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Concrete In Australia : December 2013
40 Concrete in Australia Vol 39 No 4 FEATURE: RHEOLOGY designs. Characterising the fresh properties of concrete using rheology can provide valuable information and relies on a direct scientific assessment rather than using an empirical approach. Data presented in this paper was used to draw four main conclusions: Workability of concrete cannot be accurately measured by using consistence tests such as the slump test and allowance must be made for harsh and/or viscous concrete mixes. High performance concrete in particular may require much higher consistence levels to ensure not just sufficient workability but that other properties such as durability are not compromised Rheology of self-compacting concrete can be roughly inferred from empirical tests such as slump flow and T500 time but these do not provide definitive guidance for all SCC mixes. Characterising the rheology of SCC also allows other properties of the material, such as pumping pressures and surface finish to be predicted before production. Inclusion of fibres into concrete, whether rigid or flexible, will affect the rheology of FRC and allowance needs to be made in concrete mix designs. Allowance for higher fibre doses involves increasing the fine aggregate content of FRC mixes together with the use of chemical admixtures. Slip-form performance of concrete is not easy to achieve since the material must be relatively stiff without becoming too viscous. Achieving both of these properties simultaneously can be achieved using polymer additions that significantly reduce plastic viscosity at relatively low slump levels required for slip- forming. Having access to rheological testing equipment is not essential to develop a better understanding of fresh properties of concrete. Understanding the framework within which fresh testing is based can however be improved by knowing the relevance of rheological properties on fresh properties. This will in turn provide a more scientific basis for comparison and improve optimisation of concrete mixes. ACKNOWLEDGEMENTS The use of the concrete viscometer based at the University of Canterbury, Christchurch, New Zealand is gratefully acknowledged and was used to generate rheological properties discussed in this paper. REFERENCES 1. Tattersall, GH and Banfill, PFG, “The rheology of fresh concrete”, Pitman, London, 1983. 2. Wallevik, OH and Wallevik JE, “Rheology as a tool in concrete science: The use of rheographs and workability boxes”, Cement and Concrete Research, 41, 2011, pp. 1279-1288 . 3. Yammine, J, Chaouche, M et al, “From ordinary rheology concrete to self compacting concrete: A transition between frictional and hydrodynamic interactions”, Cement and Concrete Research, 38, 2008, pp. 890-896. 4. Ryan, WS and Samarin, A, Australian Concrete Technology, Sydney, Longman Cheshire, 1992. 5. Cortes, DD, Kim, H-K et al, “Rheological and mechanical properties of mortars prepared with natural and manufactured sands”, Cement and Concrete Research, 38, 2008 pp. 1142-1147. 6. New Zealand Standards, NZS3111 Method of test for water and aggregates for concrete, Wellington 1986. 7. Feys D, De Schutter,G et al, “Parameters influencing pressure during pumping of self compacting concrete”, Material and Structures, 46, 2013, pp. 533 -555 . 8. Wallevik OH, “Rheology – A scientific approach to develop self-compacting concrete”, Proc. Third Int. RILEM Symp. on Self-Compacting Concrete, Reykjavik, 2003, pp. 23-34 . 9. Koehler E, “Use of rheology to design, specify and manage self-consolidating concrete” Proc of 10th Int. Conf. on Recent Advances in Concrete Technology and Sustainability Issues, 2012. 10. Martinie, L, Rossi P et al, “Rheology of fiber reinforced cementitious materials: classification and prediction”, Cement and Concrete Research, 40, 2010, pp. 226-234. 11. Bartos PJM and Hoy CW, “Interactions of particles in fibre reinforced concrete”, Production methods and workability of concrete, E and FN Spon, London, 1996, pp. 451-461. 12. Choi, M, Roussell, N, et al, “Lubrication layer properties during concrete pumping”, Cement and Concrete Research, 45, 2013, pp. 69 -78. 13. Haigh, CJ, “Latex and acrylic based waste paint as admixture in concrete masonry blockfill”, Masters thesis, University of Auckland, 2008. Figure 6: Rheological properties required for slip forming concrete. 36-40 Mackechnie.indd 40 36-40 Mackechnie.indd 40 25/11/13 2:58 PM 25/11/13 2:58 PM