Decoded: Aggregates Terminology (Part 2 of 5 in the Decoded Terminology Series)

Successful construction projects depend on close coordination among professionals with diverse technical specialties—from general contractors and subcontractors to civil, structural, and geotechnical engineers.

Although these disciplines operate within a shared professional language shaped by experience, tools, and field conditions, each relies on its own set of technical terms and expressions—many of which extend well beyond what’s covered in a classroom.

Bridging these language gaps isn’t always easy, and on fast-paced jobsites where time is limited, clarity matters. The information below offers a practical starting point for understanding key terms and acronyms related to aggregates.

Aggregates and Aggregate Classification Terms

Most construction sites use some type of crushed stone aggregate—and often multiple types, for multiple applications. The term, “aggregate” can refer to any granular material used in construction, and aggregates can also be classified, like soils.

Here are some of the most frequently used terms related to this work: 

• Reclaimed Asphalt Pavement (RAP): 
  RAP is recycled pavement material produced by ripping up or milling old asphalt surfaces, which is then crushed and reused, primarily in new asphalt mixtures. It’s a highly sustainable alternative to virgin materials and often reduces paving costs by utilizing existing aggregates and binder. 
  
  
• Recycled Crushed Concrete (RCC)/Recycled Concrete Aggregate (RCA): 
  The acronyms RCC and RCA refer to the construction material produced by crushing, screening, and cleaning debris from demolished concrete structures like roads and buildings. Primarily used for road bases, backfill, and in new concrete mixes, RCC/RCA is a sustainable, cost-effective alternative to virgin aggregate. 
  
  
• Aggregate Base (AB)—aka Aggregate Base Course (ABC), Graded Aggregate Base (GAB), Road Base/Road Bond, Macadam Base Course (MBC), Crusher Run, etc. 
  The above terms (in addition to other names used by specific agencies such as state DOTs), refer to a highly compactible blend of crushed stone ideal for creating stable, durable bases for the construction of roads, buildings, and other structures. Typically ranging from 1 ½″ (38 mm) or 3/4″ (19mm) down to 3/100 of an inch (0.075 mm), the specific gradation and smallest and largest sizes may vary depending on the application, location, and local standard practices. 
  
  
• Well-Graded Aggregate: 
  Well-graded aggregate consists of a balanced, continuous distribution of particle sizes, ranging from coarse to fine, designed to minimize voids and maximize density. 
  
  
• Gap-Graded Aggregate: 
  Gap-graded aggregate is a material with one or more intermediate particle sizes intentionally absent, resulting in a particle distribution containing mostly large and very small particles. It’s primarily used to optimize concrete mix design. 
  
  
• Open-Graded Aggregate: 
  Open-graded aggregate (OGA) is a crushed, angular stone (often ASTM #57 or #8) containing few or no fine particles—resulting in 30–40% void content. It’s designed to provide superior drainage, frost heave resistance, and high load-bearing capacity in permeable paving, road bases, and retaining walls.

Want to learn more?

We cover more geotechnical terms and abbreviations in our Beneath the Build series on YouTube! Click here to the first episode and learn more.

This blog is part of a 5-part Decoded Terminology Series, click here to read part 1.