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Detail  > Leachability and Concrete
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Leaching is the process by which a liquid dissolves and removes the soluble components of a material. With respect to cement, leaching can be discussed two ways: potential leaching from products made with cement or “recycled” products, for example crushed concrete used for road base stabilization, and the use of cement to control the leaching of waste materials, such as fly ash and slag. When these materials are added to cement, they are effectively controlled. If they are landfilled or otherwise stored other measures are needed to prevent or control leaching of contaminants.
 
 
In brief, cementitious materials are tested and certified for use in concrete products in contact with drinking water. The extensive test program is performed on standard drinking water exposed to cement products; results are compared to the U.S. EPA National Primary Drinking Water Standards, ensuring that certified cements do not contribute to potential adverse human health effects. Read on for more detail.
Cement and Concrete in Drinking Water Systems

 

ANSI/NSF61 Drinking Water System Components – Health Effects is a voluntary consensus standard. Nearly all U.S. states have adopted regulations requiring products in contact with drinking water comply with the standard to demonstrate they are safe. Standard 61 addresses two issues: 1) Do contaminants leach or migrate from the material into the drinking water; and 2) if so, is the level of migration acceptable from a public health viewpoint?

ANSI/NSF61 testing is performed on cement used in items such as concrete pipes and storage tanks, to ensure that they are safe for storing or conveying drinking water.
 
Most state agencies require mortar and concrete products used in drinking water systems to be certified. Producers of these products may in turn require their materials, such as cement, to be certified. It is often advantageous for cement producers to have their cement certified since certified cement is effectively “pre-qualified”, meaning product manufacturers can switch among brands and types of certified cements and still maintain end product certification.
 
Some states also regulate the cement itself, depending on its particular use in the drinking water system. Certified cement producers have the benefit of the “NSF” (NSF International) or “UL” (Underwriters Laboratories) mark on the product, indicating the cement has passed rigorous testing and is safe for use in drinking water systems. The product will be also be listed in the NSF or UL directory of approved products, which can be viewed at their websites: www.nsf.org and www.ul.com. The cement certification process is summarized below. For further information on Standard 61 background and certification process, see References 1, 2, 3, and 4.
 
 
  • Cement manufacturers contact a certifying organization to initiate the process. Certifying organizations include NSF International of Ann Arbor, Michigan, and Underwriters Laboratories of Northbrook, Illinois.
     
  • The certifying organization performs a detailed review of the manufacturer’s production process and quality control records; cement samples are collected for testing.
     
  • The cement is used to fabricate mortar cubes for testing. Extreme care is taken to avoid introducing even trace levels of contaminants during specimen fabrication. Cubes are then exposed to standard drinking water. ·
     
  • The water is analyzed for a range of potential contaminants, including organics, regulated metals, radionuclides, dioxins, and furans.
     
  • The results are compared to Maximum Acceptable Levels, generally 10% of U.S. EPA National Primary Drinking Water Standards.
     
  • Annual unannounced plant visits and follow-up testing verify certification.
 

Mortar cube fabrication, as well as curing, drying, and testing are performed very carefully, using specialized tools and procedures to prevent contamination.
Leaching of Other Concrete Components

 

 
In some concretes, pozzolan and slag cements can be used as partial replacements for portland cement. Type IP cement is a portland cement with a pozzolan and Type I(SM) is a portland cement with slag cement (REF 5). Multiple supplies of cement Types IP and I(SM) have been tested in the ANSI/NSF61 program described above, and found acceptable for use in concrete for drinking water systems (REF 6). Slag cement has also been accepted.
 
The “After-Life” of Concrete Products
Another approach to leachability involves the re-use of concrete products, such as for road stabilization. Sloot (REF 7), concludes “with the possible exception of cadmium, metals such as lead and zinc are unlikely to become critical environmentally, even in the 'second life' of cement mortars.”
References
1. “General Information, Toxicology Data Review Submission – A- Form”, NSF International, website: http://www.nsf.org/DWA/pdf/61sec9.pdf
2. Kanare, H.M., “Certifying Portland Cement to ANSI/NSF 61 for Use in Drinking Water System Components”, PCA R&D Serial No. 2041, Portland Cement Association, 1995.
3. “Certifying a Portland Cement to ANSI/NSF Standard 61”, website: www.nsf.org/newsletters/waterworks99-1/portland.html.
4. “Drinking Water Certification Program”, website: www.ul.com/water/
5. “Standard Specification for Blended Hydraulic Cements”, ASTM C595-02a, West Conshohocken, PA.
6. NSF Certified Drinking Water System Components: NSF Product and Service Listings, NSF International, website: http://www.nsf.org/Certified/PwsComponents/
7. Sloot, H.A. van der, “Characterization of the leaching behaviour of cement mortars to assess long term environmental behaviour during their service life and their recycling stage”, ECN-RX--98-026, Energy Research Centre of the Netherlands, 1998, website: http://www.ecn.nl/library/reports/1998e/rx98026.html.