This guide breaks down everything you need to know about crushed limestone grades, including how they’re categorized, which grades work best for specific applications, and how to avoid costly ordering mistakes.
Crushed limestone is a versatile, durable aggregate used throughout construction. It’s made by blasting, crushing, and screening limestone rock into various sizes for use in roads, driveways, drainage systems, concrete mixes, and more.
The reason it’s so widely used comes down to three qualities: it’s strong, it compacts well, and it’s available in a wide range of sizes to match different structural and functional needs. Those sizes, or grades, are what make crushed limestone grades so important to understand.
When contractors talk about different grades of limestone, they’re usually referring to standardized sizes and gradations that match DOT or ASTM specs. These are the most common grades you’ll encounter in the Midwest:
CA-6 (1″ Minus): CA-6 is one of the most popular limestone aggregates for base layers. It contains fines that help bind the rock together and compact into a stable, smooth surface.
CA-7 (1″ Clean): CA-7 is a clean, uniform limestone with no fines. It’s commonly used for drainage applications, backfill, or behind retaining walls where water needs to flow freely.
CA-10 (3/8″ Chips): CA-10 is a fine limestone chip often used in decorative surfaces, finish layers, or chip seal applications. It’s also used in some concrete mixes.
CA-11 (3/4″ Clean): CA-11 is another clean limestone product similar to CA-7 but slightly smaller. It works well in pipe bedding and trench backfill applications.
Rip Rap (RR1 to RR7): For erosion control, slopes, and shoreline projects, rip rap offers heavier limestone chunks ranging from 3″ clean to 1000lb boulders.
Every grade serves a purpose, and knowing which one to use is critical to a smooth, efficient jobsite.
Limestone grades are primarily determined by size and use case. The size is measured through sieve testing, which sorts aggregate by particle size using a standardized mesh screen system. Grading also considers whether the material is:
Each grade aligns with specific construction needs, some compact tightly to form a solid base, while others allow water to pass through freely. Understanding this distinction helps prevent ordering errors.
For roads and heavy-use surfaces, start with a grade that compacts well and holds up under pressure. CA-6 (1″ minus) is the go-to material for base courses under asphalt or concrete. It contains a mix of larger particles and fine dust, allowing it to lock together under pressure and form a solid, load-bearing surface. This grade is ideal for:
Driveways often use a two-layer system:
This approach balances strength with aesthetics, creating a smooth surface that drains properly and stands up to vehicle traffic.
When drainage is the goal, clean aggregate with no fines is essential. CA-7 (1″ clean) and CA-11 (3/4″ clean) are top choices. These grades are perfect for:
Their uniform size allows water to pass through without clogging, which helps maintain performance and prevent flooding or soil erosion.
Backfilling behind structures like retaining walls or utility lines requires a material that offers both stability and drainage. Depending on the project, contractors often use:
Choose based on whether your application needs drainage, compaction, or both.
Pipe bedding requires uniform, small-size material that cushions the pipe and supports even settlement. CA-11 or washed chips like CA-10 are often ideal. This ensures:
Choosing the right crushed limestone grade is easier when you’ve got a knowledgeable supplier. Columbia Quarry Co. offers a wide range of limestone materials and sizes. Discover more.
Some jobs call for DOT-approved limestone aggregate, while others do not. The difference comes down to:
At Columbia Quarry Co., we supply both DOT and non-DOT materials. If you’re working under MoDOT or IDOT contracts, ask us which grades are approved and verified with testing documentation. We’ll help you stay in compliance from the first load.
Different regions may have slightly different names for limestone grades. In the Midwest, CA-grade naming is common. But other states or suppliers might use alternatives like “1” minus” or “3/4” clean.”
Always refer to a limestone grade chart when comparing materials from multiple suppliers. At Columbia Quarry Co., we’re happy to walk you through how our grades align with local specs and project needs.
Getting the right limestone aggregate delivered the first time saves money, labor, and downtime. Here’s how to make sure your order matches your job:
Know Your Project Specs: Check your blueprints or job requirements for size, compaction needs, and drainage requirements. Don’t guess.
Use the Right Terminology: Make sure you’re speaking the same language as your supplier. “Clean” vs. “minus,” CA-7 vs. 1” gravel. Small differences matter.
Ask for Help: If you’re unsure, ask your supplier for recommendations based on your job type. At Columbia Quarry Co., we work with contractors daily to match material to the job.
Confirm Availability: Some grades, like rip rap or specialty chips, may be in higher demand. Always call ahead to confirm what’s in stock and when it can be delivered.
Knowing your crushed limestone grades means fewer surprises and smoother builds. With so many applications relying on specific size and compaction performance, contractors can’t afford to guess when ordering. Matching the right grade to the right job leads to better drainage, stronger bases, and satisfied clients.
At Columbia Quarry Co., we bring more than materials; we bring insight. From road base to pipe bedding, our limestone experts can guide you to the right grade, get it delivered quickly, and keep your project moving without a hitch. Let’s talk rock today.
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