The compressive strength test is a crucial procedure in assessing the ability of a material to withstand axial loads. In the context of construction materials like concrete, the compressive strength is a key parameter. The Indian Standard (IS) code that provides guidelines for the compressive strength test of concrete is IS 516:1959 – “Method of Tests for Strength of Concrete.”
Here is a basic methodology for conducting the compressive strength test according to IS 516:1959:
Apparatus Required:
- Compression Testing Machine:
- The compression testing machine should conform to the requirements of IS 14858:2000.
- Cubical or Cylindrical Molds:
- The molds should conform to the requirements of IS 10086.
- Weighing Balance:
- Capable of weighing up to 10 kg and accurate to 1 gram.
- Tamping Rod:
- A steel rod 16 mm in diameter and 600 mm long.
- Mallet:
- A mallet weighing 0.59 kg.
- Steel Trowel:
- A steel trowel about 150 mm long and 100 mm wide.
- Measuring Cylinder:
- A graduated cylinder for measuring water.
Procedure:
- Sample Collection:
- Collect samples of concrete in accordance with the relevant standard.
- Preparation of Test Specimens:
- Prepare test specimens either in the form of cubes (150 mm x 150 mm x 150 mm) or cylinders (150 mm diameter x 300 mm height).
- Mixing of Concrete:
- Prepare concrete mixtures in accordance with the mix design and standard procedures.
- Filling the Molds:
- Fill the molds with the freshly mixed concrete in layers approximately 5 cm deep. Compact each layer with 25 strokes of the tamping rod.
- Finishing the Surface:
- After filling the mold, strike off the excess concrete using the trowel so that the surface of the concrete is level.
- Curing:
- Cure the specimens in a curing tank or by covering them with wet hessian cloth for a specified period (typically 7 or 28 days).
- Testing:
- After the curing period, remove the specimens from the molds and wipe off any water from the surface. Place the specimen on the compression testing machine and align it properly.
- Loading:
- Apply a load gradually without shock, at the rate of 140 kg/cm² per minute until the specimen fails. Note the maximum load sustained by the specimen.
- Calculations:
- Calculate the compressive strength using the formula:
[ f_c = \frac{P}{A} ]
where ( f_c ) is the compressive strength, ( P ) is the maximum load, and ( A ) is the cross-sectional area of the specimen.
- Reporting:
- Report the compressive strength of the specimen in megapascals (MPa).
Precautions:
- Ensure that the testing machine is calibrated.
- The testing environment and curing conditions should comply with the standard specifications.
- Handle specimens carefully to prevent damage.
Always refer to the latest version of the relevant IS code for the most accurate and up-to-date procedures and requirements.
The compressive strength test is a crucial procedure in assessing the ability of a material to withstand axial loads. In the context of construction materials like concrete, the compressive strength is a key parameter. The Indian Standard (IS) code that provides guidelines for the compressive strength test of concrete is IS 516:1959 – “Method of Tests for Strength of Concrete.”
Here is a basic methodology for conducting the compressive strength test according to IS 516:1959:
Apparatus Required:
- Compression Testing Machine:
- The compression testing machine should conform to the requirements of IS 14858:2000.
- Cubical or Cylindrical Molds:
- The molds should conform to the requirements of IS 10086.
- Weighing Balance:
- Capable of weighing up to 10 kg and accurate to 1 gram.
- Tamping Rod:
- A steel rod 16 mm in diameter and 600 mm long.
- Mallet:
- A mallet weighing 0.59 kg.
- Steel Trowel:
- A steel trowel about 150 mm long and 100 mm wide.
- Measuring Cylinder:
- A graduated cylinder for measuring water.
Procedure:
- Sample Collection:
- Collect samples of concrete in accordance with the relevant standard.
- Preparation of Test Specimens:
- Prepare test specimens either in the form of cubes (150 mm x 150 mm x 150 mm) or cylinders (150 mm diameter x 300 mm height).
- Mixing of Concrete:
- Prepare concrete mixtures in accordance with the mix design and standard procedures.
- Filling the Molds:
- Fill the molds with the freshly mixed concrete in layers approximately 5 cm deep. Compact each layer with 25 strokes of the tamping rod.
- Finishing the Surface:
- After filling the mold, strike off the excess concrete using the trowel so that the surface of the concrete is level.
- Curing:
- Cure the specimens in a curing tank or by covering them with wet hessian cloth for a specified period (typically 7 or 28 days).
- Testing:
- After the curing period, remove the specimens from the molds and wipe off any water from the surface. Place the specimen on the compression testing machine and align it properly.
- Loading:
- Apply a load gradually without shock, at the rate of 140 kg/cm² per minute until the specimen fails. Note the maximum load sustained by the specimen.
- Calculations:
- Calculate the compressive strength using the formula:
[ f_c = \frac{P}{A} ]
where ( f_c ) is the compressive strength, ( P ) is the maximum load, and ( A ) is the cross-sectional area of the specimen.
- Reporting:
- Report the compressive strength of the specimen in megapascals (MPa).
Precautions:
- Ensure that the testing machine is calibrated.
- The testing environment and curing conditions should comply with the standard specifications.
- Handle specimens carefully to prevent damage.
Always refer to the latest version of the relevant IS code for the most accurate and up-to-date procedures and requirements.