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FOUNDRY SANDUser Guideline


Embankment

INTRODUCTION

Although cities surrounding foundries have historically used spent foundry sand as a construction material, past environmental concerns have limited the use of foundry sand in this manner. State DOTs in Wisconsin, Ohio, Iowa, Illinois, and Indiana have characterized the environmental liability associated with spent foundry sand to be the dominant issue limiting its use.(1) A reexamination of the environmental effects of ferrous foundry sand began in the early 1990s. Most of this work showed that foundry sand did not cause groundwater or surface water contamination (see References 2, 3, 4, 5, 6), and that the measured concentrations were below the U.S. EPA drinking water limits.(5) Several states have allowed full use of foundry sand with little or no restrictions, though the majority of states continue to place restrictions on foundry sand use and require some type of encapsulation.(7)

Economic and environmental concerns dominate the issue of recycling foundry sand which is creating incentives for foundries to seek states with regulations more favorable to the industry.(8) As a means of reducing the cost of landfilling, foundries are often willing to pass a substantial portion of cost savings to end users of spent sand. For example, savings in material cost for an Indiana Department of Transportation (INDOT) embankment project is estimated to be $145,000 as a result of using spent foundry sand.(9)

PERFORMANCE RECORD

A 275 m long and 9 m high prototype embankment was constructed for the INDOT with 43,000 m3 of spent foundry sand. The highway embankment consisted of three sections constructed of foundry sand, clay, and natural sand. Geotechnical instrumentation of this test section included settlement plates, vertical and horizontal inclinometers, total pressure cells, piezometers, and a sealed double-ring infiltrometer. Environmental monitoring consisted of six groundwater monitoring wells adjacent to the foundry sand and natural sand embankments. Groundwater quality was measured before and after the construction.(1)

Prior to construction, a test pad was built to determine method specification for compaction of foundry sand. A smooth drum vibratory roller and a heavy rubber-tire roller were used for comparison. Lifts of 20 cm (8 in) at a water content between 12 and 15 percent compacted using six passes of a rubber-tire roller was found to be optimal. Smooth drum and smooth drum vibratory rollers were found to be relatively ineffective in compacting spent foundry sand.(10)

Geotechnical performance of the foundry sand was found to be comparable to that of the natural sand. Foundry sand had acceptable strength and compressibility with standard penetration N-values ranging from 33 to 54.(11) The hydraulic conductivity of foundry sand can be quite low (<1x10-5 cm/s) which is considerably lower than natural sand and cannot be considered free flowing. Leachate collected from a demonstration embankment indicated metal concentrations below regulatory reuse criteria and typically below drinking water standards, indicating that foundry sand would not have a negative impact on environmental quality.(1)

Dust control was found to be an issue during construction. This concern was alleviated by watering the surface regularly.(10) Foreign objects did not pose a serious problem (i.e. punctured tires), although foundry operators should screen out objects at the plant.(10) In all, project managers were pleased with the performance of foundry sand.(1)

ENGINEERING PROPERTIES

The major components of foundry sand are quartz sand (70 to 80 percent), clay (5 to 15 percent), additives (2 to 5 percent), and water (up to 4 percent).(8) Chemical binders include phenolic, furfuryl alcohol, and other inorganic binders.(8) Specific gravity ranges from 2.39 to 2.70.(12;13;14) Grain size distribution is very uniform, with nearly all spent sands containing particles in the range of 0.6 to 0.15 mm.(4) The plasticity index for clay-bound foundry sand can range from nonplastic to 12 percent.(14) The consistency and uniformity of foundry sand may make it a better engineering material than naturally occurring sand.

Standard Proctor results on pure foundry sand yield an optimum water content near 12 percent and a maximum dry density near 1750 kg/m3 (109 lb/ft3).(5;14) The addition of 5 percent lime lowers the maximum dry density and increased optimum moisture content whereas the addition of 5 percent cement has little effect on both dry density and water content.(5)

Direct shear tests on loose specimens give a cohesion between 0 and 5 kPa (100 psf) and an internal angle of friction between 30° and 34°.(14) Dense specimens (as-compacted) yield a cohesion between 17 and 28 kPa (334 and 585 lb/ft2) and an internal angle of friction between 39° and 43°.(13;14)

For design with geosynthetics, interaction coefficients from pullout tests ranged from 0.2 and 1.7 in the normal stress range of 10 to 50 kPa (209 to 1044 lb/ft2).(13) Recommendations for design include a frictional efficiency (Eφ = tanδ / tanφ), woven geotextile interaction coefficients (Ci), and geogrid interaction coefficients are shown in Table 5.

Table 5. Recommended parameters for design of foundry sand and geosynthetics.(13)

Parameter Value
Frictional efficiency  
Geotextile 0.6
Geogrid 0.6
Geomembrane (textured) 0.7
Geogrid interaction coefficients  
Normal stress < 20 kPa (415 lb/ft2) 1.0
Normal stress > 20 kPa (415 lb/ft2) 0.5 – 0.8
Geotextile interaction coefficients  
Normal stress < 20kPa (415 lb/ft2) 1.0
Normal stress > 20 kPa (415 lb/ft2) 0.3 – 0.5

Hydraulic conductivity of compacted spent foundry sand is generally low and in many cases cannot be considered free flowing. Typical permeability values of compacted foundry sand are in the range of 10-5 to 10-9 cm/s.(1;8;15;16)

Freeze-thaw tests conducted per ASTM D 560(17) show that the resistance of foundry sand to winter conditions was generally better than a reference material (clayey gravel), except for lime amended mixtures which were at the verge of disintegration after eight cycles. The hydraulic conductivity ratio (Kr = Kn/Ki) ranges from 2 to 24 with increasing values for higher cycles. The unconfined compressive ratio (qur = qun/qui) remains nearly constant between the first and eighth cycle after losing 40 to 50 percent of their initial strength after the first cycle.(5)

ENVIRONMENTAL

A study on concentrations of metals in leachate beneath a foundry sand test plot found concentrations comparable to natural soils.(18) Leachates from the waste foundry sand were found to be non-hazardous as defined by the Resource Conservation and Recovery Act and not statistically different from a nearby natural soil embankment.(10) However, studies have found leaching concentrations of zinc, lead, chromium, and iron in foundry sand to be above the U.S. EPA drinking water limits, although the difference was within 10 percent.(19;20)

The use of foundry sand as an embankment of fill material is an unencapsulated use and therefore has the potential for contaminant leaching. For leachate testing in embankment applications, the synthetic precipitation leaching procedure (SPLP) is believed to be most representative of fill applications.(21) Use of foundry sand in embankments and as a fill requires good management and care to ensure that no negative impacts occur to the environment. In particular, areas with sandy soils possessing high hydraulic conductivities and areas near shallow groundwater or drinking aquifers should be given careful consideration. An evaluation of groundwater conditions, applicable state test procedures, and water quality standards should be consulted, as well as ensuring proper construction and environmental modeling.

REFERENCES

A searchable version of the references used in this section is available here.
A searchable bibliography of foundry sand literature is available here.

  1. Partridge BK, Fox PJ, Alleman JE, Mast DG. Field demonstration of highway embankment construction using waste foundry sand. Transp Res Rec 1999(1670):98-105.
  2. Ham RK, Boyle WC. Leachability of foundry process solid wastes. Journal of Environmental Engineering 1981;107(1):155-170.
  3. Lovejoy MA, Ham RK, Traeger PA, Wellander D, Hippe J, Boyle WC. Evaluation of selected foundry wastes for use in highway construction. In: Proceedings of the 1996 19th international Madison waste conference, sep 25-26 1996. Madison, WI, USA: University of Wisconsin-Madison/Extension, Madison, WI, USA; 1996.
  4. Naik TR, Singh SS. Performance and leaching assessment of flowable slurry. J Environ Eng 2001;127(4):p359.
  5. Guney Y, Aydilek AH, Demirkan MM. Geoenvironmental behavior of foundry sand amended mixtures for highway subbases. Waste Manage 2006;26(9):932-45.
  6. Lee T, Benson C. Leaching behavior of green sands from gray-iron foundries used for reactive barrier applications. Environmental Engineering Science 2006;23(1):153-67.
  7. Abichou T, Edil TB, Benson CH, Bahia H. Beneficial use of foundry by-products in highway construction. In: Geotechnical engineering for transportation projects: Proceedings of geo-trans 2004, jul 27-31 2004. Los Angeles, CA, United States: American Society of Civil Engineers, Reston, VA 20191-4400, United States; 2004.
  8. Winkler E, Bol’shakov AA. Characterization of foundry sand waste. Chelsea Center for Recycling and Economic Development, University of Massachusetts; 2000. Report nr 31.
  9. Fox PJ, Mast DG. Geotechnical performance of a highway embankment constructed using waste foundry sand. Purdue Libraries; 1998. Report nr FHWA/IN/JTRP-98/18.
  10. Fox PJ, Mast DG. Salvaged sand. Civil Engineering 1997;67(11):53.
  11. Mast DG. Field demonstration of a highway embankment using waste foundry sand. West Lafayette, ID: Purdue University; 1997.
  12. Federal Highway Administration. Foundry sand facts for civil engineers. Federal Highway Administration (FHWA); 2004 May 2004. Report nr FHWA-IF-04-004.
  13. Goodhue MJ, Edil TB, Benson CH. Interaction of foundry sands with geosynthetics. J Geotech Geoenviron Eng 2001;127(4):353-62.
  14. Javed S, Lovell CW. Use of waste foundry sand in highway construction. Department of Civil Engineering, Purdue University; 1994 July, 1994. Report nr C-36-50N.
  15. Abichou T, Benson CH. Foundry green sands as hydraulic barriers: Laboratory study. Journal of Geotechnical & Geoenvironmental Engineering 2000 12;126(12):1174.
  16. Abichou T, Benson CH, Edil TB. Foundry green sands as hydraulic barriers: Field study. J Geotech Geoenviron Eng 2002;128(3):206-15.
  17. ASTM D560-03 standard test methods for freezing and thawing compacted soil-cement mixtures. In: Annual book of ASTM standards. West Conshohocken, Pennsylvania: ASTM; 2003.
  18. Freber BW. Beneficial reuse of selected foundry waste material. In: Proceedings of the 1996 19th international Madison waste conference. Madison, WI, USA: University of Wisconsin-Madison/Extension, Madison, WI, USA; 1996.
  19. Lee T, Benson C. Using foundry sands as reactive media in permeable reactive barriers. Madison, WI: Dept. of Civil and Environmental Engineering, University of Wisconsin-Madison; 2002. Report nr Geo Engineering Report 02-01.
  20. Coz A, Andres A, Soriano S, Irabien A. Environmental behavior of stabilized foundry sludge. J Hazard Mater 2004 2004 Jun 18;109(1-3):95-104.
  21. Tikalsky P, Bahia H, Deng A, Snyder T. Excess foundry sand characterization and experimental investigation in controlled low-strength material and hot-mixing asphalt. U.S. Department of Energy; 2004. Contract No. DE-FC36-01ID13974.

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Last Update 7/28/08