Multi-scale flow, permeability, and heat transport in low-carbon and traditional building materials

TL;DR

This study combines XCT imaging and numerical modeling to analyze pore structures and transport properties in various building materials, revealing how heterogeneity influences permeability and heat transfer, and introduces a multi-scale approach for material optimization.

Contribution

It presents the first multi-scale investigation of pore structure, flow, and heat transport in building materials using combined experimental and numerical methods.

Findings

Heterogeneous and multi-scale pore structures significantly affect permeability and thermal conductivity.

Including sub-resolution porosity impacts bulk property calculations, especially in heterogeneous materials.

The workflow can be adapted for other porous materials in different industries.

Abstract

Permeability and heat transport through building materials ultimately dictates their insulatory performance over a buildings service lifetime. Experiments combining XCT with numerical modelling are an accepted method of studying pore scale processes and have been used extensively in the oil and gas industry to study highly complex reservoir rocks. However, despite the obvious similarities in structure and application, these techniques have not yet been widely adopted by the building and construction industry. An experimental investigation was performed on the pore structure of several building materials, including conventional, historic, and innovative, using XCT and direct numerical simulation. Six samples were imaged at between a 4 and 15 micron resolution inside a micro-CT scanner. The porosity and connectivity were extracted with the grain, throat, and pore size distributions using image analysis. The permeability, velocity, and thermal conductivity were then investigated using GeoChemFoam, our highly-versatile and open source numerical solver. It was found that each material had a unique, heterogeneous and sometimes multi-scale structure that had a large impact on the permeability and thermal conductivity. Furthermore, it was found that the method of including sub-resolution porosity directly effected these bulk property calculations for both parameters, especially in the materials with high structural heterogeneity. This is the first multi-scale study of structure, flow and heat transport on building materials and this workflow could easily be adapted to understand and improve designs in other industries that use porous materials such as fuel cells and batteries technology, lightweight materials and insulation, and semiconductors.