Preservation Of Cement

Professional Practice - I

Why Preservation of Cement is Important?

Once we have bought the cement, the next step is storing it correctly.

Moisture : If cement is not stored properly, it can absorb moisture from the atmospheric air or any other source, causing cement to react with it chemically. The binding property and strength of cement depends on its capacity for chemical reaction. For this the strength of cement will be affected.

Period of Storage : Prolonged storage of cement, where moist air may gain access, decreases the strength of the cement and make it appear to be coarser and amount of water required to make up a neat cement paste of standard consistency increases and setting time is also increased. In worst cases lump formation even render the cement unusable.

For prevention of cement against deterioration and retaining its freshness its storage should be such that no dampness or moisture is allowed to reach cement either from the ground, walls or from the environment. This becomes important during the humid season and in coastal regions when atmospheric air contains higher amount of moisture in it.

Storage & preservation of Cement :1. Main requirement is weather-proof building or shed with following properties :

(a) Walls having water-proof masonry construction.(b) The roof should be R.C.C. or leak-proof.(c) The windows should be few and small in sizes and kept shut. This is to prevent moisture ingress.(d) Dry Coarse of Soling.(e) The floor should be preferably of concrete of 15 cms. thick. Care should be taken to drain away rain water to protect the floor from dampening.

2. Accumulation of water around the godown or shed, shall be avoided.

3. Cement bags should not be stored against the wall. A space of 40 cms. should kept between wall and stacks.

4. Cement bags should be stored from level of 15-20 cms. above the floor level by providing wooden planks to avoid penetration of moisture.

5. Sometimes owing to pressure on lower layer of the bags warehouse pack or pack-set can develop in the bags. This can be avoided by not stacking more than 10 bags high for white cement & not stacking more than 20 bags high for grey cement.

6. When putting new warehouse in use, Please ensure that interior is completely dry.

7. If the stack is more than 7 bags high, please arrange the bags in header and stretcher formation i.e. alternatively lengthwise and breadthwise so as to tie them together to avoid chance of toppling over. 8. Cement bags should be placed close to each other in the stack so as to reduce air penetration.

9. When the bags are required to be stored for longer period or to be stored during monsoon then for extra safety it is always advisable to cover the stock with water-proof tarpaulin or polythene sheet.

10. During wet/cold weather the outside temporary storage should be avoided.

11. Cement in gunny bags, paper bags and polyethylene bags shall be stored separately.

12. Godown shall be cleaned, repaired & painted as & when needed.

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Note: BIS prescribes that cement should be used within 90 days of its production. In case it is used at a later date then it should be tested before use.

Sometimes cement requirement of a day or two may have to be stored at site in the open. In such cases cement bags should be laid on a dry platform made of wooden planks resting over brick-masonry concrete, dry sand agregates raised about 15 cms. above the ground level.

The stack must be kept fully covered with tarpaulin or polythene sheet and protected against atmospheric moisture. Temporary storage or open storage should not be adopted in wet weather.

Temporary Storage at Site

When the bags are required to be removed for use, follow the ‘First In First Out' rule (FIFO system) i.e. the oldest cement to be used first. For this purpose, each consignment of cement should be stacked separately and identified by a placard bearing the date of arrival.

Remove the bags from two or three tiers at the back.

Do not remove bags from only one tier in the front.

Removal of Cement Bags

Good axioms of proper inventory management are:o Buy only the quantity required for the week or for the fortnight.o See that cement bag is not torn.o Do not allow workers to use hooks or sharp tools to lift the bags.o Sometimes, when the cement bag is brought down, it may appear hard (pack

lumps) because of the load of the bags above it. Roll the bag two to three times before opening it.

Stepping of Tiers while Removing Cement Bags

SL No. Age in months Loss of Strength (%)

1. 3 5 to10

2. 6 20 to 30

3. 12 30 to 40

Approximate reduction in strength with age(in standard water tight storage condition)

Effect of Storage on Strenght of Cement

The cement when stored for longer period of time loses its strength characteristics. The strength of cement when used after one year of its production loses its strength by about 30-40% on application as compared to that of freshly produced cement.

The following information normally printed on a standard cement bag may be noted at the time of receiving cement bags :

1. Type of cement2. IS certification Mark3. Approximate net weight of cement4. Week, month and year of manufacture5. Manufacturer’s name and registered Trade Mark, if any

Information Available on a Standard Cement Bag

NOTE : The following dimensions may be considered -Length of Cement bags : 70 cm (average)Width : 35 cm (average)Thickness : 14 cm (average)

SOUVIK MONDALD.C.E.(2nd

Year)Roll : 62

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