This question was previously asked in

UP Jal Nigam Civil 2016 Official Paper

Option 2 : Limestone and clay

**Explanation:**

The main constituents of Portland cement is argillaceous and calcareous material.

Argillaceous materials are clay, shale, etc.

Calcareous materials are limestone, Chalk, etc.

__Characteristics____ of an Ordinary Portland cement (OPC):__

1. It is available in 3 grades – OPC 33, OPC-43 and OPC-53 and the number 33, 43, 53 corresponds to 28 days characteristic compressive strength of cement as obtained from standard test on cement.

2. Initial setting time shall not be less than 30 minutes and final setting time should not be more than 10 hours.

3. Soundness lies from 5 to 10 mm when calculated from Le-Chatelier’s method.

4. Residue by weight shall not be more than 10 % when sieved on 90 micron sieve and sieved for 15 minutes continuously.

5. It tensile strength 10-15 % of the compressive strength.

6. Its tensile strength should not be less than 2 MPa and 2.5 MPa after 3 days and 7 days respectively.

7. Its compressive strength for 33 grade at 3 days, 7 days, and 28 days is 16 MPa (160 kg/cm2), 22 MPa (220 kg/cm2) and 33 MPa (330 kg/cm2) respectively.

8. Total loss on ignition shall not be more than 5 %.