Navigating the world of gravel size can be as intricate as selecting the perfect gemstone. According to the National Stone, Sand & Gravel Association (NSSGA), the aggregates industry produces about 2.4 billion tons of crushed stone, sand, and gravel each year, with sizes ranging from fine powder to larger stones the size of golf balls. The commonly used numerical system, which classifies gravel from the fine #10 up to the substantial #1, correlates more with the material's intended use rather than its precise dimensions, as noted by the Federal Highway Administration. Whether you're laying a new driveway or creating a drainage system, selecting the correct gravel size is crucial for the success and longevity of your project. By understanding the specific requirements of your endeavor, you can make an informed decision that ensures stability and aesthetic appeal.
Basics of Sizing
The gravel sizing system can be confusing on first glance, and isn’t always exactly consistent from place to place. Most manufacturers and distributors around the world use a numeric coding system that corresponds to larger guidelines about project specifications, and though there’s usually general industry consistency, it isn’t always exact. People who have stringent sizing specifications are usually wise to talk directly with a distributor or manufacturer to get more information on what is available and what the specifications are.
Screenings Gravel
The smallest of all gravel sizes is usually size #10, which is also commonly known as screenings gravel. This gravel is typically around 1/8th of an inch (0.32 centimeters) in diameter, making it similar in appearance to coarse sand. Often, screenings gravel is used as the base for bricks, paving stones, and other similar items. In some cases, it can also be packed into the crevices created when other, larger stones are stacked, therefore aiding in the prevention of slippage. Size #10 gravel can be made from a variety of larger stones, but is most often made from slag or limestone.
Size #67 is usually about the same size as #10, but often has a slightly different purpose. It’s commonly used as fill in roadways and concrete slabbing. Gravel labeled size #5 is similarly little more than a fine powder; it’s often used in paving to help seal everything together and to fill in crevices between larger pieces.
Middle-Grade Sizes
Size #57 is another of the more popular gravel sizes. This particular size of gravel ranges in diameter from 3/4th of an inch (1.9 centimeters) to 1 inch (2.54 centimeters) in diameter. This gravel is often used for paving walk or driveways, at it can be walked and driven on with relative ease. Though size #57 serves many purposes, it usually is avoided for use in areas that are prone to become muddy.
There are a number of other mid-range sizes available in many places, too, most of which are designed with specific projects or uses in mind. Size #3, for instance, is usually 1.5 to 2 inches (about 3.8 to 5 cm) in diameter, and is often best for residential draining projects; #8, which is usually 3/8 to 1/2 an inch (1 to 1.2 cm) across, is frequently used in asphalt and concrete mixtures. Gravel labeled #411 is usually a mixture of #57 and stone dust, and is particularly useful for patching potholes and sealing things like retaining walls.
Decorative Options
Gravel known as size #1 is relatively large. Typically, this gravel ranges in diameter from 2.5 inches (6.35 centimeters) to 4 inches (10.16 centimeters). It can be difficult to work with, as it generally cannot be shoveled and instead must be moved individually, stone by stone. As with other types of very large gravel, size #1 is primarily used as decoration, and can be found in yards, gardens, or even parks. This type of stone is typically available in washed river gravel, slag, or limestone, though other materials may be available in some cases.
Making the Choice
In most cases, people should choose their gravel based on the needs of their project rather than the numerical code on the label. Though sizing is more or less consistent from place to place, the only way to be sure about a bag’s contents is to read the description carefully or to talk with a sales professional about exactly what is inside. Contractors who are really familiar with regional sizing specifications and differences between brands and materials are often in the best position to give seasoned advice.
What’s Gravel
Depending on what part of the country you’re from, you might recognize gravel right away. If you are from more rural parts of the nation, gravel might have coated narrow back roads to country homes out of the way of busy cities. If you’re from more urban areas, gravel sometimes fills vacant lots or empty flower beds. Those are just examples of gravel that you can readily see. Gravel is, in truth, all around us. Gravel is small pieces of crushed stone made of rock pieces and commercially manufactured fragments from more significant concrete pieces.
What Does Gravel Look Like
Gravel, typically, looks like an extensive collection of light gray dusty rocks of variable sizes when seen on roads, landscaping, or other visible areas. For the most part, it is about the size of a handful of berries and just as irregular. Suppose you can imagine holding a handful of strawberries, blackberries, blueberries, raspberries, and a few cranberries for good measure. In that case, you can imagine holding the general size makeup of a handful of gravel.
Gravel also comes in more uniform size options ranging from very small to much more significant. Depending on the supplier, you may also purchase gravel with different hues; there are visible color differences between limestone, basalt, and sandstone, the primary contributors to gravel production in the United States.
Where Does Gravel Come From
Gravel comes from three typical sources, sometimes more. The availability and price of gravel will depend on the purpose and the supply in the local area.
Mined Gravel
Generally, gravel comes from quarries. Larger rocks are mined out from rock quarries and crushed into specific sizes to create, among other things, gravel. The gravel goes through several different screening and washing processes to transform the giant rock sheets from the quarry into the decorative gravel you see in expert landscaping, for example.
Natural Gravel
Gravel can also come from the beds of natural water sources and other similar geographical formations with rocky base formations. This source material is often difficult to come by and can disrupt nearby ecosystems, and is generally frowned upon. Natural gravel sources from geographical formations include:
- Bench
- Bank
- Plateau
- Creek
Production Gravel
Other gravel can come from all different sources. Some construction and demolition crews are careful in breaking down buildings and structures to save out more significant pieces of concrete to repurpose back into gravel. Gravel is often the basis of many buildings alongside steel beams and concrete; once demolition occurs, the larger pieces can be crushed again, provided there is no biohazard to contaminate the materials.
What Is Gravel Used For
Gravel has an impressive number of uses. Many of which are foundational, both literally and figuratively, to modern society. Gravel ranges wildly in size and shape in purpose and price.
Landscape Design
Gravel can retain moisture better than soil and mulch. Further, it does not decompose into the ground and requires replacement infrequently, and weeds have a more difficult time pushing up through the rocks. For these reasons, landscaping companies and homeowners choose gravel as part of their landscaping schemes.
Erosion Maintenance
Ecological crews and damage control crews in areas like Louisiana, Texas, and Florida experience hit after hit of brutal weather. Erosion is a significant issue when rough storms take away layers of integral soil. Scientists and ecologists have worked together to use gravel as a solution to combat erosion in hard-hit areas. Gravel can be used as a top layer on soil, dams, levies, and sandbags to help prevent dirt and other necessary components from being removed by violent water influx.
Construction Necessity
To say that gravel is a construction necessity is an understatement. Construction is built on the back of gravel, and without it, the world would be a very different place. The basis of other building materials, foundations, blasting materials, aggregate, slag, and others rely on gravel as the main component.
Roadway Surfacing
Gravel is used as the aggregate foundation for roadways, too. In less urban areas, there are still gravel-only roads with no aggregate foundation underneath. Gravel there is simply layered onto a cleared dirt pathway; gravel may be refreshed from time to time.
Agricultural Applications
Gravel is also used as a soil mix-in for farmers across the nation. Because of the mineral composition of specific gravel, farmers use it to increase the acidity of their soil. Crop growth can be dependent on the proper pH balance of farmed earth. Further, if farmers breed chickens, tiny pieces of gravel are often combined with poultry feed. Believe it or not, to break down their food, poultry needs a mix of the smallest size gravel to aid in digestion.