Development and Verification of an Integrated Physicochemical and Geochemical Modelling Framework for Performance Assessment of Cement-Based Materials

Abstract

In this study, a multi-scale model called DuCOM (Durability COncrete Model), which is developed by the Concrete Laboratory at the University of Tokyo, is extended by coupling the geochemical code PHREEQC. The coupled numerical framework can address physicochemical and geochemical processes such as the hydration of cement particles, pore structure formation, multispecies transport, activity effect, thermodynamic reaction between aqueous solution and solids, etc. in cementitious materials, and therefore, it can potentially be used to assess the long-term durability of concrete structures. The model prediction for the composition of cement hydrates, pore solution chemistry, calcium profiles for the cement paste exposed in pure water, and calcium and sulphur profiles for the cement paste immersed in the sodium sulphate solution are qualitatively and quantitatively compared with experimental results obtained from literature. Finally, the importance of the strong coupling among various processes and mechanisms in the DuCOM-PHREEQC system is discussed.

Scale-Dependent ASR Expansion of Concrete and Its Prediction coupled with Silica Gel Generation and Migration

“…Figures 23b and 23c show the computed ASR expansion of concrete with and without the idealized leaching impact by solving the already verified multi-ion modeling (see Chapter 2, Nakarai et al 2006 andIshida 2014). As discussed in Chapter 3, the simulation of larger gel permeability (κ * =10 -18 ) brings about better correlation at the early age when amorphous phase of silica gel is thought be dominant like viscous liquid.…”

Space-Averaged Non-Local Analysis of Electric Potential for Polarization Reactions of Reinforcing Bars in Electrolytes

“…The conductivity of concrete is closely linked with the multi-ion concentration, micro-pore structures of CSH solid, the degree of saturation and the several solvents of salts. When we integrate the transient kinetics of solved ions in electrolytes, the Nernst-Plank equation shall be applied for multi-chemo thermodynamics (Bard et al 1980;Elakneswaran and Ishida 2014). The conductivity of electrolytes is assumed to be simply constant here, since the primary aim of this study is to verify the scheme of the simulation qualitatively.…”

Accelerated reactive transport simulations in heterogeneous porous media using Reaktoro and Firedrake

“…Given the inherent complexity of modeling physical and chemical processes individually, reactive transport codes comprise a combination of specialized packages (i.e., one for the physics and another for the chemistry). Several examples of such coupling are given next: HP1/HPx [40] (based on HYDRUS [89] and PHREEQC), PHT3D (merged from capabilities ofMT3DMS [107] and PHREEQC), COMSOL-PHREEQC iCP [74], COMSOL-PHREEQC [31], COMSOL-GEMS [6], CSMP++GEM [105], DuCOM-Phreeqc [26], GeoSysBRNS [17], Matlab-IPhreeqc [73], OGS-Chemapp [59], OGS-GEM [47], OGS-IPhreeqc [33], ReactMiCP [29], ReacTran [31], TReacLab [41]. A comprehensive overview of these packages' advantages and limitations is presented in [28] and [22].…”