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Fiber-reinforced Concrete and MEKA Fiber Dosing Systems

Fiber have been used as a reinforcement material since many years and this application is not actually new to mankind. In ancient Egypt clay bricks were reinforced by straw and it was also found that even in earlier ages thousands of years ago asbestos had been used with the same purpose – to get more flexible and solid construction material. Research is going on in nowadays and several types of fiber are being used by thousands of construction companies worldwide.

Usage of Fiber-reinforced concrete

The main purpose of fiber-reinforcement is to increase concrete’s structural integrity and improve flexural behavior. On the other hand, it is a more economical way comparing to regular steel reinforcement. There are many different types of fiber that can be used in concrete reinforcement.

Advantages of using Fiber reinforced concrete

  • Provides strong concrete for lower costs
  • Is a good alternative to steel rebar
  • Less corrosion with steel and no corrosion with plastic
  • Improved tear/tensile strength
  • Provides crack resistance

Types of fiber:

  • Steel
  • Plastic (Polyester, Polypropylene, Polyethylene)
  • Glass
  • Natural materials (Wood cellulose, Bamboo)

Steel fibers are commonly glued/sticked as 5-30 pcs per part or more which disperse in contact with water to provide better mixing and distribution in concrete

While steel fibers are mostly functional after formation of cracks, plastic polypropylene fibers prevent the formation of these cracks

Classification according to volume fraction

Low volume fraction (<1%):

Fibers are used to reduce shrinkage cracking. These fibers are used in slabs and pavements that have large exposed surface leading to high shrinkage crack.

Moderate volume fraction (between 1 and 2%) :

The presence of fibers at this volume fraction increase the modulus of rupture, fracture toughness, and impact resistance.

High volume fraction (greater than 2) :

The fibers used at this level lead to strain hardening of the composites.

MEKA Fiber Dosing Systems

When fibers are used in small amounts it is common to order fiber in small pre-weighed packs and let the fiber directly into the plant mixer or mixer truck without need for special fiber feeding system. But when it comes to high capacity mass production with high precision and homogeneity this is where MEKA shows its best.

MEKA Fiber Dosing equipment includes highly accurate steel/hard plastic and soft fiber dosing systems with a range of dosing capacities shown in the table to suit the individual needs of our customers. MEKA Fiber Feeding Systems are with integrated conveyor and with a storage available on request as well as additional equipment custom-made for the requirements of our customers.

Fiber weighing and feeding process can be integrated into the automation of the concrete plant to ensure full control over mixing quality and homogeneity. All fiber dosing-feeding equipment is produced in accordance with CE and EMC directives.

Function

The machine dosing tray is commonly filled up with fibers from big bags, but it can also be boxes or paper bags. Crane or forklift can be used for loading. By using indicators from the control panel on the fiber feeder or directly from concrete plant computer the desired weight per batch can be set. We use negative weighing method. Weighed fibers are fed by the fiber feeding conveyor onto aggregates on the mixer feeding belt conveyor or into skip hoist. Fiber flow is adjusted according to aggregate flow to provide better distribution and to pre-mix fiber and aggregates.

Construction

Cylindrical body with spiral escalating fiber pass ways is mounted on a robust steel framework. Two vibrators with adjustable amplitude provide tray movement for transfer of fibers.

Feeding capacity and content

Feeding capacity varies depending on the type of fiber used.

Power supply:

The vibrator engines are made for 380-400V/3ph/50Hz. Insulation class IP56. 60Hz version is available upon request.

Control system:

Sensitive loadcells provide high accuracy weighing with less than 1% tolerance (depending on the type of fiber). The amount per batch can be adjusted by using indicators on the feeder or if fully integrated directly from the batch computer. With full integration several report types are available.

Installation and start-up:

Fiber Dosing & Feeding unit comes pre-wired ready for operation and can be set up very quickly.