EN 13450: Aggregates for Railway Ballast – Requirements & Testing (2026 Guide)

The stability of a train track depends on what lies beneath it. EN 13450 (Aggregates for railway ballast) is the European Standard that defines the characteristics of the crushed stones that support the sleepers and rails.

Ballast is not just random gravel. It is a carefully engineered component that performs three critical functions:

1. Distributing the extreme weight of the train to the subgrade.
2. Providing lateral resistance to keep the track geometry aligned.
3. Allowing rapid drainage of rainwater to prevent soil erosion.

Key Technical Requirements of EN 13450

To meet the standard, aggregates (typically granite, basalt, or porphyry) must pass rigorous physical and geometric tests. Soft rocks like limestone are generally rejected for mainlines.

1. Resistance to Fragmentation (Los Angeles Coefficient – $LA_{RB}$ )

This test simulates the impact forces the stone will face under passing trains. A sample is placed in a rotating drum with steel balls.

• The Metric: The percentage of the stone that turns into dust.
• The Rule: Lower is better.
  • $LA_{RB} \le 16$: Required for High-Speed Lines (> 200 km/h).
  • $LA_{RB} \le 20$: Standard for conventional mainlines.

2. Resistance to Wear (Micro-Deval – $MDE_{RB}$)

While LA measures impact, Micro-Deval measures attrition (stones rubbing against each other). As trains vibrate the track, stones grind together.

• Why it matters: If stones wear down easily, they produce “fines” (dust) that clog drainage, leading to “mud pumping” and track failure.
• Target: High-quality ballast typically requires an $MDE_{RB}$ value of less than 12.

3. Particle Shape (Flakiness Index – $FI$)

EN 13450 demands cubical stones with sharp edges. Flat or elongated (flaky) stones are dangerous because they break easily and do not interlock effectively.

Grading Categories (Sieve Analysis)

The size of the ballast is strictly controlled. If stones are too small, they clog drainage; if too large, they don’t support the sleeper evenly. The most common grading categories in Europe are:

FAQ: Common Questions on Railway Ballast