### 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 (fâ‚œ) 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).

- Flexural Strength (fâ‚œ) calculated using the formula:$${f}_{t}=\frac{PL}{b{d}^{2}}$$Where:
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.

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