Sand is a naturally-occurring material that consists of tiny particles like shells, corals, and decomposed rocks. This material is used in the construction and aggregate industry to make asphalt, concrete, and mortar. Sand is also used as a decorative material for landscaping projects. If you work in these types of industries, it’s important to know how sand is made and what processes it goes through to achieve the final product.
In this article, we’ll be discussing everything you need to know about sand and how processing plants create this fine material.
How sand is manufactured
There are five basic processes, used by sand suppliers, that involve preparation of sand and these are:
- – Natural decomposition
- – Extraction
- – Sorting
- – Washing
- – Crushing (exceptional)
The processing plant is responsible for preparing sand after it has been acquired. In most cases, the plant is located within close vicinity of the material’s natural deposit (i.e. river beds, beaches, inland dunes, and open pits) to reduce transportation costs. The majority of processing plants are stationary while others are mobile and can be transported from one location to another when remote construction projects are required.
Asphalt production plants and/or mixed concrete plants usually operate on the same site as the processing plant to facilitate the entire asphalt and concrete-making processes. We’ll break down the processes that sand goes through before it’s ready for construction purposes.
- Natural decomposition
Natural decomposition is where solid rocks are broken down due to natural forces like moving glaciers, the impact of rocks falling on top of each other, and water expanding in cracks during freezing. Rock chunks are further broken down into smaller particles through vegetation, rain, and mechanical forces as the smaller particles are worn down by water and wind.
Grains of rock that get carried by waterways eventually make their way to river banks while others end up at sea (where they join with coral or shell fragments to create beaches). Rock grains that are carried by wind create sand dunes.
- Sand extraction
Extraction of sand is pretty straightforward. A front loader (a heavy duty vehicle with a wide bucket up-front) scoops up the sand from riverbanks and dumps it into a conveyor belt for transportation. Floating dredges are used to extract sand underwater wherein the dredges use a rotating cutter head to agitate the sand deposits and gets sucked up by a suction pipe. The sand-water mix is then pumped through a pipeline towards the plant for sortation.
Once the sand arrives in the processing plant, the material is mixed with water (if scooped up by a front loader) and passes through a perforated screen to filter out sticks, rocks, lumps of clay, and other foreign material. If the sand contains too much soil or clay, it passes through a blade mill to break the soil into smaller particles.
From there, the sand passes through several perforated plates/screens with various hole sizes to segregate the material according to size. The plates/screens measure from 10 ft. (3.1m) up to 28 ft. (8.5m) and are tilted with an angle of 20-40°. The coarsest screen is placed on top while smaller ones are located underneath to separate the particles. Vibration is used to pass the material onto the screen.
Sand washing is done to remove any remnants of soil or clay. Sand that comes out of the coarsest screen is washed with a log washer. The log washer essentially separates large gravel particles with smaller sand particles before the latter is pumped through a classifying tank. As the mixture of water and sand passes through the tank, the sank sinks to the bottom and is collected by a series of bins. The sand is then removed from the bins and are washed again for the final time before being transported to conveyor belts for storage.
The last step is crushing, which is an optional process for when sand is needed to be crushed in order to produce specific shapes or sizes that aren’t naturally available. The sand goes through a rotating cone crusher where it falls between an upper rotating cone and a fixed lower cone. Particles that are larger between the distance of the cones are crushed while the resulting particles fall to the bottom to be collected.
As you can see, sand goes through many processes before the final product is achieved. To ensure strict quality control, large-scale processing plants use computers to determine the feed rate of the material, the vibration rate of the plates/screens, and the flow of water through the classifying tank. Asphalt and concrete mixes require specific distribution sizes of aggregates to achieve the right mix, making the role of processing plants that much more important.
Hopefully with this article, you’ve gained a better understanding of how sand is acquired and how processing plants manufacture this material for use in construction and aggregate applications.