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Technical Tip of the demonstration to make sure that they were (a) (b) fully cured and at full strength. The beams had a column cross section that was 12 x 12 in. (300 x 300 mm), with the length of the damaged area on two of the four columns being approximately 18 in. (450 mm) long. The third column was damaged a day or two before the demonstration by bending it until it cracked. The fourth column was left whole and used as a control beam during testing. Once spraying was finished, the repaired beams were immediately removed from the ground and taken directly to the Texas A&M Civil Engineering lab for testing. The entire process for this demonstra- tion, including shotcreting the beams, getting the beams out of the ground, and transferring them over to the high bay lab for testing, took less than 5 hours. Fig. 8: Bonding abilities of Tekcrete Fast to portland cement With less than 5 hours of curing time for the Tekcrete Fast section, the beams tested were shown to fail outside of the repaired section—that is, the times are very predictable, with no flash set, but original concrete failed while the section repaired with the ability to cure very quickly, within with Tekcrete Fast did not. This is shown in the far 15 minutes of shotcreting. Tekcrete Fast can be right picture in Fig. 7, and Fig. 8 shows the bonding cut back and trimmed in small areas, if needed, of Tekcrete Fast with the concrete beams. and according to Carl Baur, “bonds like nothing I have seen in my 20 years of gunite.” Conclusions In conclusion, Tekcrete Fast and its dry-mix Acknowledgments shotcrete delivery system has repeatedly dem- The authors wish to acknowledge the contri- onstrated that it has an overwhelmingly superior butions to this article from the research team: rate of strength development to conventional T. Robl, UK CAER; P. Mills, Minova USA Inc.; portland-cement-based shotcrete. It has excellent J. Wiseman, UK CAER; and T. Duvallet, UK CAER. bonding capabilities, and its potential for disaster recovery has been demonstrated. Tekcrete Fast is References an easy, one-bag sand/cement mixture, or “beam Service, College Station, TX, 2015, https://teex.org/Pages/,” Texas A&M Engineering Extension®1. “Disaster City in a bag,” and has been proven to be nozzleman- about-us/disaster-city.aspx. (last accessed September 28, 2015) friendly, with a very wide water range. The set 2. Minova USA Inc., Tekcrete Fast Technical Data Sheet. Anne Oberlink is an Associate Research Scientist for the Environment Coal Technologies (ECT) group at the University of Kentucky Center for Applied Energy Research (UK CAER). Her research interests involve the use of conventional and clean coal combustion by-products in cement and concrete; the use of industrial slags, dry scrubber materials, and fluidized bed systems in cement and concrete; the beneficiation technologies for ponded and landfilled ash materials; and development of ultra-high-performance cement and concrete, among many other interests. Oberlink holds two MS degrees in chemistry: one from Southern Illinois University- Edwardsville and one from the University of Kentucky. Bob Jewell is a Senior Research Engineer for the Environmental and Coal Technologies (ECT) group at the University of Kentucky Center for Applied Energy Research. His research encompasses process development for ash beneficiation, including ash sampling techniques, the fabrication of new low energy, and low-CO2-emitting construction materials including cements and concretes from coal by-products. Additionally, Jewell is focused on the development of smart energy-harvesting cementitious materials for civil engineering structures. He is the author of numerous technical reports and publications, as well as one patent. He has more than 10 years of energy research experience related to coal by-product use and has been a leading researcher on projects for the U.S. Department of Energy and the National Institute for Hometown Security. He received his master’s degree from the University of Kentucky in 2004 in geological sciences and in 2015 received his PhD in civil engineering. Shotcrete • Fall 2015 43


2015FallShotcreteEMag
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