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A numerical and experimental investigation into multi-ionic reactive transport behaviour in cementitious materials

Freeman, Brubeck 2017. A numerical and experimental investigation into multi-ionic reactive transport behaviour in cementitious materials. PhD Thesis, Cardiff University.
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This thesis describes a FE approach to the simulation of reactive transport problems and a simple experimental procedure for the determination of transport parameters in cementitious materials. A comprehensive fully coupled reactive-thermo-hygro-chemical model was developed based on the governing equations of mass and enthalpy balance. The model takes into consideration advective-dispersive transport of solutes, heat flow, advective-diffusive moisture flow, and chemical reactions. The FEM, Euler backward difference scheme and Newton-Raphson iteration procedure were employed to solve the system of nonlinear equations. To address the numerical challenge associated with such coupled simulations, three problem reduction schemes were proposed, each of which uses a reduced set of species, termed ‘indicators’, for full computation. The response of the remaining species is computed at each time step from the transport of the indicators. The difference between the schemes lies in the number of indicator species used and in the method employed for calculating the transport of the remaining species. Firstly the development of the experimental procedure is presented including the design of a porous concrete mix, a discussion of the problems encountered and the results of an advective-diffusive case. Following this, the model is validated and verified against a number of problems, beginning with a moisture transport problem and ending with a multi-ionic reactive transport problem. It was found that the model was able to accurately capture the transport behaviour. The range of applicability of each of the reduction schemes is then investigated through an example problem concerning the reactive transport of 16 chemical species, before verifying each of the schemes against the full model through the consideration of three example problems. The reduction schemes were found to perform well in accurately capturing the transport behaviour whilst greatly reducing the number of coupled equations to be solved, and the computational cost of the simulation

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Reactive Transport; Problem Size Reduction; Multi-Ionic Transport; Coupled Models; Finite Element; Cementitious Materials.
Date of First Compliant Deposit: 2 November 2017
Last Modified: 18 May 2021 09:20

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