cube test of concrete

Compressive Strength Test

This test give us an idea about all the characteristics of concrete. With the help of this test we can check that whether Concreting has been done properly or not. and compressive strength is the ability of material or structure to carry the loads on its surface without any crack or deflection. A material under compression tends to reduce the size, while in tension, size elongates

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.

The cubes are generally tested at 7 & 28 days unless specific early tests are required and Strength of concrete increase with age showen in Below Table :

Age Strength percent

1 day 16%

3 days 40%

7 days 65%

14 days 90%

28 days 99%

Procedure of Test
For this test mainly 150mm * 150 mm * 150 mm cubes are used

Clean the mounds properly and apply oil inside the cube frame

Fill the concrete in the molds in layers approximately 50mm thick

Compact each layer with not less than 35 strokes per layer using a tamping rod (steel bar 16mm diameter and 600 mm long, )

Level the top surface and smoothen it with a trowel

The concrete cubes are removed from the moulds between 16 to 72 hours, usually this done after 24 hours. Remove the specimen from water after specified curing time and wipe out excess water from the surface.Take the dimension of the specimen to the nearest 0.2mm And then place the specimen in the machine in such a manner that the load shall be applied to the opposite sides of the cube cast.Align the specimen centrally on the base plate of the machine.Rotate the movable portion gently by hand so that it touches the top surface of the specimen.

Apply the load gradually without shock and continuously at the rate of 140 kg/cm2/min. till the specimen fails

Record the maximum load and note it

as example

 Reading     640kn

result 640/22.5 =28.44N/mm2