LAB IN YOUR GRASP - KARAKTERISASI MATERIAL BETON : 09 SETTING TIME BINDER (ASTM C 191-19)

Summary

In this video, Adlizie and Panglima from the Geopolymer Research Consortium demonstrate a unique lab test on the setting time of a cement and fly ash binder mix. They explore how fly ash, as a partial cement substitute, enhances workability and compressive strength in concrete while affecting setting time. The test, following ASTM C191-19, includes detailed steps on preparing the paste, mixing, and using the Vicat needle to measure setting times. The final results show an initial setting time of 213 minutes and a final setting time of 305 minutes, meeting ASTM C150-20 standards.

Takeaways

• 😀 The video demonstrates a lab testing process for a cement and fly ash binder mix, presented by Adlizie and Panglima from Geopolymer Research Consortium LBE Green Concrete.
• 😀 Fly ash can substitute a portion of cement in concrete to improve workability and potentially increase compressive strength.
• 😀 The use of fly ash affects the setting time of concrete, making a setting time test necessary.
• 😀 The setting time test follows the ASTM C191-19 standard, similar to previous tests done on pure cement.
• 😀 The binder mix for the test consists of 70% cement and 30% fly ash, with a water-to-binder ratio of 30.5% determined from the normal consistency test.
• 😀 Tools used include a Vicat ring and needle, mixer, digital scale, acrylic plates, plastic spoon, latex gloves, and other standard lab equipment.
• 😀 The mixing procedure involves carefully combining the binder and water, resting, and mixing again to achieve a uniform paste according to ASTM C305.
• 😀 The paste is shaped into balls, placed into the Vicat ring, and flattened, ensuring the specimen is free of spillage and the surface is even.
• 😀 Initial setting time is measured when the Vicat needle penetration reaches 25 mm, and final setting time is when it reaches 0 mm, with this test resulting in 213 minutes initial and 305 minutes final.
• 😀 The test results meet ASTM C150-20 requirements, confirming the binder's setting time is within acceptable limits (minimum initial 45 min, maximum final 375 min).
• 😀 Proper specimen preparation, careful needle placement, and vibration-free testing are essential for accurate results.
• 😀 This test provides insight into the behavior of fly ash-cement binders, which is critical for sustainable concrete applications.

Q & A

What is the main purpose of using fly ash in concrete?

Fly ash is used as a cementitious material to substitute cement in the concrete mix. It reduces friction between particles, which enhances the workability and maintains the water-to-cement ratio, ultimately improving compressive strength.

How does the use of fly ash affect the setting time of concrete?

Fly ash affects the setting time of concrete by extending the time it takes for the mixture to harden. This is why the setting time test is crucial to determine how long it takes for the binder to react with water until it hardens.

What does the setting time test measure?

The setting time test measures the duration needed for a binder (cement and fly ash mix) to react with water until it reaches a hardened state. The test determines the initial and final setting times.

What are the initial and final setting times for the binder tested in the video?

In the video, the initial setting time was found to be 213 minutes, and the final setting time was 305 minutes for the binder (cement and fly ash mix).

What standard is referred to for conducting the setting time test in the video?

The setting time test follows the guidelines of ASTM C191-19, which specifies the procedures for determining the setting time of cement and its mixtures.

How is the water-to-binder ratio determined for the test?

The water-to-binder ratio is calculated based on the normal consistency test. In this case, the water-to-binder ratio is 30.5%, which means 91.5 grams of water are used for 300 grams of binder.

Why is the mixer used during the preparation of the binder paste?

The mixer is used to ensure the paste is smooth and evenly mixed, which is important for achieving consistent results. It helps to break down clumps and ensure the uniform distribution of water within the binder.

What is the role of the Vicat needle in the setting time test?

The Vicat needle is used to measure the penetration depth into the paste. The test is designed to track the time it takes for the needle to reach certain depths, which indicates the setting stages of the binder.

What happens if the needle does not penetrate to a depth of 25 mm?

If the needle does not reach a depth of 25 mm, the test is paused for 15 minutes, and the measurement is repeated at a different point, ensuring the test is conducted correctly.

How does the setting time test comply with ASTM C150-20?

The setting time test complies with ASTM C150-20, which specifies that the initial setting time of cement should be at least 45 minutes and the final setting time should not exceed 375 minutes. The test results in the video meet these criteria.