Compressive strength test, mechanical test measuring the maximum amount of compressive load a material can bear before fracturing. The test piece, usually in the form of a cube, prism, or cylinder, is compressed between the platens of a compression-testing machine by a gradually applied load.
🎨Compressive Strength Test Of Concrete Cubes
To identify the compressive strength of concrete.
🔰Apparatus & Equipment:🔔
1. Compression test maker,
2. Cube mould of 15 cm size,
3. Curing Tank,
4. Tamping bar,
5. Weighing balance.
🔰Specimen For Test:
The cube samples will be of 15 x 15 x 15 cm. If the biggest small size of the aggregate does not go beyond 2 cm, then cube samples of 10 cm might be utilized as an option.
🔰Casting Of Concrete Cubes:
The active ingredients must be proportioned based on style requirement.
Mixing Of Concrete:
The concrete must be blended either by hand or in a lab maker mixer in such a way regarding lower waste of water and other products.
The maker blending must be done as follows:
1. Add one half of the coarse aggregate into the blending drum.
2. Then include cement and great aggregates and lastly include the staying coarse aggregates.
3. Add the needed quantity of water.
4. Start the blending maker until the resulting concrete offers consistent texture.
The blending must be done on a watertight, non-absorbent platform with a trowel or shovel utilizing the following treatment:
1. Mix the cement and great aggregates completely in dry condition.
2. Add Coarse aggregates and completely combine with cement and great aggregates.
3. Add the needed quantity of water and blend it correctly till the concrete ends up being uniform of preferred consistency.
🔰Sampling Of Concrete Cubes:
1. Fill the mould with newly blended concrete in layers roughly 5 cm deep.
2. Compact the concrete either by vibrator or by utilizing the tamping bar. ( Minimum 35 strokes per layer for 15 cm cubes and 25 strokes for 10 cm cubes).
3. Finish the top level of the mould utilizing a trowel.
4. Cover the mould with a glass plate or gunny bag to safeguard evaporation.
🔰Curing Of Concrete Cubes:
1. Keep the specimens in a location, devoid of vibration, in damp air and at a temperature level of 27°C ±2° C for 24 hours.
2. After 24 hours, mark and get rid of the samples from the mould.
3. Submerge the cubes right away in fresh and tidy water till secured prior to the test. The water must be restored every 7 days.
🔰Procedure Of Compressive Test:
1. Remove the specimens from water prior to 30 minutes of the screening.
2. Remove any loose sand or other product from the surface of the specimens and let them dry.
3. Clean the bearing surface of the compression screening maker.
4. Now put the cube in the screening maker in such a way that the load is used o the opposite sides of the cubes.
5. Align the axis of the specimen with the centre of thrust of the spherically seated platen.
6. Apply the load progressively at a rate of 140 kg/cm² per minute until the cube collapse.
7. Note down the optimum load used to the specimen and any other uncommon activities at the time of failure.
🟡Points To Be Remembered :
🟩1. Age Of Test:
The test ought to be done at 7 days and 28 days.
🟩2. Number Of Specimen:
At least 3 specimens, ideally from various batches for screening at each chosen age.
Let presume the optimum used load is 400 KN = 400000 N
Cross-sectional location of cube =15 x 15 = 225 cm²
Compressive strength = 400000/225 = 1778 N/cm² = 1778/9.81 = 181 Kg/cm² [ 1kg =9.81 N]
|Specimen 1||Specimen 2||Specimen 3|
|380 KN||400 KN||425 KN|
|(380000/225) / 9.81
= 172 kg/cm²
|(400000/225) / 9.81
= 181 kg/cm²
|(425000/225) / 9.81
= 192 kg/cm²
|Average Compressive Strength||= (172+181+192)/3
= 181.66 Kg/cm²
This test ought to be done at a temperature level of 27°C ± 2°C.
🔰Compressive Strength Of Concrete Over Time:
🔰Compressive Strength Of Concrete At 7 & 28 Days: