Abrasion Resistance of Aggregates - Los Angeles, Dorry & Deutsch Test Procedures

Abrasion resistance indicates the toughness and durability of aggregates when subjected to rubbing, grinding, impacts, and other mechanical degradation. Standardized abrasion tests quantify the resistance of aggregates to abrasive wear under controlled conditions. Common abrasion tests specified by Indian standards include Los Angeles, Dorry, and Deutsch methods.

Aggregates being tested for abrasion resistance

Los Angeles Abrasion Test

The Los Angeles abrasion test is used for coarse aggregates to determine abrasion resistance and suitability for various construction applications as per IS:2386 Part 4.

• Coarse aggregate samples are taken in the required size range, generally passing 20mm sieve and retained on 12.5mm sieve. The total sample weight should be 5kg.
• The Los Angeles testing machine consists of a hollow steel cylinder closed at both ends, with an internal shelf diameter of 700mm and length of 500mm.
• A hardened steel abrasive charge is placed in the cylinder along with the aggregates to be tested. The quantity of abrasive charge is dependent on the aggregate impact value.
• The cylinder is rotated around its horizontal axis at a speed of 30-33 rpm. Due to the lifting action as the cylinder rotates, the materials inside fall from the shelf, resulting in abrasion and degradation as the aggregates and abrasive charge tumble.
• After the cylinder completes 500 revolutions, the materials are discharged and sieved through a 1.7mm sieve. The loss in weight, which represents the abrasion loss, is calculated using the formula:

% Loss = (Original Wt. of Sample - Final Wt. of Sample) / Original Wt. x 100

Lower percentage loss values indicate aggregates with higher abrasion resistance and mechanical strength. Typical acceptance limits are:

• 35% max for wearing surfaces
• 30% max for concrete roads and runways
• 40% max for other concrete structures

The Los Angeles abrasion test produces realistic abrasion action and is commonly specified for assessing aggregates used in concrete, road construction, railways, and other applications.

Dorry Abrasion Test

The Dorry abrasion test is designed for aggregates sized above 10mm. It provides an alternative abrasion resistance measurement to the Los Angeles test.

• Coarse aggregate sample is placed in the Dorry testing machine, consisting of a disc made of cast iron or steel of 140-150mm diameter.
• The disc rotates in a hemispherical cast iron cup at a speed of 28-29 rpm.
• The cup dimensions are - 200mm internal diameter at the bottom, 140mm internal diameter at the top, and depth of 140mm.
• 1kg of aggregate sample is tested along with four cast iron spheres weighing 390-445g each that cause abrasive action.
• The apparatus is run for 500 revolutions. The sample is then removed and sieved through 2.36mm sieve.

Abrasion loss percentage is calculated using the same formula as the Los Angeles test above. Lower values indicate higher abrasion resistance.

Deutsch Abrasion Test

This method is specifically used for aggregates smaller than 10mm in size.

• In the Deutsch testing machine, aggregates are placed in an octagonal cast iron cup of 240mm diameter and 200mm depth.
• The cup is rotated in a horizontal plane at 25-27 rpm during the test.
• 300g of aggregate sample is taken along with 5 hardened steel balls of 48mm diameter that provide abrasive action.
• The cup rotates for 100 revolutions, after which the sample is removed and sieved through a 1.18mm sieve.

The abrasion loss percentage is calculated using the standard formula. Lower values indicate better abrasion resistance. Limits are 5-20% loss based on application.

Comparing Abrasion Tests

The Los Angeles abrasion test sees the most widespread use for aggregates in construction as per IS codes. The Dorry test also produces valuable data but is less common. The Deutsch test is specially designed for smaller aggregates. In all cases, lower percentage loss values indicate tougher aggregates suitable for applications involving substantial abrasive forces over the structure lifetime.