1. INTRODUCTION 1.1 General Foundry sand is high quality silica sand with uniform physical characteristics. It is a byproduct of ferrous and nonferrous metal casting industries, where sand has been used for centuries as a molding material because of its thermal conductivity. It is a byproduct from the production of both ferrous and nonferrous metal castings. The physical and chemical characteristics of foundry sand will depend in great part on the type of casting process and the industry sector from which it originates. In modern foundry practice, sand is typically recycled and reused through many production cycles. Industry estimates that approximately 100 million tons of sand is used in production annually of that 6 - 10 million tons are discarded annually and are available to be recycled into other products and in industry. The automotive industries and its parts are the major generators of foundry sand. Foundries purchase high quality size-specific silica sands for use in their molding and casting operations. The raw sand is normally of a higher quality than the typical bank run or natural sands used in fill construction sites. The sands form the outer shape of the mold cavity. These sands normally rely upon a small amount of bentonite clay to act as the binder material. Chemical binders are also used to create sand “cores”. Depending upon the geometry of the casting, sands cores are inserted into the mold cavity to form internal passages for the molten metal. Once the metal has solidified, the casting is separated from the molding and core sands in the shakeout process.
Figure 1.1 Metal casting in a foundry
In the casting process, molding sands are recycled and reused multiple times. Eventually, however, the recycled sand degrades to the point that it can no longer be reused in the casting process. At that point, the old sand is displaced from the
References: 1. Abichou T. Benson, C. Edil T., 1998a.Database on beneficial reuse of foundry by-products. Recycled materials in geotechnical applications, Geotech. Spec. Publ.No.79, C. Vipulanandan and D.Elton, eds., ASCE, Reston, Va., 210-223
3. Naik, T. R., and Singh, S. S., (1997a). Permeability of flowable slurry materials containing foundry sand and fly ash. J. Geotech. and Geoenvir. Engg., ASCE, 123(5), 446–452.
4. Naik, T. R., and Singh, S. S., (1997b). Flowable slurry containing foundry sands. J. Mat. in Civil. Eng., ASCE, 9(2), 93–102.
5. Naik, T. R., Singh, S. Shiw, and Ramme, W. Bruce, April, 2001.Performance and Leaching Assessment of Flowable Slurry. Journals of Environmental Engg. , V. 127, No. 4, pp 359-368.