Cement is a fine powder produced through the combination of limestone clay and other minerals in a high Temperature kiln. The resulting substance is ground into a fine powder which forms the key ingredient in concrete, mortar and other construction materials.
The method that structures are formed has changed drastically because to cement which is sometimes referred to as the “glue” of the construction industry. Modern buildings, from basic residences to tall skyscrapers, depend heavily on cement to maintain their strength and longevity. We will explore cement’s composition, varieties, uses, and significance in creating sturdy foundations as we go deeper into the subject in this extensive post.
Here are few Important points
- Cement is produced by pulverizing clinker formed from calcinating raw materials like lime (CAO), silicate (SiO2), aluminium (Al2O3), and iron oxide (Fe2O3) to obtain a powder form.
- When mixed with water, cement forms a paste that binds fine and coarse aggregates, resulting in a hard and durable mass known as concrete.
- The finer the grains of cement, the better its setting property, and consequently, the greater its strength.
- Cement exhibits good hydration, enabling it to set faster compared to other binding materials like lime.
- contact with water, cement undergoes an exothermic chemical reaction, releasing heat.
- Cement is assumed to have a specific gravity of 3.15, contributing to its density and strength.
Types of cement
- Ordinary Portland cement (OPC)
- 33 grade – is :269-1989
- 43 grade – IS: 8112-1989
- 53 grade – IS: 12269-1987
- Rapid hardening cement – IS 8041-1990
- Extra Rapid Hardening cement
- Low Heat Portland cement – IS :12600 -1989
- Portland slag cement – IS 455-1989
- Portland pozzolana cement – IS: 1489-1991 (part 1 and part 2)
- Sulphate resisting Portland cement IS: 812330-1988
- White Portland cement IS: 8042-1989
- Coloured Portland cement – IS: 8042-1989
- Hydrophobic cement – IS: 8043-1991
- High alumina cement – IS:5452-1989
- Super sulphated cement – IS: 6909-1990
- Special cement
- Masonry cement
- Air entraining cement
- Expansive cement
1. Ordinary Portland cement (OPC)
When it comes to artificial cement, Ordinary Portland Cement (OPC) takes the lead as the most prevalent and well-known variety. This cement, known by its abbreviation OPC, is essential to building because it acts as a binder to solidify structures. We go into the subtleties of OPC in this part, including its grading into several grades and the related compressive strengths.
The Breakdown of OPC (Ordinary Portland Cement) 43 Grades
OPC (Ordinary Portland Cement) 43 Grade 33 – IS: 269-1989
Technical Features
OPC (Ordinary Portland Cement) Grade 33, conforming to IS: 269-1989 standards, is characterized by its moderate strength profile. Its compressive strength is in the range of 28-day curing norms, making it appropriate for uses where high strength is not an important requirement. The grade’s chemical composition is meticulously balanced to achieve a balance between strength and workability.
Importance and Applications
OPC(Ordinary Portland Cement) Grade 33 finds its significance in scenarios where concrete mixes with strength up to 20 N/mm² (M20) are sufficient.
It is frequently used in normal building operations such as plastering masonry work and low-stress settings. The moderate strength makes it a reliable choice for projects that prioritize workability and where exposure to sulphates is not a major concern.
OPC (Ordinary Portland Cement) 43 grade – IS: 8112-1989
Technical Features
OPC (Ordinary Portland Cement) Grade 43, adhering to IS: 8112-1989 specifications, is engineered for enhanced compressive strength compared to its 33-grade counterpart. This grade goes through extensive manufacturing procedures to provide the best particle size – distribution and chemical composition. It strikes a balance between durability and strength.
Importance and Applications
The enhanced compressive strength of OPC (Ordinary Portland Cement) Grade 43 makes it a versatile choice for a wide range of construction projects, where strength and durability are essential, it is appropriate for residential, commercial, and industrial projects. This grade is frequently used in foundations bridges and reinforced concrete structures where the capacity to sustain heavy loads is crucial.
OPC (Ordinary Portland Cemen) 53 grade – IS: 12269-1987
Technical Features
At the peak of the strength spectrum of OPC (Ordinary Portland Cement) is grade 53 as per IS: 12269-1987 standards. This grade is engineered for exceptional compressive strength which is achieved through rigorous quality control processes that ensure consistent particle fineness and structure.
Importance and Applications
The exceptional strength of OPC (Ordinary Portland Cement) Grade 53 makes it an ideal choice for critical construction projects. Such as Highrise buildings bridges and infrastructure projects that demand structural integrity under heavy loads. The grade of Cement is specially formulated for scenarios where high strength cannot be compromised, and the ability to withstand extreme conditions is imperative.
2. Rapid hardening cement – IS 8041-1990
- Finer Composition: Rapid Hardening Cement (RHC) – IS 8041-1990 has finer particles compared to Ordinary Portland Cement (OPC).
- C3S and C2S Ratio: RHC (Rapid hardening cement) contains more tricalcium silicate (C3S) and less dicalcium silicate (C2S) than OPC.
- Quick Strength: Its 1-day strength matches OPC’s 3-day strength with the same water-cement ratio.
- Swift Shuttering Removal: RHC ((Rapid hardening cement) quick setting allows early formwork removal, saving time and resources.
- Road Openings: Ideal for roadwork where fast traffic reopening is essential.
- Cost Difference: RHC (Rapid hardening cement) costs around 10-15% more than OPC due to its unique properties.
- Frost Tolerance: RHC (Rapid hardening cement) matures rapidly, making it safe to withstand frost exposure.
3. Extra Rapid Hardening cement
- Extra Rapid Hardening Cement is a specialized cement type designed to achieve exceptionally high early strength development in a short period.
- It is obtained by mixing of chloride( Not exceeding 2% by weight of the rapid hardening cement) With rapid hardening cement.
- Addition of Cacl2 imparts Quick Setting exhibits a rapid setting time, often achieving substantial strength within a few hours of mixing.
- Particle Fineness: Extra Rapid Hardening Cement contains finely ground particles, contributing to its accelerated strength gain.
- Higher C3S Content: This cement type usually contains a higher proportion of tricalcium silicate (C3S), which contributes to early strength development.
- Usage in Urgent Projects: It is primarily used in projects requiring urgent construction, repairs, or modifications.
- Emergency Repairs: Extra Rapid Hardening Cement is invaluable for emergency repairs enabling swift restoration of structures.
- Maximum time of using this cement is 20 minutes for mixing, transportating, placing and compaction,
- Formwork Removal: Due to its rapid setting, formwork can be removed early, expediting construction progress.
- Shorter Curing Period: The early strength development of this cement allows for a shorter overall curing period.
- Road Repairs: It’s commonly used in road repair projects where quick strength gain and early reopening of roads are critical.
- Cold Weather Applications: Extra Rapid Hardening Cement is effective even in cold weather conditions due to its rapid strength development.
- Specialized Applications: This cement type finds significance in scenarios demanding prompt construction, emergency repairs, and situations where quick formwork removal is essential.
4. Low Heat Portland cement – IS :12600 -1989
- Low Heat Portland Cement adhering to IS :12600 -1989 standards is a specialized cement type designed to minimize heat generation during the hydration process.
- Reduced Heat Evolution: Unlike standard Portland cement, low heat cement generates significantly less heat during the setting and hardening stages.
- Composition Control: This cement type carefully controls the proportions of tricalcium silicate (C3S) and dicalcium silicate (C2S) to regulate heat evolution.
- Benefits in Large Structures: Low heat cement is particularly useful in large concrete structures where heat buildup could lead to cracks or structural issues.
- Mass Concrete Projects: It’s extensively used in massive concrete constructions like dams, foundations, and large retaining walls.
- Nuclear Reactor Structures: Low heat cement is favored in nuclear reactor buildings where temperature control is crucial to prevent unwanted reactions.
- Prevention of Thermal Cracking: Its property of generating less heat during hydration reduces the risk of thermal cracking in massive concrete elements.
- Cold Weather Applications: It’s beneficial in cold weather conditions, as slower heat generation avoids temperature differentials.
- Cost Consideration: Low heat cement may have a slightly higher cost due to its specialized manufacturing process.
- Durability: Despite its focus on heat reduction, low heat cement maintains the same durability as standard Portland cement.
5. Portland slag cement – IS 455-1989
- This cement is made by intergrading portland cement clinker and granulated blast furnace slag.
- The proportion of slag shall not be less than 25% or more than 65% by weight of cement.
- The slag should be granular blast furnace slag having high lime content which is produced by rapid quenching of molten slag obtained during manufacture of pig iron in blast furnace.
- In ordinary blast slag cement we have gained strength more slowly than in ordinary Portland cement.
- The heat of hydration of Portland blast furnace slag cement is lower than that of OPC. Hence this cement can be used for large scale concreting but is unsuitable for cold climates.
- It has a fairly high sulphate resistance, making it suitable for use in environments exposed to sulphate (in soil or groundwater).
- It is used for all the purposes for which ordinary Portland cement is used. Due to low heat evolution, it can be used extensively in concrete structure such as dams, foundations and bridge abutments. etc.
6. Portland pozzolana cement – IS: 1489-1991 (part 1 and part 2)
- Is can be Produced either by grinding together Portland cement clinker and pozzolana with the addition of gypsum or by blending uniformly Portland cement and fine pozzolana .
- As per the latest amendment, the proportion of pozzolana may vary from 15 to 35% by weight of cement clicker. Earlier it was 10% to 25%
- A Pozzolanic material is essential a silicious or aluminous material which is itself possess no cementitious properties, which is finally divided form and in the presence of water reacts with the calcium hydroxide liberated in the hydration process at ordinary temperature to produce compounds possessing cementitious properties. This known as pozzolanic action l.e
- Ca (OH)2+Pozzolana +water A C-SSH(gel)
- The pozzolanic material generally used for manufacturing of Portland pozzolana cement are calcined clay (IS:1489 part 2 of 1991) or Fly ash (US: 1489 part 1 19991)
- Fly ash in a waste material generated in a thermal power station, when powered coal is used as a fuel.
- PPC Produces less heat of hydration and offers great resistance to the attack of impurities in water than OPC.
- Reduced Heat Generation: The presence of pozzolanic materials lowers heat of hydration, making PPC suitable for massive concrete structures.
- Higher Durability: Pozzolanic reactions result in denser concrete with lower permeability, increasing resistance to aggressive chemicals and long-term durability.
- Eco-Friendly Nature: The incorporation of industrial byproducts like fly ash reduces the demand for clinker production, thus reducing carbon emissions and environmental impact.
- Infrastructure Applications: Portland Pozzolana Cement is extensively used in construction projects, including dams, bridges, residential complexes, and marine structures.
- Quality Control: IS: 1489-1991 (Part 2) provides guidelines for testing and assessing the conformity of PPC to ensure it meets the specified standards.
7. Sulphate resisting Portland cement IS: 812330-1988
- SRPC (Sulphate resisting Portland cement) is a special purpose cement used in applications where there is a risk of sulphate attack.
- Sulphate attack is the chemical reaction of sulphate ions present in the environment with the cement in concrete,
- which can cause the concrete to crack and deteriorate.
- SRPC is made with a lower content of Tricalcium Aluminate (C3A) than Ordinary Portland Cement (OPC). C3a is the most reactive component of cement and the main component that is attacked by sulphate ions.
- The lower C3a content in SRPC makes it more resistant to sulphate attack.
- SRPC is also commonly mixed with other materials, such as fly ash or ground granulated blast furnace slag, which can further improve its resistance to sulphate attack.
- SRPC is used in a variety of applications where there is a risk of sulphate attack, such as:
- dams and other hydraulic structures
- Bridges and other concrete structures exposed to seawater
- sewage treatment plants and other industrial facilities with high levels of sulphates in the environment
Note
SRPC (Sulphate resisting Portland cement) is a valuable material for use in applications where there is a risk of sulphate attack. It offers superior long-term durability and resistance to chemical attack, making it a cost-effective choice for many projects.
8. White Portland cement IS: 8042-1989
- The process of manufacturing white cement us the same but the amount of iron oxide which is responsible for greyish colour is limited to less than 1%
- Sodium alumimo Fornite (Cryclite)Na3AlF6 is added to act as flux in the absence if iron oxide
- The Properties of white cement is nearly same as OPC
- Whiteness of white cement is measured by ISI Scale or Hunler’s Scale.
- The whiteness should not less than 70% on ISI scale and on Hunler’s Sclae it is generally 90%
- The strength of white cement is much Higher than what is stated in IS :8042 – -1989 The code for white Cement
- Grey colour of OPC is due to thin white cement FE2O3Fs is limited to 1% sodium alumimo Fornite (Cryclite)Na3AlF6 is added to act as flux in the absence of iron Coloured Portland cement
9. Hydrophobic cement – IS: 8043-1991
IS: 8043-1991 is the Indian Standard specification for hydrophobic cement.
A cement that has been treated with a hydrophobic agent is known as hydrophobic cement. With the aid of this substance, cement particles become water-repellent, preventing water from accessing the concrete and harming it.
The following are the specific requirements of IS: 8043-1991 for hydrophobic cement:
- The cement must have a minimum compressive strength of 32.5 MPa at 28 days.
- The cement must be free of visible cracks and impurities.
- The cement must have a water absorption of less than 5%.
10. High alumina cement – IS:5452-1989
- High alumina cement is very different in composition from Portland cement.
- In this cement the C3A Content is very low dye to which it is resistant to sulphur attacks and Chemical attacks.
- It sets quickly and alliins higher ultimate strength in a short period. Its strength after 1 day is about 40N/mm2 and that after 3 days is about 50N/mm2
- It is characterized by its dark colour, high early strength, high heat hydration.
- The raw material is used for its manufacture consists of limestone (or chalk) and bauxite which is a special clay with high alumina content.
High alumina cement has a number of advantages over ordinary Portland cement (OPC), such as:
- Higher compressive strength
- Better resistance to heat and fire
- Better resistance to chemical attack
- Good durability
11. Super sulphated cement – IS: 6909-1990
- Super sulphated cement is made from well granulated blast furnace slag (80-85%)
- Calcium sulphate (10-15%) and Portland cement (1-2%) and in ground finer than the Portland cement.
- In this cement C3A which is susceptible to sulphated id limited less than 3.5%
- Sulphate resisting cement can also be produced by the addition of extraction oxide before firing this combine with alumina which would cohesive from C3A instead forming C4AF which is nit attacked by sulphates
- It should be used in places with temperature us below 40 degree C
Compressive strength should be below as
- 3 Days = 1 Hr = 15N/mm2
- 7 days = 2hr = 22N/mm2
- 28 days = 4 hr = 30n/mm2
- It has low heat hydration
12. Special cement
Masonry cement
Bricks, blocks, and other masonry units are bound together with the use of a cement known as “masonry cement.” hydrated lime, Portland cement, and other additives are combined to produce it.
Masonry cement has a number of advantages over ordinary Portland cement (OPC), such as
- It is more workable and easier to apply.
- It results in a link that is stronger and more durable.
- It is less likely to crack or contract.
Numerous masonry applications call for the usage of masonry cement, including
- Building walls
- Laying bricks
- Installing concrete blocks
- Repairing masonry
Air entraining cement
- A type of cement with tiny air bubbles is called air entraining cement. These air bubbles provide the concrete better workability and increase its resistance to freezing and thawing.
- Air entraining cement is made by adding air-entraining agents to Portland cement. These agents are typically based on soaps or oils.
Air entraining cement is used in a variety of concrete applications, such as
- Foundations
- Bridge decks
- Tunnels
- Concrete pipes
- Exterior concrete
Oil well cement
An oil well’s walls are sealed with oil well cement, a particular kind of cement. Portland cement, unique additives, and water are the main ingredients used in its production.
- Oil well cement has a number of advantages over ordinary Portland cement, such as:
- It is more resistant to high temperatures and pressures.
- It is more fluid and easier to pump.
- It forms a stronger and more durable seal.
Oil well cement is used in a variety of oil well applications, such as
- Casing cementing
- Liner cementing
- Grouting
- Acidizing
Frequently Asked Questions
The selection of an OPC grade should consider factors like anticipated loads, environmental conditions, and project requirements. Projects with higher load demands and exposure to extreme conditions often benefit from higher-grade OPC varieties.
While higher-grade OPC varieties may exhibit slightly reduced workability due to their greater compressive strength, modern construction techniques and additives can effectively address this concern, ensuring optimal workability without compromising strength.
Rapid Hardening Cement (RHC) exhibits a finer particle composition and a distinct ratio of tricalcium silicate (C3S) to dicalcium silicate (C2S) when compared to OPC.
The accelerated setting of RHC allows for the early removal of formwork, leading to significant time and resource savings in construction projects.
When mixed with water, cement forms a paste that binds fine and coarse aggregates together, resulting in a hard and durable mass known as concrete. The finer the cement particles, the better its setting properties and subsequent strength.
White Portland Cement has limited iron oxide content, resulting in its distinct white color. It may include sodium alumino fornite (cryolite) as a flux. Its whiteness is measured on ISI or Hühlers scales, and its strength surpasses the IS:8042-1989 code for white cement.
Hydrophobic Cement (IS: 8043-1991) is treated with hydrophobic agents to make cement particles water-repellent. It prevents water from penetrating concrete, enhancing its durability and performance.
High Alumina Cement (HAC) has distinct composition and properties, including higher resistance to heat, fire, and chemicals. It is suitable for applications requiring exceptional strength and durability such as refractory concrete furnaces and chemical plants.
Super Sulphated Cement (IS: 6909-1990) is useful in applications where sulphate attack is a concern, such as dams, bridges, and environments with sulphate-rich conditions. It offers strength, durability, and resistance to chemical attack.
Special Cement includes various types tailored for specific purposes:
Masonry Cement for bricklaying and plastering.
Air Entraining Cement with air bubbles enhancing freeze-thaw resistance.
Expansive Cement for controlled expansion and structural stability
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