Spajic steel fibers are concrete reinforcing material which in combination with concrete provides certain advantages in comparison with traditional reinforcement. Spajic steel fibers are made from low carbon, cold drawn steel wire, designed to provide concrete with temperature and shrinkage crack control, enhanced flexural reinforcement, improved shear strength and increase the crack resistance of concrete.
Fibers are sometimes referred to as structural fibers and are intended to carry load and, therefore, are used to replace traditional reinforcement in certain non-structural applications as well as minimize and/or eliminate both early and late age cracking.
Fibers are generally classified according to their length, although sometimes the diameter and/or aspect ratio are considered.
Company Spajic produces its own production lines for steel fiber manufacturing and because of that, it is able to produce and offer a wide range of different fiber types.
Considering their application, as well as for easier understanding, Spajic company has made the following classification:
• Hook ended steel fibers
• Corrugated steel fibers
• High Performance Steel fibers
• Microfibers (name related to the dimension of the steel fibers)
For reinforce concrete different types of steel fibers can be used.
Advantages of the fiber reinforced concrete
Normal concrete is brittle and frangible, while fiber reinforced concrete has priority over the normal concrete because of its higher strength and its capacity to prevent frangibility. The advantages of steel fibers reinforced concrete in comparison with normal concrete can be summarized as:
1- Good impact strength
2- Good ductility
3- High load bearing capability after being cracked
4- Tensile, bending and cutting strength
5- High resistance
The concrete industrial ground-floor slab is a key structural element in most industrial enterprises. It has two functions: first to sustain the operational loads from loaded racking system, goods stored directly on the floor, fork-lift truck wheel loads and mezzanine floors, and transfers them to the supporting soil without any structural failures or unaccepted settlements; second to provide suitable wearing surface upon which the operations in the facility may be carried out efficiently and safely. This dual role of industrial ground-floor slab has concentrated attention on its critical contribution to the success of modern commercial facilities.
Applications of SFRC (steel fibers reinforced concrete)
SFRC is generally used to inhibit cracking, improve resistance to impact, to resist dynamic loading and material disintegration. SFRC can be used without any other additional reinforcement in almost all application where flexural stresses are not overwhelming like beams for instance.
Major and potential applications for steel fibers are:
• Industrial floors
• Shotcrete and tunneling
• Foundation slabs
• Refractory concrete
• Hydro structures
• Airport and highway paving
Steel fiber dosage recommendation
The recommended dosage of steel fibers is usually between 20 and 40 kg/m3. The greater the dosage rate the greater is the flexural strength of the concrete. Generally the fibers are added last to the fresh concrete, care being taken to ensure that no clumps are added and the fibers are rapidly moved from the entry point to the mixer. Alternatively they may be added onto the aggregate with use of Spajic fiber disentangling and loading machine. As long as the aspect ratio of the fiber is less than 50, the fibers may be dispensed directly without any risk of balling. With higher aspect ratios Spajic suggest mandatory use of fiber disentangling and loading machine. However, visual inspection during pouring is necessary to check fiber distribution is satisfactory.
Make sure to add steel fibers into concrete mix as last ingredient, mix at highest speed for 3-5 min per kg of fibers in order to prevent clumps formation into the concrete mixture.