Ordinary Portland Cement is the most important cement type as it is widely used and all the research and tests on cement are carried out on OPC in general.
Altering the chemical composition of OPC can produce cement with unique characteristics to obtain a desired performance in a given environment to suit a specific purpose. For this, additives or raw materials are used.
What is Ordinary Portland Cement?
Ordinary Portland Cement Definition: Ordinary portland cement is a cementing material obtained by fine grinding of portland clinkers with a little amount of gypsum to adjust the setting time and prevent flash setting.
It possesses binding property to bind the materials together as well as adhesive properties.
Composition of Ordinary Portland Cement
Ordinary Portland Cement composition is given below:
95-100 % portland cement clinker are used while 0-5 % of minor constituents are present. These can be cementitious materials or filler materials, which can enhance workability or water retention capacity of cement.
A general composition of OPC is tabulated below:
Use of Gypsum in Ordinary Portland Cement
Gypsum is added in OPC at the time of grinding to adjust the setting time of cement and to prevent the flash setting of cement.
Manufacture of Ordinary Portland Cement
Production of Ordinary Portland Cement is done either by wet process or by dry process.
In general, manufacture of OPC can be understood as follows:
- Calcareous materials like cement rock, limestone, chalk, marine shell, etc and argillaceous materials like clay, shale, slate, blast furnace slag, etc are taken first in specified proportions.
- These are then mixed dry or wet and then crushed and grinded in a kiln
- As a result, clinkers are obtained to which a small amount of gypsum is added to prevent flash setting
- The clinkers are then grinded into fine powder and stored in silos
Ordinary Portland Cement Grades
USA and UK have one specification for cement. While Germany has 5 grades for cement. Same system is followed in India.
Until 1973, however, only grade 33 cement was available. In 1973-75, Indian Railway introduced prestressed concrete sleepers whose minimum characteristic strength requirement was 50 N/mm2. But OPC 33-grade could only give 33 N/mm2.
Therefore, Railways developed their own specification for sleeper cement that has minimum characteristic strength of 52.5 N/mm2 at 28 days.
With the advancement in cement technology, soon more and more factories started producing high grade cement. Hence, modern cement plants were established.
| Grade-33 | IS: 269 – 1989 | C33 |
| Grade-43 | IS: 8221 – 1989 | C43 |
| Grade-53 | IS: 12269 – 1989 | C53 |
| Sleeper cement | IRS: T-40 – 1985 | C43-C53 |
Advantages of Higher Grade Cement
Higher grades of cement can be achieved by improving the quality of cement. to improve cement quality, following parameters can be observed-
- Using high quality limestone
- Using modern equipment
- Maintaining better particle size distribution
- Finer grinding
- Better packaging
Even though cement of higher grades is costly, it can provide 10-20 % of savings in cement consumption.
It has faster rate of development of strength.
IS: 10262 has classified cement based on 28-day compressive strength as follows:
| Cement Type | Compressive Strength (MPa) | Grade |
| Type A | 32.5 – 37.5 MPa | C33 |
| Type B | 37.5 – 42.5 MPa | |
| Type C | 42.5 – 47.5 MPa | C33 |
| Type D | 47.5 – 52.5 MPa | *available as C43 in market |
| Type E | 52.5 – 57.5 MPa | C53 |
| Type F | 57.5 – 62.5 MPa |
Classification of Cement as per IS: 10262
Ordinary Portland Cement 33 Grade
For OPC grade 33 cement, the compressive strength should not be less than 33 N/mm2 at28 days. Actual strength obtained is much more than specified. The compressive strength should be tested as per test procedure mentioned in IS: 4031- 1988.
It has now almost become obsolete.
Ordinary Portland Cement 43 Grade
43 grade Ordinary Portland Cement has a minimum compressive strength of 43 N/mm2 at 28 days.
It is the most commonly available cement grade in Indian market today.
Ordinary Portland Cement 53 Grade
53 grade Ordinary Portland Cement has a minimum compressive strength of 53 N/mm2 at 28 days.
Optimum particle size distribution and super crystallised structure accounts for the high strength of 53 grade cement.
Ordinary Portland Cement Types
There are five types of cement as per ASTM classification –Type I, Type II, Type III, Type IV, and Type V. Out of these, Type I cement is ordinary portland cement. It is used for general construction where special properties of cement type II, III, IV, and V are not required.
Ordinary Portland Cement Characteristics
Physical Characteristics of Ordinary Portland Cement
1. Fineness
It is a measure of size of cement particles.
It is expressed in terms of specific surface of cement
2. Setting Time
Setting time of cement is related to plasticity of cement paste.
Initial setting time is the time at which cement paste starts losing plasticity. While final setting time is the time at which the cement loses its plasticity completely.
3. Compressive Strength
It is the compressive strength of cement at the end of 28 days. It is an important measure based on which cement is graded.
4. Density
The bulk density of OPC varies considerably depending on how it is stored and handled as voids are considered in it.
For example, during transportation, cement gets consolidated because of vibration, thus increasing bulk density. Hence, cement quantity should always be specified by weight and not volume.
5. Specific Gravity
Specific gravity of OPC with voids is around 3.15 as per ASTM C 188.
The above value of specific gravity is for cement made of limestone and clay. It may vary if different constituents are taken.
Specific gravity of cement does not represent the quality of cement in any way.
Specific gravity of cement is used to calculate mix proportions.
6. Heat of Hydration
Quantity of heat liberated on complete hydration of cement at a given temperature in terms of cal/g of hydrated cement is heat of hydration.
Silicates and alumina present in cement react with water forming a binding material which solidifies to form a hard mass. This reaction of cement with water is called hydration of cement.
As hydration of cement is an exothermic reaction, heat is evolved in the process which is called heat of hydration. It is around 120 cal/g.
Heat of hydration of OPC is 37 cal/g at 5 ° C while it is 80 cal/g at 40 ° C.
Total heat of hydration remains constant for cement. If more heat is released at earlier stages, less heat is evolved later.
About 50 % of total heat is liberated between 1 and 3 days. Around 75 % heat is liberated by 7 days. 83-91 % of the heat is liberated within 6 months.
7. Soundness of cement
Some constituents in cement undergo expansion after the setting of cement. This is an undesirable phenomenon as the expansion of constituents after setting may cause cracks in cement.
The cement exhibiting expansion of its constituents is unsound cement.
For OPC, the Le Chattlier value should not be more than 10 mm while Autoclave value should not be more than 0.8 %.
Chemical Characteristics of Ordinary Portland Cement
1. Lime saturation factor
It is the ratio of
For OPC, the minimum lime saturation factor for 33 grade and 43 grade cement is 0.66 % while for 53 grade cement, it is 0.8 %.
The maximum lime saturation factor 33 grade, 43 grade and 53 grade cement is 1.02 %.
2. Alumina iron ratio
The minimum alumina iron ratio for OPC of grade 33, grade 43, and grade 53 is 0.66 %.
3. Insoluble residue
The maximum insoluble residue for grade 33 cement is 4 % while the tolerance for grade 43 and 53 cement is only 2 %.
4. Magnesia
The magnesia content in OPC should not exceed 6 %.
5. Loss on ignition
The loss on ignition should not be more than 5 % for grade 33 and grade 43 cement. While loss on ignition for grade 53 cement should be limited to 4 %.
6. Sulphuric anhydride
Maximum sulphuric anhydride when C3A is less than or equal to 5 is 2.5 %.
When C3A is more than 5, the maximum limit is 3 %.
Every standard has its own criteria-
As per BS: 12 – 1996
Magnesia is limited to 5 %, insoluble residue is limited to 1.5 %, loss on ignition is limited to 3 % while chloride is limited to 0.1 %.
As per ASTM C 150- 05
Magnesia is limited to 6 %, insoluble residue is limited to 0.75 %, and loss on ignition is limited to 3 %.
Ordinary Portland Cement Properties
Properties of Ordinary Portland Cement are discussed below in detail-
Compressive Strength of Ordinary Portland Cement
Compressive Strength of Ordinary Portland Cement after 3 days for 33grade cement is 16 MPa, for 43 grade cement is 23 MPa, and for 53 grade cement is 27 MPa.
Unit Weight of Ordinary Portland Cement
Density of Ordinary Portland Cement
Specific Gravity of Ordinary Portland Cement is 3.15.
Initial Setting Time of Ordinary Portland Cement is 30 minutes. The initial setting time should not be less than 30 minutes.
Final Setting Time of Ordinary Portland Cement is 600 minutes.
Ordinary Portland Cement Specification
Specifications for Ordinary Portland Cement are described here.
IS 269 specifications for ordinary Portland cement:
Physical and Chemical Requirements-
Storage
Cement should be stored at such a place where it can be easily inspected. The place should be weather-tight to prevent dampness from creeping into the room.
Packing
Cement can be packed in the following way-
- Jute sacking bag conforming to IS: 2580
- Multi-wall paper sacks conforming to IS: 11761
- Light weight jute conforming to IS: 12154
- HDPE/PP woven sacks conforming to IS: 11652
- Jute synthetic union bags conforming to IS: 12174
- Composite bag – Approved
Each bag should have net quantity of cement- 50 kg. it can also be available for net quantities of 25 kg, 10 kg, 5 kg, 2 kg, or 1 kg.
Marking
Following marking are necessary on the cement bag as mentioned in the standard-
- Manufacturer’s name & his registered trademark
- Cement type with grade- Ordinary Portland Ceemnt 33 grade
- Net quantity in kg
- “Use no hooks”
- Batch number stating week, month, and year of packaging
- Address of manufacturer
- Type & percentage of additives or improvers added, if any
Sampling
The samples should be taken and tested within one week of the delivery. If not possible, then samples can be stored in air-tihgt containers and tested within 3 months.
Tests
Testing of cement should be done in laboratories to ascertain the physical and chemical characteristics of cement.
Rejection
If the cement does not comply with any clause mentioned in the standard, it may be rejected.
Ordinary Portland Cement Advantages
The advantages of OPC are described below:
- It provides compressive strength even in early phase, hence construction can be done speedily
- It has low alkali content preventing alkali-aggregate reaction
- C3A is less, hence it can resist sulphate attack
Ordinary Portland Cement Uses
- Masonry work
- Plaster work
- Pointing work
- Laying of floor, roof, etc
- Construction of lintels, beams, weather sheds, etc
Ordinary Portland Cement Applications
- Construction of commercial, residential, industrial structures
- For concrete blocks, paver blocks
- For any type of RCC structure
- For Prestressed concrete
Portland Pozzolana Cement vs Ordinary Portland Cement
Difference between Portland Pozzolana Cement and Ordinary Portland Cement is tabulated below:
White Ordinary Portland Cement
White ordinary portland cement is white in colour and is manufactured from white chalk.
In white OPC, clay containing iron oxide is omitted, as it is responsible for the grey colour of the cement. Other colouring oxides like manganese oxide, chromium oxide, etc are also omitted.
Other proportions are kept same as OPC.
Loss on ignition of white OPC is nil.
Compressive strength of white OPC is 90 % of that of 33 grade cement.
White OPC is used for floor finish, plaster work, ornamental work, etc.
Extra care should be taken during the transport of white ordinary portland cement. It should be stored in closed containers only.
White OPC is costly than OPC as it has special requirements in terms of ingredients and manufacturing process.
Shelf Life of Ordinary Portland Cement
Cement remains in good condition if it is not exposed to moisture. However, after 3 months, it should be tested again to ensure its properties.
The shelf life of ordinary portland cement is 6 months. After that, deterioration of cement starts taking place.
OPC – Today’s Scenario
Manufacture of OPC is decreasing all over the world and blended cement is taking its place. Blended cement has following advantages over OPC-
- Low energy consumption
- Reduction in environmental pollution
- Economic
- Technical advantages
In western countries, OPC usage has decreased to only 40 % of total cement production.
Cement Production details in India in the year 1998-99 are given below:
| Ordinary Portland Cement | 57 million tonnes | 70 % of total cement production |
| Portland Pozzolana Cement | 16 million tonnes | 19 % of total cement production |
| Slag Cement | 8 million tonnes | 10 % of total cement production |
In the upcoming years, the production of cement may further reduce. However, from viewpoint of general construction, OPC will still hold an important place.
Key Take Away
Ordinary Portland Cement
Definition: OPC is a finely ground powder of portland clinkers having binding and adhesive properties.
Composition: Portland cement clinkers form over 95 % part of OPC.
Manufacture: OPC is manufactured in factories by either wet or dry process.
Grades:
| Grade-33 | IS: 269 – 1989 | C33 | No longer used in market |
| Grade-43 | IS: 8221 – 1989 | C43 | Most commonly available in market |
| Grade-53 | IS: 12269 – 1989 | C53 | |
| Sleeper cement | IRS: T-40 – 1985 | C43-C53 | For prestressed concrete sleepers |
IS: 10262
| Type | Compressive Strength (MPa) | Grade |
| A | 32.5-37.5 | C33 |
| B | 37.5-42.5 | |
| C | 42.5-47.5 | C33 |
| D | 47.5-52.5 | *available as C43 in market |
| E | 52.5-57.5 | C53 |
| F | 57.5-62.5 |
Characteristics:
Physical Characteristics–
| Characteristics | 33 Grade | 43 Grade | 53 Grade |
| Fineness (min) Specific Surface | 225 m2/kg | 225 m2/kg | 225 m2/kg |
| Soundness (max) Le Chatellier value Autoclave value | 10 mm 0.8 % | 10 mm 0.8 % | 10 mm 0.8 % |
| Setting Time IST (min) FST (max) | 30 min 600 min | 30 min 600 min | 30 min 600 min |
| Compressive Strength 1 day (24 hr) 3 days (72 ± 1 hr) 7 days (168 ± 1 hr) 28 days (672 ± 1 hr) | Nil 16 MPa 22 MPa 33 MPa | Nil 23 MPa 33 MPa 43 MPa | Nil 27 MPa 37 MPa 53 MPa |
| Bulk Density |
Chemical Characteristics–
| Characteristic | 33 Grade Cement | 43 Grade Cement | 53 Grade Cement |
| Lime Saturation Factor Minimum Maximum | 0.66 % 1.02 % | 0.66 % 1.02 % | 0.8 % 1.02 % |
| Alumina Iron Ratio (min) | 0.66 % | 0.66 % | 0.66 % |
| Insoluble Residue (max) | 4 % | 2 % | 2 % |
| Magnesia (max) | 6 % | 6 % | 6 % |
| Loss on Ignition | 5 % | 5 % | 4 % |
| Sulphuric Anhydride C3A ≤ 5 C3A > 5 | 2.5 % 3 % | 2.5 % 3 % | 2.5 % 3 % |
Uses/Applications: Ordinary portland cement can be used for general construction of any building type. It can be used for masonry work, pointing work, concrete blocks, paver blocks, etc. it can be used for prestressed concrete.
White OPC: White OPC has same proportions as that of OPC except for iron oxide, manganese oxide, and chromium oxide which impart colour to the cement. White chalk is used in its manufacture.
| Loss on ignition | Nil |
| Compressive strength | 90 % of 33-grade cement |
| Use | Floor finish, plastering, ornamental work |
Shelf Life: Shelf life of OPC cannot be more than SIX months. Even after 3 months of storage, it should be tested if it exhibits the required properties.
FAQ
How is ordinary portland cement as compared to high alumina cement?
As compared to ordinary Portland cement, high alumina cement has
- High early strength
- High heat of hydration
- Resistance to chemical attack
- In addition to the above properties, high alumina cement has bauxite in its composition. Proportion of iron oxide is also more
What is the IST and FST of cement?
Initial and Final Setting Time of Ordinary Portland Cement is 30 minutes and 600 minutes respectively.
What is cement?
Cement is an adhesive and cohesive material which possess property of binding different materials together into a durable mass.
Does Cement get expired?
Cement usually remains in good condition till three months. After that, if lumps or colour change is observed in cement, it should be considered expired. Additionally, tests should be preformed to ensure the cement is in a perfect condition. The guaranteed shelf life of cement is not more than six months.