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Benefits of SCC
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Innovations in Testing SCC
The use of self-consolidating concrete (SCC) has grown tremendously since its inception in the 1980s. Different from a conventional concrete, SCC is characterized by its high flowability at the fresh state. This helps the SCC to satisfy the performance requirement in the field, such as giving a smooth surface finish, encapsulate the reinforcement without blocking of aggregates, etc. Because of the material performance in its fresh state, the existing testing methods for conventional concrete are no longer suitable for SCC.
Numerous efforts have been explored for new testing methods on SCC in the past decade. There are several organizations that collect the work in this area. The RILEM technical committee, TC 174-SCC (Self-Compacting Concrete), ASTM Subcommittee C09.47 (Self-Consolidating Concrete), ACI Committee 237 (Self-Consolidating Concrete), and TRB Committee AFN10 (Basic Research and Emerging Technologies Related to Concrete) are good examples. Symposiums and workshops on this topic were given by these organizations and several test methods on the flowability of SCC have been popularized since then.
Among the existing test methods, slump flow test, using the traditional slump cone, is the most common testing method for flowability (or filling ability) and was standardized in September 2005 as ASTM C 1611. During the test, the final slump flow diameter and T50 (time needed for concrete to reach a spread diameter of 20 in. (50 cm)) are recorded. The U-Box, L-Box, and especially J-ring (ASTM C 1621) tests are used for the evaluation of passing ability. These fresh properties are governed by the rheological properties of the material and some studied have been conducted in the lab to investigate the correlation among the measured parameters from above-mentioned methods (e.g. correlating T50 and the flow velocity at L-box test to the plastic viscosity). A good test method that can help to quantitatively determine the viscosity and the yield stress of SCC in the field is urgently needed. Segregation resistance is another important issue for SCC. Surface settlement test and the penetration test are two methods to evaluate the resistance to segregation of SCC in the field. However, these methods focus on the static segregation of SCC and the theoretical background for these methods is still unclear. There are no proper test methods for evaluating the dynamic segregation of SCC.
Researchers at the Center for Advanced Cement-Based Materials (ACBM) are targeting development of new test equipment and methods for in-situ evaluation of SCC with an emphasis on viscosity, yield stress, and segregation resistance. The research strategies are: (1) to better understand the fundamental aspect of rheology; (2) to develop new techniques based on simple concepts; and (3) to develop the corresponding equipment that is both lab- and field-friendly. To be different from the existing methods for testing SCC, it is required that these new methods can help to evaluate the properties of SCC not only qualitatively but quantitatively. The research tracks are subdivided into two parts: rheological properties and segregation resistance, which will be described in the following sections of this paper.
Lead Author: Zhihui Sun, University of Louisville
Contributing Authors: Lin Shen, University of Illinois at Urbana-Champaign Amedeo Gregori, University of LAquila, Italy Raissa Ferron, Northwestern University Leslie Struble, University of Illinois at Urbana-Champaign David Lange, University of Illinois at Urbana-Champaign Kamal H. Khayat, University of Sherbrooke Surendra P. Shah, Northwestern University
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