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Asbestos cement product curing & stabilization
asbestos cement roofing, siding & millboard
production methods
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Curing & stabilization of cement-asbestos products: this article describes how asbestos cement roofing, siding, pipe, and other products were cured after the wet manufacturing process. Curing methods for asbestos-cement varied from autoclave, air-drying, to storage under-water!
Cement asbestos materials: this article series describes asbestos cement products & materials and the history of their production and use. This article includes text & data Adapted from Rosato (1959 out of print) on the production and use of asbestos-containing materials, adding photographs, inspection, repair and maintenance advice, and updates on asbestos hazards involved in the installation, repair, or demolition of asbestos cement products such as roofing and siding or asbestos millboard that remain in place on buildings.
Our page top photograph shows badly broken cement asbestos roofing shingles on a building in upstate New York.
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Curing Processes for Asbestos Cement Products
The following text is adapted & expanded from Rosato p. 73-75 [1] © 2013 InspectApedia.com
Three basic processes are available for curing the asbestos-cement products. These are similar to the procedures used for ordinary concrete materials, however, they are usually maintained under better actual control. The oldest procedure is wet curing.
The products are allowed to age in a warm humid atmosphere from 21 to 28 days.
[Click to enlarge any image]
Pipe products, under this system, are frequently stored under water after approximately 7 days of curing in air.
Typically, with cement products, the strength of asbestos-cement products increases as time passes. This condition is particularly true in the first year.
Occasionally, the products are cured for approximately a day in moist steam at atmospheric pressure. The average curing temperature is approximately 85 °C. The tempera-ture-time cycle varies and depends upon the product. Atmospheric steam curing is essentially an acceleration of normal curing; it cures products without requiring a long time cycle.
Figure 3.3. Asbestos-cement product being cured in autoclave.
(Courtesy Johns-Manville Corp.)Autoclave curing is more popular. See Figure 31. It uses saturated steam at pressures between 100 and 250 psi. This process is not simply an accelerated cure, giving an ade-quately cured product in one day, but it also alters the character of the material.
The Italian inventor, Dr. Morbelli, started the process of substituting finely ground, pure silica flour for a portion of the cement in the mixture.
The silica flour and the cement react under the curing conditions to form a crystalline product in place of the typical cement gel.
This method takes into consideration the chemical reac-tion between calcium hydroxide and silica which forms a hydrated calcium silicate. The silica is added to the com-position of the product to react with the calcium hydroxide which is formed when the cement reacts with water. Steam cure under pressure provides for the chemical reaction.
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Citations & References
In addition to any citations in the article above, a full list is available on request.
- [1] ASBESTOS HISTORY & PROPERTIES [Book online] D.V. Roasato, engineering consultant, Newton MA, Reinhold Publishing Co., NY, 1959, Library of Congress Catalog No. 59-12535. We are in process of re-publishing this interesting text. Excerpts & adaptations are found in InspectApedia.com articles on asbestos history, production & visual identification in and on buildings.
- [2] "Asbestos in Plastic Compositions", A.B. Cummins, Modern Plastics [un-dated, pre 1952]
- [3] "Asbestos in Your Home," Spokane County Air Pollution Control Authority, Spokane WA 509-477-4727 www.scapa.org provides a one-page image, a .pdf file drawing of a house warning of some possible sources of asbestos in the home. The sources are not ranked according to actual risk of releasing hazardous levels of airborne asbestos fibers and the list is useful but incomplete.
- [4] The US EPA provides a sample list of asbestos containing products epa.gov/earth1r6/6pd/asbestos/asbmatl.htm
- [5] "Characterization of asbestos exposure among automotive mechanics servicing and handling asbestos-containing materials", Gary Scott Dotson, University of South Florida, 1 June 2006, web search 3/9/2012 original source: scholarcommons.usf.edu/cgi/viewcontent.cgi?article=3505&context=etd [copy on file as /hazmat/Automotive_Asbestos_Exposure.pdf ].
- [6] Photos of theater wiring possibly containing asbestos are from http://filmhacks.wordpress.com/2007/07/10/photos-and-a-question/ - used by permission, September 2008. Thanks to randomblogmail
- [7] Thanks to Susan Kimball, Argus Pacific Corp., Puget Sound, WA, for pointing out that some products are permitted to contain more than 1% asbestos fibers by current standards provided that the fibers are encapsulated in an appropriate binder. Argus Pacific, in Seattle, WA 98119, 206.285.3373, is an industrial hygiene firm who also provide OSHA and DOSH regulated training in Washington State, providing classes in asbestos, lead, mold, hazardous waste, emergency response, and other occupational health, safety, and professional development topics. -- September 2008.
- [8] " Work Practice for Window Removal and Window Putty Patching With Less Than Or Equal To 1% Asbestos Window Putty and Caulking" University of Washington, 2002 http://www.washington.edu/admin/asbestos/1putty.html
- [9] How do I Manage Asbestos in our House or Apartment Building?, Illinois Department of Environmental Conservation, provides this article at http://www.epa.state.il.us/small-business/asbestos-in-home/
- [10] Asbestos Awareness Training Outline [PDF], Michigan Department of Licensing and Regulatory Affairs, Michigan Occupational Safety & Health Administration, Construction Safety & Health Administration - asbestos program, Michigan Department of Licensing and Regulatory Affairs Michigan Occupational Safety & Health Administration, Construction Safety and Health Division, Asbestos Program, 7150 Harris Drive, P.O. Box 30671, Lansing, Michigan 48909-8171 Phone: 517.322.1320, Fax: 517.322.1713, Web: www.michigan.gov/asbestos E-mail: asbestos@michigan.gov, web search 3/9/12, original source www.michigan.gov/
- [11] Damian Murphy, Marin OHS&E Consulting,Mairin OHS&E Consulting Pty Ltd 18-20 Kirk Street Moe Vic 3825 P: 03 5127 2311 F: 03 5127 2399 E: enquiries@mairin.net.au, personal correspondence to Daniel Friedman. 3/12/2013 Website: www.mairin.net.au
- [12] Asbestos in buildings - employee notice, University of Washington dept. of Environmental Safety, http://www.ehs.washington.edu/ohsasbestos/index.shtm
- [13] Window putty to be exempted from asbestos removal by State of Maine - http://list.uvm.edu/cgi-bin/wa?A2=SAFETY;wYpdKg;20010307113643-0500A
- [14] EPA Region 6 identifies window putty as asbestos containing - http://www.epa.gov/earth1r6/6pd/asbestos/asbmatl.htm
- June 1997 - Window Putty - OSHA case cites contractor for asbestos exposure during removal of window putty http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEASES&p_id=1091
- [15] Asbestos Identification and Testing References
- Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed the basis for current work by asbestos identification laboratories.
- Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
- Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone
- [16] EM>ASBESTOS IN YOUR HOME U.S. EPA, Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
- "Handling Asbestos-Containing roofing material - an update", Carl Good, NRCA Associate Executive Director, Professional Roofing, February 1992, p. 38-43
- [17] EPA Guidance for Controlling Asbestos-Containing Materials in buildings, NIAST, National Institute on Abatement Sciences & Technology, [republishing EPA public documents] 1985 ed., Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
- [18] EPA ASBESTOS MATERIALS BAN: CLARIFICATION 1999
- [19] Building Failures, Diagnosis & Avoidance, 2d Ed., W.H. Ransom, E.& F. Spon, New York, 1987 ISBN 0-419-14270-3
- [20] Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on ASBESTOS, ITS INDUSTRIAL APPLICATIONS, ROSATO 1959, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print, text and images available at InspectAPedia.com).
- In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
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