The initial setting time of concrete refers to the duration starting from the moment water is added to cement until the point when a 1mm square section needle can no longer penetrate the cement paste in the Vicat’s mould, placed 5mm to 7mm from the bottom of the mould. This test is crucial for determining the time taken by cement to reach its initial setting state, from the moment it is mixed to the time it is transported and placed in the form of concrete.
Procedure to Find Setting Time of Cement
Apparatus Required
The Vicat’s apparatus, balance, measuring cylinder, stop watch, glass plate, enamel tray, and trowel are all common tools used in the field of materials testing. These tools play an important role in determining the physical properties of various materials, such as cement, concrete, and mortar.
The Vicat’s apparatus, for example, is used to measure the setting time of cement and other materials. It consists of a plunger, a frame, and a measuring device. The balance, on the other hand, is used to measure the weight of different materials with high accuracy.
A measuring cylinder is a cylindrical container with a scale used to measure the volume of liquids and other materials. The stop watch is used to accurately measure the time it takes for materials to set or harden.
The glass plate and enamel tray are used to mix and prepare different materials, while the trowel is used to apply and spread these materials. All of these tools are essential for conducting accurate and reliable materials testing and analysis.
Test Procedure
Before starting the test procedure to determine the amount of water needed to give a paste normal consistency, a consistency test must be conducted. The test requires 400 grams of cement and 0.85 times the weight of cement in water to prepare a neat cement paste. The gauge time should be between 3 to 5 minutes. The time should be recorded (T1) at the instant when water is added to the cement paste.
Next, the Vicat mould should be filled with the cement paste prepared above, ensuring that the surface of the paste is level with the top of the mould. This cement block is referred to as a test block. The test block should be confined in the mould and placed on a non-porous plate under the rod bearing the needle.
The needle should be lowered gently until it touches the surface of the test block and quickly released to allow it to penetrate into the test block. Initially, the needle should completely pierce the test block. This procedure should be repeated every 2 minutes by quickly releasing the needle until it fails to pierce the block for about 5mm measured from the bottom of the mould. The time at which this occurs (T2) should be noted.
Fig 1: Vicat’s Apparatus used for determination of setting time of cement
Observations
The given context seems to be incomplete, as it includes only some incomplete information about a cement testing process. However, I can still try to rewrite it based on what is given:
In a cement testing process, some measurements were taken. The weight of the cement used in the test is unknown, as it is not provided. However, it is given that 0.85 times the quantity of water required for standard consistency was added to the cement. The exact quantity of water added is also unknown. The time at which the water was first added to the cement was recorded as T1 in seconds. The exact value of T1 is not provided either. Additionally, the time when the needle failed to penetrate 5 mm to 7 mm from the bottom of the mold was recorded as T2 in seconds. The value of T2 is also not given.
Calculations
Initial Setting Time = T2-T1
Result
The initial setting time of the given sample of cement= _____ min
Precautions
To ensure accurate results in the initial setting time test, certain precautions must be taken. Firstly, it is crucial to release the initial and final setting time needles with care to avoid any disturbance to the cement paste. Secondly, the experiment should be conducted in a location that is free from any vibrations or other external disturbances that may affect the outcome of the test. It is also important to clean the needle after each use to prevent any residue or debris from affecting the results. Additionally, the position of the mould should be slightly shifted after each penetration to prevent repeated penetration at the same location, which could skew the results. Finally, the test should be performed under specified environmental conditions to ensure consistency in the experiment. By following these precautions, the initial setting time test can be conducted with precision and accuracy.
Standard Specification of Setting Time for Different Type of Cement
The setting time of cement can vary depending on the admixtures added during its manufacture. Different types of cement may have different setting times based on these additives. The Indian Standards IS 4031 and IS 269 provide a list of standard setting times for various types of cement.
Table-1: Setting Time for Different Type of Cement
| Cement Type | Initial Setting Time in Min As per IS Codes |
| OPC(33) | 30 |
| OPC(43) | 30 |
| OPC(53) | 30 |
| SRC | 30 |
| PPC | 30 |
| RHPC | 30 |
| PSC | 30 |
| High alumina | 30 |
| Super sulphated | 30 |
| Low heat | 60 |
| Masonry cement | 90 |
| IRS-T-40 | 60 |