Diffusivity and Microstructure in Cement-Based Materials

The diffusivity of ions and molecules in cement-based materials is governed by the intricate pore network and its evolution during hydration. As cement hydrates, capillary pores, gel pores and interfacial transition zones form a hierarchical microstructure that dictates transport pathways. Key parameters such as pore size distribution, connectivity and tortuosity determine how aggressive agents—salt ions, chlorides and moisture—penetrate and degrade concrete. Advanced imaging and simulation techniques have revealed that even minor changes in water-to-cement ratio, admixture content or curing regime can alter microstructural features and, consequently, diffusivity by orders of magnitude. Understanding these relationships is critical for predicting service life, designing durable blends using supplementary cementitious materials and optimising protective treatments to mitigate corrosion and deterioration in civil infrastructure worldwide.

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Recent multi-scale computational frameworks have linked three-dimensional microstructure generation to chloride diffusivity prediction by capturing pore size-dependent transport. By combining digital microstructure models with pore network reconstruction algorithms, researchers have shown that accounting for multi-modal pore size distributions reduces prediction errors by up to 25% compared with homogeneous-diffusivity approaches, leading to more accurate forecasts of chloride ingress in concrete.

Integrated lattice Boltzmann and finite-difference models have been developed to simulate ionic diffusion in unsaturated concrete, explicitly resolving nano- to meso-scale features and moisture distribution. These studies demonstrate that diffusivity strongly depends on water saturation level, pore connectivity and aggregate content, with the interfacial transition zone acting as a critical barrier when saturation falls below 90%, thereby retarding ion transport.

A self-consistent homogenisation approach has provided compact analytical relations linking porosity, pore diffusivity and overall cement paste diffusivity. By modelling pore space as an assembly of randomly oriented channels, this method confirms that layered water and surface interactions significantly reduce effective pore diffusivity relative to bulk solution values, offering a rigorous yet tractable route to upscale microstructural transport behaviour to the component scale.

Diffusivity and Microstructure in Cement-Based Materials publication trend

The graph below shows the total number of articles in diffusivity and microstructure in cement-based materials across all publications each year (not limited to Nature Index journals).

Technical terms

Diffusivity: Measure of the rate at which ions or molecules move through the pore network of a material.

Microstructure: The arrangement and connectivity of phases and pores at micro- to meso-scale within cementitious systems.

Pore size distribution: Statistical representation of pore diameters within the cement matrix affecting diffusion pathways.

Tortuosity: Ratio expressing the convoluted length of transport paths relative to straight-line distance.

Representative elementary volume (REV): The minimum volume over which a measured property reliably represents the bulk material behaviour.

Interfacial transition zone (ITZ): The region around aggregate particles with distinct microstructural and transport characteristics.

References

1. Modeling the chloride transport in concrete from microstructure generation to chloride diffusivity prediction. Computer-Aided Civil and Infrastructure Engineering (2024).
2. Multiscale modelling of ionic diffusivity in unsaturated concrete accounting for its hierarchical microstructure. Cement and Concrete Research (2022).
3. Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes. Transport in Porous Media (2017).