**COMPRESSIVE STRENGTH TEST ON CEMENT**

**Aim:**

To determine the compressive strength of cement

**Apparatus Required**

1. Non porous enamel tray

2. Trowel

3. Cube mould of size 7.06cm

4. Platform vibrator (or) Equipment for hand compaction

5. Compression testing machine

6. Balance to measure weight

**Significance of the test:**

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 compressive strength at the laboratory before the cement is used in important works.

**Strength Test:**

Strength test are not done on neat cement paste because of difficulties of excessive shrinkage and subsequent cracking of neat cement. Strength of cement is indirectly found on cement – sand mortar in specific proportion.The cubes are prepared for this purpose. The cubes are then tested in compression testing machine at the end on three days and seven days. Testing of cubes is carried out on their three sides without packing. Thus the cubes are tested at each time.

**Procedure:**

**Preparation of cement mortar cubes:**

- Take 555 gms of standard sand, 185gms of cement (i.e.ratio of cement to sand is 1:3) in a non porous enamel tray and mix them with a trowel for one minute.
- Add water quantity (P/4 + 3.0) % of combined weight of cement and sand and mix the three ingredients thoroughly until the mixture is of uniform colour. The time of mixing should be less than three minutes and not more than four minutes.
- Immediately after mixing fill the mortar into a cube mould of sizes 7.06cm.
- Compact the mortar either by hand compaction in a standard specified manner or on the vibrating table.
- Place the moulds in cabin at a temperature of 27º ± 2º C for 24 hours
- Remove the specimen from the moulds and submerge them in clean water for curing.

**Testing of cement mortar cubes:**

- Take the cube out of water at the end of three days with dry cloth. Measure the dimensions of the surface in which the load is to be applied. Let be ‘L’ and ‘B’ respectively.
- Place the cube in compressive testing machine and apply the load uniformly at the rate of 35N/mm
^{2}. - Note the load at which the cube fails. Let it be ‘P’.
- Calculate the compressive strength of the cube by using formula. The compressive strength at the end of three days should not be less than 16N/mm
^{2} - Repeat the same procedure (steps 1 to 4) for other two cubes.
- Repeat the whole procedure (Step 1 to 5) to find the compressive strength of the cube at the end of 7 days and it should not be less than 22 N/mm
^{2}.

Tabulation

**(a)**

**For 3 days strength:**

Sl.No. | Length (L) in mm | Breadth (B) in mm | Load (P) in N | compressive strength in N/mm^{2} |

1 | | | | |

2 | | | | |

3 | | | | |

Average =

**(b)**

**For 7 days strength:**

Sl.No. | Length (L) in mm | Breadth (B) in mm | Load (P) in N | compressive strength in N/mm^{2} |

1 | | | | |

2 | | | | |

3 | | | | |

Average =

**Result:**

Compressive strength of cement at 3 days = N/mm

^{2}.Compressive strength of cement at 7 days = N/mm

^{2}
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ReplyDeleteWhat should be done if there are less moulds available?

ReplyDeleteWhen can we demould the sample?

Is it necessary to keep the sample in the mould for 24 hours?

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