Listed in Road Maintenance
Anyone who has worked around highway departments, contractors, or quarries quickly learns that construction aggregate terminology can be confusing. The same material may have three different names depending on the county, contractor, engineer, quarry, or generation of highway employees involved in the conversation. A superintendent may ask for "crusher run," an engineer may specify "dense graded aggregate," and the quarry invoice may list "Item 4." In many cases they are essentially the same material. In other cases, two materials with nearly identical names may behave very differently once installed. Understanding these materials is important because selecting the wrong aggregate can lead to premature pavement failure, drainage problems, frost heaves, pipe settlement, or erosion issues.
Why Aggregate Names Are So Confusing
Aggregate names generally come from one of several sources:
- State Department of Transportation specifications
- AASHTO material standards
- Quarry product names
- Local or regional slang
- Historical highway specifications
- Screen sizes used during crushing
As a result, there is no single universal naming system.
For example:
- Crusher Run
- Dense Graded Aggregate (DGA)
- Aggregate Base Course (ABC)
- Quarry Process (QP)
- 21A
- 21AA
- 304
- 411
- Item 4
All describe members of the same family of dense graded road base materials, although exact gradations vary by region and specification. This explains why some highway superintendents insist that "Item 4" exists while some engineers insist it does not. In many states it absolutely was or still is a specification item number, while in others the term never officially existed and survives only as local terminology. Both sides are often technically correct depending on geography and era.
Dense Graded Base Materials
Crusher Run
Also known as:
- Crusher Run
- Dense Grade Aggregate (DGA)
- Quarry Process (QP)
- Road Base
- Item 4
- 21A
- 21AA
- ABC
Crusher run consists of crushed stone mixed with stone dust and fines ranging from dust up to approximately 1 to 1½ inches in size. Because it contains fines, it compacts extremely well and creates a hard, stable surface.
Typical uses:
- Gravel roads
- Road subbase
- Shoulder repairs
- Driveway construction
- Building pads
- Utility trench backfill
- Temporary access roads
This is probably the single most commonly used aggregate in highway departments.
Type 2 and Type 4 Base
Different states use different numbering systems for road base materials. In New York, highway crews commonly refer to "Type 2" or "Type 4" crushed stone base materials. Elsewhere, similar products may be called Item 4, 304, 21A, or crusher run.
Typical uses:
- Gravel road surfaces
- Pavement subbase
- Shoulder stabilization
- Parking lots
- Utility trench restoration
The important factor is not the name but the gradation specification supplied by the engineer or DOT. Two materials called "Type 4" from different states may not be identical.
Clean Stone Products
Unlike crusher run, clean stone products contain little or no stone dust. This allows water to pass through freely.
#57 Stone
Typically 3/4 to 1 inch angular stone.
Typical uses:
- Pipe bedding
- French drains
- Underdrains
- Catch basin backfill
- Septic systems
- Edge drains
- Concrete production
Because it drains extremely well but compacts poorly, it should not be used as road base.
#67 Stone
Usually slightly smaller than #57 stone.
Typical uses:
- Pipe bedding
- Drainage layers
- Asphalt mixes
- Utility trench backfill
#8 Stone
Often called pea stone or chip stone.
Typical uses:
- Surface dressing
- Walkways
- Decorative stone
- Thin drainage layers
#1 Stone
Large open graded stone ranging up to approximately 4 inches.
Typical uses:
- Underdrains
- Large drainage systems
- Stabilization layers
- Wet soil stabilization
Surge Stone
Very large crushed stone, often 3 to 8 inches or larger.
Typical uses:
- Building unstable road bases
- Wet subgrades
- Temporary construction roads
- Stabilizing soft areas
Riprap and Erosion Control Stone
Riprap
Riprap consists of large angular rock designed to resist moving water. Sizes range from roughly football-sized stone to rocks weighing several tons.
Typical uses:
- Ditch stabilization
- Streambank protection
- Culvert outlets
- Bridge abutments
- Pond embankments
- Slope protection
Angular stone locks together and resists movement far better than rounded stone.
Light Riprap
Usually 6 to 12 inch stone.
Typical uses:
- Ditches
- Culvert ends
- Moderate flow channels
Heavy Riprap
Typically 12 to 24 inch stone or larger.
Typical uses:
- Streambanks
- Major drainage channels
- Spillways
- Bridge protection
Gabion Stone
Large rock placed inside wire baskets called gabions.
Typical uses:
- Retaining walls
- Stream stabilization
- Erosion control
Armor Stone
Very large decorative structural stone.
Typical uses:
- Shoreline protection
- Retaining walls
- Bridge approaches
Natural Gravel Products
Bank Run Gravel
Material excavated directly from pits with little or no processing.
Contains a mixture of:
- Sand
- Gravel
- Clay
- Silt
- Small rock
Typical uses:
- Fill material
- Embankments
- Low-cost road construction
Because consistency varies significantly, engineers generally avoid using it under modern pavements.
Screened Gravel
Natural gravel that has been screened to remove oversized material.
Typical uses:
- Gravel roads
- Driveways
- Fill
Pea Gravel
Rounded stone approximately 1/4 to 1/2 inch in diameter.
Typical uses:
- Landscaping
- Decorative applications
- Pipe bedding in some applications
Because the rounded particles roll over one another, pea gravel performs poorly as road base.
Sand Products
Sand may be one of the most misunderstood construction materials because multiple products appear nearly identical while serving completely different purposes.
Concrete Sand
Also known as:
- Sharp Sand
- C33 Sand
- Construction Sand
This is coarse, angular sand.
Typical uses:
- Concrete production
- Asphalt production
- Utility bedding
- Road construction
Mason Sand
Much finer and more uniform than concrete sand.
Typical uses:
- Mortar
- Brick laying
- Block work
- Playgrounds
Many highway departments use mason sand for winter traction because it flows through spreaders well.
Bedding Sand
Clean sand used around utilities.
Typical uses:
- Pipe bedding
- Utility trenches
- Electrical conduit installations
Fill Sand
Lower quality sand containing some fines.
Typical uses:
- Raising grades
- General fill
- Site work
Filter Sand
Very clean, carefully graded sand.
Typical uses:
- Underdrains
- Stormwater treatment systems
- Infiltration basins
- Sand filters
Winter Sand
Highway departments often use a locally sourced coarse sand specifically for winter operations.
Typical uses:
- Ice control
- Blending with road salt
Stone Dust
Also called:
- Crusher Dust
- Screenings
- Quarry Dust
This is the fine material produced during crushing operations.
Typical uses:
- Paver bases
- Trail surfaces
- Shoulder repairs
- Filling voids in crusher run
Stone dust compacts extremely well but drains poorly.
Recycled Materials
Recycled Asphalt Pavement (RAP)
Crushed reclaimed asphalt pavement.
Typical uses:
- Gravel roads
- Temporary roads
- Shoulder repairs
- Base stabilization
Recycled Concrete Aggregate
Crushed concrete from demolition projects.
Typical uses:
- Subbase construction
- Fill material
- Temporary roads
Many highway departments increasingly use recycled materials to reduce costs.
A Simple Rule for Choosing Material
Most aggregate selection decisions can be simplified to one question:
Do you want water to move through the material or not?
If the answer is yes, use clean stone with little or no fines.
Examples:
- #57 stone
- #67 stone
- Riprap
- Pea gravel
If the answer is no, use dense graded material containing fines.
Examples:
- Crusher run
- Type 4
- Item 4
- DGA
- Road base
This single distinction explains the majority of aggregate choices made by highway departments every day.
Road and drainage construction relies heavily on aggregate materials, yet the terminology surrounding those materials often creates confusion and arguments that can last decades. A superintendent may ask for Item 4, the engineer may specify dense graded aggregate, and the quarry may invoice crusher run. More often than not, everyone is talking about nearly the same material. The important question is not what the material is called. The important question is what the specification requires and what job the material is expected to perform once it reaches the ground. Choosing the right aggregate for drainage, compaction, frost resistance, and structural support is ultimately far more important than winning the argument over what to call it.