Aggregate Processing Plant Design Overview
Aggregate processing plants transform blasted rock or excavated sand and gravel into saleable products meeting specification requirements for construction applications. Successful aggregate plant design balances product quality, production capacity, operating cost and environmental considerations.
Understanding Aggregate Specifications
Different construction applications require different aggregate properties:
Concrete Aggregate:
- Low aggregate crushing value (ACV) for strength
- Low flakiness and elongation index
- Good particle shape (cubical preferred)
- Low water absorption
- No harmful materials (clay lumps, organic impurities)
Asphalt Aggregate:
- High angularity for asphalt binder adhesion
- Clean, dust-free surfaces
- Low polished stone value (PSV) for skid resistance in surface courses
- Specific gradation requirements
Road Base/Sub-base:
- High California Bearing Ratio (CBR)
- Good grading stability
- Lower specifications than concrete/asphalt
Primary Crushing
Primary crushing typically uses jaw or impact crushers to reduce excavated or blasted rock to -150mm or smaller:
Jaw Crusher Configuration:
- Most common for hard rock aggregate
- Handles large feed and hard material
- Produces less fines than impact primary
Impact Crusher Configuration:
- Good for softer limestone and recycled materials
- Produces more cubical product from the start
- Handles sticky materials better
Aggregate Processing Plant Design
Secondary and Tertiary Crushing
Secondary crushing typically uses cone or impact crushers:
Cone Crushers:
- Excellent for hard rock applications
- Produces cubical product with consistent grading
- Lower operating cost per ton for hard materials
Impact Crushers:
- Better for softer materials
- Excellent for manufactured sand production
- Good for recycling applications
Screening and Classification
Screens separate crushed material into different size fractions:
- Pre-screening: Removes fine material before secondary crushing
- Post-screening: Classifies product into different sizes
- Dewatering screens: Removes moisture from washed products
Typical screen configurations:
- 2-deck: Three products (e.g., 0-5mm, 5-20mm, 20+mm)
- 3-deck: Four products (adding 5-10mm, 10-20mm, etc.)
- 4-deck: Five products for complex gradings
Washing Systems
Washing is required when:
- Material has high clay or silt content
- Specifications require clean, dust-free aggregate
- Producing concrete sand or mortar sand
Equipment Options:
- Log washers: Heavy-duty scrubbing for sticky materials
- Scrubbing trommels: Integral washing and screening
- Sand screws: Classify and dewater fine materials
- Hydrocyclones: Desliming and classification
WSHT designs complete aggregate processing plants, from concept through detailed engineering, with equipment supply and commissioning support.
