**Compressive strength of cement and cement mortar,** hi guys in this article we know about compressive strength of cement and cement mortar by making cube test pressing with hydraulic machine.

**Compressive strength of cement** is determined by cube test on cement mortar cubes compacted by means of a standard vibration hydraulic machine. Standard vibration for making cube is 12000 +- 400 vibration per minute and it will vibrate for 2 minute.

**Standard sand according to IS:650** is known as innor sand obtained from Tamil Nadu used for the preparation of cement mortar. For the preparation of cement mortar we use cement sand ratio is 1:3 in which one part is cement and 3 part is sand.

**Make a small size of 3 cube having specimen (l × b × h) 70.6mm×70.6mm×70.6mm**. Large Size of cube is not made because of shrinkage and cracking.

**Compressive strength of cement in N/mm2**

Compressive strength of cement is calculated in N/mm2 or MPa.

33N/mm2 – 53N/mm2 is Compressive strength of cement mortar after curing of 28 days.

**Compressive strength of cement** is calculated in 1day,3 days, 7 days and 28 days after curing period. As we know there is different types of cement ordinary Portland cement Portland pozzolana cement Portland slag cement and so many types.

**There is a table** given for the compressive strength of cement mortar according to curing time of 1days,3days,7days & 28 days. And where compressive strength is measured in N/mm2 or MPa.

Cement 1 Day 3 Days 7 Days 28 Days

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OPC(33) — 16 22 33

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OPC(43). — 23 33 43

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OPC(53) — 27 27 53

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SRC. — 10 16 33

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PPC — 16 22 33

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RHPC 16 27 — —

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PSC — 16 22 33

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High alumina. 30 35 — —

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Super sulphated — 15 22 30

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Low heat — 10 16 35

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Masonry — — 2.5 5.0

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IRS-T-40 — — 37.5 —

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**Compressive strength of cement test**

**1) For the cube test we require following appartus**

● Cube mould size 70.6 ×70.6×70.6 mm3(IS:10080)

● Vibration machine Should be as per IS:10080

● Balance 1000 g

● Measuring cylinder 200 ml

● and other apparatus is used for cube test is

Enamel tray, Trowel, Poking rod,Cement Mould

**2) environmental condition:** the temperature should be 29℃ or 25℃ are represented as temperature 27 ± 2°C, humidity should be 65 ± 5%

**3) cement sand ratio:**_ cement sand ratio for preparing mortar is 1:3 in which one part is cement and 3 part is sand.

**Test procedure for compressive strength of cement**

Take 200 g of cement and 600 g of standard sand (1:3) and mix them dry thoroughly.

Add cement consistency is 2 for water (where P is % of water required for preparing paste of standard consistency) to the dry mix of cement and sand and mix thoroughly for a minimum of 2 minutes by vibrator at the rate of 12000+- 400 per minute to obtain a mix of uniform colour.

Place the thoroughly cleaned and oiled (on interior face) mould on the vibrating machine and hold it in position by clamps provided on the machine for the purpose.

Fill the mould with entire quantity of mortar using a suitable hopper attached to the top of the mould for facility of filling and vibrate it for 2 minutes at a specified speed of 12000±400 per minute to achieve full compaction.

Remove the mould from the machine and keep it in a place with temp of 27±2°C and relative humidity of 90% for 24 hours.

At the end of 24 hrs remove the cube from the mould and immediately submerge in fresh clean water. The cube be taken out of the water only at the time of testing.

Prepare at least 3 cubes in the manner.

Place the test cube on the platform of a compressive testing machine without any packing between the cube and the plates of the testing machine.

Apply the load steadily and uniformly, starting from zero at a rate of 35 N/mm2/minute.

**Cement compressive = load/ cross sectional area F= p/A**

Where, F = cement compressive strength

P=Maximum load applied to the cube. (N)

A=Cross sectional area (Calculated from the mean dimensions) (mm2)

**● PRECAUTIONS:-**

1)The mould should be oiled before use

2)The weighing should be done accurately

3)The temperature and humidity must be accurately controlled

4) Increase the load gradually during testing.

5) The cubes should be tested immediately after taking out of water and not allowed to dry until they fail under testing.

6) The gauging time should be strictly observed.

7) The cubes should be tested on their sides and not on their faces.

**● Technical discussion:-**

Strength tests are not made on a neat cement paste because of difficulties of moulding and testing with a consequent large variability of test results.

Compressive strength is influenced by the cement type, or more precisely, the compound composition and fineness of cement.

It should be assumed that two types of cement meeting the same minimum requirements will produce the same strength of mortar or concrete without modification of mix proportions.

● **Time and strength gain:** time and strength of cement relationship are non linear.

1) 1 day of curing time cement gain its strength about 16% of total strength

2) 3 days of curing time cement gain its strength about 40% of total strength

3) 7 days of curing time cement gain its strength about 65% of total strength

4) 14 days of curing time cement gain its strength about 90% of total strength

5) 28 days of curing time cement gain its strength about 99% of total strength

6) 3 months of time cement gain its strength about 110% of total strength

7) 6 months of time cement gain its strength about 115% of total strength

8) 1 year of time cement gain its strength about 120% of total strength.

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