The Crucial Role of Abrasion Testing in Road Construction

Our roads face a relentless barrage of heavy traffic, environmental stressors, and other wear and tear factors. Predicting how materials will hold up under these conditions is challenging, yet essential. One of the most effective ways to guarantee the quality of paving materials is through rigorous abrasion testing of the aggregates used in hot-mix asphalt (HMA).

Abrasion testing assesses the quality and durability of mineral aggregates by subjecting them to abrasion and impact. Among the most widely used methods are the Los Angeles (L.A.) Abrasion Test and the Micro-Deval Test. These tests yield critical data on the durability of aggregate samples, helping engineers make informed decisions.

The process involves preparing samples with specific masses of particle size fractions, processing them in testing devices, and washing them over a sieve to determine the percentage loss due to abrasion. This method provides a direct measure of the aggregate's ability to withstand various stresses.

The Micro-Deval Test has gained traction as an economical and accurate method for aggregate abrasion testing. Originating in France in the 1960s, this test evaluates the toughness, abrasion resistance, and durability of mineral aggregates as they are ground with steel balls in water.

Abrasion loss is a key metric determined by measuring the amount of material passing through a 1.18mm (No. 16) or 75µm (No. 200) sieve after testing. Aggregates with low abrasion loss are less likely to degrade significantly during handling, mixing, or placing, leading to better long-term pavement performance. The test methods differ for fine and coarse aggregates, ensuring precise and relevant results for various material types.

1. Sample Preparation: Aggregate samples are separated into individual size fractions of required masses, typically 500g for fine aggregate and 1,500g for coarse aggregate.

2. Immersion: The sample is soaked in tap water for at least an hour in the Micro-Deval Jar or another suitable container.

3. Adding Abrasive Charge: Magnetic stainless steel balls are added to the water-immersed sample. The jar is then securely covered and placed on the Micro-Deval machine.

4. Testing: The machine rotates the jars at 100rpm for a specified duration or number of revolutions.

5. Washing and Measuring Loss: After testing, the sample is washed over a specified sieve. The percentage loss is calculated by comparing the oven-dried mass of the retained sample to the original sample weight. Fine aggregates use a 75µm (No. 200) sieve, while coarse aggregates use a 1.18mm (No. 16) sieve.

Micro-Deval testing requires calibration aggregates, which can be sourced locally and compared to a Laboratory Reference Aggregate available from the Ontario Ministry of Transportation.

The Micro-Deval Test offers several advantages over other methods, including smaller equipment size, lower sample quantities, and a straightforward procedure. Operators can run two samples simultaneously, enhancing efficiency and cost-effectiveness.