What property of aggregates does the Los Angeles Abrasion test primarily evaluate?

The Los Angeles Abrasion test (ASTM C131 or AASHTO T 96) primarily evaluates the abrasion resistance and toughness of aggregates. Abrasion resistance refers to the aggregate's ability to withstand the wearing and grinding action of other materials, while toughness refers to its ability to absorb energy and resist fracture under impact. The Los Angeles Abrasion test simulates these conditions by placing a specified amount of aggregate, along with steel spheres, inside a rotating drum. As the drum rotates, the steel spheres impact and grind against the aggregate, causing some of the aggregate to break down into smaller particles. After a specified number of revolutions, the material is sieved, and the amount of material passing a designated sieve size (typically the #12 sieve) is measured. The percentage of material lost is reported as the Los Angeles Abrasion loss. A lower Los Angeles Abrasion loss indicates higher abrasion resistance and toughness, meaning the aggregate is more resistant to degradation under abrasive conditions. This is particularly important for aggregates used in pavements and other applications where they are subjected to significant wear and tear. For example, aggregates used in highway pavements should have a low Los Angeles Abrasion loss to ensure the pavement's durability and resistance to rutting and degradation under traffic.