What Does the Los Angeles Abrasion Test Measure?

What the test measures

The Los Angeles abrasion test measures how much a coarse aggregate breaks down when it is tumbled with steel spheres in a rotating drum. It combines impact, as the aggregate and spheres drop from a shelf inside the drum, with abrasion and grinding as the drum keeps turning.

The result is the percentage of the sample, by mass, that ends up finer than the No. 12 (1.70 mm) sieve. It is widely used as an indicator of the relative quality of aggregate sources of similar mineralogy, and to screen out material that is too soft for the intended use.

Simulating real-world wear in a lab

Aggregate used in pavements and bases is subjected to repeated abrasion and impact over its service life — from traffic loading, compaction equipment, and handling during production and placement. The LA abrasion test simulates this by tumbling a sample with steel spheres in a rotating drum, producing a controlled, repeatable measure of how much the material degrades.

How the test is run

The Los Angeles machine is a steel drum about 28 in (711 mm) in diameter with an internal shelf that lifts the aggregate and steel spheres and drops them on each rotation. A graded, washed and dried sample is loaded with a specified number of spheres and rotated at 30 to 33 rpm.

Why durability matters beyond initial strength

An aggregate can look strong initially but break down faster than expected under the combined abrasion and impact it experiences once in service, generating fines that can clog drainage layers or reduce a pavement structure's designed performance over time. The LA abrasion result gives specifiers a way to screen for this before the material is ever placed.

Degradation during construction matters too. A soft aggregate can generate fines under the roller alone, changing the gradation of a base course from what was tested at the quarry — see What Is Aggregate and Why Does Gradation Matter?.

Calculating the percent loss

Everything that broke down finer than the No. 12 sieve counts as loss: LA loss = (original mass − mass retained on No. 12) ÷ original mass × 100.

Example: a 5,000 g Grading B sample retains 3,850 g on the No. 12 sieve after 500 revolutions. Loss = (5,000 − 3,850) ÷ 5,000 × 100 = 23.0%. The LA Abrasion Value Calculator does this from your masses; it reports the raw loss and leaves the pass/fail limit to your specification.

How the result is applied

Project specifications set a maximum acceptable LA abrasion percent-loss for a given application — surface-course aggregate exposed to the most wear typically has a stricter (lower) limit than base-course or fill material used deeper in the structure, though the exact limits always come from the applicable specification rather than a single universal number.

Limits range from 50% for concrete coarse aggregate under ASTM C33 down to 25–30% in the strictest asphalt specifications. The guide to what an LA abrasion result means tabulates common limits and typical values by rock type.

Reading more into the result

• Part-way loss: California Test 211 describes weighing the sample after 100 revolutions, then returning the whole sample — including the material that passed the No. 12 sieve — to the drum for the remaining revolutions. It cautions that losing those fine particles at the check generally makes the final percent wear higher than normal.
• Rock type: hard igneous rock such as basalt or trap rock generally tests lower than soft limestone or sandstone, while granite varies widely — the guide to LA abrasion results lists typical ranges by rock type. Quality varies within every rock type; Limestone in Construction discusses this.
• Complementary tests: the Micro-Deval test (ASTM D6928) measures wear with water present, and sulfate soundness (ASTM C88) indicates resistance to weathering.

Common mistakes

• Using the wrong grading or sphere charge for the sample's size.
• Not washing and drying the sample before and after testing.
• Comparing C131 and C535 results as if they were the same test.
• Treating a single result as representative of a variable quarry face.

Further reading

The guide to what an LA abrasion result means goes deeper on interpreting results against common specifications, and Crushed Stone vs Gravel covers how source rock affects aggregate choice.