White ordinary Portland cement known as “White Cement” is one of the most important raw materials used in construction of a building. White cement with the exception of whiteness has same properties as Gray ordinary Portland cement has. It is as durable and strong as Gray ordinary Portland cement and has high degree of whiteness. White ordinary Portland cement should confirm to IS: 8042-1989.
Manufacturing of white cement
The manufacturing process of white cement is somewhat different from manufacturing process of gray cement. During manufacturing if metal oxides i.e. iron and manganese are added, they help in increasing the whiteness of cement. Because of change in manufacturing process and cost of raw materials, white cement is costlier than gray cement.
Where to use white cement?
White cement due to its whiteness is mainly used for architectural beauty, interior and exterior decorations such as terrazzo tiles and floorings, ornamental concrete products such as idols and swimming pools etc.
Mixing pigments to obtain required color
These days a number of colored cements are available in the market. Colored cements have same properties as white cement has. Alternatively one can make colored cement of his choice by just mixing color pigment. To obtain brightly, colored concretes and mortars, inorganic pigments are added in white cement. When pigments are added with ordinary cement, they may produce attractive colors but they are somewhat dull. With white cement, bright reds, yellows and greens can be readily produced. Blue concrete can also be made at some more expense. The pigments may be added at concrete mixer to mix them uniformly. To secure uniform color, the pigments must be mixed very intimately with cement preferably in a ball mill.
Production of Different Colors with Pigments and White Cement
| S. No. |
Required Color |
Commercial Name of Color |
Appropriate Qty. of Pigment (Kg. per bag of cement)
Light shade Medium shade
|
| 1. |
Grays Blue-Black & Black |
Germantown lamp black
OR Carbon black OR Black oxide of Manganese OR mineral black
|
0.25 0.50
0.25 0.50
0.50 1.00
0.50 1.00
|
| 2. |
Blue |
Ultramarine Blue |
2.30 4.10 |
| 3. |
Brownish Red to Dull brick |
Redoxide of Iron |
2.30 4.10 |
| 4. |
Bright Red to Vermilion |
Mineral Turkey Red |
2.30 4.10 |
| 5. |
Red Sand Stone to Purple Red |
Indian Red |
2.30 4.10 |
| 6. |
Brown to Reddish Brown |
Metallic Brown (Oxide) |
2.30 4.10 |
| 7. |
Buff colonial
Tint and Yellow |
Yellow ochre or
Yellow Oxide |
2.30 4.10
1.00 2.00
|
| 8. |
Green |
Chromium Oxide or
Greenish Blue ultra-Marine |
2.30 4.10
2.70 ---- |
Note:
1. Only first quality lamp black should be used.
2. In case of carbon black, as it is light in weight it requires thorough mixing.
3. For general use Black oxide or mineral black is most advantageous. For getting black shade, use 5 kg oxide per bag of cement.
Specification of white cement
1. Fineness
There are following two methods to check fineness of Portland cement.
- Method 1: After sieving, the cement on IS test Sieve No.9 (B.S. Sieve No 170) should not exceed 10% in case of Ordinary Portland Cement.
- Method 2: Specific surface by Air Permeability Method should not be less than 2150 sq. cm/ kg in case of Ordinary Portland Cement.
2. Soundness
Alternatively autoclave expansion should not be more than 0.5% when tested according to IS 269 of 1989.
3. Setting time
Setting time of any type or any grade of cement when tested by VICAT apparatus method described in IS: 4031 should confirm following requirement.
- Initial setting time: Not less than 30 minutes
- Final setting time: Not more than 600 minutes i.e. 10 hours
4. Compressive Strength
After 28 days compressive strength of cement concrete mix for various types of cement concrete mix is following.
Compressive strength of cement concrete mix
| S. NO. |
Type of Mix |
Ratio of Mix |
Compressive strength |
| 1. |
M 10 |
1:3:6 |
100 kg. Per cm square |
| 2. |
M 15 |
1:2:4 |
150 kg. Per cm square |
| 3. |
M 20 |
1:1.5:3 |
200 kg. Per cm square |
Note: Cement concrete cubes filled in above mentioned cement ratios should be tested after curing for 7 days and the strength of cement concrete should not be less than 70%.
How to ensure quality of white 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 older from the date of manufacturing.
Guidelines for quality assurance
- Cement bag bears date of manufacturing
- One cement bag has 50 Kg. weights
- Cement bags are not hand stitched
- Consignment must have identification mark on the package
- Cement is packed in bags of synthetic jute or polypropylene bags
- Factory manufactured instead of plant manufactured
- Bears manufacturer's name or his trade mark , grade and type of cement
- Not older than six weeks from the date of manufacturing
- The bags are not torn by side and stitched in later
- Cement bags are packed in water proof paper bags.
- Not partially set due to moisture or have small lumps in bags
- Not pressed or have lumps due to high pressure of stack, having more than 10 to 12 bags
Precautions while transporting cement
- Carry bags in clean vehicle which is not dustier or on earth etc. as it reduces the strength of cement.
- Take cement bags under covered Polythene or ‘Tarpaulin’ during monsoon season.
- Labor should not tear bags while loading and unloading cement bags.
Precautions while stacking/storing white cement
- Store cement in moist proof area otherwise quality of cement will be affected
- Stack cement bags in dry, leak proof and moisture proof shed/fumes
- Place cement bags on dry brick floors, wooden crates or planks
- Don’t place cement bags on the earth in any case
- Don’t make stack of bags higher than 10 bags to avoid lumps under pressure
- Don’t stack up cement bags with outer walls to protect it from dampness
- Pile up cement bags from different manufacturer separately
- Make use of cement on first come first serve basis
- Cover cement bags with polythene during monsoon season
- Keep cement bags close to each other to reduce air circulation
Caution for storage/stacking
- When construction work is assigned to a contractor, make sure he takes proper care of cement. Many times contractors do not take care for proper storage of cement at site as it costs them labor and money. This results in reduction in strength of cement as shown in the table below.
- In some cases, it is observed that after laying RCC slab on some parts of building, the contractor dismantles his temporary store at site and places cement bags on ground floor of building which is under construction. It is not good as cement bags may draw moisture from floor and walls of new building and results in reduction of strength in cement because new building is wet due to construction work in progress.
Reduction in cement strength due to storage
| S. No |
Storage Period |
Reduction in Strength |
| 1. |
Fresh cement |
Nil |
| 2. |
Three months old |
20% |
| 3. |
Six months old |
30% |
| 4. |
12 Months old |
40% |
| 5. |
24 Months old |
50% |