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Created: 2024/07/06 15:20

Experiment no. 08

Experiment name: Determination of initial setting time & final setting time of cement

Objective

The objective of this experiment is to,

1. Determine the initial and final setting times of Mir Portland Composite Cement.

Significance

Understanding the setting times of cement is critical in construction. These timings are essential for,

1. Proper mixing of cement
2. Whether to use accelerator or retarder.
3. Arranging formworks.
4. Deciding on transportation, and placement methods.

Apparatus

1. Beaker
2. Balance
3. Glass plate
4. Stopwatch
5. Thermometer
6. Hydrometer
7. Mixing pot
8. Trowel
9. Mask and hand gloves
10. Vicat apparatus with plunger
11. Sample: PCC Mir Brand

Data sheet

Calculation

• Amount of cement = $650\text{[PARSE ERROR: Undefined("Command("space")")]}gm$
• Normal consistency = $29\mathrm{\%}$

Therefore, Amount of water = $650\times 0.29=188.5\text{[PARSE ERROR: Undefined("Command("space")")]}gm$

Graph

Result

The initial setting time was found to be 69 minutes, and the final setting time was 92 minutes for the Mir PCC.

Discussion

The initial and final setting times of Mir Portland Composite Cement were determined to be 69 minutes and 92 minutes, respectively, through penetration testing using the Vicat apparatus.

The penetration depth was more than 40 mm at 30 and 45 minutes, indicating that the paste was still very fluid. At 60 minutes, the penetration was 32 mm, showing that the paste had begun to harden but was still plastic. By 69 minutes (interpolated from the graph), the penetration depth fell within 25 mm indicating initial setting.

At 75 minutes, the penetration was 19 mm, showing significant hardening. By 90 minutes, the penetration reduced to 2 mm, indicating that the cement had almost completely hardened. The final setting time of 92 minutes was determined from the graph where the penetration depth reached nearly 0.5 mm.