Specification of Cement
The cement required for construction should be factory-manufactured from a reputed manufacturer. It must not be from the local plant manufacturer. Care should be taken that the cement is properly packed from the factory, not be hand packed locally. While taking supply of cement manufacturing date, grade and type should be checked. The cement should not be more than six weeks old from the date of manufacturing.
Precautions While Purchasing Cement
Cement is the most important raw material used in a building. You should ensure the quality of ‘Cement’ using the following guidelines.
1. The cement should be factory manufactured instead of plant manufactured.
2. The cement should be packed in the bags of synthetic jute or polypropylene bags.
3. The cement bags should not be hand stitched.
4. The cement bag should bear manufacturer's name or his trade mark on it if any.
5. The cement bag should bear the grade and type of cement.
6. The cement bag consignment must have identification mark on package.
7. The cement bag should indicate the date of manufacturing.
8. One cement bag should have 50 Kg. weight.
9. The cement bags should not be older than six weeks from the date of manufacturing.
10. Do not purchase cement bags which are partially set due to moisture. Do not purchase if there are small lumps in the bags.
11. Do not purchase cement bags which are pressed or have lumps due to high pressure of stack having more than 10 to 12 bags.
12. Do not take cement bags which are torn by side and stitched in later.
Precautions While Transporting Cement Bags
1. Care should be taken to carry the bags in a clean vehicle which is not dustier or on earth etc. It will reduce the strength of the cement.
2. During monsoon season the cement should be carried under covered Polythene or ‘Tarpaulin’.
3. Care should be taken that the labor should not tear the bags while loading and unloading the cement bags.
Precautions While Stacking Cement at Site
Store cement in a moist proof storage area other wise quality of cement will be affected.
1. Cement should be stacked in a shed/fumes, which is dry, leak proof and moisture proof.
2. Cement should be placed on dry brick floors, on wooden crates or on the planks.
3. In any case, the cement bags should not be stored on the earth.
4. The stack should not be higher than 10 bags to avoid lumps under pressure.
5. The cement bags should not be stacked with outer wall.
6. Cement from different manufacturers should be stacked separately.
7. The cement should be used on first come first used basis.
8. During monsoon season cement bags should be covered with polythene.
9. The cement bags should be kept close together to reduce air circulation.
1. When construction work is given to a contractor, make sure he takes proper care of the cement. A lot of time contractors do not care for proper storage of the cement at site as it costs them labor time (money). This results in reduction of strength of cement as the table below shows.
2. In some cases it has been seen that after laying the RCC slab on some part of the building, the contractor dismantles his temporary store at the site and places cement on ground floor of the building which is under construction. This is not good as the cement bags may draw moisture from the floor and walls, as the new building is wet due to construction work in progress, which results in reduction of strength in cement.
Reduction in Cement Strength Due To Storage
| S. No
|| Storage Period
|| Reduction in Strength|
|| Fresh cement
|| Three months old
|| Six months old
|| 12 Months old
|| 24 Months old
1. Due to absorption of moisture by cement during storage, cement retards in hardening and reduces the strength.
2. It is okay for cement to absorb up to 1.2% moisture as this level of moisture is acceptable but if absorption exceeds 5%, the cement is destroyed for all practical purposes.
3. Different types of cements should not be mixed while using them for constructional purposes.