Proper precautions for the storage of cement such as duration and place of storage, arrangement, atmospheric moisture content etc. is necessary after the process of manufacturing and before using it in the construction site.
Because the cement hygroscopic nature, the cement absorbs moisture from the atmosphere very actively and hardens like stone which cannot be used for constructional purpose. So, storage of cement should be done with care.
Precautions for Proper Storage of Cement
Cement should not be stored normally. There are some precautions to be considered in the storage of cement. Following are the different situations against which precautions are to be taken:
- Atmospheric moisture content
- Duration of cement storage
- Place of storage
- Arranging cement bags
- Withdrawal of cement bags
1. Moisture Content at Place of Storage
Moisture content or dampness is the main hazard for the cement. The moisture present in the atmosphere is enough for the cement to become useless material. The cement should be stored in such a way that it cannot expose to the atmosphere. So, air tight bags are used to pack the cement.
The absorption of moisture from atmosphere will also depends up on the quality of cement. If the cement is finely grained and very good in quality, then it will absorb moisture vigorously. Hence, extra care should be taken for this type of cement and it is better use it in its fresh stage.
In any case if it is exposed to atmosphere, the present of moisture content is to be tested. If the moisture content is more than 5% then it is not useful for the construction.
2. Duration of Cement Storage
Time of storing is also a factor that affects the cement especially its strength. Longer the time reduces the strength of cement. It is preferred that the cement should not be stored for more than 3 months. However, if it is stored more than 3 months the strength of cement should be tested before using it.
The following table gives us the percentage reduction of strength of cement for different time periods.
|Period of storage||Fresh stage||3 months||6 months||1 year||5 years|
|% Reduction in strength at 28 days||0%||20%||30%||40%||50%|
If the cement is stored for longer time and strength is found to be reduced, then it is not good for construction. But however, it can be reactivated by different methods like vibro grinding etc. vibro grinding improves fineness quality of long period stored cement and make it fit for the constructional purpose.
3. Place of Cement Storage
The bags of cement should not be stored in open places. Preferably specially designed storage sheds are good for cement storage. They can be used for longer periods.
The main purpose of special design is to provide waterproof floors, roofs and walls. The floor of shed should be well above the ground level. Small windows with air tight doors should be provided. Proper drainage should be provided inside and outside the shed to drain water in any case.
In general, one bag of cement contains 50 kilograms of cement, 20 bags of cement will require 1 cubic meter to store. Based on this the dimensions of storage shed are designed.
4. Arrangement of Cement Bags
A wooden platform of height 150 to 200 mm is prepared above the floor of storage shed to avoid the direct contact between the floors and cement bags.
On the prepared wooden platform, the cement bags should be arranged one above the other which forms stack of cement bags. Each stack should not consist not more than 10 bags of cement. The stack should not touch the walls of shed and it should be considerably 300 mm away from the external walls. Each stack should be closely connected to avoid the circulation of air.
To prevent collapsing of high stacks, cross arrangement of bags one above the other is preferable. All the stacks are covered with water proof layer for long term protection. Passage width of 900mm to 1000mm is provided between the stacks. The stack should consist same type of cement and for each stack date of placing should be noted to know their period of storage.
5. Withdrawal of Cement Bags
When the time of using arrives, Withdrawal of cement bags from stacks happens. The cement bags should be taken out in such a way that the bag first placed in storage shed should be withdrawal first.