Information on the most widely used ASTM standards within the materials testing industry
ASTM C39 / C39M : Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
ASTM C39 determines the compressive strength of cylindrical concrete specimens such as molded cylinders and drilled cores. It is limited to concrete having a unit weight in excess of 50 lb/ft3 (800 kg/m3).
A compressive axial load is applied to molded cylinders or cores until failure occurs. The compressive strength of the specimen is calculated by dividing the maximum load achieved during the test by the cross-sectional area of the specimen. The results of this test method are used as a basis for quality control of concrete.
Cylinders cast and cured in the field are transported to the laboratory within 24-to-48 hours of production. Cylinders are then cured in water (or high-humidity chamber) for the specified curing period (e.g., 7-days, 28-days, etc.). On the date the cylinder has cured for the specified period of time, the cylinder is removed from the water tank and tested in compression with strength and failure mode reported.
Preferred Test Sample Size:
Typically 4" x 8" or 6" x 12" cylinders
Number of Test Specimens:
3 but typically several specimens per set of cylinders
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Compressive strength of concrete: Out of many test applied to the concrete, this is the utmost important which gives an idea about all the characteristics of concrete. By this single test one judge that whether Concreting has been done properly or not.
Compressive strength of concrete depends on many factors such as water-cement ratio, cement strength, quality of concrete material, quality control during production of concrete etc.
Test for compressive strength is carried out either on cube or cylinder. Various standard codes recommends concrete cylinder or concrete cube as the standard specimen for the test. American Society for Testing Materials ASTM C39/C39M provides Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens,
For cube test two types of specimens either cubes of 15 cm X 15 cm X 15 cm or 10cm X 10 cm x 10 cm depending upon the size of aggregate are used. For most of the works cubical moulds of size 15 cm x 15cm x 15 cm are commonly used.
This concrete is poured in the mould and tempered properly so as not to have any voids. After 24 hours these moulds are removed and test specimens are put in water for curing. The top surface of these specimen should be made even and smooth. This is done by putting cement paste and spreading smoothly on whole area of specimen.
These specimens are tested by compression testing machine after 7 days curing or 28 days curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails. Load at the failure divided by area of specimen gives the compressive strength of concrete.
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