FORCETECH

FAQs

FAQS

Most frequent questions and answers

Steel fibers are thin filaments of steel often used for their high tensile and abrasive properties.

Unlike welded wire reinforcement or rebar, which is specifically located in a single plane, steel fibers are distributed uniformly throughout the concrete matrix. The primary function of steel fibers is to modify micro and macro cracking. While rebar are designed to bridge cracks once they appear. Steel fibers are used to control cracking so that the composite will behave in a manner that we want rather than what conventional reinforcement allows. Steel fibers go to where the cracks originate while conventional reinforcement lets the cracks grow until they reach the reinforcement

A few key attributes of concrete improved by steel fibers can be highlighted as:

•Increased flexural strength.
• Extreme fatigue resistance.
• Greater impact resistance.
• Less porous.
• More effective composition against and spalling.
• Elimination of shrinkage cracks.
• Excellent resistance to corrosion.

When added to the concrete mixture, steel fibers enhance many of concrete’s mechanical characteristics like toughness, durability and tensile strength. It also helps in eliminating shrinkage cracks.

Steel fibers can be introduced into the concrete at the batch plant or job-site. Consult ACI 544.3R or CFS’s brochure titled Mixing, Placing and Finishing SFRC for more details on the proper methods of adding fibers to concrete.

When fibers were first introduced to the market, balling was an issue due to the high aspect ratio and long length. Our standard fibers have aspect ratios of less than 50 and are either 1” or 1 1/2” in length. As the aspect ratio increase above 50 or the length exceeds 1 1/2”, the tendency of fibers to ball increases. This is the reason some of our competitors must collate their fibers to reduce the chances of fiber balls.

Pumping has been used to transport SFRC on many projects. In general a mixture that will pump satisfactorily without fibers will pump with fibers. In pumping SFRC, the chute from the ready mix truck should be 12” above the grate on the hopper. This will prevent the fiber from bridging the gaps in the grate and ensure a steady flow of concrete to the pump. The grate should never be removed from the hopper.

Both can be used on a SFRC floor. Shake-on toppings can act as a fiber suppressor and limit the number of fibers on the surface. If liquid hardeners are used the floor should be moist cured for 7 days and allowed to air dry per manufacturer’s recommendations before installing the liquid hardener.

​Laser Screeds and steel fibers are an ideal combination for today’s floors. The Laser Screed improves the floor flatness and increases productivity while the steel fibers improve the performance of the slab. Another advantage is that the steel fiber reinforcing is included in the concrete mix and does not impede the movement of the Laser Screed. This is not true with conventional reinforcement as it must be “chaired” in position before the concrete is deposited on the subgrade. This decreases the mobility of the Laser Screed and makes it almost impossible to get the mesh in the proper position.

While there is always a chance of a fiber being on the surface of the slab, following the finishing techniques discussed in ACI 544.3R will keep them to a minimum. CFS’s fibers are designed to be the best finishing fibers on the market. To quote TR-63, “While high-quality surfaces can be achieved with any fiber type, small slit sheet steel fibers tend to be easier to finish.” In fact many of our competitors recommend that a shake-on hardener should be used as a fiber suppressor to hide fibers which are on the surface of the slab.

No, there are no safety concerns to be imposed with good workplace safety practices in place of steel fibers. For more information, please refer to our safety data sheets.

The two of the primary purposes for reinforcing slabs-on-ground are for shrinkage and temperature control. SFRC is an economical way of controlling cracks due to changes in temperature or volume changes as the concrete ages. For rebar to control these cracks positioning is important. Positioning is important when using WWR or rebar. WRI states that when on layer of reinforcement is used, it should not be allowed to be below mid depth. In general, positioning at ⅓ the depth below the surface is sufficient. This is extremely difficult with the common practice of using a Laser Screed to strike-off the concrete. This problem is eliminated with the use of SFRC since the fibers are randomly distributed throughout the concrete.
No. If you use steel fibers, and if the concrete mix is designed so that it would have good workability without fibers, you should expect no unusual difficulties in placing and finishing.
No fibers in concrete are purely mechanical in nature and, therefore, have absolutely no impact on the setting time of concrete. The setting time is a chemical function impacted by factors such as time and temperature. Water content and chemical admixtures also have an influence on set time.
No Steel fiber reinforced concrete has the advantage of reduced settlement and more uniform bleeding. To the uninformed eye, this may make the concrete look drier and unnecessary additional water. The typical saturated appearance of mixing water coursing to the surface in non-fiber concrete is absent when Steel fiber reinforcement is employed. Workability is not affected with standard application rates of fiber reinforcement and no additional water is needed.
Yes Steel fiber reinforced concrete develops an isotropic quality, having a uniform quality cross section, which allows the concrete to stiffen and set from the inside out.
​Typical reinforced concrete with steel fiber contains less than 0.5% vol. Steel fibers and just over 0.75% vol. These fibers are discontinuous and are not interconnected. Due to the addition of steel fibers, tests show only a slight decrease in electrical resistivity. However, there is still substantial resistance to current flow. Much more dominant are the effects of moisture content and aggregate composition than the addition of steel fibers.
Steel fibers and vice versa are not a replacement for synthetic micro fibers. Both types of fibers provide very different concrete properties so that the fields of applications do not overlap. Both types of fibers can be used complementary rather than a substitute. While steel fibers provide post crack resistance and thus act as reinforcement, synthetic micro fibers reduce cracking due to plastic shrinkage and improve concrete fire resistance. They have no reinforcing effect.
For casting inside, the most commonly used choice for consolidating the concrete is innervibration. In prefabricated sector, form vibration is usually used. When removing the shapes.For instance, strengthened precast buildings are vibrated during casting of steel fiber to strengthen 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.
Only from forms where there is a joint can fibers protrude. In the middle of a form, they can’t protrude. If the joints are caulked before concrete placement, this can be minimized. It is not always possible to calculate each joint, however. The number of fibers protruding is a function of joint accuracy and fiber dosage. Wider joints are capturing more fibers than tighter joints. The fibers can be knocked down quickly with a hand sanding block or a small angle grinder after the formwork is removed.
Only from forms where there is a joint can fibers protrude. In the middle of a form, they can’t protrude. If the joints are caulked before concrete placement, this can be minimized. It is not always possible to calculate each joint, however. The number of fibers protruding is a function of joint accuracy and fiber dosage. Wider joints are capturing more fibers than tighter joints. The fibers can be knocked down quickly with a hand sanding block or a small angle grinder after the formwork is removed.
Contraction joints can be installed using either a wet saw or an early entry saw. For wet saws the depth should be ¼ the depth for slabs less than 6” thick. For slabs over 6” thick or slabs with over 40 pounds of steel fiber per cubic yard of concrete, the saw cuts should be ⅓ the depth. For early entry saws, the manufacturer’s recommendation should be followed.
No plastic liner faults have ever been recognized owing to fiber punctures. During concrete positioning, the abrasion from sharp aggregates presents as great a risk to the liner as do the steel fibers. After positioning, the fibers tend to shift and reorient during vibration, which relieves the stress of an individual fiber on the liner produced during placement.Many SFRC projects are built with cast-in-place and sprayed in direct contact with waterproof membranes.
Steel fiber concrete compresses the schedule of construction, allows alternative methods of construction or design solutions and increases durability. The higher costs of steel fibers are overcompensated by the savings when a project is delivered faster with less effort and labor.
Highways and roadways. Shortcrete in mining/tunneling, explosive and impact resistance structures, industrial floorings etc.