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The Los Angeles Abrasion Test (LAA) is an important test method for evaluating the wear and crushing resistance of coarse aggregates, widely used in road construction, construction, and mining.
This test simulates the mechanical friction and impact to which aggregates are subjected during transportation, construction, and use, quantifying their wear resistance and providing a scientific basis for the suitability of construction materials. Aggregates, as the primary component of building materials such as concrete and asphalt mixtures, have a direct impact on the lifespan and safety of engineering structures.
The LA Abrasion Test, through standardized testing procedures, effectively evaluates the performance stability of aggregates under long-term loads and environmental conditions, providing critical data for material selection and quality control.
The LA machine defined in this standard is a simple ball mill of specific size and shape. The standard rock charge is set at 2.5-5 kg (5.5-11.0 lb), depending on particle size. The mill's drum features a single shelf that scoops up the test sample and steel balls from the bottom, lifts them, and then drops them, generating a crushing impact force. The interaction between the drum, steel balls, and the sample at the drum bottom further abrades and grinds the sample. A complete test requires the drum to rotate 500 times at a speed of 30-33 revolutions per minute. The crushed sample is then separated from fine dust, placed on a sieve, washed, dried, and weighed. The test reports the mass loss due to abrasion and impact as a percentage of the initial sample mass. The maximum acceptable loss for road base is 45%; more demanding surface layers must be 35% or less.
The steel ball bearing hardness test uses a standard steel ball mixed with aggregate and subjected to impact with the aggregate during a specified number of revolutions in the drum. The percentage of wear due to friction with the steel balls is determined and is referred to as the wear value.
The sample is prepared by taking the portion of the aggregate sample that remains on a 1.70 mm (No. 12) sieve and placing it in a large rotating drum with shelves attached to the exterior wall.
The standardized procedure for the Los Angeles abrasion loss test must comply with the following specifications:
ASTM C131 / C131M-20. "Standard Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine," applies to coarse aggregates with a particle size less than 37.5 mm and specifies the test procedures, instrumentation requirements, and result calculation methods.
ASTM C535-16. "Standard Test Method for Resistance to Degradation of Large-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine," applies to large-size aggregates with a particle size greater than 19 mm and provides additional requirements for large-particle materials.
GB/T 14685-2022. "Pebbles and Crushed Stone for Construction," is a Chinese national standard that specifies the Los Angeles abrasion loss index requirements for aggregates.
EN 1097-2:2020. "Tests for mechanical and physical properties of aggregates - Part 2: Methods for the determination of resistance to fragmentation," specifies the test method for the resistance of aggregates to fragmentation.
The prepared sample is placed in an abrasion testing machine.
The specified number of steel balls is then placed in the machine, and the drum is rotated at 30-33 rpm for 500 revolutions per minute.
The material is then separated into material passing through a 1.70 mm (No. 12) sieve and material retained on a 1.70 mm (No. 12) sieve.
The sample is dried in an oven.
The % loss due to abrasion is calculated by calculating the difference between the retained material (larger particles) and the original sample weight. The difference in weight is reported as a percentage of the original weight, referred to as the "percent loss."
The sample should be washed and dried at 105°C to 110°C and should meet one of the observation grades.
The Los Angeles abrasion test is an empirical test; it does not directly correlate with the field performance of aggregates. Field observations generally do not show a good correlation between Los Angeles abrasion values and field performance. Abrasion values cannot predict field performance. Specifically, the test may not be satisfactory for certain types of aggregate. Some aggregates, such as slag and some limestones, have high Los Angeles abrasion losses but perform well in the field. In aggregates with higher Los Angeles abrasion losses, Los Angeles abrasion losses appear to be closely related to dust formation during handling and HMA production. Higher Loss abrasion loss values generally result in greater dust generation.
For an aggregate to perform satisfactorily in pavement applications, it must be sufficiently hard to withstand the abrasive effects of prolonged traffic. Soft aggregates are quickly reduced to dust, while hard aggregates are quite resistant to crushing.
This test also determines the quality of the aggregate.
Abrasion tests are widely used as an indicator of the relative quality or capacity of mineral aggregates.
The Los Angeles Abrasion Loss Test, a classic method for evaluating aggregate durability, has been widely recognized in the global engineering community for its scientific and practical validity. Through standardized testing procedures and precise instrumentation, this test not only provides a basis for quality control for material suppliers but also offers reliable support for engineering designers to optimize material mixes and extend the life of structures.
In the future, with the development of intelligent testing technology, testing accuracy and efficiency are expected to be further improved, pushing the construction materials evaluation system to a higher level.
Abrasion testing determines the relative mass, toughness, and durability of mineral aggregates when subjected to impact and abrasion. The values obtained from Micro Deval and LA abrasion tests provide information on the performance of aggregates in use. This test provides insight into the long-term wear properties of asphalt and concrete aggregates. As part of a quality control or quality assurance program, it is also a good indicator of variations in aggregate source properties.
The LA abrasion test uses a large, dry sample and abrasive material placed in a drum with a shelf. A shelf moves the sample and abrasive up and down the drum, exerting significant impact forces on the aggregate particles. Losses in this test are due to particle breakage and dry grinding. The Micro-Deval test, on the other hand, involves wet grinding of smaller samples in a smooth drum; losses are related to wear and abrasion.
Although there are difficulties in correlating their results, both tests are considered predictive of aggregate toughness and durability. Applicability often depends on the level of acceptance within a particular region or jurisdiction.
LA Abrasion is a long-established test with a wealth of data that most designers can use and understand. This equipment is larger and more expensive than the Micro-Deval, but it is simple, reliable, and easy to use. Modern designs make the equipment safer, with enclosures to limit noise, dust, and moving parts. Before deciding which method to use, you should consider which test is most likely to be used for your project.
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