Crushed stone aggregate comes in a variety of sizes and shapes that are suited to various applications in a construction project. Contractors cannot assume that any sized stone will work for their structures. They need to understand the key differences between the various types and sizes of aggregate needed for construction.
For example, you should use large stones for a smooth path, otherwise, the stones would make the surface bumpy and difficult to walk on. Likewise, using large stones were small stones are actually needed could increase the overall building costs unnecessarily. Large stones are heavier and more expensive to transport, so they are less practical for certain building projects.
Choosing the correctly-sized stone for the job will ensure that a concrete structure is finished to a higher quality and standard. These buildings will be stronger, more durable and keep their value for longer. When planning a project, be sure to choose the right size of crushed stone aggregate.
Types of crushed stone
- Crushed and screened – This is the most basic type of crushed stone that you can get. Large granite rocks are crushed and the various chipped stones are fed into a screen filter that separates them into specific sizes. These stones are not cleaned or treated, so may carry some excess rock dust.
- Washed clean – These are crushed and screened stones that are fed into a washer to remove the rock dust and any additional mud or debris. These stones are clean and do not have any contaminants that could affect dam projects or a concrete batch.
- Gravel – This is a smoother form of crushed stone that is often used for landscaping projects and to make stone pathways. Gravel comes in a variety of sizes and is more suited to decorative purposes than functional building applications.
- Quarry process – This type of crushed stone is also known as ‘dense-grade aggregate’. It is a combination of stone dust and crushed stone aggregate of various sizes. The stone dust makes the batch more dense as it fills the spaces between the stone chips.
- Riprap stone – This is one of the largest types of coarse aggregate. Some of the pieces can be as large as 23 centimetres in diameter. These mini-boulders are often used in heavy concrete applications, such as high-rise foundations and bases for large roads.
- Stone grits – These are fine particles of stone that are a by-product of the crushing process. They are 5 millimetres or less in diameter and are technically the smallest size of coarse aggregate available (before being classified as rock dust).
Crushed stone sizes and their uses
Small crushed stone (5mm or less) is often used as a functional surface layer on top of a compacted base for landscaping and decorative purposes. This size of stone is ideal for paths, driveways, patios, parking lots, water features and concrete pots.
Medium crushed stone (5mm to 2cm) is ideal for use as a layer on top of a larger crushed stone foundation. The medium stones will settle into the gaps between the larger stones and provide a stable and supportive layer for concrete. Medium crushed stone is also used in most general concrete applications for buildings.
Large crushed stone (2cm to 6cm) is ideal for foundations and filling sub-bases for roads, pavements and airport runways. These large rock particles give a strong and durable base support for concrete and bricks. Sometimes large crushed stone is used for decorative landscaping purposes or to build retaining walls with mortar.
Mixed crushed stone (variety of the sizes above) is often used to build solid foundations for most buildings. It can also be used to build semi-permanent roads and driveway surfaces, such as dirt roads to remote villages and walking trails. Mixed crushed stone is a dense and compact mix that creates solid surfaces as the smaller particles settle into the gaps between the larger particles.
These guidelines should help contractors to choose the right size of crushed stone for their needs. Not all crushed stone is the same, and certain structures call for a certain size of particle. Most general concreting jobs require medium crushed stone. The right size of aggregate can improve the quality and durability of concrete and building projects.
LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges.
LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.
At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.