Los Angeles Abrasion Test: Procedure, Limits and Values

The Los Angeles abrasion test is the standard way U.S. agencies check whether a coarse aggregate is tough enough for roads. A measured sample is tumbled with steel spheres inside a rotating drum, then sieved to see how much of it broke down. That percentage, the LA abrasion loss, shows up in almost every state spec for asphalt, concrete and base stone. Here is how the test runs, how to read the number and where it falls short.

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The short version

Standards: AASHTO T 96 and ASTM C131 for small-size coarse aggregate. ASTM C535 covers larger stone.
What happens: about 5,000 grams of stone and a charge of steel spheres turn 500 times in a steel drum.
Result: percent of the sample that passes the No. 12 (1.70 mm) sieve afterward. Lower means tougher.
Where it is used: Pavement Interactive notes that an NCAT study found 47 states using it, which made it the predominant toughness test in the country.

Why toughness matters

Stone takes a beating long before traffic ever touches it. It is crushed, stockpiled, fed through a plant, dropped into trucks, dumped, spread and rolled. A weak aggregate breaks down along the way, which changes the gradation the mix was designed around and adds dust. Once in service, the stone also has to carry tire loads down to the base. Open-graded and gap-graded mixes, like stone mastic asphalt, are especially demanding because the coarse stones touch each other directly with little fine material to cushion them.

How the test is run

Reduce and wash the sample. Split the field sample to test size, wash it and oven-dry it at 230 °F (110 °C) to constant mass.
Build the grading. Sieve the stone into size fractions and recombine them into whichever of the four standard gradings (A, B, C or D) best matches the material. The total is about 5,000 grams.
Load the drum. Put the sample and the steel sphere charge in the drum: 12 spheres for grading A, 11 for B, 8 for C and 6 for D.
Tumble. Turn the drum 500 revolutions at 30 to 33 per minute. A shelf inside lifts the stone and spheres and drops them, so the stone gets impact as well as grinding.
Sieve and weigh. Empty the drum, separate the material on a coarser sieve and then the No. 12 sieve, wash and dry what stays on the No. 12, and weigh it.

With drying time on both ends, Pavement Interactive puts the full cycle at about three days from sampling to final weight, even though the drum itself runs only about 15 minutes.

The calculation

LA abrasion loss (%) = (original mass − mass retained on the No. 12 sieve) ÷ original mass × 100.

Example (made-up numbers): 5,000 grams go in and 3,600 grams stay on the No. 12 sieve afterward. Loss = (5,000 − 3,600) ÷ 5,000 × 100 = 28 percent.

Common spec limits

Hot mix asphalt: there is no single Superpave limit. Agencies set their own, and the range reported across U.S. states runs from about 25 to 55 percent maximum loss, with 40 or 45 the most common.
Concrete: limits tend to be similar to those for hot mix.
Stone mastic asphalt: AASHTO caps loss at 30 percent.

Always check the current spec for the agency or project, since some set different limits by layer or traffic level.

Typical values by rock type

Published ranges give a feel for how different rocks behave. These come from Pavement Interactive's summary, and any given quarry can land outside them:

Rock type	LA abrasion loss (%)
Basalt	10 to 17
Dolomite	18 to 30
Limestone	19 to 30
Quartzite	20 to 35
Granite	27 to 49
Gneiss	33 to 57

That is part of why dark, dense trap rock has a reputation as tough road stone, and why some granites need a closer look.

Where the test falls short

It is empirical. Research summarized by Pavement Interactive found LA loss did not predict field performance well.
Some materials fool it. Certain slags and limestones post high losses yet hold up fine on the road.
It breaks, it does not polish. The drum smashes particles. Skid resistance depends more on how a stone polishes, which is why agencies use other tests for surface aggregates. See polished aggregate on asphalt.
Micro-Deval as a partner. The Micro-Deval test tumbles stone wet in a smaller drum with small steel balls and tends to wear particles down rather than break them. NCAT found it a better predictor, and Maine relies on it instead of LA abrasion.

How it fits with other aggregate tests

LA abrasion is one of several source tests. Gradation comes from a sieve analysis, durability against freeze-thaw from soundness tests, and particle shape from fractured-face and flat-and-elongated counts. A quarry's test history usually covers all of them, and DOT-approved stone has already cleared them, which is one reason buying an approved product is the easy path for paving and base work.

Questions people ask

What does the Los Angeles abrasion test measure?

It measures how much a coarse aggregate breaks down when tumbled with steel spheres in a rotating drum. The result, the LA abrasion loss, is the percent of the original sample that ends up passing a No. 12 sieve. Lower numbers mean tougher stone.

How many revolutions are used in the LA abrasion test?

For small-size coarse aggregate under AASHTO T 96 and ASTM C131, the drum turns 500 times at 30 to 33 revolutions per minute. The large-size version, ASTM C535, uses a bigger sample and more revolutions.

What is a good LA abrasion value?

Lower is better. Pavement Interactive reports that U.S. state limits for coarse aggregate in hot mix range from about 25 to 55 percent loss, with most states at 40 or 45. AASHTO sets 30 percent as the maximum for stone matrix asphalt.

How many steel balls are used?

The charge depends on the grading. Gradings A, B, C and D use 12, 11, 8 and 6 spheres. The sample is built to one of those gradings to match the aggregate being tested.

Is the LA abrasion test a good predictor of performance?

Only partly. NCAT research summarized by Pavement Interactive found that LA loss did not predict field performance well, and some slags and limestones lose a lot in the drum but perform fine. It does track dust generation fairly well. Some agencies also run the Micro-Deval test.

Does LA abrasion matter for a gravel driveway?

Indirectly. A soft stone that breaks down quickly turns into fines and dust, which can mean ruts and mud sooner. Quarry-run products sold for DOT work usually already meet a state abrasion limit.

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