Introduction: Exploring Different Types of Cement
Cement is a fundamental building material used worldwide, offering diverse types to suit various construction needs. The types of cement available today are tailored to meet specific performance criteria, achieved by modifying the chemical composition of Ordinary Portland Cement (OPC), adding innovative materials, or utilizing alternative raw materials. These variations ensure durability, strength, and adaptability in challenging environments.
Understanding the different types of cement is crucial for selecting the right one for your project, whether it’s for rapid hardening, enhanced durability, or resistance to chemical attacks. In this article, we will explore the most commonly used types of cement, their unique properties, manufacturing processes, and practical applications in modern construction. Following are the most common types of cement used in construction:
1. Rapid Hardening Portland Cement
Rapid Hardening Portland Cement (RHC) is engineered to exhibit unique properties, achieved through adjustments in chemical composition or the incorporation of additives and distinct raw materials. It stands apart from Ordinary Portland Cement (OPC) due to its specific characteristics tailored for certain environmental conditions.
Manufacturing Process and Composition
RHC typically contains a higher lime content, often obtained by elevating the C3S content or through finer grinding of OPC clinker (450 m²/kg). The focus in producing RHC lies in its hardening properties and heat emission rather than setting rate. This allows for a slightly increased gypsum addition during manufacturing, regulating the setting rate. As a result, RHC achieves the same strength in a single day that ordinary cement might require three days to attain.
Properties and Suitability
However, RHC exhibits notable traits such as higher shrinkage and increased water demand for optimal workability. The cost of RHC typically stands at about 10% more than that of ordinary cement. Nevertheless, concrete crafted with RHC offers durability against frost exposure, maturing at an accelerated rate.
Key Properties
- Initial Setting Time: 30 minutes (minimum)
- Final Setting Time: 10 hours (maximum)
- Compressive Strength:
- 1 Day: 16.0 N/mm²
3 Days: 27.5 N/mm²
Applications
Rapid Hardening Portland Cement finds its niche in applications requiring swift strength development. It’s particularly suitable for road and bridge repairs and scenarios demanding load-bearing capacity within a short timeframe.
2. High Alumina Cement
Distinct from Portland cement, High Alumina Cement is crafted by fusing precise proportions of materials: 40% bauxite, 40% lime, 15% iron oxide, and minor amounts of ferric oxide, silica, and magnesia at exceptionally high temperatures. The fundamental requisite is an alumina content of no less than 32%. This fusion yields a finely ground product wherein the primary cement component is monocalcium aluminate (CA).
Chemical Reactions and Strength Development
Upon interaction with water, CA produces dicalcium octahydrate hydroaluminate and aluminum oxide hydrate. This chemical interplay results in the formation of dicalcium hydroaluminate gel, leading to rapid consolidation and crystallization. Notably, this cement lacks C3A, rendering it highly resistant to sulfates while offering high early strength and a heightened heat of hydration.
Setting and Strength Properties
Despite not being quick-setting—exhibiting an initial setting time of 30 minutes (minimum), extending up to 2 hours—High Alumina Cement ensures a final setting time not surpassing 600 minutes. Remarkably, it achieves substantial strength within 24 hours, reaching a compressive strength of 30.0 N/mm² after one day and 35.0 N/mm² after three days. Additionally, unlike ordinary Portland cement, there’s no free hydrated lime post-setting and hardening.
Specifications and Applications
To meet standards, this cement should possess a fineness of no less than 225 m²/kg and expansion not exceeding 5 mm. High Alumina Cement demonstrates resistance to fire, sea water, acidic water, and sulfates, making it ideal for applications in refractory concrete, various industries, and precasting. However, it’s crucial to avoid its use in environments where temperatures exceed 18°C
Composition of Typical High Alumina Cement
| Component | Chemical Formula | Percentage Range |
|---|---|---|
| Alumina | Al2O3 | 37 – 41% |
| Lime | CaO | 36 – 40% |
| Iron Oxide | Fe2O3 | 9 – 10% |
| Silica | SiO2 | 3 – 8% |
| Titanium | TiO2 | 1.5 – 2% |
| Insoluble Material | – | 1% |
| Magnesium | MgO | 1% |
3. Supersulphated Portland Cement
Manufactured through the intergrinding or precise blending of granulated blast furnace slag (no less than 70%), calcium sulfate, and a small quantity of 33-grade Portland cement, Supersulphated Portland Cement (SPC) stands distinct. Notably, it restricts tricalcium aluminate content to less than 3.5%, a constituent vulnerable to sulphates.
Resistance and Water Properties
Enhanced water resistance characterizes concretes made from SPC due to the absence of free calcium oxide hydrate. The presence of slag binds the latter into low-solubility calcium hydroaluminates and low-basicity calcium hydrosilicates. This differs from common Portland cement concretes that retain a significant amount of free calcium oxide hydrate, potentially weakening over time due to washout.
Performance and Suitability
SPC exhibits satisfactory frost and air resistances but lags behind common Portland cement in concrete resilience. Its lower resistance is attributed to the susceptibility of low-basicity hydrosilicates to humidity fluctuations and reduced effectiveness against water and frost combined actions.
Key Properties
- Heat of Hydration: Low
- Resistance: Chemical attacks, particularly against sulphates
- Compressive Strength (minimum):
- 72 ± 1 hours: 15 N/mm²
- 168 ± 2 hours: 22 N/mm²
- 672 ± 4 hours: 30 N/mm²
- Fineness: 400 m²/kg
- Expansion Limit: 5 mm
- Setting Time: Initial – not less than 30 minutes; Final – not more than 600 minutes
Applications
While sharing similarities in application with common Portland cement, SPC’s superior water resistance recommends its preference in hydraulic engineering installations and constructions intended for moist environments. It finds utility in various scenarios, such as RCC pipes in groundwater, concrete structures in sulphate-rich soils, and sewers handling industrial effluents. However, it’s not advisable for use in constructions frequently exposed to freezing-and-thawing or fluctuating moistening-and-drying conditions.
4. Portland Slag Cement
Portland Slag Cement (PSC) is produced either by intimately intergrinding a blend of Portland cement clinker and granulated slag, with the addition of gypsum or calcium sulfate, or by a uniform blending of Portland cement and finely ground granulated slag. Granulated slag is a non-metallic byproduct primarily composed of glass containing silicates and alumino-silicates of lime and other bases, typically developed alongside iron in blast furnaces or electric pig iron furnaces. It is obtained by rapid chilling or quenching of molten slag using water, steam, or air.
Composition and Properties
The slag component in Portland Slag Cement ranges from 25 to 65%. Its chemical requisites align with those of 33-grade Portland cement. The specific surface of slag cement should not be less than 225 m²/kg, with expansion limited to 10 mm and 0.8% when tested by the Le Chatelier and autoclave methods, respectively. The setting times and compressive strength requirements match those of 33-grade ordinary Portland cement.
Utilization and Applications
Portland Slag Cement finds application in areas similar to Ordinary Portland Cement (OPC). However, owing to its lower heat of hydration, it’s particularly suitable for mass concreting projects such as dams and foundations. Its reduced heat generation during the setting process makes it advantageous in scenarios where controlling the temperature rise within the concrete mass is crucial.
5. Low Heat Portland Cement
Low Heat Portland Cement (LHC) aims to limit the heat generated during hydration by minimizing the tricalcium aluminate content while incorporating a higher percentage of dicalcium silicate and tetracalcium alumino ferrite. This controlled composition restricts the heat of hydration, capped at 272 J/g at the end of 7 days and 314 J/g at 28 days. Despite a slower rate of strength development, LHC ultimately achieves the same strength as Ordinary Portland Cement (OPC). The specific surface area of this cement is typically increased to around 3200 cm²/g to meet these specifications.
Properties and Specifications
LHC exhibits reduced heat evolution during setting compared to standard Portland cement. Expansion tests conducted by the Le Chatelier method and autoclave test should not exceed 10 mm and 0.8%, respectively. Additionally, the initial setting time must not be less than 60 minutes, while the final setting time should not exceed 600 minutes. The compressive strength requirements are as follows:
- 72 ± 1 hour: Minimum 10 N/mm²
- 168 ± 2 hours: Minimum 16 N/mm²
- 672 ± 4 hours: Minimum 35 N/mm²
6. Portland Pozzolana Cement
Portland Pozzolana Cement (PPC) is produced by either grinding Portland cement clinker and pozzolana, typically fly ash (constituting 10-25% by mass of PPC), or by intimately and uniformly blending Portland cement and finely ground pozzolana. Pozzolana, which can be burnt clay, shale, or fly ash, lacks inherent cementing value but possesses the unique property of combining with lime to form a stable lime-pozzolana compound with cementitious properties. This interaction eliminates free lime from the cement, enhancing its resistance to chemical attacks, making it particularly suitable for marine applications.
Hardening and Properties
The hardening process of Portland Pozzolana Cement involves the hydration of Portland cement clinker compounds and the subsequent interaction between pozzolana and the released calcium hydroxide during clinker hardening. This interaction results in the formation of water-soluble calcium hydrosilicate, imparting greater water-resisting properties to PPC compared to ordinary Portland cement.
Properties and Specifications
PPC exhibits a slower rate of strength development but attains comparable ultimate strength to ordinary Portland cement. The compressive strength requirements are as follows:
- 72 ± 1 hours: Minimum 16.0 N/mm²
- 168 ± 2 hours: Minimum 22.0 N/mm²
- 672 ± 4 hours: Minimum 33.0 N/mm²
The initial and final setting times should not be less than 30 minutes and exceed 600 minutes, respectively. Furthermore, drying shrinkage should not exceed 0.15%, while the fineness should not be less than 300 m²/kg.
Applications
PPC’s attributes, including low heat evolution and enhanced resistance to chemical attacks, make it suitable for use in mass concrete structures such as dams and in locations with high temperatures.
7. Quick Setting Portland Cement
Quick Setting Portland Cement is manufactured by reducing the quantity of gypsum and adding a small percentage of aluminum sulfate. Additionally, it undergoes a finer grinding process compared to ordinary Portland cement.
Properties
This cement variant exhibits rapid setting times, distinguishing it from standard Portland cement:
- Initial Setting Time: 5 minutes
- Final Setting Time: 30 minutes
Use
The primary application of Quick Setting Portland Cement is in scenarios where concrete needs to be laid underwater or in running water. Its ability to set quickly makes it particularly advantageous in such conditions, ensuring efficient and reliable concrete placement even in challenging environments.
8. Masonry Cement
The manufacturing process involves grinding Portland cement clinker and intimately mixing it with pozzolanic material (fly ash or calcined clay), non-pozzolanic (inert) materials (like limestone, conglomerates, dolomite, granulated slag), waste materials (such as carbonated sludge, mine tailings), gypsum, and air-entraining plasticizer in suitable proportions.
Frequently Asked Questions
The most common type of cement used for bricks is Ordinary Portland Cement (OPC). It provides the necessary strength and durability for bonding bricks in construction. Additionally, Masonry Cement is also used for brickwork due to its workability and smooth finish.
Yes, there are various types of cement, each tailored to specific construction needs. These include Rapid Hardening Cement, High Alumina Cement, Portland Pozzolana Cement (PPC), Low Heat Cement, and many more. Each type has unique properties suitable for different applications.
There are numerous types of cement, but the most commonly used include Ordinary Portland Cement, Rapid Hardening Cement, High Alumina Cement, Portland Pozzolana Cement, Supersulphated Cement, Low Heat Cement, and others. These types are designed to meet diverse construction requirements.
Light-curing is typically associated with dental or specialized cements. While traditional construction cements like Portland Cement or High Alumina Cement are not light-cured, certain niche industrial or repair cements may have light-curable properties.
For pool valves, especially PVC pool valves, specialized PVC solvent cements are recommended. These cements create a strong bond by chemically fusing the pipe and valve surfaces. It is essential to use a type suitable for Pentair PVC pool valves or other specific brands, depending on the material compatibility.
