Lattice Boltzmann Modelling of Water Sorption in Calcium Silicate Hydrate Structures
Creators: name: Borg, Miryea Nicole
Publisher: name: University of Surrey
Year: 2023

description: Cementitious materials are the most commonly used construction material worldwide, able to be sourced from local and abundant resources. Despite this, the cement manufacturing industry has a substantial carbon footprint due to the creation of greenhouse gases emitted during production. To reduce the environmental impact of the cement production industry, an understanding of the hydration of cementitious materials, their durability and degradation patterns is critical. The durability of cementitious materials is closely related to the characteristic fluid transport properties throughout the
description: material. The microstructure of cement hydrates have a nanoscopically semi-crystalline, microscopically amorphous structure that has recently been shown to undergo reversible and irreversible changes during water adsorption and desorption processes. Lattice Boltzmann (LB) methods have previously been used to investigate cement permeability during sorption cycles.<br>
description: <br>
description: This work introduces a LB modelling framework for fluid sorption, coupled to a dynamic model of cement hydrate microstructure upon which it is possible to explore ideas of water sorption, anomalous transport and relaxation in cement emergent from nuclear magnetic resonance and other experimental studies. Investigation of water dynamics through a simplified quasi-continuous sheet and a colloidal growth model of the hydrate
description: microstructure are explored. The LB method is implemented, including a multiphase pseudo-potential flow model and a partial bounce back multiscale approach. This is done to understand the effect of capillary forces on changing the hydrate structure. The effect of moving boundaries between hydrate sheets experiencing transient fluid induced pressures is analysed and incorporated within a MATLAB modelling environment. The
description: implementation of the LB method in the MATLAB environment allows for the investigation of structural changes arising from capillary/disjoining-pressure forces. This model is used to investigate the pore size distribution and behaviour of liquid transport properties. Results show qualitative agreement with ideas associated with anomalous sorption and dynamic microstructure in cement hydrates emergent from recent Nuclear Magnetic
description: Resonance (NMR) experiments and other experimental data. In particular, LB simulations show (i) a diminution of gel pore sized nano-porosity in favour of more even smaller inter-layer sizes porosity and more larger intra-hydrate sized porosity upon drying with a recovery of pore size distribution on rewetting hat occurs on a slower time-scale than that of the water content changes as seen experimentally by Gajewicz (Cement and Concrete Research 86 (2016) 12-19) and (ii) changes in diffusion and permeability transport parameters that mimic those leading to anomalous (non-Fickian) water sorption as found experimentally and discussed by Hall et al. Cement and (Concrete Research 124 (2019) 105835) and by McDonald et al. (Cement and Concrete Research 146 (2021) 106475).<br>