The Effective Mechanical Properties of Cement Mortar Based on the Greyscale Marker of its Microstructure Images

The effective homogeneous properties of the cement mortar were determined using the hierarchical image-based finite element method. Cement mortar was prepared with a composition of 1:1 (i.e. one part cement and one part sand) by weight in which three grades of standard sand were mixed equally (grades 1–2 mm, 0.5–1 mm, and 0.09–0.5 mm as per IS 650). The microstructure of the cement mortar was reconstructed using the X-ray computed tomography (XCT) technique at a resolution of 8.92 μm. The reconstructed images of the hardened cement mortar showed a combined distribution of greyscale values within the phases. Thus, the segmentation of the fine particles became too difficult, although the segmentation of the voids at this resolution of length scale was carried out by defining a suitable greyscale cut-off value. It is hypothesized that young’s moduli of the small particles in the image of mortar are directly related to the histogram of the greyscale values as these values are directly proportional to the density profile of the material. An image-based hierarchical finite element model is developed for the homogenization of cement mortar wherein the mechanical behaviour of the particles is related to the greyscale values. It is observed from this study that the homogenization window has a significant effect on the effective properties.