Time of Setting of Hydraulic Cement by Vicat Needle ASTM C 191

Summary

This video demonstrates how to determine the setting time of hydraulic cement using the Vicat apparatus. It explains the process of mixing cement with water and using both thick and thin needles to measure the cement's setting time. The initial setting time is recorded when the thin needle penetrates the paste up to 25 mm, while the final setting time is noted when the thick needle no longer penetrates the paste. This process helps identify how long the cement takes to hydrate and solidify properly.

Takeaways

• ⏲️ The video explains how to determine the setting time of hydraulic cement using the VCAT needle.
• 🧪 Setting time refers to the duration it takes for cement to fully react or hydrate with water.
• 🔧 The required materials for this test include the VCAT apparatus, two needles (thick and thin), a mixer, a timer, 650 grams of cement, and a specified amount of water.
• 💧 The water amount is determined by a normal consistency test, covered in a previous video.
• 🕒 Start the timer as soon as water is added to the cement in the mixing bowl.
• 🌀 Mix the cement paste thoroughly, as demonstrated in the normal consistency test.
• ⏳ After 30 minutes, use the thin needle on the VCAT apparatus to measure the penetration of the cement paste every 15 minutes.
• 📏 When the penetration reaches 25 mm or less, it marks the initial setting time.
• 🛠️ Switch to the thick needle to continue testing the cement paste until the needle no longer penetrates the paste, indicating the final setting time.
• ✅ By following this process, you can determine both the initial and final setting times of hydraulic cement using the VCAT needle.

Q & A

What is the purpose of the VCAT needle test for hydraulic cement?

The purpose of the VCAT needle test is to determine the setting time of hydraulic cement, which is the time needed for the cement to react or hydrate completely with water.

What materials and equipment are required to perform the VCAT needle test?

The materials and equipment required include the VCAT apparatus, two needles (thick and thin), a mixer, a timer, 650 grams of cement, and a defined amount of water determined by the normal consistency test.

How is the amount of water needed for the test determined?

The amount of water required is determined through a normal consistency test, which is covered in a previous video.

What is the first step in performing the VCAT needle test?

The first step is to put the cement in the mixing bowl and add the defined amount of water. Then, start the timer at the exact moment the water is added to the cement.

How long should the cement paste be left after mixing?

The cement paste should be left for 30 minutes after mixing before proceeding with the needle test.

How is the initial setting time of cement determined?

The initial setting time is determined by placing the thin needle on the VCAT apparatus and repeating penetration tests every 15 minutes until a penetration depth of 25 millimeters or less is achieved.

How is the final setting time of cement determined?

The final setting time is determined by placing the thick needle on the VCAT apparatus and repeating penetration tests every 15 minutes until the needle fails to penetrate the base surface.

What is the significance of the initial and final setting times in the VCAT needle test?

The initial setting time represents the period during which the cement begins to hydrate and form a paste, while the final setting time indicates when the cement has fully set and can no longer be penetrated by the needle.

Why is it important to test the setting time of hydraulic cement?

Testing the setting time of hydraulic cement is important to ensure it has adequate time to hydrate and develop strength before it is exposed to loads or other environmental conditions.

What is the time interval between each penetration test during the VCAT needle test?

Penetration tests are performed every 15 minutes until the required setting time measurements are achieved.