Residual Flexural Tensile Strength (RFTS) of Concrete Beams
Standard(s): BS EN 12390‑5, BS EN 14651: 2005
Lab Test
The Residual Flexural Tensile Strength (RFTS) test measures the post-cracking performance of fibre-reinforced concrete beams. Conducted in accordance with BS EN 12390-5 and BS EN 14651:2005, the test evaluates how well the concrete continues to carry load after cracking. This is particularly important for fibre-reinforced concrete where fibres are designed to bridge cracks and provide additional toughness.

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The Process

A concrete beam specimen is placed on two lower support rollers within a flexural testing machine. A load is applied through upper loading rollers at a controlled rate, causing the beam to bend. As the beam cracks, the load and crack opening displacement are recorded. These measurements allow the residual flexural tensile strength values to be calculated at different stages of crack development.

The Reason

Fibre-reinforced concrete relies on fibres to provide strength after the initial cracking of the concrete matrix. The RFTS test measures this post-crack performance, confirming whether the fibres provide the required structural behaviour. This information is essential when fibres are used to partially or fully replace traditional reinforcement.

The Application

Residual flexural tensile strength testing is widely used for fibre-reinforced concrete in applications such as industrial floors, tunnels, sprayed concrete linings, and precast elements. The results help engineers confirm that the fibre-reinforced concrete meets design requirements for toughness, crack control, and structural performance.

Frequently Asked Questions

Can Amtest carry out RFTS testing for fibre-reinforced concrete beams?

Yes. Amtest provides Residual Flexural Tensile Strength testing in accordance with BS EN 12390-5 and BS EN 14651 to verify the structural performance of fibre-reinforced concrete.

Why is residual flexural tensile strength testing required?

The test confirms how well fibre-reinforced concrete performs after cracking. Amtest testing helps engineers verify that the fibres provide the required post-crack load capacity.

What types of fibres can be assessed using the RFTS test?

RFTS testing can be used to evaluate concrete reinforced with steel, polypropylene, or other structural fibres.

Can Amtest test concrete beams cast specifically for fibre testing?

Yes. Amtest can receive and test purpose-cast beam specimens prepared for fibre-reinforced concrete testing and provide detailed laboratory reports.

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Residual Flexural Tensile Strength (RFTS) of Concrete Beams

Flexural strength testing evaluates the resistance of concrete beams to bending forces. This test is critical for understanding the tensile strength of concrete, which influences its behaviour under load.

How is the Test Performed?

  1. Specimen Preparation
    Prismatic specimens (standard beam shapes) are prepared according to relevant standards, such as BS EN 12390-5.
  2. Application of Load
    The specimen is subjected to a bending moment using upper and lower rollers. These rollers evenly distribute the load across the beam to simulate real-world conditions.
  3. Measurement of Maximum Load
    The test records the maximum load sustained by the specimen before failure.
  4. Calculation of Flexural Strength
    Using the dimensions of the specimen and the applied load, the flexural strength is calculated, typically expressed in megapascals (MPa).

Importance of Flexural Strength Testing

  • Structural Design Validation: Ensures concrete beams can withstand expected loads in bridges, floors, and other structural elements.
  • Quality Control: Confirms the concrete mix meets design specifications for strength and durability.
  • Performance Evaluation: Assesses the effectiveness of additives, reinforcements, or curing methods in enhancing tensile strength.

Flexural strength testing is a key component in ensuring the reliability and safety of concrete structures, providing valuable insights into material performance under bending stresses.

BS EN 12390‑5, BS EN 14651: 2005