Multiscale modeling elastic properties of cement-based materials considering imperfect interface effect

- Homogeneous properties of cement pastes were measured by CMS.
- Combined experimental and theoretical methods were used to determine phase volume fraction.
- Multiscale model considering imperfect interface effect was verified at different scales.
- The imperfect interface can be characterized by interface sliding parameter.
- Curing age and material proportion both affect the imperfect interface property.

Imperfect interface between the inclusions and the matrix has a significant influence on the macro properties of the composites. In this study, the effective elastic properties of cement pastes with water/cement (w/c) ratios of 0.3, 0.4, and 0.5 were homogenized from the calcium silicate hydrate (CSH) scale based on a multiscale model. The perfect and imperfect interfaces between inclusions and the matrix were assumed for the prediction. The imperfect interface is characterized by spring-layers of vanishing thickness in the tangential directions, and an interface sliding parameter (π/d) is used to reflect the imperfection of the interfaces. The predicted results were then compared to the measured one by instrumented indentation as well as the existing data from the literature. It is found that the perfect interface condition would overestimate the elastic modulus of cement-based materials. However, the homogenization scheme with imperfect interface can predict the effective elastic properties very well. This indicates that the imperfect interface may exist in cement-based materials and affect the effective elastic properties. The imperfect interface effect appears to be less significant with increasing curing age and vary with the mix proportion of cement-based materials. Therefore, the imperfect interface conditions should be adopted in the homogenization of the elastic properties for cement-based materials.