber Reinforced Concrete. These steel macro- bers will also improve impact, shatter, fatigue and abrasion resistance while increasing toughness of concrete. Dosage rates will vary depending upon the reinforcing requirements and can range from 25 to 100 lbs/yd3 (15 to 60 kg/m3).
 
PRIMARY APPLICATIONS
 
Commercial and industrial slabs on ground
' Bridge decks, overlays and pavements
' Precast concrete applications
' Shotcrete, tunnel linings and slope stabilization ' Mass concrete and composite deck construction
 
FEATURES/BENEFITS
 
' Increases impact, shatter and abrasion resistance of concrete
' Reduces segregation, plastic settlement, and shrinkage cracking of concrete
' Provides three-dimensional reinforcement against macro-cracking
' Increases overall durability, fatigue resistance and texural toughness
' Reduction of in-place cost versus wire mesh for temperature / shrinkage crack control ' Easily added to concrete mixture at any time prior to placement
 
TECHNICAL INFORMATION
Steel Fibres - Advantages And Disadvantages
As a rule of thumb, small fibres tend to be used where control of crack propagation is the most important design consideration. High fibre count (number of fibres per kg) permits finer distribution of steel fibre reinforcement throughout the matrix ' and consequently, greater crack control during drying process. On the other hand, because they exhibit better matrix anchorage at high deformations and large crack widths, longer, heavily deformed fibres afford better post-crack "strength". However, unlike shorter fibres, the dramatically reduced fibre count of longer product yields correspondingly less control of initial crack propagation.
'
Properties of reinforcement
When steel fibres are added to mortar, Portland cement concrete or refractory concrete, the flexural strength of the composite is increased from 25% to 100% - depending on the proportion of fibres added and the mix design. Steel fibre technology actually transforms a brittle material into a more ductile one. Catastrophic failure of concrete is virtually eliminated because the fibres continue supporting the load after cracking occurs. And while measured rates of improvement vary, Steel fibre reinforced concrete exhibits higher post-crack flexural strength, better crack resistance, improved fatigue strength, higher resistance to spalling, and higher first crack strength, Figure 2 shows concrete flexural strengths when reinforced at various fibre proportions. Additionally, deformed fibres provide a positive mechanical bond within the concrete matrix to resist pull-out. Steel fibres are available in lengths from 38 mm to 50 mm and aspect ratios between 40 and 60. The fibres are manufactured either deformed or hook end, and conform to ASTM A-820.
 
'
Steel fibre reinforced concrete (SFRC) Floor slabs. 
Conventional practice usually concentrates welded wire fabric reinforcement within a single plane of a floor slab. Fabric does very little to reinforced the outer zones, which is why spalling is common at the joints and edges. The primary function of welded wire fabric is to hold the floor slab together after the first small hairline cracks have propagate to larger fractures. This serves to maintain some degree of "structural integrity". Conventional wisdom's approach to floor slabs is to maintain "material integrity" through SFRC mix designs. This integrity is accomplished by: 
Increasing the initial first crack strength.
Large numbers of fibres intercepting the micro-cracks and preventing propagation by controlling tensile strength.
Unlike rebar and welded wire fabric, fibres are dispersed throughout the slab to reinforce isotropically, so there is no weak plane for a crack to follow.
Increases in flexural strength can make it possible to use a thinner slab and eliminate the cumbersome welded wire fabric.
Whether it is for lighter duty commercial service or for heavy manufacturing, SFRC slabs are capable of withstanding any load. The only variable is the addition rate of fibre, which could be as low as 12.5kg/m3 to as high as 100 kg/m3.
'
How they save time and money
COMPLETELY ELIMINATE STEEL FABRIC REINFORCEMENT, SAVING ON BOTH MATERIALS AND LABOUR
Reduce slab thickness giving savings in concrete and placement costs.
Possibilities of wider joint spacing. Save on joint forming costs and joint maintenance
Simplicity of construction. Simpler joints and no more errors in steel fabric positioning
Increase speed of construction. Save time and reduce costs.
'
Technical and user benefits
Significantly reduced risk of cracking.
Reduced spalling joint edges.
Stronger joints.
High impact resistance.
Greater fatigue endurance.
Reduced maintenance costs.
Longer useful working life
'
Typical areas of applications include
Industrial Ground Floor Slabs ' Warehouses, Factories, Aircraft Hangers, Roads, Bridge Decks, Parking Areas, Runways, Aprons and Taxiways, Commercial and Residential Slabs, Piling, Shotcrete, Tunnels, Dams and stabilisation.
'
Improved strength and durability
Steel fibre reinforced concrete is a castable or sprayable composite material of hydraulic cements, fine, or fine and coarse aggregates with discrete steel fibres of rectangular cross-section randomly dispersed throughout the matrix. Steel fibres strengthen concrete by resisting tensile cracking. Fibre reinforced concrete has a higher flexural strength than that of unreinforced concrete and concrete reinforced with welded wire fabric. But unlike conventional reinforcement ' which strengthens in one or possibly two directions ' Steel fibres reinforce iso tropically, greatly improving the concrete's resistance to cracking, fragmentation, spalling and fatigue. When an unreinforced concrete beam is stressed by bending, its deflection increases in proportion with the load to a point at which failure occurs and the beam breaks apart. This is shown in Figure 1. Note that the unreinforced beam fails at point A and a deflection of B. A Steel fibre reinforced beam will sustain a greater load before the fist crack occurs (point C). It will also undergo considerably more deflection before the beam breaks apart (point D). The increased deflection from point B to point D represents the toughness imparted by fibre reinforcement. The load at which the first crack occurs is called the "first crack strength". The first crack strength is generally proportional to the amount of fibre in the mix and the concrete mix design.
Two theories have been proposed to explain the strengthening mechanism. The first proposes that as the spacing between individual fibres become closer, the fibres are better able to arrest the propagation of micro cracks in the matrix. The second theory holds that the strengthening mechanism of fibre reinforcement relates to the bond between the fibres and the cement. It has been shown that micro cracking of the cement matrix occurs at very small loads. Steel fibres, then service as small reinforcing bars extending across the cracks. So as long as the bond between the fibres and cement matrix remains intact the Steel fibres can carry the tensile load. The surface area of the fibre is also a factor in bond strength. Bond strength can also be enhanced with the use of deformed fibres, which are available in a variety of sizes.
'
Product mix designs 
The proportions of Steel fibres in mix designs usually range from 0.2% to 2.0% (15 to 150 kg/m3 ) of the composite's volume. Key factors to consider largely depend on the application under consideration and/or the physical properties desired in the finished project. Mix designs with fibre proportions above 60kg/m3 are usually adjusted to accommodate the presence of millions of steel fibre reinforcing elements. The adjustments are an increase in the cement factor, a reduction in the top size of the coarse aggregate and the addition of a super plasticiser. Prototype testing is recommended to determine the optimum design for each application.
'
Advantages 
Reinforcing concrete with Steel fibres results in durable concrete with a high flexural and fatigue flexural strength, improved abrasion, spalling and impact resistance.
The elimination of conventional reinforcement, and in some cases the reduction in section thickness can contribute to some significant productivity improvements. Steel fibres can deliver significant cost savings, together with reduced material volume, more rapid construction and reduced labour costs.
The random distribution of Steel fibres in concrete ensures that crack free stress accommodation occurs throughout the concrete. Thus micro cracks are intercepted before they develop and impair the performance of the concrete.
Steel fibres are a far more economical design alternative. 
Disadvantages
Steel fibres will not float on the surface of a properly finished slab, however, rain damaged slabs allow both aggregate and fibres to be exposed and will present as aesthetically poor whilst maintaining structural soundness.
Fibres are capable of substituting reinforcement in all structural elements (including primary reinforcement), however, within each element there will be a point where the fibre alternative's cost saving and design economies are diminished.
Strict control of concrete wastage must be monitored in order to keep it at a minimum. Wasted concrete means wasted fibres.
'
PSI CRIMPED STEEL FIBER | SPC WEB
DESCRIPCIÓN
STEEL MACRO-FIBER
DESCRIPTION
 
PSI CRIMPED STEEL FIBER are low carbon, cold drawn steel wire bers designed to provide concrete with temperature and shrinkage crack control, enhanced exural reinforcement, improved shear strength and increase the crack resistance of concrete. PSI Crimped Steel Fiber complies with ASTM C, Standard Speci cation for Fiber Reinforced Concrete and Shotcrete and ASTM A820, Type I, Standard Speci cation for Steel Fibers for Fiber Reinforced Concrete. These steel macro- bers will also improve impact, shatter, fatigue and abrasion resistance while increasing toughness of concrete. Dosage rates will vary depending upon the reinforcing requirements and can range from 25 to 100 lbs/yd3 (15 to 60 kg/m3).
 
PRIMARY APPLICATIONS
 
Commercial and industrial slabs on ground
' Bridge decks, overlays and pavements
' Precast concrete applications
' Shotcrete, tunnel linings and slope stabilization ' Mass concrete and composite deck construction
 
FEATURES/BENEFITS
 
' Increases impact, shatter and abrasion resistance of concrete
' Reduces segregation, plastic settlement, and shrinkage cracking of concrete
' Provides three-dimensional reinforcement against macro-cracking
' Increases overall durability, fatigue resistance and texural toughness
' Reduction of in-place cost versus wire mesh for temperature / shrinkage crack control ' Easily added to concrete mixture at any time prior to placement
 
TECHNICAL INFORMATION
Additional reading:
Unlocking the Best: Key Questions to Ask When Ordering Steel Fiber Concrete Enhancement
 
Typical Engineering Data
Material '''''''''''''''''''''' low carbon cold drawn steel wire
Deformation'''''''''''''''''''.. continuously deformed circular segment
Typical Dosage Rates ''''''''''''''. 25 ' 100 lb/yd3 (15 ' 60 kg/m3)
Available Lengths''''''''''''''''.. 1 1'2' (38 mm), 2' (50 mm)
Aspect Ratio'''''''''''''''''''' 34, 45
Tensile Strength'''''''''''''''''.. 140 ' 180 ksi (966 '  MPa)
Appearance '''''''''''''''''''.. bright, clean wire
 
PACKAGING
 
PSI Crimped Steel Fibers are packaged in 55 lb (25 kg) bags;  net lbs ( kg) per pallet.
 
SHELF LIFE
 
3 years in original, unopened package.
 
DIRECTIONS FOR USE
 
PSI Crimped Steel fibers can be added to the concrete mixture at any time prior to placement of the concrete. It is generally recommended to add any fiber material at the ready-mix concrete plant during batching. The actual dosage rate will vary depending upon the application and performance requirements for each project. Fibers must be mixed with concrete for a minimum of four (4) to ve (5) minutes at maximum mixing speed, depending on the mixer type, to ensure complete dispersion and uniformity. The addition of PSI Crimped Steel Fiber, at provided dosage rates, will decrease the measured slump of concrete; however, additional water should not be added. The use of water reducers and/or superplasticizers, such as Eucon , Eucon MRX or the Plastol series of admixtures may be necessary to maintain desired workability.
Add other admixtures independently from fiber addition. When used properly, and placed in a concrete mix of sufficient workability, the fibers will not adversely alter the compressive or texural strength of concrete or shotcrete.
 
CLEAN-UP
 
Loose fiber material may be disposed in proper receptacles for refuse. Finishing equipment with fibers embedded in concrete should be thoroughly cleaned.
 
PRECAUTIONS/LIMITATIONS
 
' Use of fibers may cause an apparent loss in measured slump of concrete. This may be offset with the use of a water reducing admixture if necessary.
' Fibers should never be added to a 'zero-slump' concrete. Ensure a minimum concrete slump of 3' (80 mm) prior to addition of any fiber material. Fibers may also be added in loose form to aggregate charging devices.
' In all cases, consult the Material Safety Data Sheet before use.
 
Typical Engineering Data
Material '''''''''''''''''''''' low carbon cold drawn steel wire
Deformation'''''''''''''''''''.. continuously deformed circular segment
Typical Dosage Rates ''''''''''''''. 25 ' 100 lb/yd3 (15 ' 60 kg/m3)
Available Lengths''''''''''''''''.. 1 1'2' (38 mm), 2' (50 mm)
Aspect Ratio'''''''''''''''''''' 34, 45
Tensile Strength'''''''''''''''''.. 140 ' 180 ksi (966 '  MPa)
Appearance '''''''''''''''''''.. bright, clean wire
 
PACKAGING
 
PSI Crimped Steel Fibers are packaged in 55 lb (25 kg) bags;  net lbs ( kg) per pallet.
 
SHELF LIFE
 
3 years in original, unopened package.
 
DIRECTIONS FOR USE
 
PSI Crimped Steel fibers can be added to the concrete mixture at any time prior to placement of the concrete. It is generally recommended to add any fiber material at the ready-mix concrete plant during batching. The actual dosage rate will vary depending upon the application and performance requirements for each project. Fibers must be mixed with concrete for a minimum of four (4) to ve (5) minutes at maximum mixing speed, depending on the mixer type, to ensure complete dispersion and uniformity. The addition of PSI Crimped Steel Fiber, at provided dosage rates, will decrease the measured slump of concrete; however, additional water should not be added. The use of water reducers and/or superplasticizers, such as Eucon , Eucon MRX or the Plastol series of admixtures may be necessary to maintain desired workability.
Add other admixtures independently from fiber addition. When used properly, and placed in a concrete mix of sufficient workability, the fibers will not adversely alter the compressive or texural strength of concrete or shotcrete.
 
CLEAN-UP
 
Loose fiber material may be disposed in proper receptacles for refuse. Finishing equipment with fibers embedded in concrete should be thoroughly cleaned.
 
PRECAUTIONS/LIMITATIONS
 
' Use of fibers may cause an apparent loss in measured slump of concrete. This may be offset with the use of a water reducing admixture if necessary.
' Fibers should never be added to a 'zero-slump' concrete. Ensure a minimum concrete slump of 3' (80 mm) prior to addition of any fiber material. Fibers may also be added in loose form to aggregate charging devices.
' In all cases, consult the Material Safety Data Sheet before use.
If you want to learn more, please visit our website Refractory Anchors Manufacturer.