Sulphate Resisting Cement is a variety of Portland Cement that is formulated with a limited amount of tricalcium aluminate (C3A) to maintain it below 5% and (2C 3A +C4AF) to be below 25%. This restriction helps in decreasing the formation of sulphate salts, which in turn reduces the likelihood of sulphate attack on the concrete.
By restricting the formation of sulphate salts, Sulphate Resisting Cement offers a range of advantages. It enhances the durability and longevity of concrete, making it an excellent choice for construction projects in areas with high soil and water sulphate levels. Additionally, it can resist the impact of acidic and sulphate-rich environments, making it suitable for use in environments such as marine structures, sewage treatment plants, and industrial facilities.
Sulphate Resisting Cement has distinctive characteristics and properties that make it a reliable construction material. It has a low heat of hydration, which means that it generates less heat during the curing process, resulting in less thermal stress on the concrete. It also has a lower permeability, making it less vulnerable to the penetration of aggressive substances such as sulphates and chlorides.
Despite its many advantages, Sulphate Resisting Cement also has some disadvantages. It is a more expensive option than regular Portland Cement, and its strength development is slower, requiring more time to reach full strength. Additionally, its use is limited to certain conditions and environments, and it is not suitable for all types of construction projects.
Overall, Sulphate Resisting Cement is an excellent choice for construction projects in areas with high sulphate levels or where concrete is exposed to sulphate-rich environments. Its unique properties and characteristics make it a reliable and durable construction material, although it may not be suitable for all projects due to its higher cost and slower strength development.
Composition of Sulphate Resisting Cement
Sulphate-resisting cement has a low range of tricalcium aluminate, resulting in only a small amount of calcium aluminate forming during hydration. This limited formation of calcium aluminate reduces the formation of calcium sulpho-aluminates caused by the reaction between calcium sulphoaluminate and sulphate salts. Sulphate aluminates, which are highly expansive and can cause significant damage to concrete, are greatly reduced by the use of sulphate-resisting cement.
Properties of Sulphate Resisting Cement
Sulphate resisting cement is a type of cement that is specifically designed to resist the harmful effects of sulphates. Sulphate attack on concrete is a common problem that can result in serious damage to structures such as bridges, dams, and buildings. The reaction between sulphates and the components of ordinary Portland cement can cause expansion and cracking of the concrete, leading to significant structural damage.
Sulphate resisting cement contains a lower percentage of tricalcium aluminate (C3A) than ordinary Portland cement. C3A is the compound that is most susceptible to sulphate attack, so reducing its content in the cement can significantly improve its resistance to sulphates. Additionally, sulphate resisting cement contains a higher percentage of silicates and aluminates, which can further enhance its resistance to sulphates.
Another important property of sulphate resisting cement is its ability to maintain its strength in the presence of sulphates. Sulphates can react with the hydration products of cement, causing them to break down and weaken the concrete. However, sulphate resisting cement has a lower porosity and a denser microstructure than ordinary Portland cement, which can help to prevent sulphates from penetrating into the concrete and causing damage.
Overall, the properties of sulphate resisting cement make it a suitable choice for construction projects in areas where sulphate attack is a concern. Its ability to resist sulphate attack and maintain its strength over time can help to ensure the long-term durability and safety of concrete structures.
Table 1: Properties of sulphate resisting cement
| Property | Values |
| Fineness | 280+ or -10 sq m /kg |
| Setting time | |
| Initial | 80 min |
| Final | 240 min |
| Soundness | |
| Lechatelier (mm) | 2 (max) |
| Autoclave | 0.25(max) |
| Compressive strength | |
| 3 days | 30 + or – 3 |
| 7 days | 45 + or – 3 |
| 28 days | 65 + or – 3 |
| Tri calcium aluminate | 0.035 |
| Magnesia | 0.02 |
| Loss on ignition | 0.02 |
Characteristics of Sulphate Resisting Cement
This particular cement boasts multiple benefits, making it an excellent choice for construction projects that require high durability and resistance to harsh environments. One of its key features is its ability to provide maximum resistance to chloride ions, which reduces the risk of corrosion in reinforced steel.
In addition to its corrosion-resistant properties, this cement also offers a high level of concrete performance and structural integrity in highly aggressive sulphate and acidic environments. This makes it a great option for structures that will be exposed to extreme conditions, such as bridges or water treatment plants.
Another advantage of this cement is its increased workability and pumpability. This allows it to be easily mixed and transported, making it a more efficient and effective choice for large-scale construction projects.
Finally, this cement is known for its significantly improved later-age concrete strengths. This means that structures built with this cement will have greater longevity and durability, reducing the need for costly repairs or replacements over time. Overall, this cement is a top choice for any construction project that requires high-quality, long-lasting results.
Uses of Sulphate Resisting Cement
Sulphate Resisting Cement is a specialized type of cement that is highly recommended for a variety of construction projects. It is particularly useful for foundations and piling works, as well as any construction that will come into contact with soils or ground water containing high levels of sulphate salts – typically more than 0.2% or 0.3% g/l, depending on the specific application.
This type of cement is also ideal for use in concrete surfaces that will be exposed to alternate wetting and drying, such as bridge piers, concrete surfaces in tidal zones, and aprons. In addition, it is highly effective for use in effluent treatment plants, chimneys, cooling towers, and coastal protective works like sea walls, break waters, and tetrapods.
Furthermore, Sulphate Resisting Cement is highly recommended for building projects near seacoasts, as well as for chemical industries, water storage facilities, sumps, and drainage works. It is also well-suited for underground projects where sulphate is present in the soil and water, as it provides excellent resistance against the corrosive effects of sulphate salts.
Overall, Sulphate Resisting Cement is a highly versatile and effective building material that is an excellent choice for a wide range of construction projects, especially those that involve exposure to sulphate salts or other corrosive substances.
Fig 1: Use of Sulphate Resisting Cement in Pile Construction
Advantages of Sulphate Resisting Cement
Sulphate resisting cement is known to be highly effective in safeguarding concrete against the formation of sulpho-aluminates and providing resistance to sulphate attack. This protection helps to improve the durability and longevity of structures, particularly in aggressive environments.
One of the benefits of using sulphate resisting cement is its ability to achieve very high compressive strength through an economical concrete mix design. This is particularly advantageous as it enables structures to bear heavier loads without compromising their integrity.
Another advantage of this type of cement is its low heat of hydration, which can help to prevent shrinkage cracks from occurring. This is because the cement generates less heat during the curing process, which reduces the risk of the concrete cracking or becoming distorted.
Sulphate resisting cement also improves the corrosion resistance of steel by preventing sulphate attack. This is because the cement protects the steel from exposure to sulphates, which can cause the steel to corrode and weaken over time.
Overall, the use of sulphate resisting cement can significantly enhance the performance and lifespan of concrete structures, particularly in environments where they are exposed to aggressive conditions.
Disadvantages of Sulphate Resisting Cement
Sulphate resisting cement (SRC) is not a suitable option in areas where there is a risk of chloride attack as it may lead to the corrosion of rebar. If both chlorides and sulphates are present, it is recommended to use Ordinary Portland Cement (OPC) with a C3A content between 5 and 8. However, it is important to ensure that the curing process is carried out correctly and with great care for a minimum of 8-10 days.
It is worth noting that SRC is not recommended for use in marine construction. This is because marine environments typically contain high levels of chlorides, which can be extremely corrosive to steel reinforcement. Therefore, if you are working on a project in a marine environment, it is important to use OPC with the recommended C3A content and ensure that proper curing techniques are used to prevent any potential damage.