Recycled Foundry Sand – Uses & Applications

Recycled Foundry Sand can be defined as a resultant product of the of the ferrous and nonferrous metal casting industry, where sand has been used for centuries as a molding material because of its superior thermal conductivity. In present day foundries, sand is generally recycled and reused through different production cycles. According to industry experts, approximately 100 million tons of sand is used in production every year. Out of this 100 million tons of sand, 6 to 10 million tons is discarded every year that cane be recycled into other products and industries.

Sand used at foundries is of superior quality, as companies adopt stringent physical and chemical tests to ensure production of defect free castings. Foundries make considerable investments for the quality control of their sand systems with rigorous testing done to ensure consistency.

Though there are several methods of casting, including - die casting, investment casting, and permanent mold casting, sand casting is by far the most preferred casting technique. There are 2 different methods of using sand in metal casting industry -

• As a molding material that forms the external shape of the cast component
• As a core that forms the internal void spaces in products such as engine blocks.

As sand grains do not naturally adhere to each other, binders are used to cause the sand to stick together and retain its shape during the introduction of the molten metal into the mold and the cooling of casting.

Types of Foundry Sand Suitable for Recycling
Generally two types of binders are used in metal casting industry -

• Clay bonded systems (green sand)
• Chemically bonded systems (resin sands)

Both these types of sand are suitable for recycling and beneficial reuse, however they have different physical and environmental properties.

Uses of Recycled Foundry Sand
Sand from ferrous and aluminum foundries comprise more than 90 % of available sand and is usually best suitable for recycling. Ferrous and aluminum foundries are generally big in size in comparison to other nonferrous foundries and because of the nature of their production, they have more uniform sand streams. This type of sand has a history of uses in different types of construction applications.

Some innovative foundries are finding ways to recycle their used sand. Some other type of non-ferrous sand, or mixed sand streams can be recycled if they fulfill the environmental testing requirements of the regulatory agencies and the required performance standards of the industry.

As with other materials, transportation costs are usually the highest cost factor in the recycling of foundry sand. Considering the cost factor, the best option for the recycling of foundry sand will typically match the volume and characteristics of the foundry sand with businesses and construction projects in nearby areas.

Given below are some of the markets that have the potential to absorb recycled foundry sand from different types of foundries -

• Construction Projects
• Cement Kiln Feedstock
• Flowable Fill
• Manufactured Soils

In some other cases, foundry sand can be used to replace a part of the fine aggregate in several other types of applications, most of which exist at a commercial scale in different markets and countries. These applications include -

• Hot Mix Asphalt
• Ready Mix Concrete
• Precast Concrete Products
• Bricks and Pavers
• Grouts and Mortars
• Landill Daily Cover
• Landfill Construction Material