The initial setting time of concrete is the point at which the cement paste begins to harden, while the final setting time is the point at which the cement paste has hardened enough for a 1mm needle to leave a mark in the compound of the pattern, a However, there is no 5 mm needle.
Theoretically, the initial setting time of concrete is the time between the addition of water to the cement and the point at which a square needle of 1 mm cross section no longer penetrates the cement paste, which is placed in a Vicat 5 mold. 7 mm from the bottom of the mold is placed remotely.
Final setting time is the time between adding water to the cement and the point at which a 1mm needle leaves an impression in the mold paste, but a 5mm tip leaves no impression.
Let's discuss some important facts about setting concrete.
- It is important that the cement does not harden too quickly or too slowly. There must be sufficient time before concreting and the concrete must harden within a reasonable time to develop its strength.
- Setting should not be confused with hardening, which is the increase in mechanical strength after a special pressed accessory has provided a certain resistance to penetration into the material.
- Setting time is the time required for a cement paste to harden to a certain consistency. The initial setting time is the moment at which the glue begins to lose its plasticity.
- The initial setting time is necessary to delay the hydration or curing process.
- The final setting time is the point at which the paste completely loses its plasticity. This is the time needed for the cement paste or cement concrete to harden sufficiently and take the shape of the mold into which it is poured.
Below are some of the signs of concrete setting.
- Low concrete slump
- Low Workability of Concrete
- Showing the plastic nature of concrete
- Resistance to movement
- Difficulty vibrating
If such behavior is observed, the condition of the concrete should be checked to ensure there are no problems.
The problems mentioned above can even arise from a loss of workability of the concrete due to the low water content or the use of highly effective water-reducing additives and the passage of some time before concreting.
