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As Per Is 516: 1959 Sampling of Material In Lab
A representative sample of the materials of concrete, as per the cube testing IS code, for use in the particular concrete construction work shall be obtained by careful sampling.
Test samples of cement shall be made up of a small portion taken from each of a number of the bag on the site test samples of aggregate shall be taken from a larger lot by quartering.
As Per Is 516 Cl 2.6.1: Machine Mixing For Cube In Lab
As per the IS 516 code, the period of mixing shall be not less than 2 minutes after all the materials are in the drum, and shall continue till the resulting concrete is uniform in appearance.
When using pan mixers, the concrete shall be heaped together before sampling.
As Per Is 516 Cl 2.6.2: Hand Mixing Procedure For Cube In Lab
- The cement and fine aggregate shall be mixed dry until the mixture is thoroughly blended and is uniform in colour.
- The coarse aggregate shall then be added and mixed with the cement and fine aggregate until the coarse aggregate is uniformly distributed throughout the batch, and
- The water shall then be added, and the entire batch mixed until the concrete appears to be homogeneous and has the desired consistency.
- If repeated mixing is necessary, because of the addition of water in increments while adjusting the consistency, the batch shall be discarded and a fresh batch made without interrupting the mixing to make trial consistency tests.
- Mixers, the concrete shall be heaped together before sampling.
As Per Is 516 Cl 2.9.3: Tamping Bars / Road For CubeÂ
The tamping bar shall be a steel bar 16 mm in diameter, 0·6 m long, and bullet-pointed at the lower end.
As Per Is 516 Cl 2.10.1: Cube Compacting dy Hand
Concrete Cube:Â For cubical specimens, in no case shall the concrete be subjected to less than 35 strokes per layer for 15 cm cubes or 25 strokes per layer for 10 cm cubes.
As Per Is 516 Cl 2.12.1: Cube Curing In Lab
The test specimen- shall be stored in a place, free from vibration, in the moist air of at least 90 percent relative humidity and at a temperature of 27° ± 2°C for 24 hours ± 0.5 hours from the time of addition of water to the dry ingredients.
After this period, the specimens shall be marked and removed from the molds and, unless required for a test within 24 hours, immediately submerged in the clean, fresh-water, or saturated lime solution and kept there until taken out just prior to test.
The water or solution in which the specimens are submerged shall be renewed every seven days and shall be maintained at a temperature of 27° ± 2°C. The specimens shall not be allowed to become dry at any time until they have been tested.
As Per Is 516 Cl 3.3: Cube Curing In Filed
The test specimens shall be stored on the site at a place free from vibration, under damp matting, sacks, or other similar material for 24 hours ± 0.5 hours from the time of adding the water to the other ingredients.
The temperature of the place of storage shall be within the range of 22° to 32°C. After the period of 24 hours, they shall be marked for later identification, removed from the molds and unless required for testing within 24 hours, stored in clean water at a temperature of 24° to 30°C until they are transported to the testing laboratory.
They shall be sent to the testing laboratory well packed in damp sand, damp sacks, or other suitable material so as to arrive there in a damp condition not less than 24 hours before the time of the test.
On arrival at the testing laboratory, the specimens shall be stored in water at a temperature of 27° ± 2°C until the time of the test.
Records of the daily maximum and minimum temperature shall be kept both during the period of the specimens remain on the site and in the laboratory
As Per Is 516 Cl 5.6./ 6.6: Report For Concrete CubeÂ
As per Is code 516 below report
- Identification Mark
- Date of test
- Age of specimen
- Curing Condition including date of manufacture of a specimen in the field,
- Weight of specimen,
- Dimensions of a specimen,
- Cross.Sectional area,
- Maximum load,
- Compressive strength, and
- The appearance of a fractured face of concrete and type of fracture if these are unusual
Frequently asked questions (FAQ) related to concrete cube testing as per IS 516:1959 standards:
What is the purpose of concrete cube testing?
Concrete cube testing is conducted to assess the compressive strength of concrete, which is essential for ensuring the quality and durability of concrete structures.
Why is it important to obtain a representative sample of materials for concrete cube testing?
Obtaining a representative sample ensures that the test results accurately reflect the properties of the concrete used in construction, helping to make informed decisions about its strength and quality.
What are the recommended mixing procedures for concrete cubes in the laboratory?
IS 516 outlines both machine mixing and hand mixing procedures. Machine mixing involves a minimum mixing period of 2 minutes until the concrete is uniform in appearance. Hand mixing involves specific steps to ensure thorough blending of materials.
How should concrete cubes be compacted by hand?
Concrete cubes should undergo a specified number of strokes per layer using a tamping bar to ensure proper compaction, as per IS 516 standards.
What are the guidelines for curing concrete cubes in the laboratory?
Concrete cubes are to be cured in a controlled environment of at least 90% relative humidity and a temperature of 27°C ± 2°C for 24 hours. After this initial period, they are submerged in water or a saturated lime solution until testing.
What are the recommended procedures for curing concrete cubes in the field?
Concrete cubes in the field are initially stored under damp conditions for 24 hours, then submerged in water until transported to the testing laboratory. Temperature monitoring and proper packaging are crucial during this process.
What information should be included in a concrete cube testing report as per IS 516?
The report should include identification marks, test date, specimen age, curing conditions, specimen weight and dimensions, cross-sectional area, maximum load, compressive strength, and details of any unusual fractures observed.
What precautions should be taken during concrete cube testing to ensure accurate results?
It’s important to adhere strictly to the specified procedures for sampling, mixing, compacting, curing, and testing to minimize variables that could affect the accuracy of test results.
How often should concrete cube testing be conducted during a construction project?
Concrete cube testing should be performed regularly at different stages of construction to monitor the quality of concrete batches and ensure compliance with design specifications.
What are the implications of test results indicating low compressive strength in concrete cubes?
Low compressive strength may indicate issues with materials, mixing procedures, curing methods, or construction practices, necessitating corrective measures to ensure structural integrity and durability.
