What is Concrete?
Concrete is a heterogeneous mixture of aggregate and cement paste which gradually gains the strength by process of hydration. Concrete gains its strength with time. The concrete cube test Procedure is given below.
The strength of concrete depends upon the batching process, mixing process, quality of aggregates, cement, and water.
Strength of Concrete at with Passing Time
|Days of casting||Strength gain|
Concrete is supposed to resist all the compression load in a Reinforced cement concrete structure. There might be a lot of discrepancy due to poor workmanship and quality of the material and mixing processes.
Therefore, to get the strength of the concrete as per design concrete are to be tested under field condition. Cube test is a destructive method to determine the compressive strength of the concrete. The compressive force is the resistance against push force.
Concrete cube test Procedure
- Firstly, in a clean and dry pan, fine and coarse aggregates is taken by weight. The quantity of material taken should be enough to prepare at least 3 cubes of 150mm in size.
- It would be better if well-graded aggregates are used. In general, clean and dry aggregate passing 20mm sieve size is used for coarse aggregates and aggregates passing through sieve 4.75 mm and retaining on 75 microns is used for fine.
- Cement is added and mixed till uniform color is achieved.
- Water cement ratio is chosen according to the grade of concrete. The water-cement ratio should be 0.38 to complete the hydration process. The increased water-cement ratio decreases the strength of the concrete.
- After the concrete is mixed, a slump test is done to check the workability of the concrete.
The standard cone with a height of 30 cm and a diameter of holes 10 and 20 cm is taken. The cone has two arms to facilitate the operation of the slump test.
Firstly, the cone is placemaking a small diameter upwards on the firm surface and presses on both arms to prevent movement of the cone. Then fill the cone making layers.
Compact the layer with a tamping rod of 16 mm diameter of 0.6m length for about 25 times. After filling the cone, pull the cone in an upward direction. Measure the slump value and check the workability of the concrete.
Slump test procedure is discussed in IS code 1199.
- The mold is cleaned and oiled before placing the concrete. Also, leakages are repaired if any.
- The concrete is placed making layers, at least 3. Each layer is properly compacted, all the work is to be finished before the initial setting time of the cement.
- The mould is placed under the shade for at least 24 hours and cubes are placed in a water bath for 7 days. The temperature of the water should be 27ºC ±2ºC Water in the water bath should be changed every 7 days.
- On the 28th day of casting, a compression test is performed. The load is applied in the direction of compaction.
- The cube should remove from the water bath half an hour prior to testing, let the cube dry.
- The cube is firmly placed on the machine and the initial recording is noted.
- The load is applied axially at a rate of 140kg/cm2 per minute. Final reading when the cube collapses is also noted.
Compressive strength = Average from 3 specimens are used to obtain the compressive strength of the concrete.
I hope this article on “Concrete cube test Procedure” remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Rukshana Shresth