Microstructural characterization and numerical evaluation of interfacial transition zones in cement-based composites with biomineralized-coated aggregates

The interfacial transition zone (ITZ) in cement-based composites is a thin region surrounding aggregates, typically 20–50 https://www.w3.org/1998/Math/MathML" display="inline"> μ m thick, characterized by higher porosity and lower stiffness than the bulk paste. Its properties are governed by mix composition, aggregate characteristics, and curing conditions, making it a critical factor influencing stiffness, crack initiation, and durability. This study quantitatively evaluates the mechanical influence of ITZ characteristics using image-based modeling. High-resolution X-ray micro-computed tomography (micro-CT) was employed to characterize ITZ geometry and property gradients near aggregate boundaries. These experimentally derived characteristics were implemented into finite element (FE) models, representing the ITZ as a zone with distance-dependent material properties. Parametric simulations examined the effects of ITZ on damage propagation. A bio-inspired modification was further investigated by coating aggregates with a bacteria-induced calcium carbonate layer through microbially induced calcium carbonate precipitation (MICP). The biomineralized coating produced a denser and more homogeneous ITZ, improving bond strength and reducing microcracking. Digital simulations confirmed enhanced load transfer and delayed crack initiation in MICP-modified specimens. The integration of microstructural imaging, biomineralization, and numerical modeling provides an effective approach to design durable and sustainable cementitious materials.