Abrasion Testing in Highway Engineering

Aug 24, 2024

Laboratory Measurement in Highway Engineering

Introduction

  • Focus on aggregates used in road pavement surfaces.
  • Aggregates experience wear due to vehicle movement.
  • Friction between tires and pavement leads to abrasion.
  • Dust particles on the road surface enhance abrasion.

Importance of Abrasion Resistance

  • Aggregates must possess sufficient resistance to abrasion.
  • This property is evaluated using the abrasion value test.

Types of Abrasion Tests

  • Los Angeles Abrasion Value Test
  • Deval Abrasion Test
  • Dorrie Abrasion Test

Equipment Required for the Los Angeles Abrasion Test

  1. Los Angeles Abrasion Machine
    • Hollow steel cylinder: 17 cm diameter, 15 cm length.
    • Rotates about the horizontal axis.
    • Removable cover with a clamp.
    • Steel shelf projecting radially, 12.5 cm from opening.
  2. Abrasive Charge
    • 12 steel balls, 48 mm diameter, weighing 392-445 grams each.
  3. Weighing Machine
    • Electronic balance, 5-10 kg capacity, accuracy of 1 gram or better.
  4. Sieves
    • Size: 1.7 mm, with additional sizes depending on grading selected.

Aggregate Selection for Testing

  • Grading depends on designated use:
    • WBM: Grading II
    • SDBC: Grading B, C, or D
  • For Grading B:
    • 2.5 kg of material passing 20 mm sieve and retained on 12.5 mm sieve.
    • 2.5 kg of material passing 12.5 mm sieve and retained on 10 mm sieve.

Sample Preparation

  1. Dry material in an oven at 105-210°C for 4 hours.
  2. Allow the material to cool to room temperature.
  3. Measure exact quantity and weight of the material.
  4. Use 11 steel balls for the abrasive charge.

Test Procedure

  • Ensure the cylinder is clean before starting.
  • Place aggregate sample and abrasive charge in the cylinder.
  • Fix the cover and check that the counter reads zero.
  • Run the machine at 32-33 revolutions per minute:
    • 500 revolutions for Grading B.
  • Aggregates experience abrasion and impact during the test.

Post-Test Procedure

  1. Open the steel cover and remove crushed material.
  2. Sieve the material through a 1.7 mm sieve.
  3. Determine the weight of fraction passing the sieve.
  4. Calculate the loss and less abrasion value:
    • Weight of fraction passing the sieve as a percentage of total material taken.

Results and Conclusion

  • Example result: Los Angeles abrasion value found to be 26.6%.
  • Conclusion: Sample is suitable for construction in SDBC.
  • Importance of the Los Angeles abrasion value test noted for its ability to measure resistance to abrasion and impact.

Closing

  • Acknowledgment of the significance of testing aggregates for road construction suitability.