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Fig. 10—Tortuosity for all mixtures. pozzolanic reactions that refine the pore structure of the matrix, thus reducing permeability and enhancing durability. 2. All transport properties show that the shotcrete process, including mixtures of shot wet-mix shotcrete with and without accelerator, and dry-mix shotcrete with and without accelerator have transport properties that are close to or even better than that of cast shotcrete and cast-in-place concrete. 3. All of these improved transport properties, including reduced boiled absorption and volume of permeable voids, reduced rapid chloride penetration resistance, reduced coefficient of diffusion, increased tortuosity, and reduced permeability lead to reduced porosity for the samples from the shotcrete process. The lower porosity leads to a lower coefficient of diffusion of chloride, which means that it will take a longer time for Cl– to diffuse to the depth of the reinforcement. Therefore, the matrix is more protective and results in a more durable structure. 4. BA and VPV results correlate well with the CoDs and permeability. Considering the fact that it takes a complex array of tests values to get values for CoDs and permeability, it might be a better choice to use BA and VPV as durability indicators for shotcrete quality control proposes. In summary, the results of this extensive comparative study of the basic and transport properties of wet-mix and dry-mix shotcretes, compared to cast concrete, demonstrates that properly applied shotcrete can provide equivalent or superior durability performance to cast-in-place concrete for like mixtures. AUTHOR BIOS ACI member Lihe Zhang is an Engineer at LZhang Consulting and Testing Ltd. He received his BEng in materials engineering from Chongqing JianZhu University, Chongqing, China, in 1998; his MASc in materials engineering from Tongji University, Shanghai, China, in 2001; and his PhD in civil engineering from the University of British Columbia, Vancouver, BC, Canada, in 2006. He is Chair of ACI Subcommittee 506-F, Shotcrete-Underground, and a member of ACI Committees 370, Blast and Impact Load Effects; 506, Shotcreting; and 544, Fiber-Reinforced Concrete. His research interests include fiber-reinforced concrete, shotcrete, durability, self-consolidated concrete, and new product research and development. Dudley Morgan, FACI, is a consulting engineer. He is a past member of ACI Committees 506, Shotcreting, and 544, Fiber-Reinforced Concrete. Sidney Mindess, FACI, is Professor Emeritus in the Department of Civil Engineering at the University of British Columbia. His research interests include cement and concrete technology. ACKNOWLEDGMENTS This research project was initially submitted to the Canadian National Science and Engineering Research Council (NSERC). Funding was granted through NSERC Industrial Research & Development Funding Post-Doc program, but was subsequently suspended due to the fact that the selected postdoctoral fellow withdrew from the program. NSERC’s support is appreciated. The program was consequently funded by LZhang Consulting and Testing Ltd with financial contributions from the American Shotcrete Association and a number of individuals including M. Cotter, C. Burkert, M. Von der Hofen, and W. Drakeley. Their support is gratefully acknowledged. REFERENCES 1. ASTM C642-06, “Standard Test Method for Density, Absorption, and Voids in Hardened Concrete,” ASTM International, West Conshohocken, PA, 2006, 3 pp. 2. ASTM C1202-12, “Standard Test Method for Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration,” ASTM International, West Conshohocken, PA, 2014, 8 pp. 3. ASTM C1792-14, “Standard Test Method for Measurement of Mass Loss versus Time for One-Dimensional Drying of Saturated Concretes,” ASTM International, West Conshohocken, PA, 2014, 4 pp. 4. USACE/NAVFAC/AFCESA/NASA, “Specification UFGS-03 31 29 (Aug. 2012) Division 03 – Concrete, Section 03 31 29 Marine Concrete,” 67 pp. 5. ACI Committee 506, “Guide to Shotcrete (ACI 506R-05),” American Concrete Institute, Farmington Hills, MI, 2005, 45 pp. 6. CSA A23.1/23.2, “Concrete Materials and Methods of Concrete Construction/Test Methods and Standard Practices for Concrete,” Canadian Standards Association, Toronto, ON, Canada, 2014, 691 pp. 7. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 2014, 519 pp. 8. Vincent, L., “STADIUM Lab Training Manuel,” SIMCO Technology, 2013, 43 pp. 9. Morgan, D. R., Shotcrete, A Compilation of Papers, American Shotcrete Association, Farmington Hills, MI, 2008, 424 pp. 10. Samson, E.; Marchand, J.; Henocq, P.; and Beausejour, P., “Recent Advances in the Determination of Ionic Diffusion Coefficients Using Migration Test Results,” RILEM Proceedings 58 – CONMOD, E. Schlangen and G. de Schutter, eds., Delft, the Netherlands, 2008, pp. 65-78. 11. Dyer, T., Concrete Durability, 2014, Taylor and Francis Group LLC, London, UK, pp. 192-208. Reprinted from the ACI Materials Journal by kind permission of the American Concrete Institute. https://www.concrete.org/publications/internationalconcreteabstractsportal.aspx?m=details&ID=51688829 4368 4 ACI Materials JSohuortncarel/tMe •a Sy-uJmumnee r2 2001166


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