Categories: Building Material and Construction

The compressive strength of hardened cement is the most important of all the properties. Therefore, it is not surprising that the cement is always tested for its strength at the laboratory before the cement is used in important works.

**Why the compressive strength test of Cement is important?** Compressive Strength Test on Cement mortar is calculated to find out whether the Cement conforms IS specifications or not and whether it can develop required strength or not when used in Concrete.

Any kind of strength testings are not done directly on Cement itself because of properties like shrinkage and cracking. So Compressive strength test on Cement either done in the form of mortar or concrete. In this article, we will take a look at the compressive strength test of cement mortar using standard sand conforming to IS 650-1991.

**Note:** This article is on Compressive Strength Test on Cement Mortar not on Compressive Strength Test on Concrete

Compressive Strength of any material or structure is the ability to carry the load on its surface without cracking or bending. The compressive strength of a material or structure gives an idea about the load-carrying capacity of that material or structure.

Compressive strength test is a method used to find out the resistance of any material or structure and ability of that structure or material to recover after the application of Compressive force on the surface for a defined period of time.

In the Compressive Strength test we apply a push force on both the faces of specimen and the maximum force the specimen bears without failure is noted down and that is the Compressive strength of that Cement.

**Also Read: 6 Tests on Cement | Lab Tests**

Compressive strength is calculated as the ratio of the maximum load carried by specimen to the **exposed surface area** of specimen. The formula for Compressive strength is **F=P/A** where F is Compressive strength in (MPA), P is load applied in (N) and A is surface area in (sq m).

Compressive strength test of cement done using UTM(Universal Testing Machine) or CTM(Compression testing machine).

To determine Compressive Strength of Cement.

- Vibration Machin
- Poking Rod
- Cube Mould
- Weighing Balance
- Trowel
- Stopwatch
- Graduated Glass Cylinder

- Appliances used for mixing should be clean, water used for mixing should be Distilled Water and that should be at room temperature.
- The quantity of Cement and sand should be 185 grams and 555 grams(ratio 1:3).
- Water required is equal to (p/4 + 0.3) percent of the combined weight of Cement and Sand.
- Place on the nonporous plate the mixture of cement and sand mix it dry by the use of trowel for at least a minute then with water for not less than 3 minutes and not greater than 4 minutes until the paste gets uniform colour. If the uniform colour is not obtained even after 4 minutes then the procedure should be repeated for with another mix.

- Clean the mould with distilled water dry it and then apply oil to the inner faces.
- Immediately after mixing of the mortar, place the mortar in the cube mould of 7.06cm and prod with the help of the rod. The mortar shall be prodded 20 times in about 8 sec to ensure the elimination of entrained air.
- If the vibrator is used, the period of vibration shall be 2 minutes at the specified speed of 12000 ± 400 vibrations/minute. Then place the cube moulds in temperature of 27±2 °C and 90% relative humidity.
- After completion of vibration remove the mould from vibrator and level the surface by trowel or blade.

- After completion of compaction place the specimen in a moist closed room for 24 hrs. Then remove the mould and immediately put the block into the water until removals for the tests.
- The water in which these cubes are placed shall be changed in 7 days and should be at room temperature.
- During changing of water the cubes are not allowed to dry And should be removed for Compressive Strength Test in 7, 14, and 28 days.
- During testing, the load shall be applied uniformly from 0 at a rate of 35 N/mm² per minute.

- Test the specimen on a 7 day period.
- The temperature should be 27±2 °C and relative humidity 90%.

Sr. No. | Days | Weight of Cement Cube (gm) | Cross-Sectional Area (mm²) | Load (N) | Crushing Load (N/mm²) | Average Compressive Strength (MPa) |
---|---|---|---|---|---|---|

1 | ||||||

2 | 7 | |||||

3 | ||||||

4 | ||||||

5 | 14 | |||||

6 | ||||||

7 | ||||||

8 | 28 | |||||

9 |

**Note:** As per IS: 516-1959 Minimum three specimens should be tested on each testing time (that means three specimens at 7 days, three specimens @ 14 days & 28 days) If the strength of any specimen varies by more than 15% of average strength, such specimen should be rejected.

Exposed Area of Block= 15cm × 15cm = 225cm²

Compressive Strength on 7th day= Maximum Load carried by Specimen / Exposed Area of Block

Exposed Area of Block= 15cm × 15cm = 225cm²

Compressive Strength on 14th day= Maximum Load carried by Specimen / Exposed Area of Block

Exposed Area of Block= 15cm × 15cm = 225cm²

Compressive Strength on 28th day= Maximum Load carried by Specimen / Exposed Area of Block

Average 7 days Compressive Strength =_ _ _ _

Average 14 days Compressive Strength =_ _ _ _

Average 28 days Compressive Strength =_ _ _ _

The compressive strength of cement is the ability of the cement to resist or sustain under the compression.

Compressive Strength of Cement of different grades at 7 and 28 days are given below

A compressive strength test is a method used to find out the resistance of any material or structure and ability of that structure or material to recover after the application of compressive force on the surface for a defined period of time.

In the Compressive Strength test, we apply a push force on both the faces of the specimen and the maximum force the specimen bears without failure is noted down and that is the Compressive strength of that Cement.

(IS:4031-Part 6-1988) is the IS code for the procedure for the tests to evaluate the physical properties of different types of hydraulic cements.

Compressive strength is calculated as the ratio of the maximum load carried by specimen to the **exposed surface area** of specimen. The formula for Compressive strength is **F=P/A** where F is Compressive strength in (MPA), P is load applied in (N) and A is surface area in (sq m).

Compressive Strength Test on Cement mortar is calculated to find out whether the Cement conforms IS specifications or not and whether it can develop required strength or not when used in Concrete.

12 months ago

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