Used foundry sand

A review and study of foundry waste sand quality and composition was performed in Finland. Data were collected from literature and from own experiments [169, Orkas, 2001], 

In several studies, chemical analyses on used foundry sands from various sources were performed. A summary of the most significant results is presented in Table 3.49. The data show that the contents of metallic and organic harmful compounds in used foundry sand are normally low. Generally, the contents of organic and metallic harmful compounds are higher in green sands compared to chemically-bonded sands. Inorganic sands are basically very clean. 

Compound Green sand (mg/kg) Organic sand (mg/kg) Inorganic sand (mg/l  

The Castings Development Centre (CDC) analysed the PAH-values (total PAH, naphthalene and carcinogenic PAH) and phenol contents from different used foundry sands. The results are shown in Table 3.50. For a given sand production line, the variations in the PAH and phenol contents in used sand are relatively low. 

Sand system Naphthalene Carcinogenic PAH Total PAH Total (mg/kg) Leachable (ugd) 

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Siilfuric acid from iron pyrites Paint pigments roasting of metallic oxides Refractory clays calcination of refractory clay to reduce shrinkage Foundry sand removal of carbon from used foundry sand Fullers earth calcination of fuller s-earth material... 

Foundry sand removal of carbon from used foundry sand... 

The type of foundry sand used is not critical and the useful foundry sands include aU of the ones conventionally used in the metal casting industry. Thus, these sands can be zircon sands (zirconium silicates), silica sands, for example, quartz, aluminum silicate, chromite, olivine, staurolite and their mixtures. 

R. Siddique, G. Schutter, and A. Noumowe, Effect of Used Foundry Sand on Mechanical Properties of Concrete , Construction and Bilding Materials, 23 (2009), 976-980. 

Resins. As mentioned above, both furfural and furfuryl alcohol are widely used in resin apphcations. Another resin former, 2,5-furandimethanol [1883-75-6] (BHME), is prepared from furfuryl alcohol by reaction with formaldehyde. It is usually not isolated because oligomerization occurs simultaneously with formation (competing reaction). Both the monomer and oligomers are very reactive owing to difuntionahty, and are used primarily as binders for foundry sand (72) and fiberglass insulation (147,148). 

Iron oxide is also used for nonpigmentary applications, eg, ferrites (qv) and foundry sands making total world demand for iron oxide close to 1 X 10 t. The principal worldwide producers of iron oxide pigments are Bayer AG (ca 300,000 t/yr worldwide), and Harcros Pigments Inc., a subsidiary of Harrisons Crosfield PLC. In the United States, Bayer produces the Bayferrox line of iron oxide pigments in New Martinsville (see Iron compounds). 

Carbon dioxide is widely used in the hardening of sand cores and molds in foundries. Sand is mixed with a sodium siHcate binder to form the core or mold after which it is contacted with gaseous carbon dioxide. Carbon dioxide reacts with the sodium siHcate to produce sodium carbonate and bicarbonate, plus siHcic acid, resulting in hardening of the core or mold without baking. 

Outside the field of biomaterials it has been patented for use as a cement for underwater pipelines, as a foundry sand and as a substitute for plaster... 

Foundries purchase new, virgin sand to make casting molds, and the sand is reused numerous times within the foundry. However, heat and mechanical abrasion eventually render the sand unsuitable for use in casting molds, and a portion of the sand is continuously removed and replaced with virgin sand. The removed sand becomes spent foundry sand, which is discarded from the foundry facility. 

Physical properties involve tests of the physical index parameters of the materials. For spent foundry sand, these parameters include particle gradation, unit weight, specific density, moisture content, adsorption, hydraulic conductivity, clay content, plastic limit, and plastic index. These parameters determine the suitability of spent foundry sand for uses in potential applications. Typical physical properties of spent green foundry sand are listed in Table 4.5. 

Source From AFS, Alternative Utilization of Foundry Waste Sand, final report (Phase I) for Illinois Department of Commerce and Community Affairs, American Foundrymen s Society, Des Plaines, IL, July 1991. Javed, S. and Lovell, C.W., Use of Foundry Sand in Highway Construction, Joint Highway Research Project No. C-36-50 N, Purdue University, West Lafayette, IN, July 1994. Javed, S., Lovell, C. W., and Wood, L.E., Waste Foundry Sand in Asphalt Concrete, in Transportation Research Record, No 1437, Transportation Research Board, Washington, DC, 1994. 

The beneficial reuse of foundry solid waste has long been carried out informally, particularly in the U.S. Foundry solid waste has always been used as fills around the foundry or nearby neighborhood. With the promulgation of strict environmental protection laws, foundry solid waste is now required to be landfilled. Later, spent foundry sand was selected as a daily cover for landfills that are cover short. However, many recyclers believe that foundry solid waste should not necessarily be disposed of in landfills where other hazardous industrial waste belongs, simply because the main fraction of foundry solid waste is nonhazardous and has value in fully or partially substituting for currently in-use materials, for example, construction aggregates, soils, and minerals. Thus, reuse of foundry solid waste is marketable. 

Spent foundry sand is thought of as a beneficial substitute for fine sand for use in portland cement concrete. Prior to acceptance of inclusion, test standards applied on conventional fine sand shall be referred to as the standards for spent foundry sand to compare the physical properties of conventional sand and spent foundry sand. The most important parameters are particle size distribution, fineness modulus, dust content, density, organics content, deleterious materials content, and grain shape. Although no spent foundry sand satisfies all of the specifications, foundry sand can be blended with conventional sand to be incorporated into the concrete matrix. The replacing ratio normally starts at one-third. 

Spent foundry sand can be used as a good source of silica in manufacturing portland cement. Also, the clay fraction of foundry sand is an additional source of iron and aluminum oxides. According to the portland cement industry, spent foundry sand can be beneficially used in the manufacture of Portland cement, as sand possesses the following characteristics ... 

Natural sand is a major component of most flowable fill mixes. Ferrous spent foundry sand can be used as substitute for natural sand (fine aggregate) in flowable fill.48 49 Spent sands from nonferrous foundries and foundry baghouse dust can contain high concentrations of heavy metals that may preclude their use in flowable fill applications. Some of the engineering properties of spent foundry sand that are of particular interest when foundry sand is used in flowable fill applications include particle shape, gradation, strength characteristics, soundness, deleterious substances, and corrosivity. 

Most spent foundry sand discarded is green sand. The primary components of green sand are silica and bentonite. Thus, green sands are essentially a sand-bentonite mixture, which makes them potentially useful as a liner and cover materials, that is, for hydraulic barrier layers. 

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