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Fig. 8: Rust bleeding through a plaster finish of a swimming pool due to reinforcement corrosion Jonathan E. Dongell is Director of Research & Development, Pebble Technologies, Scottsdale, AZ. Dongell has worked in concrete construction and with cementitious materials spanning over 30 years. His roles have included technician, superintendent, manager, contractor, and President. He was Past President, Whitestone Cement Company, Scottsdale, AZ (1998-2005) and Universal White Cement Co, Inc., Glendale, AZ (1992- 1998). He is a member and past Chair of ACI Committee 524, Plastering, and is a member of ACI Committees 201, Durability of Concrete; 225, Hydraulic Cements; 232, Fly Ash in Concrete; 308, Curing Concrete; 350, Environmental Engineering Concrete Structures; and 555, Concrete with Recycled Materials. Dongell also serves on the ACI Concrete Research Council (CRC) and the ASA Pool & Recreational Shotcrete Committee. He is a voting member of ASTM International main committees and several subcommittees, including C4.01, Cement, Lime, Gypsum, and C4.02, Concrete and Aggregates. Dongell is the author of several books, including The Durability of Cementitious Materials in a Water Contact Environment. He is an inventor and holds three patents on cementitious materials. Dongell is a designated expert witness in the fields of cement, concrete, stucco/plaster, and water chemistry. He was the recipient of the Del Bloem Distinguished Service Award in 2008. *The intent of this article is to promote proper shotcrete workmanship and materials practices. While there are many products that have been shown to lessen corrosion and extend the service life (such as pozzolan, slag, densifiers, sacrificial anodes, epoxycoated reinforcement, and many others) these were not within the scope of this article. Fig. 7: Complete corrosion of reinforcement grid due to inadequate coverage. Corrosion reaction creates internal stress and delamination of cover material of shotcrete based on the structure’s in-service use and placement environment. Quality shotcrete and good design practices are the key to corrosion protection and overall durability by ensuring that inadequacies (Fig. 4 through 8), such as thin concrete cover, poor compaction, high water-cementitious materials ratios (w/cm), low cement content, and poor curing conditions are avoided. References 1. Dongell, J. E., “Durability and Exposure Conditions of Cementitious Materials – Deterioration Mechanisms,” Shotcrete, V. 17, No. 2, Spring 2015, pp. 8-10. 2. Morgan, D. R., “Freeze-Thaw Durability of Shotcrete,” Shotcrete, V. 5, No. 2, Spring 2003, pp. 30-37. 3. Glassgold, I. L., “An Evaluation of Shotcrete Durability,” Concrete International, V. 11, No. 8, Aug. 1989, pp. 78-85. 4. Hubacek, A., and Hela, R., “Study of Durability of Sprayed Concrete,” Recent Researches in Business Administration, Product Design, and Marketing, World Scientific and Engineering Academy and Society, 2013, pp. 71-75. 5. Reading, T. A., “Durability of Shotcrete,” Concrete International, V. 3, No. 1, Jan. 1981, pp. 27-33. 6. ACI Committee 506, “Guide to Shotcrete (ACI 506R-16),” American Concrete Institute, Farmington Hills, MI, 2016, 52 pp. 7. Hamilton III, H. R.; Boyd, A. J.; and Vivas, E., “Permeability of Concrete – Comparison of Conductivity and Diffusion Methods,” University of Florida, Department of Civil and Coastal Engineering, Project 00026899, though grant from Florida Department of Transportation – Research Management Center, available through National Technical Information Services, Springfield, VA, 22161, June 2007. 8. Obla, K.; Lobo, C.; and Lemay, L., “Specifying Concrete for Durability,” NRMCA Concrete InFocus, Winter 2006, pp. 42-50. 9. Bolduc, L.-S., and Jolin, M., “Shotcrete Boiled Water Absorption,” Shotcrete, V. 12, No. 1, Winter 2010, pp. 12-17. 10. Verbeck, G. J., “Mechanisms of Corrosion of Concrete,” Corrosion of Materials in Concrete, SP-49, American Concrete Institute, Farmington Hills, MI, 1975, pp. 21-38. 11. Ma, F.-Y., “Corrosion Effects of Chlorides on Metals,” Pitting Corrosion, Mar. 2012, pp. 141-145, 150. www.shotcrete.org Summer 2017 | Shotcrete 57


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