Testing of industrial products - Aggregates for construction

The Los Angeles test method

The principle of the method

In the Los Angeles test used in the cross-testing experiments reported here, a 5000 +/- 5 g test portion of 10/14 mm aggregate is rolled in a steel drum together with 11 steel balls of total mass 4775 +/- 85 g . The drum has an internal diameter of 710 +/- 3 mm and rotates at 32 +/- 1 r/min . A projecting plate inside the drum lifts some of the steel balls and aggregate each time the drum rotates, so that the steel balls fall, causing the aggregate to be fragmented.

The rolling continues for 500 revolutions, after which the percentage of the test portion that passes a 1.60 mm sieve is determined by washing then sieving. This percentage is the Los Angeles coefficient, described in this Report as being measured in "LA units".

The proposed CEN method

The Los Angeles test has been used in the USA for many years - it was adopted as an ASTM method in 1938. The CEN version of the test method has been developed by the committee responsible for drafting test methods for determining physical properties of aggregates (CEN/TC 154/TG 7), and is similar to the ASTM method. The most significant difference between the CEN and ASTM methods is that in the CEN method masses and dimensions are specified in metric units, whereas in the ASTM method they are specified in imperial units.

Participants in the cross-testing experiments were sent copies of the method that was the version that was sent to CEN members for CEN enquiry in December 1993. According to this draft, the Los Angeles test is to be the reference method, in European Standards, for determining the resistance of coarse aggregates to fragmentation.