What is the significance of the LA abrasion test?

The Los Angeles abrasion test is primarily used to measure the wear resistance of coarse aggregate under friction and impact. This test simulates the mechanical wear experienced by aggregate during transportation and construction, assessing its resistance to wear and crushing, ensuring its ability to withstand traffic loads and environmental impacts in real-world applications.

Aggregates experience significant wear and tear during their service life. Generally speaking, aggregates should be hard and tough enough to resist crushing, degradation, and disintegration during various activities associated with manufacturing, stockpiling, production, paving, and compaction. Furthermore, aggregates must be able to effectively transfer loads from the pavement to the underlying layers and ultimately to the roadbed. These properties are particularly important for open-graded or gap-graded hot mix asphalt (HMA), as these mixtures lack the cushioning effect of fine aggregate and are subject to higher contact stresses on the coarse aggregate. Aggregates with insufficient wear and polishing resistance can lead to premature structural failure and/or reduced skid resistance. Furthermore, poor wear resistance can generate excessive dust during the hot mix asphalt production process, potentially creating environmental issues and mixture control problems.

Given the above issues, tests that predict aggregate toughness and wear resistance are crucial. The LA abrasion test is the predominant test method in the United States; 47 states use it.

How to conduct the LA abrasion test?

• Check and record the initial sample mass to the nearest gram.
• Select and prepare the appropriate steel material.
• Check that the interior of the LA machine is clean and, if necessary, brush off any old residue.
• Seal the sample in the cylinder and secure the lid, ensuring a tight seal.
• Set the number of rotations (this depends on the grade).
• After the rotation is complete, open the lid, remove the sample and steel balls, and place them in a tray.
• You can tap the cylinder with a rubber mallet to remove any excess material remaining inside. Use a soft brush to thoroughly clean the inside of the cylinder to remove any fines, and brush the brush scraps into the tray. Exercise caution to avoid material loss.
• Now remove the steel balls from the sample.
• Nest the 300 mm sieves in the desired order.

Sieve the test sample by hand or with a mechanical sieve. Weigh all material that passes through a 1.70 mm sieve. Weigh all material with a particle size larger than 1.70 mm together to the nearest gram. The total mass of material that passes through the 1.70 mm sieve and remains on the sieve must not differ by more than 25 grams from the initial mass. Sieve material with a particle size larger than 1.70 mm through a 1.70 mm sieve until the water runs clear. Dry the washed material to a constant weight. After reaching a constant weight, allow the sample to cool to room temperature and then re-sieve as in the previous step. Combine all retained material with a particle size larger than 1.70 mm and weigh to the nearest gram.

Working Principle

The core principle of the Los Angeles Abrasion Tester is to simulate the wear process of materials under the combined effects of friction, impact, and shear. It places a sample of a specified size (such as aggregate or stone) along with steel balls into a rotating drum. As the drum rotates at a constant speed, the material inside collides and rubs against the steel balls. After hundreds of rotations, the sample is removed and the wear resistance of the material is accurately measured by calculating the percentage of mass loss before and after wear—the "wear value." The lower the wear value, the harder and more wear-resistant the material.

Practical Applications

Ensuring Every Kilometer of Our Travel

This is the most classic and important application of the Los Angeles Abrasion Tester. Whether on highways, urban thoroughfares, or rural roads, the durability of asphalt concrete pavements is directly related to driving safety, comfort, and maintenance costs. The crushed stone (aggregate) used for paving must possess extremely high wear resistance. By testing candidate stone materials in the laboratory using the Los Angeles Abrasion Tester, engineers can select the strongest and most durable materials. This ensures that the paved surface can withstand repeated rolling, wear, and impact from vehicle tires, and is less susceptible to rutting, loosening, and potholes. This ensures the safety of daily travel for hundreds of millions of people, significantly extends the lifespan of roads, and conserves public financial resources.

Building Every Building We Live In In construction

Concrete is the undisputed "star." The strength and durability of concrete depend heavily on the quality of its aggregates (sand and stone). If the aggregates used are soft and non-wear-resistant, they will break down within the concrete before the cement paste, reducing the overall strength of the concrete and compromising the safety of the building structure. Therefore, performing Los Angeles abrasion tests on construction aggregates is crucial for ensuring the long-term durability of infrastructure such as buildings, bridges, and dams. It prevents substandard materials from entering construction sites at the source, creating safe and reliable living and working spaces.

Creating a Colorful and Safe Public Environment

With the rise of urban aesthetics, colored permeable asphalt and epoxy resin flooring are widely used in park trails, school playgrounds, plazas, and community green belts. These areas not only demand aesthetics but also high levels of wear resistance and anti-slip properties. The Los Angeles abrasion tester can be used to test the wear resistance of the colored stones used in these floorings, ensuring that they retain their color and structural stability, resist flaking and wear, even under prolonged exposure to sunlight, rain, and pedestrian traffic, providing a beautiful and safe playground for residents, especially children.

Screening High-Quality Industrial Raw Materials

Raw material hardness is also a crucial characteristic in fields such as civil engineering, mining, metallurgy, and ceramics manufacturing. For example, when used as railway ballast, filter media, or certain industrial fillers, the material's abrasion resistance is crucial. The Los Angeles Abrasion Tester provides these industries with a standardized, reliable quality assessment method, helping companies select high-quality raw materials that best meet production requirements.

Precautions

1. The abrasion tester must be monitored by a dedicated person during operation. This is an effective way to improve safety. If any problems occur, the power should be turned off and checked immediately to avoid accidents.

2. After each use, disconnect the dedicated power supply and keep the instrument clean to prevent corrosion.

3. During testing, the cylinder cap must be tightly sealed. If loosened, the screw threads will be worn flat, affecting the normal operation of the instrument.

4. Install a steel-encased switch in the power supply line for the wear tester, and use a wire twice as thick as the power cord as the ground wire.

Although the Los Angeles Abrasion Tester may not be directly visible, it establishes a solid quality standard for the entire building materials industry through a series of rigorous scientific data. Like a rigorous examiner, it rejects all materials that are not wear-resistant and durable, allowing only the strongest and most reliable "candidates" into our lives. From the roads we drive on, to the homes we live in, to the parks we relax in, this "ruggedness" born from the laboratory is everywhere, silently safeguarding the convenience, safety, and quality of modern life.

2025-10-29 13:27