Where a "fibre only" solution can not reach the required strength for ULS or SLS a combined reinforcement is an excellent solution. Especially for meeting SLS conditions, adding Dramix steelfibers offer lots of benefits. The tension capacity of the steel fiber concrete will reduce the strain on the rebars. The distance between cracks will also be reduced. This results in much smaller crack openings enhancing the durability of the structure. In addition, the fibres also enhance the flexural moment resistance of the concrete section. Design rules exist to calculate crack openings and moment resistance for combined concrete structures. (Steelfibers and rebars )
@@dylanangel3143 Generally rebar per unit weight is indeed less expensive than steelfibers. However one has to consider the total cost of ownership (TCO) when making a price comparison. The amount of material (steel and concrete) needed to meet the design requirements, labour cost to apply the reinforcement, …. should be considered. For a lot of structures less steel and less concrete is needed. A reduction of construction time could result in an earlier start of the operational activity resulting in a faster return on investment ( ROI). Therefor a TCO analysis should be done on a case by case basis and is mostly favorable for the use of steelfibers.
Dramix steel fibers are coated with an innovative inhibitor to limit corrosion. Moreover, once the fibers are added to the concrete the possibility of corrosion reduces significantly. For more elaborate information check this link: bit.ly/3kKJ55F
I scrutinize about hybrid-fibers. What is the best (in terms of compression,flexural strengths,split tensile strength) hybridfiber percentage for 1m³ concrete by volume ? If i determine total volume %0.5 for 1m³ concrete, how much i use polypropylen and steel fibers? Or steel fiber and glassfiber?
From a structural perspective a combination of steel fibers and traditional rebar or steel mesh offer good strain compatibility (see design guidelines in Modelcode 2010 or the German DAfStb guideline.) It is proven that the steel fibers in this hybrid system offer substantially better crack control, improving the durability of the structure. Also for the ultimate limit state the fibres increase the resisting moment capacity. The optimal ratio depends on the project requirements and should be defined by design. For outdoor pavements, a hybrid system combining steel fibers with micro synthetic fibres is good solution. The micro synthetic fibres will reduce cracks due to plastic shrinkage while the steel fibers will increase the loading and fatigue capacity of the pavement. The optimal ratio 0,6 to 0,9 kg/m³ micro synthetic fibres added to the required dosage of steel fibers. This dosages should be defined by a design in function of the project requirements.
@@Bekaertchannel Thank you so much for your precious comment. I will scrutinize the Modelcode 2010. I will prepare 0.0135 m³ mini beam and i will use steel fibre (30mm) and polypropylen (12mm). Can you suggest me proportions?
For getting a first ‘feel’ of the product behavior in small beams we would propose to start with 30 kg/m³ steel fibers and 0,6 kg/m³ polypropylene fiber mix. After that, all combinations are possible, varying the steel fibers dosage between 20 and 40 kg/m³ and the PP fibers between 0.6 and 0.9 kg/m³. We would also compare the behavior with only steel fibers and only polypropylene fibers.
Steel is protected by the alkalinity of the concrete. However after some time the basicity of the concrete can decrease due to carbonatation. Once this protection has faded, corrosion will be initiated. When the Dramix® Steel fibre corrodes, due to the geometry of the fibres (thin diameter), the corrosion products do not exert stresses enough to crack the concrete, unlike in rebar, where this is a concern. Due to the discontinuous nature of reinforcement of Dramix®, they do not conduct the corrosion currents unlike Rebar mesh. Hence due to discontinuity, there is no propagation of corrosion even if it is initiated.
Huge problem, especially when its just small fibers. Better solution is glassfiber or a stiffer fibre like carbonfibre. And you get weight savings. 1-3% fibre makes a huge difference.
Our 45 years’ experience has proven that glued fibers provide good mixing properties. We have not seen any difference between long and small fibers. In-house tests show that neither glass nor carbon fibers offer better performance. For more details on steel fiber performance in a wide range of applications, please visit our website or contact our local sales/technical representatives. bit.ly/2S4fkho
Steelfibers can “fully” or “partially” replace longitudinal steel (mesh or rebar) in function of the application. It is up to the designer to assess how much of the traditional steel, if not everything, can be replaced. Steelfibers will have a positive impact on the ultimate limit state (ULS) and serviceability limit state (SLS). For the ULS, steelfibers will increase the moment capacity (MRd) and shear capacity (VRd) of the section. For the SLS, steelfibers reduce the crackwidth and increase post crack stiffness of the element resulting in higher durability and lower deflections.
Dear, at RCR Industrial Flooring, we use SFRC in most of our flooring projects (60 millions SF/y). For SOG, fibres are more efficient than conventional mesh to enhance bearing capacity of the slab and to control cracks (Silifibre). In higher dosages, we can even build jointless slabs (Conductil). For structural slabs (FOP Piletec, rafts Basetec), either a combination of mesh + SF, or "real" Structural Fibres (5D) only, will give the best result in terms of time of execution and safety. In this case design must be validated by independant designer (Monofloor is one).
Bekaert, can I please use your video content in a video I want to present... Might show your product being ''better than'' Helix... Also, is it possible to get some samples, I am willing to pay... Just want to know which location to contact... Finally, do you have any charts on ''supported spans"? (of course using your products)
Dear, you can definitely use this video to explain the technology of steel fibers. To receive some Dramix steel fibers, please send an email to infobuilding@bekaert.com.
The load capacity of a concrete pavement depends on several parameters such as but not limited to subbase, concrete quality, Dramix type and dosage. But with a stable subbase and a dosage of 33 pcy (or higher) of a Dramix 3D fibre the driveway should easily carry a Ford F150 truck (or similar). For more specific guidance and technical advice please contact our office in Marietta. ( +1 770 421 8520). For the construction of the concrete driveway follow the general national guidelines. (ACI 360, ACI 544,…)
Corrosion on steel fibers doesn’t affect the mechanical properties of the concrete. The fibers form a discontinuous network of reinforcements so the corrosion stays limited to the outer surface of the product. Because the fibers are small, the volume increase does not lead to concrete spalling either. If the visual aspect of the end product is important, many of our fibers come in galvanized variants as well as well to avoid any corrosion at all.
Thats going to erode very quickly unless you use very expensive stainless. Its better to just use glassfiber or moderately expensive carbon fibre. Makes for a lighter product aswell and wont erode.
Corrosion of steel fiber in concrete is not a problem. This independent of the size or diameter of the fibre. It is even generally accepted that steel fibres can have a very positive effect on the durability and lifespan of normal reinforced structures. The fibres keep the cracks smaller so decarbonization through the cracks is slowed down. We respect all sorts of building products and leave it to the designer to make the right choice of product, for the right applications, at the right cost. We see it as our task to provide technical information, based on extensive internal and external testing, codes and standards, so the designer can make a decision based on facts. However choosing against steel fibers out of concerns on corrosion would be a decision based on wrong assumptions. And this would be a pity because steel fiber concrete offers a lot of advantages to the construction world.
We did not use expensive stainless. The wires of Dramix are coated to avoid this type of erosion. And on the conventional steel used with concrete, you will have a lot more of this oxidation and erosion. We use steel fiber because the steel have more compatibility with concrete. Carbon fiber didn't.
The performance difference is only as good as the anchorage the concrete can provide. In lower strength concrete up to 40Mpa, there will be little difference in performance between these fibres or any other fibre suppliers similar shaped fibre. This video is misleading, as the claims can only be justified (if independently verified) in High Strength Precast concrete such as 80Mpa etc. where the concrete matrix is sufficient to allow the fibre hold longer.
Very good remark! The concrete strength is indeed a crucial parameter in the behaviour of steel fibres in cracked concrete sections. The type of fibre - which consists mainly of the type of anchorage, the wire strength and the wire elongation capacity - and the concrete strength are the 4 main parameters determining the concrete behaviour when cracked. The 5D fibre will indeed perform the best at very high concrete strengths, but already at the very common concrete classes C30/37 and C35/45, the difference is significant and relevant.
@@Bekaertchannel That is partly correct, as you will not see any performance difference in 25Mpa Footing mix. For example, if you tested a 1200 Mpa tensile strength fibre against a 1900 Mpa tensile strength fibre in a 25 Mpa mix of the same shape, there would be no difference in performance, due to the matrix not being sufficiently strong enough to show the fibre difference. In fact, testing in SCC at the same compressive strength will show more of a difference. This is one of the weak points of TR34 4th edition of relying on pin point values that are difficult to gauge in the real world and with so many variables. At least using Re3 values, it was expressed as a percentage of whatever concrete was to be used.
You are correct to state that a fibre with the same shape but a different tensile strength will not have any significant performance difference in a C25 concrete. But while keeping the same shape, a better performance can still be established by increasing the L/D (Length/diameter) ratio. On the other hand when we increase the tensile strength of the wire AND improve the anchorage of the fibre, the performance in a C25 will increase. That’s why a Dramix® 4D fibre with a tensile strength of 1800 N/mm² and improved hook has a significant better performance than a Dramix® 3D fibre with a tensile strength of 1200 N/mm². Alternatively, if a 4D shape would be combined with a 1200 N/mm² wire the fibre would snap at a certain crack opening rendering the material britle. The shape of the Dramix® steelfibers have been designed to make maximum use of the tensile strength capacity of the wire. The use of Re values are not in line anymore with EN testing standards and current design standards or guidelines. These guidelines use the fr1 and Fr3 (Fr4) values to calculate the moment capacity of a steelfiber reinforced concrete section.
@@Bekaertchannel There is an element of contradiction on your reply. The L/D does not change between 3D, 4D, 5D etc, therefore, why would the performance change? The tensile strength of the fibre will be irrelevant in 25Mpa concrete, regardless of how your fibre was tested. Some fibre companies are testing in high strength and then interpolating the values into lower strength concrete and this is morally wrong! You infer that a 4D fibre would snap at a certain crack width in 25Mpa concrete, but again this is misleading as it is only relevant in high strength concrete. I mentioned Re3 to explain to you that it was based on a residual strength of any concrete, rather than a specific concrete mix. Yes the EN is a Europeanised version of the Japanese Test method, but all that has been achieved with this new test method is provide a more specific Moment Capacity value to use in a design. That is fine, providing all the concrete mixes are the same as was tested. This is where the problem rises, as some manufacturers are quoting high Fr1 numbers derived from high strength concrete mixes which are then used in low strength concrete. Using the Re3 method eliminates this ambiguity (which is still current under ACI by the way) as it tests for the Residual strength of the concrete which is expressed as a percentage. Therefore, the same value Re3 % can be applied to any concrete mix for more "Real world numbers"!
Dear Andrew. I would invite you to read my earlier reply more closely without a biased mind. Within a fibre family such as 3D a higher L/D ratio will improve the performance. For a given L/D ratio a 5D will provide better performance than the 4D which in its turn will outperform the 3D. I did not state that a 4D would snap at a certain crack width in a C25 concrete. I stated the a 4D hook with a wire strenght of 1100 MPa. (similar to 3D) could snap. Just indicating that the improved 4D hook needs a higher tensile strenght of 1650 to 1800 MPa. If you would require a more indepth discussion on these topics I invite you to take contact with our local people in Australia. : bosfa.com/contact-us/
Such a lying opening statement for sales purposes. Building inspectors, where I live, do not allow steel fiber to replace rebar. Concrete is brittle? Then why are Roman Concrete structures still standing? There is a reason concrete is used; MASSIVE COMPRESSIVE STRENGTH which means LOAD BEARING CAPACITY. NOT BRITTLE! Your "load bearing capacity" animation implies that concrete has little compressive strength, yet it is an animation for tensile stress, which rebar is far superior to fibers if you must choose one. Concrete is reinforced by steel rebar to aid against tensile stress and shear stress but these stresses are much less when more compressive stress is added to the concrete. This means concrete is not brittle, it's CONCRETE!!! Steel fiber is an additive to steel rebar, not a substitution to tying less rebar like this sales pitch implies.
Concrete is indeed used in the first place for its great resistance against compressive stresses. Nevertheless, in many concrete structures nowadays, important tensile stresses are also present (not like the Roman structures). Unreinforced concrete behaves very brittle under tension and this is a major safety risk in structures. Rebar can overcome this behavior, but steel fibers too! The choice between rebar and steel fibers depends mainly on the type of structure. The TCO and technical requirements are key here. For example, in case of tunnel segments and industrial floors, steel fibers are clearly the preferred choice.
@@Bekaertchannel It is a strawman argument to suggest that Roman Concrete did not experience significant tensile stress over 2,000 years on the earthquake-prone Italian peninsula; even aqueducts spanning across rivers still exist today given that fact. The first line of this video is "concrete is brittle". Are you willing to retract from this belief? I agree that modern structures such as bridges are under more extreme stresses and require reenforcement, but reenforced concrete has been around for over 125 years, while steel fiber just 40 years; and as I claimed previously, most cities and counties where I live do not allow footers without steel rebar, fiber is just an additive. You can't make rope out of concrete "tensile strength", but while It doesn't even mention TCO in the video, the main argument is that concrete is brittle! Are you going to stand adamantly to that claim?
Unreinforced concrete is brittle by nature. Let’s substantiate this with a theoretical analysis. The uniaxial strain of concrete under tension can be defined with the following formula ε_ct=f_ctm/E_cm f_ctm : Uniaxial tensile stress of concrete (N/mm²) E_cm : Tangent modulus of elasticity of concrete (N/mm²) Let’s take a C30/37 concrete as example and base ourselves on values published in Eurocode 2: f_ctm = 2,9 N/mm² E_cm= 33.000 N/mm² ε_ct= 0,000088 Strain can also be defined with the following formula: ε_ct=∆l/l If we would cast a beam of 10m long (l) and fix it at the extremities the maximum elongation (∆l) the concrete can take before cracking would be ∆l=0,000088*10.000 mm 〖∆l〗_R=0,88 mm Alternately we all know concrete shrinks and the total shrinkage ( ε_cs) is comprised of two components: - Autogenous shrinkage strain : ε_(ca(∞))=2,5 (f_ck-10).〖10〗^(-6)=50.〖10〗^(-6) - Drying shrinkage strain : ε_(cd,∞)≈520.〖10〗^(-6) (For relative humidity of 40 %) - Total Shrinkage strain* : ε_cs=570.〖10〗^(-6) (* values for a C30/37) For the same beam of 10 m the structure will shrink : 〖∆l〗_E=5,7 mm. This means that the structure will shrink 6x more than the capacity of the material. I believe it is logical to conclude, that a restrained structure already cracking under its own physical behaviour, without even applying an external load can be called “brittle”. The Ancient Romans already knew this. That’s why their viaducts are constructed with arches so mechanistically the whole structure remains compression. The Parthenon in Rome is a unique marvel of engineering where the dome is in perfect equilibrium and fully under compression.
@@Bekaertchannel Thank You for doing the engineering proofs of what I have just said, concrete is not brittle when it remains under compression. Then why does your first claim in the video claim that concrete is brittle? I have never once implied that re-enforced concrete is not needed, and since re-enforced concrete has been around much longer than your product, it is my belief that the marketing should not be centered around a false claim, concrete is "brittle", which it is not, contrary to the initial claim in this video, and has been my central argument; rather, you should market your product as a new re-enforcement means of producing a better alternative to an already great product that has already built today's infrastructure.... Steel Rebar re-enforced concrete. Don't bash Concrete in your marketing. Instead bash the process of the labor it takes to place rebar.
In our video we don’t want to discredit any type of building material. When we mention concrete being brittle we intrinsically implied brittle under tension. That’s also why, immediately after the opening statement we show a beam under loading. We completely agree with you that there are no issues with concrete under compression. On the contrary, it’s a very good building material offering high value to the construction world. We thank you for pointing out a possible misinterpretation with the opening statement in the video.
Nothing explains better than good animation
Wonderful video guys!
thanks. this is wonderful information.
very useful
What about corrosion? Doesn’t steel fiber corrode like rebar?
That`s the reason that there are alternatives as pp monofilaments, basalt fibres.
great video
Thank you :)
Why dont make all fibers in 5D? save steel by curving it sounds more eco. love the products!
Yeah, it is but it's time intensive and needs to be reflected in the cost of the steel fibres.
@@flourishomotola5306 undersatand, thank you.
Outstanding 👌
La fibra Dramix no valdria con un hormigon c25 o c30? Gracias
So using metal straw in stone mud like hay straw in soil mud makes it stronger and much more durable. Should be very commercially viable.
Awesome. Keep it up
crimped fiber vs hooked end fiber , which one is good for ductility point of view
Do I need fibor for my indoor living room 10cm concrate floor?
Good 😊
Wouldnit be useful to add the steel fibers AND use rebar?
Where a "fibre only" solution can not reach the required strength for ULS or SLS a combined reinforcement is an excellent solution.
Especially for meeting SLS conditions, adding Dramix steelfibers offer lots of benefits. The tension capacity of the steel fiber concrete will reduce the strain on the rebars. The distance between cracks will also be reduced. This results in much smaller crack openings enhancing the durability of the structure. In addition, the fibres also enhance the flexural moment resistance of the concrete section.
Design rules exist to calculate crack openings and moment resistance for combined concrete structures. (Steelfibers and rebars )
@@Bekaertchannel rebar is cheaper
@@dylanangel3143 Generally rebar per unit weight is indeed less expensive than steelfibers.
However one has to consider the total cost of ownership (TCO) when making a price comparison. The amount of material (steel and concrete) needed to meet the design requirements, labour cost to apply the reinforcement, …. should be considered. For a lot of structures less steel and less concrete is needed. A reduction of construction time could result in an earlier start of the operational activity resulting in a faster return on investment ( ROI). Therefor a TCO analysis should be done on a case by case basis and is mostly favorable for the use of steelfibers.
What happens when all those fibers rust?
The surface of the building gets a varying rusty color. If you need a appearing surface it is better to use PP monofilaments.
What about rust ?
Dramix steel fibers are coated with an innovative inhibitor to limit corrosion. Moreover, once the fibers are added to the concrete the possibility of corrosion reduces significantly.
For more elaborate information check this link: bit.ly/3kKJ55F
I scrutinize about hybrid-fibers. What is the best (in terms of compression,flexural strengths,split tensile strength) hybridfiber percentage for 1m³ concrete by volume ? If i determine total volume %0.5 for 1m³ concrete, how much i use polypropylen and steel fibers? Or steel fiber and glassfiber?
From a structural perspective a combination of steel fibers and traditional rebar or steel mesh offer good strain compatibility (see design guidelines in Modelcode 2010 or the German DAfStb guideline.)
It is proven that the steel fibers in this hybrid system offer substantially better crack control, improving the durability of the structure. Also for the ultimate limit state the fibres increase the resisting moment capacity. The optimal ratio depends on the project requirements and should be defined by design.
For outdoor pavements, a hybrid system combining steel fibers with micro synthetic fibres is good solution. The micro synthetic fibres will reduce cracks due to plastic shrinkage while the steel fibers will increase the loading and fatigue capacity of the pavement.
The optimal ratio 0,6 to 0,9 kg/m³ micro synthetic fibres added to the required dosage of steel fibers. This dosages should be defined by a design in function of the project requirements.
@@Bekaertchannel Thank you so much for your precious comment. I will scrutinize the Modelcode 2010. I will prepare 0.0135 m³ mini beam and i will use steel fibre (30mm) and polypropylen (12mm). Can you suggest me proportions?
For getting a first ‘feel’ of the product behavior in small beams we would propose to start with 30 kg/m³ steel fibers and 0,6 kg/m³ polypropylene fiber mix. After that, all combinations are possible, varying the steel fibers dosage between 20 and 40 kg/m³ and the PP fibers between 0.6 and 0.9 kg/m³. We would also compare the behavior with only steel fibers and only polypropylene fibers.
Hello im from ecuador and i wnat to know if i can use steel fiber in concrete paviment that have a 0.15 or 0.20 cm of thickness ?
Hi Denisse. For specific questions like this you can contact our local representative, mr/ Ishay Colina at ishay.colina@bekaert.com.
U mean to say .20 m bro
But what about oxidation ?
Steel is protected by the alkalinity of the concrete. However after some time the basicity of the concrete can decrease due to carbonatation. Once this protection has faded, corrosion will be initiated. When the Dramix® Steel fibre corrodes, due to the geometry of the fibres (thin diameter), the corrosion products do not exert stresses enough to crack the concrete, unlike in rebar, where this is a concern. Due to the discontinuous nature of reinforcement of Dramix®, they do not conduct the corrosion currents unlike Rebar mesh. Hence due to discontinuity, there is no propagation of corrosion even if it is initiated.
Huge problem, especially when its just small fibers. Better solution is glassfiber or a stiffer fibre like carbonfibre. And you get weight savings. 1-3% fibre makes a huge difference.
Our 45 years’ experience has proven that glued fibers provide good mixing properties. We have not seen any difference between long and small fibers. In-house tests show that neither glass nor carbon fibers offer better performance. For more details on steel fiber performance in a wide range of applications, please visit our website or contact our local sales/technical representatives. bit.ly/2S4fkho
I think we can't replace fibers as complete steel reinforcement. It only improves the tensile strength of concrete by adding fibers.
Steelfibers can “fully” or “partially” replace longitudinal steel (mesh or rebar) in function of the application. It is up to the designer to assess how much of the traditional steel, if not everything, can be replaced. Steelfibers will have a positive impact on the ultimate limit state (ULS) and serviceability limit state (SLS). For the ULS, steelfibers will increase the moment capacity (MRd) and shear capacity (VRd) of the section. For the SLS, steelfibers reduce the crackwidth and increase post crack stiffness of the element resulting in higher durability and lower deflections.
Dear, at RCR Industrial Flooring, we use SFRC in most of our flooring projects (60 millions SF/y). For SOG, fibres are more efficient than conventional mesh to enhance bearing capacity of the slab and to control cracks (Silifibre). In higher dosages, we can even build jointless slabs (Conductil). For structural slabs (FOP Piletec, rafts Basetec), either a combination of mesh + SF, or "real" Structural Fibres (5D) only, will give the best result in terms of time of execution and safety. In this case design must be validated by independant designer (Monofloor is one).
Interesting, technology developed in Japan. But then again how many buildings clasped during an earthquake. Tensions strength overload. GG
Bekaert, can I please use your video content in a video I want to present... Might show your product being ''better than'' Helix...
Also, is it possible to get some samples, I am willing to pay... Just want to know which location to contact...
Finally, do you have any charts on ''supported spans"? (of course using your products)
Dear, you can definitely use this video to explain the technology of steel fibers. To receive some Dramix steel fibers, please send an email to infobuilding@bekaert.com.
@@Bekaertchannel , thank you kindly.
Is this good for a driveway 4" thick?
The load capacity of a concrete pavement depends on several parameters such as but not limited to subbase, concrete quality, Dramix type and dosage. But with a stable subbase and a dosage of 33 pcy (or higher) of a Dramix 3D fibre the driveway should easily carry a Ford F150 truck (or similar). For more specific guidance and technical advice please contact our office in Marietta. ( +1 770 421 8520). For the construction of the concrete driveway follow the general national guidelines. (ACI 360, ACI 544,…)
Which is code for use steel fibre concrete?
Hi Balwant. That depends on the application.
No comment on corrosion? Steel all the way up to the surface seems like a major issue.
Corrosion on steel fibers doesn’t affect the mechanical properties of the concrete. The fibers form a discontinuous network of reinforcements so the corrosion stays limited to the outer surface of the product. Because the fibers are small, the volume increase does not lead to concrete spalling either. If the visual aspect of the end product is important, many of our fibers come in galvanized variants as well as well to avoid any corrosion at all.
Thats going to erode very quickly unless you use very expensive stainless. Its better to just use glassfiber or moderately expensive carbon fibre. Makes for a lighter product aswell and wont erode.
Corrosion of steel fiber in concrete is not a problem.
This independent of the size or diameter of the fibre. It is even generally accepted that steel fibres can have a very positive effect on the durability and lifespan of normal reinforced structures. The fibres keep the cracks smaller so decarbonization through the cracks is slowed down.
We respect all sorts of building products and leave it to the designer to make the right choice of product, for the right applications, at the right cost. We see it as our task to provide technical information, based on extensive internal and external testing, codes and standards, so the designer can make a decision based on facts. However choosing against steel fibers out of concerns on corrosion would be a decision based on wrong assumptions. And this would be a pity because steel fiber concrete offers a lot of advantages to the construction world.
Agree and I don't buy their explanation below.
We did not use expensive stainless. The wires of Dramix are coated to avoid this type of erosion. And on the conventional steel used with concrete, you will have a lot more of this oxidation and erosion. We use steel fiber because the steel have more compatibility with concrete. Carbon fiber didn't.
I don't see your advertisement
Are you available in India?
Yes, we are, contact me @ 9884804043, Chennai.
anyone thinking about 3d printing a structure?
The performance difference is only as good as the anchorage the concrete can provide. In lower strength concrete up to 40Mpa, there will be little difference in performance between these fibres or any other fibre suppliers similar shaped fibre. This video is misleading, as the claims can only be justified (if independently verified) in High Strength Precast concrete such as 80Mpa etc. where the concrete matrix is sufficient to allow the fibre hold longer.
Very good remark! The concrete strength is indeed a crucial parameter in the behaviour of steel fibres in cracked concrete sections. The type of fibre - which consists mainly of the type of anchorage, the wire strength and the wire elongation capacity - and the concrete strength are the 4 main parameters determining the concrete behaviour when cracked.
The 5D fibre will indeed perform the best at very high concrete strengths, but already at the very common concrete classes C30/37 and C35/45, the difference is significant and relevant.
@@Bekaertchannel That is partly correct, as you will not see any performance difference in 25Mpa Footing mix. For example, if you tested a 1200 Mpa tensile strength fibre against a 1900 Mpa tensile strength fibre in a 25 Mpa mix of the same shape, there would be no difference in performance, due to the matrix not being sufficiently strong enough to show the fibre difference. In fact, testing in SCC at the same compressive strength will show more of a difference. This is one of the weak points of TR34 4th edition of relying on pin point values that are difficult to gauge in the real world and with so many variables. At least using Re3 values, it was expressed as a percentage of whatever concrete was to be used.
You are correct to state that a fibre with the same shape but a different tensile strength will not have any significant performance difference in a C25 concrete. But while keeping the same shape, a better performance can still be established by increasing the L/D (Length/diameter) ratio.
On the other hand when we increase the tensile strength of the wire AND improve the anchorage of the fibre, the performance in a C25 will increase. That’s why a Dramix® 4D fibre with a tensile strength of 1800 N/mm² and improved hook has a significant better performance than a Dramix® 3D fibre with a tensile strength of 1200 N/mm². Alternatively, if a 4D shape would be combined with a 1200 N/mm² wire the fibre would snap at a certain crack opening rendering the material britle.
The shape of the Dramix® steelfibers have been designed to make maximum use of the tensile strength capacity of the wire.
The use of Re values are not in line anymore with EN testing standards and current design standards or guidelines. These guidelines use the fr1 and Fr3 (Fr4) values to calculate the moment capacity of a steelfiber reinforced concrete section.
@@Bekaertchannel There is an element of contradiction on your reply. The L/D does not change between 3D, 4D, 5D etc, therefore, why would the performance change? The tensile strength of the fibre will be irrelevant in 25Mpa concrete, regardless of how your fibre was tested. Some fibre companies are testing in high strength and then interpolating the values into lower strength concrete and this is morally wrong! You infer that a 4D fibre would snap at a certain crack width in 25Mpa concrete, but again this is misleading as it is only relevant in high strength concrete.
I mentioned Re3 to explain to you that it was based on a residual strength of any concrete, rather than a specific concrete mix. Yes the EN is a Europeanised version of the Japanese Test method, but all that has been achieved with this new test method is provide a more specific Moment Capacity value to use in a design. That is fine, providing all the concrete mixes are the same as was tested. This is where the problem rises, as some manufacturers are quoting high Fr1 numbers derived from high strength concrete mixes which are then used in low strength concrete. Using the Re3 method eliminates this ambiguity (which is still current under ACI by the way) as it tests for the Residual strength of the concrete which is expressed as a percentage. Therefore, the same value Re3 % can be applied to any concrete mix for more "Real world numbers"!
Dear Andrew. I would invite you to read my earlier reply more closely without a biased mind.
Within a fibre family such as 3D a higher L/D ratio will improve the performance. For a given L/D ratio a 5D will provide better performance than the 4D which in its turn will outperform the 3D.
I did not state that a 4D would snap at a certain crack width in a C25 concrete. I stated the a 4D hook with a wire strenght of 1100 MPa. (similar to 3D) could snap. Just indicating that the improved 4D hook needs a higher tensile strenght of 1650 to 1800 MPa.
If you would require a more indepth discussion on these topics I invite you to take contact with our local people in Australia. : bosfa.com/contact-us/
Can I get your contact sir?
Dear, can you tell us where you live so we can immediately put you in touch with our local Dramix specialist?
I live and work in Doha,Qatar as a structural engineer with Gwall company
I want to learn complete design of steel fibre reinforced concrete
earthquake I wanna build a villa
Such a lying opening statement for sales purposes. Building inspectors, where I live, do not allow steel fiber to replace rebar. Concrete is brittle? Then why are Roman Concrete structures still standing? There is a reason concrete is used; MASSIVE COMPRESSIVE STRENGTH which means LOAD BEARING CAPACITY. NOT BRITTLE! Your "load bearing capacity" animation implies that concrete has little compressive strength, yet it is an animation for tensile stress, which rebar is far superior to fibers if you must choose one. Concrete is reinforced by steel rebar to aid against tensile stress and shear stress but these stresses are much less when more compressive stress is added to the concrete. This means concrete is not brittle, it's CONCRETE!!! Steel fiber is an additive to steel rebar, not a substitution to tying less rebar like this sales pitch implies.
Concrete is indeed used in the first place for its great resistance against compressive stresses. Nevertheless, in many concrete structures nowadays, important tensile stresses are also present (not like the Roman structures). Unreinforced concrete behaves very brittle under tension and this is a major safety risk in structures. Rebar can overcome this behavior, but steel fibers too! The choice between rebar and steel fibers depends mainly on the type of structure. The TCO and technical requirements are key here. For example, in case of tunnel segments and industrial floors, steel fibers are clearly the preferred choice.
@@Bekaertchannel It is a strawman argument to suggest that Roman Concrete did not experience significant tensile stress over 2,000 years on the earthquake-prone Italian peninsula; even aqueducts spanning across rivers still exist today given that fact. The first line of this video is "concrete is brittle". Are you willing to retract from this belief? I agree that modern structures such as bridges are under more extreme stresses and require reenforcement, but reenforced concrete has been around for over 125 years, while steel fiber just 40 years; and as I claimed previously, most cities and counties where I live do not allow footers without steel rebar, fiber is just an additive. You can't make rope out of concrete "tensile strength", but while It doesn't even mention TCO in the video, the main argument is that concrete is brittle! Are you going to stand adamantly to that claim?
Unreinforced concrete is brittle by nature. Let’s substantiate this with a theoretical analysis. The uniaxial strain of concrete under tension can be defined with the following formula
ε_ct=f_ctm/E_cm
f_ctm : Uniaxial tensile stress of concrete (N/mm²)
E_cm : Tangent modulus of elasticity of concrete (N/mm²)
Let’s take a C30/37 concrete as example and base ourselves on values published in Eurocode 2:
f_ctm = 2,9 N/mm²
E_cm= 33.000 N/mm²
ε_ct= 0,000088
Strain can also be defined with the following formula:
ε_ct=∆l/l
If we would cast a beam of 10m long (l) and fix it at the extremities the maximum elongation (∆l) the concrete can take before cracking would be
∆l=0,000088*10.000 mm
〖∆l〗_R=0,88 mm
Alternately we all know concrete shrinks and the total shrinkage ( ε_cs) is comprised of two components:
- Autogenous shrinkage strain : ε_(ca(∞))=2,5 (f_ck-10).〖10〗^(-6)=50.〖10〗^(-6)
- Drying shrinkage strain : ε_(cd,∞)≈520.〖10〗^(-6) (For relative humidity of 40 %)
- Total Shrinkage strain* : ε_cs=570.〖10〗^(-6)
(* values for a C30/37)
For the same beam of 10 m the structure will shrink :
〖∆l〗_E=5,7 mm.
This means that the structure will shrink 6x more than the capacity of the material.
I believe it is logical to conclude, that a restrained structure already cracking under its own physical behaviour, without even applying an external load can be called “brittle”.
The Ancient Romans already knew this. That’s why their viaducts are constructed with arches so mechanistically the whole structure remains compression.
The Parthenon in Rome is a unique marvel of engineering where the dome is in perfect equilibrium and fully under compression.
@@Bekaertchannel Thank You for doing the engineering proofs of what I have just said, concrete is not brittle when it remains under compression. Then why does your first claim in the video claim that concrete is brittle? I have never once implied that re-enforced concrete is not needed, and since re-enforced concrete has been around much longer than your product, it is my belief that the marketing should not be centered around a false claim, concrete is "brittle", which it is not, contrary to the initial claim in this video, and has been my central argument; rather, you should market your product as a new re-enforcement means of producing a better alternative to an already great product that has already built today's infrastructure.... Steel Rebar re-enforced concrete. Don't bash Concrete in your marketing. Instead bash the process of the labor it takes to place rebar.
In our video we don’t want to discredit any type of building material. When we mention concrete being brittle we intrinsically implied brittle under tension. That’s also why, immediately after the opening statement we show a beam under loading. We completely agree with you that there are no issues with concrete under compression. On the contrary, it’s a very good building material offering high value to the construction world.
We thank you for pointing out a possible misinterpretation with the opening statement in the video.