Flexural Strength of Concrete Test of Hardened Concrete

Flexural Strength of Concrete Test of Hardened Concrete

Objective:

• Measure the ability of concrete to resist deformation and failure under bending (flexural) forces.

Key Concepts:

• Flexural Strength:

  • Refers to the tensile strength of concrete at the point of fracture.
  • It's an essential property for structures subjected to bending stresses, such as beams, slabs, and pavements.

• Testing Methods:

  • Commonly employed tests include the third-point loading method and center-point loading method.
  • Third-point Loading Method: Load is applied at two points equally spaced from the center.
  • Center-point Loading Method: Load is applied at the midpoint of the concrete specimen.

• Preparation and Testing Procedure:

  • Prepare concrete specimens (typically beams) according to standards (e.g., ASTM C78/C78M).
  • Dimensions are usually defined (e.g., 150 mm x 150 mm x 750 mm beam).
  • Concrete specimens must be properly cured before testing.
  • Specimens are placed in the testing machine, and load is applied until failure occurs.
  • Record the maximum load applied to calculate flexural strength.

• Calculations:

  • Flexural Strength (fₜ) calculated using the formula:$$f_t=\frac{PL}{b{d}^2}$$Where:
    • P is the maximum load (N),
    • L is the span length (mm),
    • b is the width of the specimen (mm),
    • d is the depth of the specimen (mm).

• Importance:

  • Understanding flexural strength aids in designing durable concrete structures.
  • Helps predict how concrete behaves under real-life structural conditions.

Factors Influencing Flexural Strength:

• Concrete Mix Design: Proportions of cement, water, aggregates, and admixtures.
• Curing Conditions: Proper curing enhances strength development.
• Age of Concrete: Flexural strength increases with proper curing over time.
• Specimen Size and Shape: Dimensions should adhere to standard specifications for accurate results.
• Loading Rate: Controlled and uniform load application ensures reliable results.

Applications:

• Design and construction of pavements, roadways, industrial floors, and any structure requiring high tensile strength to resist bending.

Note: Adhering to standardized testing methods ensures consistency and reliability in measuring the flexural strength of different concrete mixes.