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ASTM D448
Standard Classification for Sizes of Aggregate for Road and Bridge Construction
Overview
ASTM D448 establishes a numerical system for classifying sizes of coarse aggregate and screenings based on their gradation (particle size distribution) as determined by sieve analysis. While its title suggests civil infrastructure use, its standardized size designations (e.g., No. 57 stone, No. 8 stone) have been broadly adopted across the construction industry for various applications including building construction and site work.
Standard Size Designations
- No. 57: Popular 3/4" to 1" stone for drainage and concrete
- No. 67: Standard 1/2" to 3/4" aggregate for concrete mix
- No. 8: Fine 3/8" to 1/2" stone for exposed aggregate surfaces
- No. 3: Large 2" to 4" stone for gabion walls and erosion control
- Each size has specific gradation requirements per sieve analysis
Permeable Pavement Applications
For permeable interlocking concrete pavement (PICP) systems, ASTM D448 is critical. The performance depends entirely on void space within aggregate layers. Open-graded aggregates like No. 57 stone ensure high percentages of interconnected voids, allowing stormwater to pass through freely and be stored in the subbase. Well-graded aggregates with mixed particle sizes would create dense, non-permeable bases unsuitable for drainage.
Complete Specification Requirements
While D448 provides clear gradation definitions, it doesn't specify other important properties like hardness, durability, or particle shape. For demanding applications like permeable pavements subject to vehicular traffic, specifications must be augmented: "Base aggregate shall be crushed stone conforming to gradation requirements of ASTM D448, Size No. 57, and shall meet durability requirements of ASTM C33." This ensures correct particle size distribution for permeability plus necessary toughness for long-term structural support.