Concrete Technology

Assessing the Quality and Quantity of Cement

Assessing the Quality and Quantity of Cement

1.Colour of the cement should be uniform and grey for 0rdinary Portland. Cement(OPC) and blackish in case of Portland Pozzolana Cement(PPC).

2.When rubbed between fingers, it should be felt like flour. If found rough, it implies adulteration, with sand/earth.

3.If hand is inserted in a bag or heap of cement,-it should feel cool. if a small quantity of cement is thrown in a bucket of water it should sink and should not float on the surface. ‘

4.Cement should be free from any hard lumps. These lumps are formed by the absorption of moisture from the atmosphere. Any bag containing such lumps should be rejected.

Physical Characteristics of Cement

Min. Compressive Strength 33 Grade 43 Grade 53 Grade
3 Days 16 N/Sq.mm 23 N/Sq.mm 27 N/Sq.mm
7 Days 22 N/Sq.mm 33 N/Sq.mm 37 N/Sq.mm
28 Days 33 N/Sq.mm 43 N/Sq.mm 53 N/Sq.mm

N=Newton

Minimum initial Setting Time of Cement = 30 Minutes

Maximum Final Setting Time of Cement = 600 Minutes or 10 hours.

Quality and Quantity of Cement

1. Weight of one bag of cement is 50 Kgs

2. 1 ton of cement equals 20 bags

3. No of cement bags = Tonnage of cement x 20

4. Tonnage of cement = No. of Bags/20

5. Storage capacity of cement godown = 20 bags per Sq. M of plan area.

6. Capacity of a truck for carrying cement =250 to 300 bags(12.5 tons to 15 tons)

Reduction in Strength of Cement due to Storage

1. 20 % reduction in strength if stored for 3 months

2. 30 % reduction in strength if stored for 6 months

3. 40 % reduction in strength if stored for 12 months

4. 50 % reduction in strength if stored for 24 months

Storage Specifications of Cement

1. Distance from wall =30 cms or 1ft.

2. Distance from floor = 15 – 23 cms to be kept on wooden sleepers

3. Bags to be stacked in layers or 10 -12

4. No. of cement bags in a row = 15

5. Ventilation and lighting : Opening should be avoided to block the movement of air to reduce moisture. Only glazing to be provided for natural lighting.

See More Calculation Quantity of Cement Sand And Aggregate In Concrete Slab

Ebook Concrete Building Scheme Design Manual

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