Table of Contents
- 1 What are the factors affecting initial setting time?
- 2 Which chemical is used to increase setting time of cement?
- 3 What is initial setting cement?
- 4 What are the initial and final setting time of cement?
- 5 How do you increase the initial setting time of concrete?
- 6 How can we increase the initial setting time of cement?
- 7 What is the chemical phenomenon that takes place in cement?
- 8 What is the setting time of the cement test?
What are the factors affecting initial setting time?
The major factors affecting the time of setting are cement composition, water-cementitious material ratio (w/cm), temperature, and admixtures. When cement hydrates faster, the time of setting is reduced. Increases in the w/cm result in increased time of setting.
Which chemical is used to increase setting time of cement?
During manufacturing process, gypsum is added to increase the initial setting time of cement and thus concrete.
Which chemical is added to reduce the initial setting time of concrete?
Retarding admixtures are used to slow the rate of setting of concrete. By slowing the initial setting time, the concrete mixture can stay in its fresh mix state longer before it gets to its hardened form. Use of retarders is beneficial for: Complex concrete placement or grouting.
Which chemical is used to setting of cement?
Detailed Solution
| Ingredients | Within limit |
|---|---|
| Silica (17 – 25 \%) | Adds strength to cement, as it forms C2S and C3S |
| Alumina (3 – 8 \%) | Provides quick setting of cement and lowers the clinkering temp |
| Iron oxide (3 – 4 \%) | Provides color, hardness , strength and helps in fusion of raw material |
What is initial setting cement?
Initial setting time of cement is defined as the time elapsed between the moments when water is added to the cement to the time when the cement paste starts losing its plasticity.
What are the initial and final setting time of cement?
Standard Specification of Setting Time for Different Type of Cement
| Cement Type | Initial Setting Time, min (min.) | Final Setting Time, min (max.) |
|---|---|---|
| High alumina | 30 | 600 |
| Super sulphated | 30 | 600 |
| Low heat | 60 | 600 |
| Masonry cement | 90 | 1440 |
What is initial setting time?
Initial setting time is the time when the paste starts losing its plasticity. Initial setting time test is important for transportation, placing and compaction of cement concrete. Initial setting time duration is required to delay the process of hydration or hardening.
What is the initial setting of cement?
The time elapsed between the moments when water is added to the cement to the time when the square needle penetrates a depth of 33 to 35 mm from the top of the mould is known as the Initial Setting Time of that cement. The initial Setting Time should not be less than 30 minutes for Ordinary Portland Cement.
How do you increase the initial setting time of concrete?
These admixtures are Accelerators and Retarders. Accelerators have been designed to significantly boost the early setting times and increase the early age strengths of concrete. Setting times of non accelerated concrete are significantly slower as temperatures get colder.
How can we increase the initial setting time of cement?
If the cement consumption is unchanged, the increase of the mixing water content will enhance the amount of capillary porosities, lower the strength of cement paste, and extend the setting time.
What do you mean by initial setting time of cement?
What are the factors affecting the time of setting of cement?
A. The major factors affecting the time of setting are cement composition, water-cementitious material ratio (w/cm), temperature, and admixtures. When cement hydrates faster, the time of setting is reduced. Increases in the w/cm result in increased time of setting. Time of setting decreases as the temperature is increased.
What is the chemical phenomenon that takes place in cement?
The chemical phenomenon that takes place are divided into 3 stages, 1. Hydrolysis and Hydration Stage The process of setting starts after the addition of water. In this process the four compounds of cement (C 3 S, C 2 S, 3CA1, 4CAFe) get hydrated.
What is the setting time of the cement test?
The setting Time of the cement test is conducted to find out the initial and final setting time of any cement. Initial Setting Time is the time elapsed between the moments that the water is added to the cement, to the time that the paste starts losing its plasticity.
What happens when cement reacts with water?
In its pure form, the finely ground cement is extremely sensitive to water. Out of the three main compounds, viz. C3A, C3S and C2S, reacts quickly with water to produce a jelly-like compound which starts solidifying and setting of cement takes place. The setting process of cement starts as it is mixed with water.