Quick setting cement is a type of cement that is specially designed to set quickly. It achieves initial set in just five minutes, and final set in just 30 minutes. This makes it an ideal choice for use in construction projects where conditions are challenging, such as in running water.
This type of cement possesses unique properties that enable it to set quickly. It is formulated with a higher percentage of C3A, which reacts quickly with water to form calcium aluminate hydrate (C-A-H). This results in the formation of a dense matrix of small crystals that quickly set and harden the cement.
The uses of quick setting cement are varied and can be applied in different conditions. It can be used for repairing structures, such as dams, tunnels, and bridges, where time is of the essence. It is also useful in emergency repair situations, such as fixing leaking pipes, and for anchoring bolts and railings.
There are several advantages to using quick setting cement. One of the primary advantages is its quick setting time, which reduces the time required to complete a project. It also allows work to be done in challenging conditions, such as in running water, and can be used in emergency repair situations.
However, there are also some disadvantages to using quick setting cement. One of the main disadvantages is that it has a lower strength compared to other types of cement. It is also more expensive than regular cement, which can make it less cost-effective for some projects.
Overall, quick setting cement is a specialized type of cement that is designed to set quickly. It possesses unique properties that make it useful in challenging construction projects, and it has both advantages and disadvantages that should be carefully considered before use.
Fig 1 : Underwater concreting using Quick setting cement
Phenomenon of Quick setting cement
The process of hardening cement occurs through a chemical reaction that takes place when water is added to it. The initial setting time of cement is 30 minutes, and the final setting time is 10 hours. However, there is a type of cement that requires a shorter setting time and faster hardening process. To achieve this, aluminium sulphate is added to the cement clinkers during the grinding process. Aluminium sulphate is an accelerating admixture that is added in a dosage range of 1% to 3% by weight of cement clinkers. Its function is to increase the rate of hydration of tricalcium silicate (C3S) and tricalcium aluminate (C3A) phases of cement, thereby providing earlier heat evolution and strength development. The use of aluminium sulphate as a catalyst in the hydration of tricalcium silicate (C3S) and tricalcium aluminate (C3A) makes the setting time of the cement faster.
Tests were conducted on concrete specimens with varying percentages of aluminium sulphate to determine their compressive strength, splitting tensile strength, and flexural strength. The results were then compared with those of normal M-20 concrete mix. It was found that the maximum increase in compressive strength, splitting tensile strength, and flexural strength occurred for quick setting cement concrete at 3 days and 7 days after casting. However, there was no significant increase in these strength properties at 28 days after casting.
In summary, the addition of aluminium sulphate to cement clinkers accelerates the setting time of the cement and improves its strength properties at an early age. However, this effect diminishes over time, and there is no considerable increase in strength properties after 28 days.
Uses of Quick setting cement
Quick setting cement is a versatile building material that finds application in various construction projects, especially in environments where conditions are challenging. It is particularly useful in underwater construction and during rainy or cold weather conditions. In situations where quick strength is needed in a short span of time, quick setting cement is the go-to option.
In addition to this, quick setting cement is also used in higher temperature conditions where water evaporates easily. It is commonly used for anchoring or rock bolt mining and tunneling. This is because it is crucial to have quick setting cement for the anchorage of rock bolts in tunnels and all underground works.
Another application of quick setting cement is for fixing concrete steps. When constructing steps, it is important to use a material that sets quickly so that the steps can be used as soon as possible. Quick setting cement is a reliable option for this purpose.
Overall, quick setting cement is an essential component in various construction projects, particularly those that require fast and reliable setting times. Its versatility and ability to be used in different environments make it a popular choice for construction professionals.
Fig 2 : Repair of steps edges with quick setting cement
Fig 3: Repair of steps edges with quick setting cement
Disadvantages of Quick setting cement
Aluminium sulphate contains a significant amount of sulphates, which increases the likelihood of sulphate attack on the reinforcement, leading to corrosion and compromised durability. When water is added to it, it must be completed quickly because the mixture sets rapidly, making it difficult to mix. In the case of quick setting cement, it is important to dissipate the heat properly to prevent cracking after setting. However, this type of cement is not widely available and can be expensive.