How to class crushed rock by size

Classifying crushed rock by size typically involves using sieves or screens to sort the material into different size ranges. Here's a general guide on how to do it:

1. Determine Your Requirements: Understand the specific size ranges you need for your project. Common classifications include:

   • Fine material: particles smaller than 0.075 mm
   • Sand: particles between 0.075 mm and 4.75 mm
   • Gravel: particles between 4.75 mm and 75 mm
   • Cobble: particles between 75 mm and 300 mm
   • Boulders: particles larger than 300 mm

2. Use Sieves or Screens: Obtain a set of sieves that match the size ranges you need. You can purchase standardized sets or make custom screens.

3. Prepare the Sample: Take a representative sample of the crushed rock. Ensure the sample size is suitable for the sieving equipment.

4. Start Sieving:

   • Place the sieves in order from largest to smallest.
   • Pour the crushed rock into the top sieve.
   • Shake the sieve stack manually or use a mechanical shaker for a consistent period.
   • Ensure each particle has the opportunity to fall through the sieves.

5. Measure and Record: After sieving, measure the amount of material retained on each sieve. Weigh each fraction and calculate the percentage of the total sample.

6. Analyze the Results: Use the data to determine the size distribution of the crushed rock. This information can guide you in meeting project specifications or adjusting production processes.

Always follow any relevant standards like ASTM or ISO to ensure accuracy and consistency in your classification process.