Ordinary Portland Cement (OPC) - Constituents, Proportions, Properties , Uses

Ordinary Portland Cement (OPC)

Introduction of Ordinary Portland Cement (OPC) 

Ordinary Portland Cement also known as ordinary cement, is widely used in construction industry.

The cement got its name OPC due to it physical characteristics it exhibits, i.e the same colour of Portland stone. The name was given by Joseph Aspdin in the year 1824.

Today in this article we are going to see the constituents, functions, Bogue's compounds etc for OPC (ordinary Portland cement)

The cement is available in the market on the grades as OPC Grade 33, Grade 43, Grade 53. In which the grade shows the compressive strength gain of concrete in 28 days in Mpa or N/mm2 

Constituents and Functions of Raw Materials in Ordinary Portland Cement (OPC) 

Ingredients	Oxide	%	Property	Excess Quantity
1. Lime	Cao	63	Make cement Sound and Strong	Make unsound, Expand & Disintegrate
2. Silica	SiO2	22	Provide Strength due to formation of C2S & C3S	Setting time increases, make it slow.
3. Alumina	Al203	6	Quick setting and Lowering the clinkering temperature.
4. Iron Oxide	Fe2O3	3	Colour, Hardness & strength which helps in fusion of raw materials during manufacture of cement.
5. Magnesium oxide	Mg0	2	Hardness and colour	Unsound
6. Sulphur trioxide	SO3	2	Sound	Unsound
7. Alkalies	K2O, Na2O	1	No use, therefore should be present in low quantity	Efflorescence

Bogue's Compounds

The above mentioned ingredients are present as Raw materials in the proportion of  2:1, in which two parts are of clays and shales, and the one part is of limestone for the manufacturing of cement.

These oxides interact with each other inside the rotary Kiln at a temperature of 1400 C to 1500 C. to form the complex compounds. This was identified by R.H Bogue's and later on was named on him as 'Bogue's Compounds' .

Other Major Compounds are

Name of compounds	Formula	Abbrivated Formula	%	Also known as
Tricalcium Silicate	3Ca0.Sio2	C3S	45	Alite
Dicalcium Silicate	2CaO.SiO2	C2S	25	Belite
Tricalcium Aluminate	3Cao.Al2O3	C3A	11	Celite
Tetracalcium Allumino Ferrite	4Cao.Al203.fe203	C4AF	9	Felite

All the For Compounds mentioned above are majorly used on the basis of there specific properties they exhibits and the proportion of usage is considered. All the 4 Compounds shows different characteristics as rapid heat of hydration resulting rapid hardening, early strength gain, Resistance against sulfur attacks etc. Due to this where or the area we are going to use the concrete, that compound cement is selected. 

The Functions of Bogue's Compounds 

1. C3S ( Tricalcium Silicate)	l Hydrates more rapidly resulting in generation of high heat of hydration. l Responsible for early strength of concrete.
2. C2S ( Dicalcium Silicate)	l Hydrates slowly, resulting in less heat of hydration. l Responsible for later strength gain of concrete. l Provides Ultimate strength gain.
3. C3A (Tricalcium Aluminate)	l It is the first compound which reacts with water, hence cause initial setting of cement. l Harmful to the durability of concrete, especially when the concrete is attacked by sulphates.
4. C4AF ( Tetracalcium Allumino ferrite)	l They react slowly with water thus generate very less amount of heat of hydration. l They have poor cementing value.

The other properties which OPC shows are as 

1)

Type	Indian Standard	Initial Setting time	Final setting time
1. OPC 33	IS :269	30 minutes	600 minutes
2. OPC 43	IS: 8112	30 minutes	600 minutes
3. OPC 53	IS: 12269	30 minutes	600 minutes

2) Its Specific Gravity is 3.12 .

3) Bulk Density is 830-1650 kg/m3.

4) Its Normal consistency is 29%

Advantages Of Ordinary Portland Cement (OPC)

• They has fast initial setting time if compared to PPC.
• They have resistance to cracks and shrinkage.

Disadvantages Of Ordinary Portland Cement (OPC)

• Cannot be used for mass concrete due to great heat of hydration.
• They are more costly than PPC.