How to Use Sisal Fibre in Concrete?

Sisal fibre, for many years, has dominated the agricultural sector as a twine due to its resistance to deterioration, strength, stretching ability, durability, and affinity for some dyeing compounds. Due to the properties of sisal, it’s now being used as a fibre reinforcement for concrete, fibreglass, and rubber.

When you include fibre reinforcement in cement paste, concrete, or mortar, it enhances the flexural strength, impact, thermal shock, resistance to fatigue, spalling, and fracture toughness. Natural fibres like wool, sisal, jute, coconut, and bamboo are more promising as fibre reinforcement concrete-based matrices. Natural fibres reinforcements are readily available, more affordable, and have low energy consumption. Plain cement based composite has firm compression but with weak tension. When cement composites face any pressure, especially in nonlinear stages, it loses its stiffness. 

Sisal fibres are developed into a pre-hardened shrinkage plastic state, where observation is made on its bending strength, tensile, and compressive capabilities. A sisal fibre reinforced concrete is a cement mixture containing fibre reinforcement which improves its structural integrity. The reinforced cement contains short discrete fibres which are randomly oriented but uniformly distributed. A fibre is a small reinforcement material with specific mechanical properties and characteristics described by the aspect ratio (a convenient parameter). The aspect ratio is defined as the ratio of the fibres’ length to its diameter. The ratio starts from 30 to 150. With the perfect ratio, the mechanical behaviour of concrete is improved.

If you want to use reinforced concrete with sisal for construction, you need to follow the below steps to have the best sisal fibre reinforced concrete.

  1. Combine the sisal fibres with the matrix like you want to make a cementitious mix.
  2. Simultaneously spray the cement slurry and fibres.
  3. Disperse the fibres in the cement slurry,and dewater to produce thin products.
  4. Place the fibres down in molds like fabrics, impregnating them with the concrete slurry. Compress the mixture to produce a dense fibre mixture.
  5. Continue impregnating the fabrics and fibre mats with the concrete slurry. Then pass the mixture through a cement bath.

Benefits of Using Fibre Reinforced Concrete

Below are the benefits of using fibre reinforced concrete in any construction:

  1. The tensile strength of the cement products is improved.
  2. Air and water voids are reduced, hence no porosity of gel.
  3. The cement products become more durable.
  4. Fibre reinforcement materials like glass and graphite improve the creep performance of the reinforced concrete.
  5. Improves the dynamic and static properties of the concrete when you use uniformly dispersed, closely spaced, and tiny reinforcement fibres.

Disadvantages of Using Fibre Reinforced Concrete

While using sisal and other fibres as reinforcement fibres reduces cracking and increases the stiffness of concrete, there are some disadvantages. Below are the disadvantages of using reinforced fibres on cement:

  1. The fibre will increase the specific gravity of the concrete; some fibres make the concrete very heavy.
  2. The wrong aspect ratio will significantly affect the strength of the concrete.
  3. More costly because of the additional raw materials, control issues, and production issues.
  4. Steel fibres suffer from corrosion, which can affect the quality of the reinforced concrete.

Bisley has been part of the concrete admixture industry since the early 1980's.

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