Cement acts as a binding agent in concrete, which blends with other materials quickly and makes the concrete as a strong homogeneous element.
The durability of the concrete depends on the properties of cement. The setting time of cement is one of the essential properties of cement.
Setting time of cement is nothing but the time required for the stiffening of the cement paste.
The setting time of cement has been classified as an initial setting and final setting time. The setting time is not constant for all types of cement; it varies.
When the cement starts to lose its plasticity (semi-liquid state) after mixing with water is known as initial setting time. The time gap between the water addition and the starting of plasticity loss is known as the initial setting time. Generally, the initial setting time of cement is in the range of 30 to 45 minutes.
When the cement completely loses its plasticity, it is known as the final setting time.
The time gap between the water addition to complete loss of cement plasticity is known as the final setting time. The maximum setting time of cement should not exceed 10 hours.
Hardening is entirely different from the final setting. In both the initial and final setting times, we can penetrate a needle to a certain depth. But after hardening, it can’t be done.
When shrinkage cracks formation completely goes off after pouring concrete, the application of load could not make any more cracks state known as hardening.
Confusing?
Take an example of Glue Gel (fevikwik gel), the time when you open the cap, the glue starts to lose its semi-solid state, which is called initial setting time. When you place that gel to the correct location, it completely loses its semi-solid state, which is known as the final setting time. After a certain period, it hardens and functions as a binding material known as a hardening state. 🙂
From the glue gel example, we could understand that if we open the glue gel gap to paste, we have to do that before the glue gel dries. Otherwise, the glue loses its stickiness and will not join the paper.
In the same way, before the cement paste loses its plasticity, we must utilize them. Or else the concrete will not become a robust homogenous element and could disintegrate in a short period.
Determining cement setting time helps plan the transport of the mixed concrete and pouring on-site without bleeding and segregation else the mixed concrete becomes harder.
The initial and final setting time of the cement can be determined by the method mentioned in IS code 4031 part 5 by the Vicat Apparatus ( IS code 5513 )
Water Content (W)
If required water content is W, then w = 0.85 x Standard Consistency
W = 0.85 x 30% (assuming 30% of cement weight water is required for standard consistency).
W = 25.5% (we should add only 25.5 grams of water)
Here we are taking 400g, so required water = 400 x 25.5% = 102 grams of water.
Initial Setting Time = T2 – T1
Final Setting Time = T3 – T1
The initial and final setting time of different types of cement has been mentioned below.
# | Cement Type | The minimum period of Initial Setting Time in (Minutes) | The maximum period of Final Setting Time in (Minutes) |
1 | OPC(33) | 30 | 600 |
2 | OPC(43) | 30 | 600 |
3 | OPC(53) | 30 | 600 |
4 | Sulphate Resistant Cement | 30 | 600 |
5 | Portland Pozzolana Cement | 30 | 600 |
6 | Rapid Hardening Cement | 30 | 600 |
7 | Portland Slag Cement | 30 | 600 |
8 | High Alumina Cement | 30 | 600 |
9 | Super sulphated Cement | 30 | 600 |
10 | Low heat cement | 60 | 600 |
11 | Masonry cement | 90 | 1440 |
12 | IRS-T-40 | 60 | 600 |
Happy Learning 🙂
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