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Technical Tip time (for example, 28 days) after the repair is The values obtained during the qualification complete and the shotcrete has developed ade- of the repair method should be treated as a refer- quate strength, a pulloff test (refer to Fig. 4 ence for the rest of the project. To assure quality through 6) should be conducted according to ICRI during the project, surface preparation should be Technical Guideline No. 210.3-2004.5 A proper tested by repeating the pulloff test periodically. bond should be typically higher than 145 psi (1 MPa), as reported in ACI 506R-056 but this value Conclusion can vary depending on the substrate to repair, as A strong, durable bond is critical to a suc- mentioned in the Report Number MERL 12-17.4 cessful concrete repair. Surface preparation is a key element to achieving a strong, durable bond, but other aspects should not be neglected, as they also play a significant role in bond performance. Curing, carbonation, material selection, exposure, and load transfer, among many other factors, can influence the bond of any repair system. references 1. Talbot, C.; Pigeon, M.; Beaupré, D.; and Morgan, D. R., “Influence of Surface Preparation on Long-Term Bonding of Shotcrete,” ACI Materials Journal, V. 91, No. 6, Nov.-Dec. 1994, pp. 560-566. 2. “Cahier des Charges et Devis Généraux,” Infrastruc- tures Routières Construction et Réparation, Éditions 2012, Fig. 4: A pulloff test being conducted on a test Publications du Québec, Quebec City, QC, Canada, 2012. panel (photo courtesy of the Centre de 3. Dufour, J.-F.; Reny, S.; and Vézina, D., “State-of-the-Art recherche sur les infrastructures en béton Specification for Shotcrete Rehabilitation Projects,”Shotcrete, V.3, No. 4, Fall 2006, pp. 4-11. (CRIB)) 4. Report Number MERL 12-17, “Best Practices for Preparing Concrete Surfaces Prior to Repairs and Overlays,” U.S. Department of the Interior Bureau of Reclamation, Technical Service Center, Denver, CO, May 2012. 5. ICRI Technical Guideline No. 210.3-2004 (formerly 03739, “Guide to Using In-Situ Tensile Pull-Off Tests to Evaluate Bond of Concrete Surface Materials,” International Concrete Repair Institute, Des Plaines, IL, 2004, 12 pp. 6. ACI Committee 506, “Guide to Shotcrete (ACI 506R- 05),” American Concrete Institute, Farmington Hills, MI, 2005, 40 pp. Simon Reny, Eng., is Manager Fig. 5: Extracted cores after pulloff tests (photo of the Technical Services for courtesy of the CRIB) King Packaged Materials Company (an ASA Corporate Member), where he is res­ ponsible for all mixture design development, quality control, and technical support. He received his degree in civil engineering from Laval University in 2004. He is a member of the American Concrete Institute; an associate member of ACI Committee 506, Shotcreting; and is a member of the Shotcreting-Guide Subcommittee and the Shotcreting-Underground Subcommittee. He is also currently President of Fig. 6: A hole after a core has been extracted the International Concrete Repair Institute’s during a pulloff test Quebec Chapter. 30 Shotcrete • Spring 2013


2013SprShotcreteEMag
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