Sustainability Series: Recycled Foundry Sand

By C.A. Lawton | February 24, 2021
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One of the main components required to produce a casting is the sand used to make the mold. In fact, industry estimates that approximately 100 million tons of sand are used in production annually. Of that, four to seven million tons are discarded and are available to be used in other manufacturing practices and industries. Due to the high levels of discarded sand, foundries are advancing their uses that are consistent, competitive, and most importantly, environmentally safe.

Since the foundry uses large amounts of this high quality silica sand, it is important to ask where that sand is going and how it is being repurposed after it is used. Only silica-based spent foundry sands from iron, steel, and aluminum foundries are evaluated in the risk assessment. Uses and applications for metal casting sand can generally be categorized into three groups: Highway and construction, aggregate substitutes, and manufactured soils. 

Highway and construction uses is one of the most popular ways foundry sand is reused. Construction projects require certain materials to level sites, create or retain walls, build embankments, or backfill structures. Additionally, metalcasting sands have been used successfully as bases and subbases under roadways, paved surfaces, and structures.  In pavement surfaces, foundry sands are also used in hot mix asphalt, cement, or concrete products.

Foundry sand is also useful as a substitute for other fine aggregates, which are granular materials such as sand, gravel, or crushed stone that, along with water and cement, are an essential ingredient in concrete. Metalcasting sands have also been shown to be effective in products such as ready mix concrete, pre-cast concrete, bricks, blocks and pavers, grouts and mortars, ceramic tiles, and other manufactured products where sand is a raw material.

Lastly, metalcasting sand is one of the primary sources for soil blending due to its composition, color, and consistency. Foundry sand that has specifically come from the molding process can safely be used in soils, both potting and manufactured topsoil. Sand is and will continue to be used as a main component in these construction sites, roadways, and soil mixtures in hopes of decreasing our footprint and instead practice sustainability.

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