Quick setting cement is the cement that loses its plasticity quicker than ordinary Portland cement, but does not achieve a higher rate of strength.
It is made by finely grinding cement clinkers by increasing the percentage of cement alumina and decreasing the percentage of gypsum.
Phenomenon of Quick setting cement:
Usually, when water is added into cement hydration, a chemical reaction occurs which hardens the cement where the initial setting time is 30 minutes and the final setting time is 10hrs.
In this cement, the setting time of cement decreases and the hardening of cement increases.
The cement clinker is grinded with aluminum sulfate, which accelerates the setting time of the cement.
Aluminum sulfate is used as accelerating admixture within a dose range from 1% to 3% by weight of cement clinker.
The mechanism action of aluminum sulfate increases the rate of hydration of the triacalcium silicate (C3S) and triacalcium aluminate (C3A) phases of cement, leading to pre-heat evolution and strength development.
It acts as a catalyst in the hydration of tricalcium silicate (C3S) and triacalcium aluminate (C3A).
Concrete samples with varying percentages of aluminum sulfate were tested for compressive strength, dividing tensile strength and flexural strength.
The results obtained in comparison to the normal M-20 concrete mixing results found that there is a maximum increase in tensile strength and splitting strength for quick-setting cement concrete installation at 3 days and 7 days of age.
However, after 28 days there is no significant increase in compressive strength, splitting tensile strength and flexural strength.
Advantages of Quick setting cement:
- It can be used in concrete repair works without disturbing the structure.
- Although it has less the setting time, the ultimate strength obtained is similar to OPC.
- Quick-setting cement has a high resistance to water.
- The amount of water required during hydration is less.
Disadvantages of Quick setting cement:
- Due to the content of sulfates in aluminum sulfate, there is a major chance of sulfate attack on reinforcement corrosion and durability is compromised.
- When water is added, the work must be completed fast otherwise it is difficult to set and mix.
- In quick-setting cement, if the heat is not destroyed properly, cracks may occur in the cement after setting.
- It is not widely available.
- It is expensive.
Uses of Quick setting cement:
- It is used for under water construction.
- It is also used in rain and cold weather conditions, where fast strength is required in a short time.
- Also used in high temperatures where water evaporates easily.
- It is used for anchoring or rock bolt mining and tunnelling.
- It is used to fixing concrete steps.
- To anchor rock bolts within the tunnel and all underground works, quick setting cement is required.
Quick setting cement is called “early strength concrete” contains a cement formula / content that allows concrete to reach 90% strength in 3 days instead of the normal 7 days.