Overview
ISO 20290-2:2019 specifies the Los Angeles (LA) test method for determining the resistance to fragmentation of coarse aggregates. The standard describes sampling considerations, required apparatus (including the Los Angeles drum and ball load), test portion preparation, the test procedure, calculation of the Los Angeles coefficient (LA) and minimum reporting requirements. This method is widely used in aggregate quality control for concrete, pavements and other civil engineering applications.
Key Topics
- Scope and purpose: Applies to coarse aggregates intended for concrete and allied uses to quantify fragmentation resistance.
- Apparatus: Los Angeles drum (711 ± 5 mm internal diameter, 508 ± 5 mm length), spherical steel balls (11 balls, 45–49 mm diameter; total ~4 690–4 860 g), ventilated oven, sieves conforming to ISO 565, balance with 0.1% accuracy, tray and revolution counter.
- Test portion and grading: Test portion mass (5 000 ± 5 g) prepared from material passing 20 mm and retained on 10 mm sieve, with specified intermediate grading (e.g., 60–70% passing 12.5 mm or 30–40% passing 11.2 mm). Annex A and B provide procedures for larger sizes and alternative narrow-range classifications.
- Procedure: Load the balls and test portion into the drum, seal the opening, and rotate at 30–33 rpm for 500 revolutions (1 000 revolutions and adjusted ball load for larger sizes per Annex A). Recover and sieve the test product, retain material on the 1.6/1.7 mm sieve and dry to constant mass.
- Calculation: The Los Angeles coefficient is calculated from the retained mass (m) using LA = (5000 − m) / 50 (reported to the nearest whole number). For larger aggregates in Annex A the formula is LA = (10000 − m) / 100.
- Test report: Must confirm compliance with ISO 20290-2 and include sample origin, size fractions used, and the LA coefficient.
Applications
- Quality control for concrete aggregates: Use LA values to screen aggregates for susceptibility to mechanical breakdown under action similar to mixing, handling and trafficking.
- Pavement and road construction: Inform selection of coarse aggregates where fragmentation resistance affects durability and skid resistance.
- Material specification and acceptance: Provide a reproducible metric (LA coefficient) for contracts, tender documents and compliance testing.
Related Standards
- ISO 565 - Test sieves (referenced for sieve aperture sizes).
- Other parts of the ISO 20290 series - consult the ISO catalogue for related test methods for mechanical and physical properties of aggregates.
This summary emphasizes the practical steps, apparatus and reporting requirements in ISO 20290-2:2019 for the Los Angeles test. For full normative details, including tolerances, annex procedures for larger sizes, and exact apparatus dimensions, refer to the official ISO 20290-2:2019 document.