Materials & Required Properties of Ballast

Materials Used for Ballast

1. Broken stone
2. Gravel
3. Coarse sand
4. Brick bats
5. Selected earth

Required Properties

• Aggregate Abrasion Values: Maximum 30%
• Aggregate Impact Test: Maximum 20%
• Soundness: Maximum 10%
• Elongation Index: Maximum 50%
• Flakiness Index: Maximum 50%
• Specific Gravity: Minimum 2.65
• Water Absorption: Maximum 1%

Ballast: Functions & Properties

Functions

• Provide a hard and level bed for sleepers
• Hold sleepers in place during passage of trains
• Transfers and distributes load from sleepers to larger area
• Provides effective drainage and keep sleeper dry
• Prevent vegetation growth
• Prevents water from percolating (capillary rise)
• Provide track stability

Desirable Properties of Ballast

• Good bearing capacity and crushing value
• Tough and wear resistant
• Good drainage property
• Non porous
• Should resist attrition and abrasion
• --Attrition: getting carried/ rubbed away by means of friction
• -- Abrasion: wearing down by means of friction
• Weather resistant
• Low lifecycle cost