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Steel Fibre
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Recommendations for Use


RECOMMENDATIONS
FOR USE OF FIBRE ISSUED BY PJSC «SILUR» AND PJSC «STALKANAT»
TO PREPARE THE STEEL FIBRE CONCRETE MIX

Steel fibre concrete mix is prepared, as a rule, in mass-produced positive action concrete-mixing machines. It is allowed to also use other kinds of mixers which make it possible to obtain a homogenous concrete mix due to:

-        selection of the optimum consistence of the steel fibre concrete with a preset placeability due to plasticizing;

-        even feeding of fibre to the mixer (it is not advisable to feed a full batch of fibre in the mixer in one portion to prepare a certain quality of the steel fibre concrete mix);

-        shorter mixing period (within the limits allowed by the applied technology);

-        it is recommended to reduce by 25-30% the batch volume when preparing the steel fibre concrete in the positive-action concrete mixers (in order to exclude possible overloading of the mixer) as compared to the similar batch volumes set for a common (heavy) concrete. If the fibre content is less than 40 kg per 1 m3 of the mix, it is permitted not to reduce the volume of the batch.

ADDING FIBRE TO CONCRETE

Fibre is fed in an even and continuous flow in 3-4 portions with a delay of 1-1.5 min. (the mixer drum should rotate).

Ready concrete mix (or the mix can be prepared directly in the concrete mixer truck) is loaded in the concrete mixer truck and a batched portion of fibre is evenly fed into the drum containing a ready concrete mix before the discharge with due observance of the fibre feed conditions.

The time of mixing the steel fibre concrete mix should not exceed, as a rule, 3 minutes. Working intervals in the mixing process are set by test in the course of mastering the technology.

RECOMMENDED BATCHES

Content of fibre in the steel fibre concrete (fibre consumption per 1 m3 of the steel fibre concrete mix) is determined by the requirements to its physical and mechanical properties required by the conditions of practical application. Depending on the application of the steel fibre concrete, the content of fibre can be recommended as follows, kg/m3:

-         industrial floor slabs: 20-40;

-        residential houses constructions: 25-50;

-        structures and facilities exposed to the environment: 40-70;

-        structures of tunnels, roads, etc.: 50-100.

 

Kind of fibre

Application

Wire fibre with curved ends

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the most wide-spread kind, convenient in processing, not inclined to formation of "hedgehogs" (plain surfaces without projecting parts), good hold of concrete

 

ADVANTAGES OF USING FIBRE
PRODUCED BY PJSC «PA «STALKANAT-SILUR»

-        considerably higher resistance to cracks and bending;

-        excellent cohesion with concrete;

-        higher impact strength;

-        higher water permeability of concrete;

-        better behaviour at shrinkage;

-        no rejections at reinforcement;

-        special equipment is not needed;

-        no lumps are formed;

-        strengthening of corners and edges;

-        simple of usage;

-        simple finishing of surfaces;

-        extended service life of constructions.

ECONOMIC BENEFITS OF STEEL FIBRE USE

-         reduction of slab thickness;

-        reduction of labour;

-        reduction of construction period;

-        easy manual or machine-made placement.

QUALITATIVE PARAMETERS OF STEEL FIBRE CONCRETE

Ø      STRENGTH - the maximum stress level which the material can withstand:

-        maximum tensile and flexural strength is higher by 50-200%;

-        maximum fatigue limit is higher by 25-30%;

-        maximum compression resistance is increased by 50-150%.

Ø      DEFORMABILITY - deformation properties of steel fibre concrete change pro rata the volumetric saturation degree and reversely proportionate to the reduced fibre diameter, all other conditions being equal;

-        initial tangent modulus is higher by 10-30%;

-        initial Poisson ratio is higher by 10-20%.

Ø      CRACKING RESISTANCE - ability of the material to prevent crack initiation and spreading:

-        crack resistance limit is higher by 30-80%.

Ø      FROST RESISTANCE - frost resistance of steel fibre concrete is higher because of the small-pore structure of the matrix containing a great number of closed pores and depends on the parameters of the fibre reinforcement and the concrete matrix structure;

-        higher frost resistance of steel fibre concrete as compared to a common concrete reaches 800%.

Ø      CORROSION BEHAVIOUR - adding fibre reinforcement in concrete considerably improves its structure and ensures high corrosive strength of fibres.

 

WIDE APPLICATION OF STEEL FIBRE PRODUCED BY PJSC «PA «STALKANAT-SILUR» IN CONSTRUCTION WILL ALLOW YOU TO OBTAIN HIGHER QUALITY AND LONG-LIFE CONSTRUCTIONS!

APPLICATION FIELDS OF STEEL FIBRE CONCRETE:

-        industrial flooring (floors of workshops and storage areas, cinema halls);Provoloka_tech_spec_clip_image002_0000

-        jointless flooring;

-        other poured floors.

Reinforcement of industrial flooring with steel fibre produced by PJSC «STALKANAT» and PJSC «SILUR» makes it possible to reduce consumption of steel and concrete, make concrete floor thickness smaller while preserving the strength parameters, considerably increase strain resistance, extend the service life and prolong the overhaul period.

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-        reinforcement at road renovation;

-        reinforcement of road base;

-        grass paver reinforcement (parking sites).

Use of steel fibre provides for a considerably greater bearing capacity and high resistance to dynamic loads. It will appreciably improve quality of the road base while allowing of reducing the total thickness of the road base, facilitates a longer service life and can be applied fast and simply.

-        pipelines;Provoloka_tech_spec_clip_image001_0000

-        subways, railroad and road tunnels;

-        water tunnels;

-        oil and gas tanks.

Steel fibre has been used both for dry and wet finishing of tunnels for more than 30 years. Due to its great technological, economic and safety ensuring advantages, steel fibre is daily used in various subterranean projects all over the world.

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-        production of concrete constructions;

-        basements made of prefabricated blocks, water wells, garages;

-        façades, walling constructions.

High quality steel fibre has a greater plasticity and better withstands dynamic loads and cracking. Steel fibre easily replaces 1 or 2 layers of conventional nets. Steel fibre concrete ensures full spacious reinforcement, excludes a necessity to reinforce with conventional nets, simplifies and speeds up construction and is more durable.

-        stabilization of slopes, inclined walls;Provoloka_tech_spec_clip_image001_0002

-        water spillways;

-        bank vaults, safes.

Steel fibre is often used in various protection structures. The main reasons are: great load-bearing capacity, high resistance to impact loads, high resistance to cracking, penetration, etc. It can be applied for reinforcing pourable concrete in various water projects, reinforcement constructions or sprayed concrete.

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-        runways;

-        service hangars;

-        port pavements, container terminals.

Steel fibre is used for the constructions which have to withstand highly specific loads and intensive dynamic movement. Evenly distributed steel fibre of PJSC «STALKANAT» and PJSC «SILUR» ensures a considerably greater load-bearing capacity, long service life and resistance to impact loads and wear, as well as reduction of repair costs. A thickness of the slab can be reduced as well. Steel fibre concrete slabs are produced fast and easily.

INDUSTRIAL BUILDING FLOORING MADE OF STEEL FIBRE CONCRETE

Floors of industrial buildings experience a complex stress condition and, depending on the load kind, the lower or upper surfaces of a slab can suffer considerable tensile stresses caused by loads exerted by stored articles, manoeuvring of lift trucks and other transport, temperature effects and a number of other reasons.

Steel fibre presents a practically ideal reinforcement for strengthening industrial floors. Steel fibre is effective to preclude opening of hair cracks which might arise in any concrete slab. Tensile stresses arising in a conventional concrete without steel fibre reinforcement may not propagate over the crack. As soon as the stress exceeds the breaking limit, the crack will propagate further and it will result in a separation of the slab into individual elements.

Adding steel fibres makes the crack opening mechanism controllable and a stress concentration at the crack end is reduced due to the fact that the fibres which cross the crack transfer a part of forces across the fibre while the fibres located immediately at the crack end take up the greater load than the surrounding concrete due to a higher elastic module.

Concrete behaviour at destruction changes from the fragile to plastic. A crack originates in those places of the slab where the tensile strength has been exceeded. Steel fibres located in the concrete section where the crack exists, act like a hinge and facilitate re-distribution of stresses in the material. Thus, as contrary to the crack behaviour in a fragile material, certain stresses act in the crack area of the steel fibre concrete and their level depends on quality and quantity of the used fibre. As a result, the load-bearing capacity of floor increases. The so-reinforced concrete absorbs more energy at destruction and its resistance to impacts and long-term loads increases.

Steel fibres are particularly effective due to their length (60 mm) and specially curved ends which ensure good cohesion with concrete. High breaking strength of the steel wire (more than 1,100 N/mm2) prevents fibre failure. Steel fibres reinforce the floor concrete in all directions, including the fibres of the upper and lower surfaces.

By virtue of fair technical properties of steel fibre concrete such floors may withstand considerably higher loads than common concrete floors. At same loads, steel fibre concrete floors may be 20-25% less thick than concrete floors reinforced with rods. Fibre consumption in steel fibre concrete comprises, as a rule, 25-40 kg per 1 m3 of the concrete mix, which is appreciably less than the consumption of the reinforcement rods in common concrete floors. Besides, in steel fibre concrete floors it is possible to increase the distance between expansion joints by 1.5-2 times, depending on the fibre consumption.

Performance of such floors is considerably improved: there are, practically, no spalling of edges at joints which is characteristic of concrete (reinforced concrete) floors as steel fibre reinforces the entire concrete volume, not individual areas; these floors have 1.5-2 times higher resistance to abrasion and dynamic loads, including the impacts produced by loads as well as considerably higher frost resistance and endurance.

As a rule, economic performance of steel fibre concrete floors is better than those of the floors reinforced with rods. Numerous western sources state that the economy is as high as 12-20%.

The steel fibre concrete floor construction is a continuous slab placed on a specially prepared base. Besides a compacted soil layer, such base can include a layer of lean concrete or a compacted layer of chippings. Existing concrete floors can also be used as a base. As a rule, a steel fibre concrete slab should not have cohesion with its base, therefore 2 layers of polythene film are placed between the base and the floor. In case of floors spanned 12 m and more, expansion joints are arranged in the floors which cut the slab by 1/3 of the floor thickness.

Composition of concrete and the quantity of fibre used per 1 m3 of the concrete mix is determined proceeding from the compression and tensile strength grade of the steel fibre concrete. While performing works in existing workshops, it is advisable to use a dry steel fibre concrete mix (a mix of coarse and fine fillers, micro fillers and fibre) supplied to the construction site in bags or crates. Cement and water are added when mixing the steel fibre concrete mix in the mixer. Settlement of the mix should be at least 10 cm. Steel and fibre concrete mix is prepared in fixed concrete mixers or mixer trucks. Mixing period should not exceed 10 min. in so as to avoid a formation of fibre lumps.

As steel fibre concrete floors shrink when settling or expand and shrink because of temperature changes, they should have a possibility of free movements. Therefore, at all walls and at rigid elements, e.g. at columns, trays, foundations, etc., it is required to place a 10 mm layer of polystyrene foam. Steel fibre concrete mix is supplied to the placement point with the aid of a vibratory bucket or concrete pumps. Steel fibre concrete mix is compacted with a vibrating beam. A speed of the vibrating beam pass should be adequate to ensure good compaction of the mix. Fluidity of the concrete mix should ensure and guarantee its good compaction.

It is not allowed to apply immersion vibrators. After compaction the surface of a freshly placed steel fibre concrete is trowelled using metal trowels.

Fresh steel fibre concrete is to be protected against wind, draughts and sunrays as long as possible. Prior to concreting, close all air openings in the building, except ventilation ducts. Directly after the final placement it is necessary to apply a compound on the floor surface to preclude quick drying or close the floor with polythene film.

Difficulties in movement of the concrete because of settlement or temperature effects may lead to formation of cracks. To avoid it, it is required to cut expansion joints in the fresh steel fibre concrete. A joint (notch) usually is 3 mm wide and at least 1/3 of the floor thickness deep. The joints formed at intervals of concreting require special care as these areas are particularly susceptible to damage. Before making an interval in concreting it is necessary to protect the joint edge with a close L-section angle and anchors. To transfer forces in joints, rods are used, one end of the rod is to be fixed in the already placed concrete while the other end remains free until the adjacent layer is placed.

After the floors have been concreted and polished, they are, sometimes, treated with various chemical compounds so as to make a surface layer of concrete more dense and impermeable for water.

Use of steel fibre concrete flooring in industrial buildings allows of getting a new floor construction characterized with increased strength, resistance to wear and cost effectiveness.

Similar advantages of steel fibre concrete can be achieved when it is used for paving runways of airports and as road pavement at the sections mostly loaded due to intensive traffic.