CONCRETE CUBE

IS CODE: 516-1959 (METHODS OF TESTS FOR STRENGTH OF CONCRETE)

This standard adopted by the Indian standard institute on 10 November 1959

Approved by building division council.

This standard covers tests for the determination of compressive strength 

Cube mould – 150x150x150, 100x100x100

The height of the mould and the distance between opposite faces shall be the specified size +0.2 mm. The angle between adjacent internal faces and between internal faces and top and bottom planes of the mould shall be 90 ± 0.5. The interior faces of the mould shall be plane surfaces with a permissible variation of 0.03 mm.

In assembling the mould for use, the joints between the sections of mould shall be thinly coated with mould oil

Temping bar- the temping bar shall be a steel bar 16 mm in diameter, 0.6 m long and bullet pointed at lower end

For cubical specimens, in no case shall the concrete be subjected to less than 35 strokes per layer for 15 cm or 25 strokes per layer for 10 cm cubes. And for cylindrical specimens, the number of strokes shall not be less than thirty per layer.    

Maximum nominal size of aggregate does not exceed 38 mm

Curing –the test specimen shall be stored on the site at a place free from vibration, for 24 hours ± ½ hour from the time of adding the water to the other ingredients. After the period of 24 hours, they shall be marked for later identification  

Testing  machine the testing machine may be of any reliable type, of sufficient capacity for tests and capable of applying the load at the rate specified in 5.5.the permissible error shall not greater than ±2 % of the maximum load. The load shall be applied without shock and increased continuously at a rate of approximately 140 kg/sq cm/minute until the resistance of the specimen of the specimen load breaks down and no greater load can be sustained

Age at test – tests shall be made at recognized ages of the test specimens, the most usual 7 and 28 days. The ages shall be calculated from the time of addition of water to the dry ingredients.

Procedure – specimen stored in water and while they are still tested immediately on removal from the water and while they are still in wet condition,

Calculation – the measured compressive strength of the specimen shall be calculated by dividing the maximum load applied to the specimen during the test by cross-sectional area. Average of three values shall be taken as the representative of batch provided the individual variation is not more than ±15 % of the average. Otherwise repeated tests shall be made

Report – the following information shall be included in the report on each test specimen

a)   1.  Identification mark,

b)     2. Date of test

c)    3.   Age of specimen,

d)     4. Curing condition, including date of manufacture of specimen in the field,

e)   5.   Weight of specimen,

f)    6.   Dimensions of specimen,

g)   7.   Cross-sectional area,

h)    8.  Maximum load,

i)    9.    Compressive strength, and

j)     10.   Appearance of  fractured faces of concrete and type of fracture,if these are unusual