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IRC recommends standard test to evaluate hardness of road aggregate is
Impact test
shape test
Los-Angeles abration test
crushing test
Los-Angeles abration test
The Los Angeles (LA) Abrasion Test is the standard test recommended by the Indian Roads Congress (IRC) to evaluate the hardness and resistance of road aggregates against mechanical wear and tear. It measures the combined effect of attrition (surface wearing) and impact (shattering) that occurs when aggregates are subjected to revolving steel balls in a drum.
The Los Angeles (LA) Abrasion Test is the standard test recommended by the Indian Roads Congress (IRC) to evaluate the hardness and resistance of road aggregates against mechanical wear and tear. It measures the combined effect of attrition (surface wearing) and impact (shattering) that occurs when aggregates are subjected to revolving steel balls in a drum.
LAAV=WoтАЛWpтАЛтАЛ├Ч100 тАФ where WpтАЛ is weight passing 1.7 mm sieve and WoтАЛ is original weight.
The test uses a cylindrical steel drum rotating at 30-33 rpm containing the aggregate sample and a specific charge of steel balls. As the drum rotates, the aggregates and steel balls are lifted and dropped, causing both impact and abrasion. After a fixed number of revolutions (typically 500 or 1000), the sample is sieved through a 1.7 mm mesh, and the mass of material passing is calculated as a percentage of the original sample weight.
Measures hardness, resistance to abrasion, and resistance to impact.
Standard revolutions for most aggregates is 500.
Higher LAAV indicates lower hardness and inferior quality of aggregate.
IRC specifies maximum allowable LAAV for different types of pavement layers (e.g., usually 30-40% for bituminous layers).
Simulates real-world traffic wear conditions effectively.
Combines both impact and abrasion mechanisms in one test.
Result depends on the grading of the sample.
Requires significant equipment investment and time.
Selection of stone aggregates for highway construction.
Quality control in road material production.
The Los Angeles Abrasion test is preferred over the Deval abrasion test because it uses abrasive charges and a larger drum capacity, providing more realistic results.
Option A (Impact test) evaluates toughness; Option B (Shape test) evaluates flakiness/elongation indices; Option D (Crushing test) specifically measures resistance to crushing under compressive loads.
C is correct тАФ The Los Angeles Abrasion test is the universally accepted IRC method for assessing the hardness (combined abrasion and impact resistance) of road aggregates.
Always remember: Aggregates in top layers require higher hardness (lower LAAV) than those in lower sub-base layers.