Ballast Quality Control Standards

Ballast Quality Control

• The Railway reserves the right to terminate the contract if the ballast supply fails to meet the specified quality standards.
• The Railway will conduct tests such as size gradation, abrasion value, impact value, and water absorption on the first 100 cubic meters of ballast supplied.
• Subsequent testing frequency for ballast supplied in stacks:
  • Size and Gradation Tests:
    • One test for each stack for a stack volume of less than 100 cubic meters
    • One test for each stack for a stack volume of more than 100 cubic meters
    • One test for each wagon regardless of the stack size
  • Abrasion Value, Impact Value, and Water Absorption Tests:
    • One test for every 2000 cubic meters
• Samples for testing should be collected using a wooden box with internal dimensions of 0.3m x 0.3m x 0.3m.
• In case of any test results not meeting the specifications, further supplies will be suspended until corrective action is taken.

Ballast Size Specifications

• Ballast retained on a 40mm square mesh sieve (machine-crushed ballast only) exceeding 60% will result in reduced payment:
  • 5% reduction for retention between 60% and 65%
  • 10% reduction for retention between 65% and 70%
• Ballast with more than 70% retention on the 40mm square mesh sieve will be rejected.
• Hand-broken ballast is exempt from the 40mm sieve analysis, but it must be well-graded between 65mm and 20mm.
• Ballast is considered undersize and will be rejected if:
  • Retention on the 40mm square mesh sieve is less than 40%.
  • Retention on the 20mm square mesh sieve is less than 98% (for machine-crushed) or 95% (for hand-broken).

Sieve Analysis Procedures

• The sieve analysis procedures are outlined:
  • Sieve Sizes:
    • Nominal sizes are used, with acceptable tolerances for the holes:
      • 65mm Square Mesh Sieve: Plus Minus 1.5mm
      • 40mm Square Mesh Sieve: Plus Minus 1.5mm
      • 20mm Square Mesh Sieve: Plus Minus 1.0mm
  • Sieve Screen:
    • Square mesh screen is required with minimum dimensions of 100cm length, 70cm breadth, and 10cm height.
  • Sieving Procedure:
    • The screen should be held horizontally and shaken vigorously.
    • Ballast pieces retained on the screen can be turned by hand to check if they pass through but should not be pushed.
  • Percentage Determination:
    • The percentage of ballast passing or retained on the sieve is determined by weight.

Impact Test Procedure

• A test sample of ballast (approx. 5kg) of size 10 mm to 12.5 mm is required for the impact test.
• The ballast used for the impact test should be randomly selected to avoid bias.
• Alternatively, ballast in the required size range can be manufactured for the test.

Water Absorption Limits

• The Chief Track Engineer (CTE) or Construction Area Officer (CAO) can relax water absorption limits for specific areas.
• Regardless of relaxation, the maximum allowable water absorption is 2.5%.