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

Construction Club at EMU

6 Mar 201602:12

Summary

TLDRThis 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.

Outlines

00:00

🕒 Setting Time Test for Hydraulic Cement

This paragraph introduces the topic of determining the setting time of hydraulic cement using the VCAT needle apparatus. The setting time is the period during which cement fully reacts or hydrates with water. The equipment required for the test includes the VCAT apparatus, two types of needles (thick and thin), a mixer, a timer, 650 grams of cement, and a specific amount of water, as calculated from a prior normal consistency test. For more information on this consistency test, a reference video link is mentioned. The preparation steps begin with placing cement in a mixing bowl and adding water, ensuring that the timer starts simultaneously.

Mindmap

Keywords

💡Hydraulic Cement

Hydraulic cement is a type of cement that hardens and sets by reacting with water, known as hydration. In the video, hydraulic cement's setting time is tested to measure how long it takes to harden after mixing with water. This is crucial in construction as it determines how long workers can manipulate the material before it becomes too stiff to work with.

💡Setting Time

Setting time refers to the time it takes for cement to harden after mixing with water. The video focuses on measuring both the initial and final setting times using the VCAT needle method. Understanding setting times helps engineers know how long they can work with the cement before it solidifies, which is essential for planning construction activities.

💡VCAT Needle Apparatus

The VCAT needle apparatus is a tool used to measure the setting time of cement. In the video, two needles—a thin and a thick one—are used to test when the cement reaches its initial and final set. This apparatus helps ensure accuracy in determining when cement has sufficiently hardened for construction purposes.

💡Initial Setting Time

Initial setting time is the time from when water is first mixed with cement until the cement paste reaches a certain level of hardness. In the video, it is determined when the thin needle penetrates only 25 millimeters or less into the paste. This marks when the cement starts losing its plasticity, meaning it can no longer be molded easily.

💡Final Setting Time

Final setting time refers to the moment when the cement paste has fully hardened. In the video, the thick needle is used to test this; the final setting time is reached when the needle can no longer penetrate the paste. This is critical because the cement must be fully set before it can support weight or continue with further construction work.

💡Cement Paste

Cement paste is the mixture of cement and water. In the video, the paste is prepared as part of the testing process, which involves mixing a defined amount of water with 650 grams of cement. The consistency of this paste is crucial for determining the setting times accurately, as it simulates the conditions under which cement would be used in real applications.

💡Normal Consistency Test

The normal consistency test is used to determine the correct amount of water required to make a standard cement paste. In the video, it is mentioned that the water content for the current experiment was determined by this test, which ensures that the cement mixture has the right viscosity for setting time testing.

💡Penetration

Penetration refers to how deep the needle can go into the cement paste during the test. In the video, the penetration of the thin needle to 25 millimeters marks the initial setting time, while the inability of the thick needle to penetrate indicates the final setting time. This method is used to gauge the cement's hardness at different stages of setting.

💡Mixing Time

Mixing time is the moment when water is added to the cement, starting the hydration process. In the video, the timer begins as soon as water and cement are mixed, which is crucial for accurately measuring setting times. Consistency in mixing ensures that the results are reliable and reflect the true behavior of the cement.

💡Hydration

Hydration is the chemical reaction between cement and water, which causes the cement to harden. The video revolves around the process of hydration, as the time it takes for cement to set is directly related to how fast it reacts with water. Monitoring hydration allows engineers to control the setting process in practical construction scenarios.

Highlights

Introduction to setting time of hydraulic cement using VCAT needle.

Explanation of the reaction of cement with water to achieve complete hydration.

List of materials required: VCAT apparatus, two needles (thick and thin), mixer, timer, 650g of cement, and a pre-determined amount of water.

Water amount is determined by a normal consistency test, which was covered in a previous video.

Step 1: Put cement in the mixing bowl and add water.

Start the timer immediately after adding water to the cement.

Preparation of the cement paste following the same method as the normal consistency test.

Let the paste sit for 30 minutes.

Use the thin needle on the VCAT apparatus to measure initial setting time.

Adjust the needle until it contacts the base, then release it.

Penetration measurement is taken every 15 minutes until 25mm or less penetration is achieved.

The time between water contact and 25mm penetration marks the initial setting time.

Switch to the thick needle and adjust for final setting time measurement.

The time between water contact and when the thick needle fails to penetrate marks the final setting time.

Conclusion: Method to determine the initial and final setting times of cement using VCAT needle.