Particle Size Distribution (PSD) refers to the proportion of perlite particles across defined size ranges, typically measured through standardized sieve analysis. PSD directly affects filtration efficiency, flowability, mechanical strength, horticultural aeration, and insulation performance.
Particle Size Distribution describes how expanded perlite particles are distributed across different size fractions. It determines:
• Flow behavior
• Packing density
• Filtration permeability
• Substrate aeration
• Mechanical stability
PSD is one of the core quality parameters in industrial perlite applications.
1.1 Coarse Grades
• Larger particles
• Higher void ratio
• Lower density
• Used in horticulture and insulation
1.2 Medium Grades
• Balanced structure
• Used in construction and lightweight concrete
1.3 Fine Grades
• High surface area
• Higher density
• Used in filtration and fillers
Lower density = higher expansion = higher porosity.
3.1 Standard Method: ASTM C136
• Oven dry sample
• Stack sieves from coarse to fine
• Shake for a fixed duration
• Weigh retained fractions
• Calculate % distribution
3.2 Laser Diffraction (Advanced Method)
• Used for ultrafine fractions (<75 µm). Provides high resolution PSD curves.
3.3 Importance of Repeatability
• Consistent PSD ensures predictable performance in:
• Filtration
• Concrete mixes
• Horticultural substrates
• Insulation systems
4.1 Filtration
Fine PSD:
• Lower permeability
• Higher clarity
• Tighter cake structure
Coarse PSD:
• Faster flow
• Lower clarity
4.2 Horticulture
Coarse PSD:
• Better aeration
• Faster drainage
• Improved root oxygenation
Fine PSD:
• Higher water retention
4.3 Construction
Balanced PSD:
• Better packing
• Improved mechanical strength
• Lower thermal conductivity
4.4 Insulation
Fine PSD:
• Lower thermal conductivity
• Higher density
5.1 Ore Hardness
• Harder ore → more coarse particles.
5.2 Expansion Conditions
• Higher temperature → more fragmentation → finer PSD.
5.3 Milling & Screening
• Post expansion processing adjusts PSD for specific industries.
5.4 Furnace Type
• Fluidized furnaces produce finer PSD than vertical furnaces.
• Natural fracture patterns
• Hydration history
• Glass viscosity
• Chemical composition
Deposits with uniform glass structure produce more consistent PSD.
Q: Does finer PSD always mean better filtration?
Yes, for clarity — but flow rate decreases.
Q: Can PSD be modified after expansion?
Yes, through milling and screening.
Q: Why does PSD vary between producers?
Differences in ore quality and furnace design.
