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Keywords: flowable concrete, Bingham model, rheology, simulation, distinct element model, three-dimension.

Summary

Flowable concrete, requiring no consolidation work in site, developed to improve the reliability of concrete and concrete structures. A large amount of experimental effort can be avoided if a numerical approach can predict the behavior of flowable concrete with reasonable preciseness. To perform the simulation of this type of concrete some method should be there to relate simulation parameter with the concrete parameters, such as Bingham parameters. Three-dimensional distinct element model (henceforth DEM) [1] was used, as a new tool here, to simulate behaviors of this type of concrete under various states. In this paper, first effort has been made to correlate and verify the Distinct Element Model parameters of the mortar and concrete simulation to the Bingham coefficients of high flow mortar and concrete. Here, Bingham coefficients mean yield value ( $\tau_0$ )and viscosity ( $\eta$ ). Why Bingham coefficients were selected instead of mix ratio? Because there is no direct relation between fresh concrete flow properties and mix ratio.

DEM parameters for mortar and concrete mean viscosity ( $V_{c}=\eta^n_d$ ), overlap between elements (), friction coefficient (), bond parameter () in normal direction, normal to shear viscosity ratio ( $V_{r}=\eta^n_d/\eta^s_d$ ) and stiffness ratio ( $S_{r}=K^n/k_s$ ). The relationship between Bingham coefficients to DEM parameters, has been plotted and described in detail. Finally, effort has also been made to propose generalized equation for mortar rheology from the DEM parameters, for quantitative analysis. These equations were then verified by simulating the mortar. After mortar verification the mortar model was combined with aggregate parameter to simulate the flowable concrete. These simulations were then verified with the experimental results of flowable concrete.

Then, some applications based on the developed model have been simulated to show that the model can be applied in all practical cases. These applications have been chosen carefully -- so that it can cover a broad range of problems. Several applications could be performed but, if the critical applications can be simulated using the proposed model, any application can be simulated. It is beyond the scope of the current research, to cover all possible applications currently available. Two classes applications were selected. One has relation to the flow of concrete and another has relation to the blocking and segregation of concrete. Both of these are important in practical problems. Other types of application were selected to show the scalability and applicability of the model.

To demonstrate the flow related problem, slump flow test has been selected. To demonstrate, that concrete can fill all places of a complicated formwork, a T-Beam has been selected. A frame packed with reinforcement was selected, to show both flow and blocking related problem. L-box was selected to show the blocking and aggregate segregation related problem. Some general test methods were selected to demonstrate the diversification in the application simulation. These are -- a coaxial cylinder rheometer test, mainly to show the velocity profile distribution inside the concrete during rotation. It is found that, the DEM model proposed in this research can be used for simulation of flowable concrete.

References

1: P. A. Cundall and O. D. L. Strack, "A Discrete Numerical Model for Granular Assemblies", Geotechnique, 29(1), 47-65, 1979.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 77 PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON CIVIL AND STRUCTURAL ENGINEERING COMPUTING Edited by: B.H.V. Topping Paper 61 Flowable Concrete: Three-Dimensional Quantitative Simulation and Applications M.A. Noor+ and T. Uomoto* +Department of Civil Engineering, Bangladesh University of Engineering and Technology, Bangladesh Center for Collaborative Research, The University of Tokyo, Japan doi:10.4203/ccp.77.61 purchase the full-text of this paper Full Bibliographic Reference for this paper M.A. Noor, T. Uomoto, "Flowable Concrete: Three-Dimensional Quantitative Simulation and Applications", in B.H.V. Topping, (Editor), "Proceedings of the Ninth International Conference on Civil and Structural Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 61, 2003. doi:10.4203/ccp.77.61 Keywords:* flowable concrete, Bingham model, rheology, simulation, distinct element model, three-dimension. Summary Flowable concrete, requiring no consolidation work in site, developed to improve the reliability of concrete and concrete structures. A large amount of experimental effort can be avoided if a numerical approach can predict the behavior of flowable concrete with reasonable preciseness. To perform the simulation of this type of concrete some method should be there to relate simulation parameter with the concrete parameters, such as Bingham parameters. Three-dimensional distinct element model (henceforth DEM) [1] was used, as a new tool here, to simulate behaviors of this type of concrete under various states. In this paper, first effort has been made to correlate and verify the Distinct Element Model parameters of the mortar and concrete simulation to the Bingham coefficients of high flow mortar and concrete. Here, Bingham coefficients mean yield value ( $\tau_0$ )and viscosity ( $\eta$ ). Why Bingham coefficients were selected instead of mix ratio? Because there is no direct relation between fresh concrete flow properties and mix ratio. DEM parameters for mortar and concrete mean viscosity ( $V_{c}=\eta^n_d$ ), overlap between elements (), friction coefficient (), bond parameter () in normal direction, normal to shear viscosity ratio ( $V_{r}=\eta^n_d/\eta^s_d$ ) and stiffness ratio ( $S_{r}=K^n/k_s$ ). The relationship between Bingham coefficients to DEM parameters, has been plotted and described in detail. Finally, effort has also been made to propose generalized equation for mortar rheology from the DEM parameters, for quantitative analysis. These equations were then verified by simulating the mortar. After mortar verification the mortar model was combined with aggregate parameter to simulate the flowable concrete. These simulations were then verified with the experimental results of flowable concrete. Then, some applications based on the developed model have been simulated to show that the model can be applied in all practical cases. These applications have been chosen carefully -- so that it can cover a broad range of problems. Several applications could be performed but, if the critical applications can be simulated using the proposed model, any application can be simulated. It is beyond the scope of the current research, to cover all possible applications currently available. Two classes applications were selected. One has relation to the flow of concrete and another has relation to the blocking and segregation of concrete. Both of these are important in practical problems. Other types of application were selected to show the scalability and applicability of the model. To demonstrate the flow related problem, slump flow test has been selected. To demonstrate, that concrete can fill all places of a complicated formwork, a T-Beam has been selected. A frame packed with reinforcement was selected, to show both flow and blocking related problem. L-box was selected to show the blocking and aggregate segregation related problem. Some general test methods were selected to demonstrate the diversification in the application simulation. These are -- a coaxial cylinder rheometer test, mainly to show the velocity profile distribution inside the concrete during rotation. It is found that, the DEM model proposed in this research can be used for simulation of flowable concrete. References 1 P. A. Cundall and O. D. L. Strack, "A Discrete Numerical Model for Granular Assemblies", Geotechnique, 29(1), 47-65, 1979. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £123 +P&P)
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