How Aggregate Shape and Size Affect Their Quality
Written By: Team Sepro | Date: 12.11.19
Aggregates come in all shapes and sizes to fulfill a wide range of duties. From concrete production to rip rap, you’ve got to choose the right aggregate for the job. Failure to do so can result in unsuccessful projects. That’s why we’ve put together a quick run-down of aggregate types, their categories, and some of the aggregate equipment used in their production.
If you have any questions about how to produce quality aggregate, make sure to contact the experts at Sepro Aggregates.
Coarse and Fine Aggregate
Aggregates are classified into two types depending on their size: fine and coarse. Fine aggregate is 4.75mm or smaller as it can pass through a #4 sieve. Coarse aggregate is greater than 4.75mm and is retained by a #4 sieve.
Fine aggregate is usually finely crushed stone, sand, silt, or clay. It’s typically used to fill the voids between coarse aggregate in concrete or as the primary material in mortar and plaster.
Coarse aggregate covers gravel, all the way up to boulders used as rip rap and shoreline protection. They have multiple uses which include:
- Being a primary ingredient in concrete
- Being the foundation of construction projects
- As railroad track ballast
- Rip rap
- Wave breakers
- And much more
There’s more to categorizing aggregate material than just coarse and fine. Its shape also plays a significant factor in what it’s used for.
Aggregates can be classified into six different categories based on their shape.
Natural aggregates shaped by wind, weather, and erosion. They don’t have any sharp edges, or flat, angular surfaces.
Also shaped by weathering, however, they are not fully rounded. They retain some of their angular features. They are typically the size of small stones or gravel.
Angular aggregates have well defined edges and flat, planar faces. They fit and lock together very well, making them a great choice for high-strength concrete. Rock crushers like a Blackhawk 100 Cone Crusher need to be used to get this angular shape.
Aggregates that are thin relative to their other two dimensions are categorized as flaky.
The aggregate is categorized as elongated when it is longer than it is thick or wide.
Flaky and Elongated Aggregates
A mix of the previous two categories. It’s long, semi-wide, and thin.
Aggregates for Rip Rap
Rip rap protects shorelines and coastal areas from erosion. Rocks used for rip rap should be blocky and angular, with sharp edges and flat surfaces. This helps the rip rap to lock into place and stabilize the coasts, even when the water is turbulent.
A Portable Rip Rap Plant has the durability necessary for this type of coarse aggregate production. It’s fitted with a SEPRO 64″ x 24′ HR Grizzly Feeder to make sure only the right sized rip rap are collected.
Aggregate used in Concrete
Flaky and elongated aggregate makes for very poor concrete since these shapes are brittle. Jaw crushers typically produce a flaky and/or elongated aggregate and are therefore used more as a primary crusher, followed by a cone crusher. This helps form the aggregate into the ideal angular shape, which is perfect for high-strength concrete.
Using the right aggregate equipment, whether it be a jaw crusher, cone crusher, or portable plant, is important for creating high quality aggregate products. For more information on Sepro’s line of aggregate equipment, or to learn more about the importance of aggregate shape and size, contact Sepro Aggregates today.