AR Glass Fiber

SOLUTIONS FOR CONCRETE REINFORCEMENT

Technical Study

Evaluation of Fiberin HD Fibre

(Tests performed by SGS. UK 1994. 95)

The tests summarized in the paper were performed to assess the benefits of a small addition (4.6kg//m3) of Fiberin HD fibre in Ready-Mix-Concrete (RMC)

The programme of tests considered the offects on the following properties, which are considered to be the most important in assessing the long-term durability of concrete:

§  Compressive Strength

§  Flexural Strength

§  Homogeneity - bleeding

§  Plastic Shrinkage Cracking - (Modified Kraai Test)

§  Permeability - Initial Sunface Absorption Test (ISAT)

§  Freeze / Thaw

Note: The modified Kraai test is performed under very aggressive conditions (blowing warm, dry air over the sample to accelerate drying). Under normal conditions the reduction in cracking may be expected to be greater.

Summary of Results:

Strength:

Compressive and Flexural testing was performed at 1, 3, 7 and 28 days At an early age the benefits of the addition of 4.6kg/m3 of FIBERIN HD are most noticeable (flexural Strength> 90% higher within the first 3 days). This can have particular benefits in precasting, where concrete products may require demoulding after 1 day. But even at 28 days the benefits of such a small addition of fibre are very noticeable (>26% higher compressive strength, and> 22% higher flexural strength). Unlike synthetic fibres, the Elastic modulus of FIBERIN HD fibre is significantly greater than that of the hardened concrete; therefore it is able to provide reinforcement not only during the setting process, but also to the hardened concrete.

Homogeneity:

FIBERIN HD fibres have a similar specific gravity to concrete, so they do not have a tendency to either float or sink in the concrete during vibration Tests have shown that the fibres also inhibit the separation of materials eyen under vibration, so that separation of the coarse aggregates and bleeding of the water are reduced, giving a more homogenous concrete. In these tests the bleeding was measured using an ASTM test, and showed a 25% reduction with the addition of FIBERIN HD fibres.

Improvement in the resistance and physical performance of the concrete (plastic crack resistance, reduced permeability and freeze/thaw resistance and are due to the reinforcing effect of the fibres, and the improved homogeneity which they provide.

Summary

Key Benefits

§  Compressive Strength: +26%

§  Flexural Strength: +22%

§  Bleeding: -25%

§  Plastic Shrinkage Cracking: -86%

§  Permeability: -50%

§  Freeze / Thaw Expansion: -66%

Resistance to Plastic Shrinkage Cracking:

The reinforcing effect of the fibres, and also the reduced bleeding, results in an improved surface to the concrete. 4.6 kg of FIBERIN HD fibre represents 132 million reinforcing filaments per m' of concrete, therefore the unreinforced area between filaments where cracks could form is minimized. In the modified Kraai test the samples are force-dried for 24 hours during the setting and hardening process. The addition of FIBERIN HD at a rate of 4.6 kg/m' gave an 86.8% reduction in the area of plastic Shrinkage Cracking. In normal, less aggressive conditions, this level of reduction may be expected to be greater.

Permeability (Initial Surface Absorption Test):

Reduced bleeding and improved homogeneity result in a better concrete surface, which in turn leads to a 50% reduction in permeability as demonstrated by the ISAT test resists). This is an important indicator of the durability of the concrete.

Resistance to Freeze/Thaw:

The reduced permeability and the effective reinforcement provided by the fibres led to a 65.9% reduction in the expansion which takes place during freeze/thaw testing, indicating improved resistance to freeze/thaw damage.

Conclusions

Even at low addition rates. FIBERIN HD fibres provide an effective distributed reinforcement in both the plastic and hardened concrete.

The addition of only 4.6 kg of FIBERIN HD fibre to RMC provides notable benefits to both the mechanical and physical properties of concrete, resulting in improved durability.