Masonry reinforcement FAQ

The most important requirement is to make sure that your base polymer is compatible with the polymer coating and/or the sizing of the Beki-shield® grains. Our datasheets provide clear recommendation of which base polymers are compatible with our different types of Beki-shield® grains. The second most important consideration is the processing temperature. This should be in the range defined in the datasheets to make sure that the sizing and/or the coating dissolves correctly. (Depending on the type of product, only sizing will be present, or sizing and coating). This will ensure that all the grains open up easily and disperse well in order to create a good electrically conductive network in the plastic component.

No failures of the plastic liner due to fiber punctures have ever been identified. the abrasion from sharp aggregates during placement of the concrete poses just as big of a threat to the liner as do the steel fibers. After placement the fibers tend to move around and re-orient themselves during vibration which relieves any pressure of an individual fiber on the liner created during placement. Many projects using SFRC are constructed with cast-in-place and sprayed shotcrete directly in contact with waterproof membranes.

No, with good jobsite safety practices in place steel fibers shall not impose any safety concerns. Please refer to our safety data sheets for further information.

Bekaert’s metal fiber filtration media are suitable for both in-depth filtration and surface filtration. Here’s a short explanation of the main differences between these two types of filtration.

In-depth filtration

This is when the contaminants or particles that have to be removed from the flow are captured within the structure of the filter medium. In other words, the particles penetrate the medium and get captured inside.

An in-depth filter has a 3D-structure and mostly consists of multiple layers. For the multiple layer media, the coarser fiber layers are placed at the flow-in side. Coarser particles are stopped by the coarser layer. Only small particles are held in the fine layer. This prevents premature blocking of the medium and increases the dirt holding capacity and on-stream lifetime.

In-depth filtration is mainly used for the filtration of liquids. A typical example is the filtration of polymers.

Since the contaminants penetrate the filter medium, off-line cleaning will be required in order to clean the filter.

Surface filtration

As its name suggests, with surface filtration the particles are stopped at the surface layer of the filter medium. The pore size will determine the size of particles that are stopped.

In many cases, the filter medium will have a multi-layer structure, with the finer fiber layers at the upstream side of the flow. The particles will form a dense cake layer at the surface of the filter. This cake formation can increase the filtration efficiency, as finer particles are retained in the dense cake.

In surface filtration, the cake formation will cause an increasing pressure drop across the filter. In the case of liquids, when the pressure drop becomes too high, a reverse filtrate flow can be initiated to remove the cake. This is called backwashing or back-flushing. In the case of gases, the cake is blown off the candle with a short blow of gas against the hot gas flow. This is called back-pulsing.

Surface filtration can be applied in both liquid and gas filtration, especially for fine filtration.

Yes, but expect a 0.4” to 1.2” slump loss through the hose depending on the steel fiber dose rate, ambient temperatures and hose length. A midrange water reducing agent (MrWr) is commonly used to enhance workability and ease of flow through pump lines. High-range water reducers (HrWr) may be required in some cases. Typically, a 4” diameter hose is required.

Yes. Introduce steel fibers after all other ingredients are already in the truck. Set the truck mixer on charging speed and add the fibers slowly into the mixer. Mix for about 5 minutes at charging speed.
The steel fibers can also be added to the aggregate batch belt, if there is safe access.

Yes, also adding fibers on site to the truck mixer is feasible. Gradually dose fibers in the mix, this is typically done via a conveyor belt.

Steel fibers can be used in concrete, mortar and grout. Generally harsh mixtures, containing very few amount of fines and/or an unsteady sieve curve at a higher fiber volume can create mixing and dispersion problems. Simply mixing steel fibers into any concrete will most probably not utilize all the positive effects fibers can provide to concrete. Depending on the type and amount of fibers adjustments to the concrete mix may need to be made.
For example:

• Increasing the content of fines
• Adjusting the grading curve
• Adjusting the amount of plasticizer

For concrete strength up to an actual strength of around 8000 psi typical fibers with normal strength wire are sufficient (majority of applications). For higher concrete strength´s than middle strength or high strength, fibers can be required to avoid a brittle behaviour. If special cements, aggregates or admixtures are used (seldom the case), a preliminary mix/pump test is recommended.

Yes, the addition of steel fibers at typical dosage rates of 25 to 65 lb/yd3 will reduce the apparent slump by 1” to 3”. However, this does not necessarily equal a reduction in workability. Use of vibratory consolidation, restores the workability to the SFRC.

The Beki-shield® product does slightly increase the strength of the final product. If you are looking for solutions specifically to increase the strength of plastics and composites through the use of stainless steel fibers, check out our detailed information on composite reinforcement with stainless steel fibers.

Yes, this EPD certificate follows the EN15804, followed by most other national certification agencies.

In those countries where regulations differ from EPD standards, we will involve the relevant parties to assess the differences and decide whether additional certification is required.

For cast insitu, internal vibration is the most used option to consolidate the concrete. Form vibration is generally used in the precast industry.

When steel fiber concrete is cast into form work a small amount of vibration of the forms helps keep the fibers from touching the forms and thereby from being visible when the forms are removed. For example, during casting of steel fiber reinforced precast structures, the forms are vibrated to consolidate the concrete. This action results in an almost fiber free surface of the structures. So allowing a short period of form vibration in the all cast-in-place structures, in addition to internal vibration where possible, will provide the best finished surface.

Please contact our headquarters. We will put you in touch with the relevant R&D and technical application engineers who can help you select the right material or can design the right product specifically for your needs. Also in the other regions outside Europe we have highly skilled technical and commercial people available who can respond to your specific requests.

The post crack strength of steel fiber concrete is a material property which is commonly used to differentiate fiber performance. This will typically be determined with a bending test and is often referred to as the residual flexural strength (see below). For the same concrete composition, steel fiber performance is a function of fiber length, diameter, aspect ratio, anchorage and tensile strength. A fiber dosage alone has no performance related value at all. AStM international has two flexural testing procedures for fiber reinforced concrete. The two testing procedures are AStM c1399 Standard test Method for obtaining Average residual-Strength of Fiber-reinforced concrete and AStM c1609 Standard test Method for Flexural Performance of Fiber-reinforced concrete. Bekaert propose the use of AStM c1609. AStM c1399 can lead to inflated post crack flexural strengths due to favorable fiber orientation and the use of a steel plate to control the first crack’s energy release.

The most important aspect for successful use of the Beki-shield® product is to make sure that the amount of shear is sufficient to open the pellets but not too much to break up the fibers in the  conductive network. The Beki-shield® grains, which contain stainless steel fibers, provide electrical conductivity by making a conductive network in the plastic part. If the shear forces are excessive, the fiber length is reduced too much, and it will become more difficult for the fibers to form the network. If this happens, the electrical conductivity of the final part will be reduced. On the other hand, it is important to have a certain amount of shear present during the processing, as shown in the figure below. Insufficient shear leads to granulates, which will also make it difficult for the stainless steel fibers to form a conductive network.

Relation of SE (= Shielding Effectiveness) vs SHEAR FORCES

Our datasheets provide clear recommendations on the parameters that influence the shear during the compounding and injection molding processes. Bekaert’s experienced application engineers are also available to help you fine-tune the settings of your processing to make sure you reach the best conductivity possible with our Beki-shield® products.

Due to the very low load levels, which are needed to reach the right levels of electrical conductivity for electromagnetic interference (EMI) shielding or electrostatic discharge (ESD) protection, the Beki-shield® products have an insignificant impact on the mechanical properties of the end product. This is clear from the figure below which compares carbon fiber (CF) with the stainless steel fibers of the Beki-shield® product. You can see that the reduction in impact strength to reach the same level of EMI shielding is significantly less with the stainless steel fibers of the Beki-shield® product than with the CF product. Do not hesitate to contact us for more information on the test below or other mechanical properties.

Bekaert recommends continuing mixing at the highest drum speed for about 4 to 5 minutes after all steel fibers are added to the truck.

Steel fiber mix designs are similar to those commonly used for plain concrete mixes. Recommended aggregate gradations and mix proportions are provided in local standards. Using the largest practical top size aggregate and a well-graded combined aggregate blend as opposed to a gap-graded blend can minimize shrinkage. Steel fibers may cause a reduction in slump due to their stiffness. This does not necessarily equal a reduction in workability. Depending on ambient temperatures and placement method, mid-range water reducers are commonly used to enhance workability for mixes with more than 30 to 40 pounds per cubic yards of steel fibers.

Along with the Fraunhofer Institute in Germany, Bekaert has conducted extensive research on the impact of stainless steel fibers on the wear of processing equipment. Tests were performed with four different polymer compounds containing four different types of fillers. In the DKI platelet test we analyzed the wear on test plates that consisted of steel typically used to manufacture cylinders or barrels of extruders. The measurements of the weight loss of the test plates and visualization of the wear pattern by chromatic confocal microscopy gave a clear indication of the impact on the wear by the different filler materials. The table below shows that the stainless steel fibers of the Beki-shield® product make no difference to wear compared to the results obtained with the pure polymer without filler materials. This is mainly due to the fact that the stainless steel fibers are very ductile, and only low amounts need to be added to reach the desired levels of conductivity. Do not hesitate to contact us for more information or to receive the complete test report.

Typical steel fiber reinforced concrete contains less than 0.5% vol. Steel fibers and hardly more than 0.75% vol. Those fibers are discontinuous and not connected to each other. Tests only show a slight decrease in electrical resistivity due to the addition of steel fibers. However, the resistance to current flow is still substantial. Effects from moisture content and aggregate composition are much more dominant than the addition of steel fibers.

Steel fiber concrete compresses the construction schedule, allows for alternative construction methods or design solutions and increases durability. When a project is delivered quicker with fewer efforts and labor, the higher costs of the steel fibers are overcompensated by the savings.

In certain applications the volume weight of steelfibers is lower as the rebar for a similar reinforcing effect. For those applications the cost/reinforcement is lower for steelfibers.

Click here to learn more.

Electromagnetic Interference (EMI) is caused by electromagnetic waves, which can originate from all sorts of different man-made or natural sources (e.g. lightning, power converters, radio antennas, wireless connection, computer clocks, ….). These electromagnetic waves can disturb the proper functioning of sensitive electronic equipment. In some cases, this interference is unacceptable and the correct functioning of your equipment needs to be guaranteed (e.g. anti-collision sensors in a car, EMG equipment, ….). In these cases it is required that a barrier is created in the housing (conductive plastic) which can act as a shield to prevent electromagnetic waves from leaving their source or entering the equipment which needs to be protected.

The barrier functions on the principle of the Faraday cage. As shown in the figure below, the Faraday cage will ensure that the power of the incoming wave is reflected and absorbed. By doing so it will reduce the power of the outgoing wave. The shielding effectiveness (SE) of this boundary is a clear indication of how well the boundary can reduce the incoming power of the electromagnetic wave. The higher the SE, the better the boundary will prevent electromagnetic waves from leaving their source or from entering the electrical device.

Shielding effectiveness is determined by the frequency, the distance from the source, the type of electromagnetic field (near or far field), the magnetic permeability, the electrical conductivity and the thickness of the boundary. The stainless steel fibers of the Beki-shield® product will make sure that the plastic housing of your electronic equipment reaches extremely high levels of electrical conductivity and thus high levels of shielding effectiveness at very low load levels. This is shown in the figure below, which compares nickel-coated carbon fiber, carbon fiber and Beki-shield®. Our white paper goes into more detail on the exact functioning of EMI shielding and how Beki-shield® provides the highest shielding effectiveness possible.

Electrostatic discharge (ESD) is a common phenomenon in daily life, usually experienced as a small electric shock after touching a metal item that is electrically isolated from the ground. ESD is caused by the difference in electrical charge between an electrically loaded item and the ground. In most cases this phenomenon is rather harmless, but in some situations it can cause damage to electronic equipment, or lead to dangerous situations in explosion-proof environments.

To prevent electrostatic charges from building up and releasing as sparks, the metal fibers from the Beki-shield® product, when added to a plastic component, create a conductive matrix. In this way the electrical charges can be reduced by “bleeding off” over the grounded part, or from contact with the air. The Beki-shield® product performs an additional valuable role by allowing metal parts to be replaced with lightweight plastic parts. Furthermore, it gives you the option to color your final product while maintaining the required electrical conductivity. Our white paper provides more information on ESD protection and how the Beki-shield® product can improve it.

An Environmental Product Declaration (EPD) is an independently verified and registered report that communicates transparent and comparable information about the lifecycle environmental impact of products in a credible way. An EPD is compliant with the ISO 14025 standard.          

Bekaert wants to help customers improve the sustainability of their construction/building assets and has therefore worked with ITB to obtain an EPD certification for its Dramix® portfolio, manufactured in Petrovice (Czech Republic), our largest manufacturing plant, as well as in Lonand (India) and Karawang (Indonesia).

Other plants will follow the same process in the near future, with our goal to have our full portfolio covered by end of 2022.

In addition, we are working with  One Click LCA to enable customers to efficiently compare Dramix® based solutions for the sustainability advantages they bring on construction/building assets and processes. It gives a base for comparison with alternative (mainly traditional) reinforcement solutions and it reinforces our commitment to incorporate lifecycle assessment into our sustainability ambition.

The residual flexural strength is equal to the post crack flexural strength of steel fiber concrete corresponding to a certain deflection in a beam bending test. It is a value from testing which has been introduced for the design of steel fiber concrete.

Steel fiber reinforced concrete is an alternative to traditional reinforced concrete for certain application areas. Steel fibers are a discontinous, 3-dimensionally orientated, isotropic reinforcement, once they are mixed into the concrete. Steel fibers bridge the crack at very small crack openings, transfer stresses and develop post crack strength in the concrete.

A variety of fiber types (material, shape, size...) are available, their effect in concrete varies. Therefore steel fiber reinforced concrete shall never be simplified as a “concrete with steel fibers”. Steel fibers may be divided into five groups:

• Type I - cold-drawn wire
• Type II - cut sheet
• Type III - melt-extracted
• Type IV - shaved cold drawn wire
• Type V - milled from blocks

The vast majority belongs to group I. the common and most performing anchorage type is the “hooked end”. For the same type of fiber, length/diameter and tensile strength have the biggest influence on fiber performance. The higher the l/d ratio, the better the performance of the steel fiber reinforced concrete.

Mechanically anchored steel fibers have been proven as reinforcement, even for structural application. Steel fibers are made from a material with well known engineering properties; e modulus, Poisson’s ratio, tensile strength and creep. The e-modulus of steel is greater than that of concrete. Thus, the steel fibers pick up the stresses quickly and affect the cracking process immediately. The long term load carrying capacity of the steel fiber reinforced concrete is significant. Steel fibers have a material specification of AStM A820. Macro synthetic fibers come in a large variety and have very different material properties. Macro synthetic fibers do not have a material specification in AStM. All macro synthetic fibers do have an e-modulus lower then that of concrete and relatively low tensile strengths. Thus, macro synthetic fibers need a certain crack width to occur prior to being able to engage in the concrete and then only moderate post crack strength values can be achieved. Macro synthetic fibers are also subject to creep which makes the long term loading capacity of the fiber lower or non existent. The rate of creep can be increased with increased ambient temperatures.

There are at least four factors to review when considering reinforcement; Modulus of elasticity, Poisson’s ratio, tensile strength and creep..

Steel fibers are not a replacement of synthetic micro fibers and vice versa. Both fiber types provide very different properties to concrete so that the applications fields do not overlap. Rather than a substitute, both fiber types may be used complementary. While steel fibers offer post crack strength and thus act as reinforcement, synthetic micro fibers reduce cracking due to plastic shrinkage and improve the fire resistance of concrete. They do not provide any reinforcing effect.

The equivalent diameters of metal fibers range from 1 to 100 µm. Standard equivalent diameters are 1.5, 2, 4, 6.5, 8, 12, 22, 30 and 40 µm.

A micron, officially called micrometer (µm), is one millionth of a meter. This is one thousandth of a millimeter. A piece of paper is usually about 100 µm thick, a human hair about 70 µm.

Absolute filter rating

The size of the largest pore in a filter is used as a reference to measure the performance of a filter medium. The size of the largest pore in a filter can be determined using the absolute pore size test.

The absolute filter rating (a) is the diameter of the largest hard spherical particle that will pass through the filter element under constant flow.

The definition of the absolute filter rating implies that 100% of the particles larger than a µm will be retained by the filter. Smaller particles are able to pass the filter, but a certain percentage of them will also be retained. The following efficiency graph illustrates this:

Nominal filter rating

The nominal filter rating is an arbitrary value, indicating a particulate size range; the filter manufacturer claims the filter removes some percentage of this size range. The nominal filter rating is defined differently by different manufacturers and is therefore ambiguous. Nominal ratings vary from manufacturer to manufacturer and cannot be used to compare filters. In case of nominal filtration, nominal filter rating refers to the filtration efficiency after cake formation.

Comparison

To compare both the absolute and nominal filter rating, their graphs are compared below. The first graph is one of a filter with an absolute filter rating of 10 µm; it is compared to a graph of a filter with a nominal filter rating of 10 µm at 98%. In this case, the absolute filter rating of the second filter is about 14 µm and the nominal filter rating of the first filter is about 9 µm.

Filtration is basically a process to separate solids from a liquid or gas stream with a porous substrate (medium). 

Separation is the process of converting a mixture or solution of chemical substances into two or more distinct product mixtures. Examples include separating two liquids of an emulsion (water in fuel) or removing liquid mist from a gas.

With the stainless steel fibers from the Beki-shield® product you can already reach very high levels of conductivity at extremely low load levels. The table below indicates the EMI shielding effectiveness and ESD protection values possible with the Beki-shield product. The most important aspect to make sure you reach these values is to limit the shear forces on the stainless steel fibers of the Beki-shield® products. Excessive shear forces will reduce the length of the fibers too much, impairing their ability to form the network, and consequently reducing the electrical conductivity of the final part.

(*) resin density: ± 1 g/cm³ - stainless steel fiber density: ± 8 g/cm³
(**) 30-1000 MHz shielding range

Our datasheets provide clear recommendations of the parameters that influence the shear during the compounding and injection molding processes. Bekaert’s application engineers are also available to help you fine-tune the settings of your processing so that you reach the best conductivity possible with our Beki-shield® products.

We currently have an EPD for Dramix® manufactured in Petrovice (Czech Republic), Lonand (India) and Karawang (Indonesia). This means that today, 80% of Dramix® steel fibers are manufactured at an EPD certified plant. We also have obtained an EPD for Mesh Track®.

Next up are our plants in Wilkes Barre (Pennsylvania, US), Izmit (Turkey) and Shanghai (China), after which all of our Dramix® plants will be fully EPD certified.

If you would like to be informed of our EPD releases and receive these documents as soon as they are available please let your Bekaert sales manager know.

According to the Bekaert guidelines, the maximum aggregate size should be limited to 2x the fiber length in order to obtain optimal performance. When coarser aggregates are used, we advise to conduct preliminary field trials in addition to SFRC performance tests.

The pandemic led to (partial) shutdowns of plants, which does not accurately portray what a normal production is usually like. As such, EPD calculations based on lifecycle data from that year would have been inaccurate. Further, some of the product lifecycle data is calculated by external agencies which only base their calculations on an entire calendar year. Therefore, the EPD's we kicked off mid 2021 or prior are based on data from 2019, and recent ones are based on data from 2021.

The Beki-shield® products consist of stainless steel fibers that provide very high levels of conductivity at very low load levels. This is particularly interesting when you need to reach high levels of electromagnetic interference (EMI) shielding or electrostatic discharge (ESD) protection at low load levels. The low load levels give you the possibility to color your end product and (in comparison with carbon black) you will have non-sloughing end products, such as castor wheels which do not leave marks on floors. Low load levels also mean that mechanical properties such as impact strength and part shrinkage are not significantly affected. The Beki-shield® product is easy and safe to use in your injection molding or compounding process and enables you to design lightweight, complex components with long-lasting conductivity. It is ideal to replace metal components that require EMI shielding properties with lightweight plastic alternatives that have high EMI shielding effectiveness.

Given the similarities in the manufacturing process, this EPD certification is a good proxy for all types of Dramix® produced at EPD certified plants.

However to be precise, we are developing a multiplier and formula together with the ITB that allows you to calculate an adjusted GWP (global warming potential, the parameter measuring CO2 emission equivalents) score for each of our fiber types. This multiplier will uploaded on this website as soon as it is available.

Fibers can only protrude from forms where there is a joint. They can not protrude in the middle of a form. This can be minimized if the joints are caulked before concrete placement. However, it is not always possible to calk every joint. The number of protruding fibers is a function of the precision of the joints and the fiber dosage.

Wider joints will catch more fibers than tighter joints. After the formwork is removed, the fibers can be quickly knocked down with a hand sanding block or a small angle grinder.

Not more than concrete.

For indoor applications such as tunnels and warehouses, no. For outdoor applications such as pavements some minor rusting may occur. Experience in highways and industrial pavements indicate that while individual fibers corrode at the surface, staining of the concrete surface does not occur. Overall aesthetics and serviceability are maintained even with the presence of individual fiber corrosion. Indoor Applications-Surface fibers in typical indoor tunnels or manufacturing floor applications remain bright and shiny under normal environmental conditions.

Outdoor Applications Without cracks-experience has shown that concrete specified with a 28-day compressive strength over 3000 psi, mixed with standard water/cement ratios, and installed with methods that provide good compaction, limit the corrosion of fibers to the surface skin of the concrete. When surface fibers corrode, there is no propagation of the corrosion more than 0.008” beneath the surface. Since the fibers are short, discontinuous, and rarely touch each other, there is no continuous path for stray or induced currents between different areas of the concrete. Outdoor Applications With cracks-laboratory and field-testing of cracked SFRC in environments containing chlorides has indicated that the cracks in concrete can lead to corrosion of the fibers passing across the crack. However, small cracks (crack widths < 0.008”) do not allow corrosion of steel fibers passing across the crack. If the cracks wider than 0.008” and are limited in depth, the consequences of this localized corrosion are not structurally significant.

A properly designed concrete mix is essential for avoiding fiber balling. In order to avoid the potential for fiber balling related to fibers with a high l/d (aspect) ratio (meaning high performing fibers), glued fiber technology has been developed. Glued fiber bundles will spread the glued bundles evenly on “macro level” and during mixing the bundles separate into individual fibers. In essence the glued bundle temporarily lowers the aspect (l/d) ratio of the fibers for easy mixing. That´s how balling can effectively be avoided and a homogenously mix of high performing steel fiber reinforced concrete can be achieved.