Quick setting cement is a type of cement that has the unique property of setting quickly. It can attain its initial set within 5 minutes and achieve its final set within 30 minutes. This makes it an ideal choice for construction projects that require special conditions, such as those that involve running water.
The properties of quick setting cement make it a highly desirable material in certain situations. Its fast setting time allows for quick construction work and rapid repairs. It can also be used in situations where traditional cement would not be effective, such as in underwater applications.
The phenomenon behind quick setting cement is due to the presence of certain additives in its composition. These additives help to accelerate the hydration process, which leads to a faster setting time. However, this also means that quick setting cement is more susceptible to shrinkage and cracking, which can limit its use in certain applications.
The uses of quick setting cement are diverse, ranging from construction work to emergency repairs. It is commonly used in projects that require fast turnaround times, such as the construction of highways, bridges, and dams. It is also used in situations where water is present, such as the repair of swimming pools and water tanks.
Advantages of quick setting cement include its fast setting time, which allows for quick construction work and rapid repairs. It also has the ability to set in underwater conditions, making it ideal for certain types of construction projects. However, its fast setting time can also be a disadvantage in certain situations, as it may lead to shrinkage and cracking.
In conclusion, quick setting cement is a highly useful material for certain construction projects. Its unique properties allow for fast construction work and efficient repairs in special conditions, such as those involving running water. However, its limitations should also be considered when determining its suitability for specific applications.
Fig 1 : Underwater concreting using Quick setting cement
Phenomenon of Quick setting cement
When water is added to cement, it undergoes hydration and a chemical reaction that causes it to harden. The initial setting time of cement is around 30 minutes, and the final setting time is approximately 10 hours. However, there is a special type of cement where the setting time needs to be reduced, and the hardening of cement needs to be faster. To achieve this, cement clinkers are ground with aluminium sulphate, which serves as an accelerating admixture. The amount of aluminium sulphate used ranges from 1% to 3% by weight of cement clinkers.
Aluminium sulphate increases the rate of hydration of tricalcium silicate (C3S) and tricalcium aluminate (C3A) phases of cement, thereby causing earlier heat evolution and strength development. It acts as a catalyst in the hydration process of tricalcium silicate (C3S) and tricalcium aluminate (C3A). To test the effectiveness of the quick setting cement, concrete specimens were prepared with varying percentages of aluminium sulphate and tested for compressive strength, splitting tensile strength, and flexural strength. The results of these tests were then compared with those of a normal M-20 concrete mix.
The research showed that the maximum increase in compressive strength, splitting tensile strength, and flexural strength occurred for quick setting cement concrete at 3 days age and 7 days age. However, there was no considerable increase in compressive strength, splitting tensile strength, and flexural strength at 28 days age.
Uses of Quick setting cement
Quick setting cement is a versatile building material that finds extensive use in various construction projects. Its unique properties make it an ideal choice for situations where quick strength is needed within a short span of time. One of the most notable applications of quick setting cement is in underwater construction projects, where its fast setting time enables workers to complete the job quickly and efficiently.
In addition to underwater construction, quick setting cement is also used in cold and rainy weather conditions, where traditional cement may not be suitable due to its slow setting time. Quick setting cement can be used in higher temperature conditions as well, where water evaporates easily, making it an excellent choice for anchoring or rock bolt mining and tunneling.
Moreover, quick setting cement is often used for fixing concrete steps and for the anchorage of Rock Bolt in Tunnel and other underground works. Its ability to set quickly enables workers to complete the task at hand rapidly and move on to the next phase of the project, thus improving efficiency and reducing overall construction time.
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
The high sulphate content in aluminium sulphate makes it prone to causing corrosion in the reinforcement, thereby reducing its durability. Additionally, when water is added, it is important to work quickly as the cement can set rapidly and become difficult to mix. Quick setting cement also poses the risk of cracking if heat is not dissipated properly during the setting process. Despite its usefulness, quick setting cement is not widely available and can be quite expensive.