The Los Angeles abrasion test (LA abrasion) is the North American standard for testing
toughness
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.abrasion and degradation) of
construction aggregate
Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates ...
or
gravel
Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone.
Gravel is classifi ...
and its suitability for road construction. Test methodology and equipment is defined in the ASTM International publications ASTM C131 for particle sizes smaller than 37 mm (1.5 inches) and ASTM C535 for sizes larger than 19 mm (3/4 of an inch); the overlapping range of 19 to 37 mm can be tested by either of two standards.
The Los Angeles machine defined in the standard is a simple
ball mill
A ball mill is a type of grinder used to grind or blend materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering. It works on the principle of impact and attrition: size reduction is done ...
of specified size and shape The standard charge of rock is set at depending on the size of the particles. The drum of the mill has a single shelf plate that scoops test samples and steel balls from the bottom, lifts them up and then drops them, creating a crushing impact. The interaction of the drum, steel balls and the samples at the bottom of the drum causes further abrading and grinding. The complete test requires 500 drum revolutions at a speed of 30-33
revolutions per minute
Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines.
Standards
ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
. Crushed sample is then separated from fine dust on a sieve, washed, dried and weighed. The test reports loss of mass to abrasion and impact, expressed as a percentage of initial sample mass. Maximum acceptable loss for the base course of the road is 45%; the more demanding surface course must be 35% or less.
The test was developed by the city engineers of
Los Angeles
Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...
Deval abrasion test Deval is a given name, a surname, Gotra of varied origins (Indian and French). It may refer to:
Surname
*Chandra Prakash Deval (born 1949), Indian poet and translator
* Charles Deval (1806–1862), French ophthalmologist
*Govind Ballal Deval (185 ...
, and adopted the LA test in 1927. In the 1930s, national studies demonstrated the Deval test did not correlate with the service record of sampled rock altogether, while an LA loss rating of less than 40% was a reliable indicator of quality. The federal standard for LA abrasion testing was formally adopted by the ASTM in 1937. Decades later, field studies found that the LA test results do not always correlate with reality, thus engineers outside of the United States developed different national standards like the French wet micro-Deval procedure or the British Standard 812.