Sulphate Resisting Cement is a variation of Portland Cement that limits the amount of tricalcium aluminate (C3A) to less than 5% and (2C3A + C4AF) to less than 25%. This restriction minimizes the formation of sulphate salts, thereby reducing the likelihood of sulphate attack on the concrete.
By limiting the formation of sulphate salts, Sulphate Resisting Cement offers several benefits. It possesses greater resistance to sulphate attacks compared to regular Portland Cement. Additionally, it provides better durability and can withstand extreme weather conditions.
Sulphate Resisting Cement is ideal for use in construction projects that require high durability, such as marine structures, foundations, and retaining walls. Its properties make it an excellent choice for locations with high sulphate content in the soil or water, where other types of cement would be vulnerable to degradation.
Despite its advantages, there are some drawbacks to using Sulphate Resisting Cement. For example, it has a slower setting time compared to other types of cement. This can increase the overall construction time, leading to higher costs. Additionally, it is more expensive than regular Portland Cement.
Overall, Sulphate Resisting Cement is an excellent choice for construction projects in environments with high sulphate content. Its unique properties make it resistant to sulphate attacks and increase its durability, making it a valuable investment for construction projects that require long-lasting, reliable results.
Composition of Sulphate Resisting Cement
Sulphate-resisting cement has a limited amount of tricalcium aluminate, which results in the formation of only a small quantity of calcium aluminate during hydration. This, in turn, reduces the formation of calcium sulpho-aluminates that occurs when calcium sulpho-aluminate reacts with sulphate salts. By using sulphate-resisting cement, the formation of sulphate aluminates, which are highly expansive and can cause significant damage to the concrete, is considerably reduced.
Properties of Sulphate Resisting Cement
The properties of sulphate resisting cement are,
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
A specialized cement is available that offers superior resistance to chloride ions, reducing the likelihood of corrosion of reinforced steel. This cement is also known for its exceptional performance in harsh environments with high levels of acidity and sulphate. In addition, it offers excellent workability and pumpability for ease of use in construction projects. This cement has been found to significantly improve the strength of concrete over time, leading to greater structural integrity and longevity.
Uses of Sulphate Resisting Cement
Fig 1: Use of Sulphate Resisting Cement in Pile Construction
Advantages of Sulphate Resisting Cement
Disadvantages of Sulphate Resisting Cement
- Sulphate resisting cement is not suitable where there is danger of chloride attack. This will cause corrosion of rebar.
- If both Chlorides and Sulphates are present, Ordinary Portland Cement with C3A between 5 & 8 should be used.
- Curing process should be done properly with great care for min of 8-10 days.
- It is not prescribed to use it in marine construction.