Aggregate
Definition
Aggregate is granular material — such as gravel, crushed stone, sand, or recycite — used as a key component in concrete, asphalt, and road base. In concrete, aggregate typically comprises 60–75% of the total volume. Coarse aggregate (gravel/crushed stone, ¾" to 1½" diameter) provides structural strength, while fine aggregate (sand) fills voids between coarse particles. Common types include pea gravel, crushed limestone, granite, and river rock. Aggregate quality directly affects concrete's strength, workability, and durability.
Why is Aggregate Important?
For homeowners, contractors, and DIY builders across the United States, understanding Aggregate is essential to accurate material estimation and cost planning. Whether you are pouring a concrete driveway, framing a deck, or calculating roofing materials, mastering this concept helps prevent costly over-ordering or project delays from material shortages.
Our free construction calculators leverage this concept to provide instant, accurate estimates — saving hours of manual measurement and arithmetic while ensuring your project stays on budget.
What is Aggregate in Construction?
Aggregate refers to the granular materials — gravel, crushed stone, sand, and recycled materials — that form the bulk of concrete, asphalt, and road base. Aggregate typically makes up 60–75% of concrete by volume and 92–96% of asphalt pavement, making it the most consumed natural resource after water.
Types of Construction Aggregate
| Type | Size Range | Common Uses | Cost/Ton (2024) |
|---|---|---|---|
| Coarse Aggregate | ¾" – 1½" | Concrete, drainage, road base | $25–$50 |
| Fine Aggregate (Sand) | <¼" (4.75mm) | Concrete, mortar, bedding | $20–$45 |
| Pea Gravel | ⅜" – ½" | Landscaping, drainage, walkways | $30–$55 |
| Crushed Stone | Various (#57, #67) | Driveways, base courses, concrete | $25–$50 |
| River Rock | 1" – 3" | Decorative, drainage, dry creek beds | $40–$80 |
| Recycled Concrete (RCA) | Various | Road base, fill, non-structural use | $15–$30 |
Standard Aggregate Gradations (ASTM/AASHTO)
| Size Number | Nominal Size | Primary Use |
|---|---|---|
| #4 | 1½" – ¾" | Railroad ballast, large drainage |
| #57 | 1" – No. 4 sieve | Most common: concrete, driveways, base |
| #67 | ¾" – No. 4 sieve | Concrete, asphalt, septic systems |
| #8 | ⅜" – No. 16 | Asphalt, pipe bedding, walkways |
| #89 | ⅜" – No. 50 | Pipe backfill, drainage, lightweight fill |
How Aggregate Affects Concrete Quality
- Shape — Angular crushed stone interlocks better than round river gravel, producing stronger concrete (5–10% higher PSI)
- Gradation — Well-graded aggregate (good mix of sizes) fills voids efficiently, requiring less cement paste and producing denser concrete
- Cleanliness — Silt, clay, and organic matter coating the aggregate weakens the cement-aggregate bond. ASTM C33 limits fines to 3–5%
- Moisture content — Saturated aggregate adds unintended water to the mix, reducing strength. Bone-dry aggregate absorbs water from the mix, reducing workability
- Maximum size — Larger aggregate generally produces stronger concrete but is harder to work with. Max size should not exceed ⅓ of slab thickness or ¾ of rebar spacing
Coverage & Estimating
| Depth | Coverage per Ton | Coverage per Cubic Yard |
|---|---|---|
| 2 inches | ~100 sq ft | ~160 sq ft |
| 3 inches | ~65 sq ft | ~108 sq ft |
| 4 inches | ~50 sq ft | ~81 sq ft |
| 6 inches | ~33 sq ft | ~54 sq ft |
Note: Coverage varies by aggregate type and density. Crushed stone weighs approximately 2,700 lbs/yd³; gravel approximately 2,800 lbs/yd³.