28 Abrasion Value Test/ Los Angeles Test (Aggregate)

Summary

This video explains the process of conducting the Los Angeles Abrasion Test on aggregates to assess their resistance to abrasion. The test involves rotating a sample of aggregates along with steel balls in a machine to simulate surface damage due to friction. The abrasion value is determined by measuring the weight of the particles that pass through a 1.7mm sieve after the test. Aggregates with low abrasion resistance can cause surface damage on structures, especially roads. The video also highlights the importance of ensuring aggregates have an abrasion value below certain thresholds to be used in concrete and road surfaces.

Takeaways

• 😀 Abrasion value test measures the resistance of aggregates to surface damage due to friction.
• 😀 Aggregates with low abrasion value lead to increased surface damage, commonly observed in concrete roads.
• 😀 High abrasion resistance in aggregates is essential to ensure long-lasting and durable road surfaces.
• 😀 The Los Angeles abrasion test simulates real-world conditions to evaluate aggregate abrasion resistance.
• 😀 A 5 kg sample of aggregate is used in the Los Angeles abrasion test, which is then rotated in a machine with steel balls.
• 😀 The test involves rotating the machine at 20 to 33 revolutions per minute for 500 total revolutions.
• 😀 Steel balls (weighing 400 to 450 grams each) help simulate the impact and wear on the aggregate surface during rotation.
• 😀 After the test, aggregates are sieved through a 1.7 mm sieve to determine the weight that has been damaged.
• 😀 The abrasion value is calculated as the percentage of aggregate weight passing through the 1.7 mm sieve relative to the original weight.
• 😀 According to IS code 283, the abrasion value should not exceed 30% for road surfaces and 50% for other concrete applications like RCC structures.

Q & A

What is abrasion in the context of aggregates?

Abrasion refers to the wearing off or damage to the surface of aggregates due to friction. It is an important property that affects the durability of materials like concrete, especially in road construction.

What is the significance of the Los Angeles Abrasion Test?

The Los Angeles Abrasion Test is used to determine the abrasion resistance of aggregates by simulating real-life friction conditions. It helps to assess how aggregates will perform under mechanical wear, which is crucial for ensuring long-lasting roads and concrete structures.

What is the sample size used in the Los Angeles Abrasion Test?

Around 5 kg of aggregate is taken for the test. This sample size is tested to measure the abrasion resistance.

What is the role of the steel balls in the Los Angeles Abrasion Test?

The steel balls, typically six balls weighing 400 to 450 grams, are used in the machine to damage the surface of the aggregate during the test. They create friction that helps assess the abrasion resistance of the material.

How is the speed of rotation controlled during the test?

The Los Angeles Abrasion Machine is rotated at a speed of 20 to 33 revolutions per minute for a total of 500 revolutions. This controlled speed ensures consistent results in measuring the abrasion resistance.

What happens after the 500 revolutions are completed in the Los Angeles Abrasion Test?

Once the 500 revolutions are completed, the aggregates are removed from the machine. The surface of the aggregates is now damaged, which allows for the evaluation of their abrasion resistance.

How is the abrasion value of aggregates calculated?

The abrasion value is calculated by finding the percentage of the aggregate weight that passes through a 1.7 mm sieve after the test. The formula is: (Original weight - weight retained on 1.7 mm sieve) / Original weight * 100.

What is the acceptable abrasion value for aggregates used in concrete?

According to IS code 283, the abrasion value for aggregates used in concrete should not exceed 30% for wearing surfaces (like roads) and 50% for non-wearing surfaces (like RCC structures).

Why is it important for aggregates to have a high resistance to abrasion?

High resistance to abrasion is important because it ensures the durability and longevity of concrete structures, particularly those exposed to constant wear like roads and pavements.

What happens if aggregates have a low abrasion value?

If aggregates have a low abrasion value, the surface of the concrete structure, such as roads, will get damaged more easily. This can lead to a decrease in the overall lifespan and performance of the structure.