How To Evaluate Aggregates

Most people believe rocks are just rocks, but if you are in construction, you know that is far from true. Rocks of all sizes and types are mined and crushed to form aggregates of different dimensions and shapes that often contain different mineral deposits. Some rocks will not make good aggregate, and that is why it is important for homeowners and contractors to understand the standards used to evaluate the different qualities of crushed rock.

•  Size

The size of the rock can determine the strength the aggregate will have when the rock is broken into parts. Those with few cracks are seen as good quality.

•  Till

The eroded rock bits found in streams and rivers are known as till. Large pieces of rock mean the original piece was large and cohesive, which creates a high-quality aggregate.

•  Fracture

The frequency of fractures can mean the rock is weak. Easier to mine, this rock type will lead to a low-quality aggregate.

•  Content

Rocks containing a high amount of impurities such as clay, silicone, or quartz are considered poor candidates for good aggregates. The reactive minerals make the structure too weak.

•  Shape

High-quality aggregate is thought to be angular, with rough surfaces and sharp pieces. The rounder a rock is, with a smooth surface, the less indicative it is of quality aggregate.

•  Breakage

Geologists can measure rock erosion. A low-quality rock will erode quickly, while a high-quality aggregate will resist the erosion of water, wind, and time.

•  Hardness

An aggregate of high-quality will be difficult to crack, crush, or break. While the quarrier may find the hard rock more difficult to work with, the above-average hardness ensures the rock won’t fracture or crush under a building’s weight.

Although each mining operation may have its own quality control standard in place when dealing with aggregates, it is important to know there are certain universal standards you can rely on. When you need crushed rock, use the seven classifications above to determine if you are getting a good-quality aggregate.