Examining the micromechanics of cementitious composites using In-Situ X-ray measurements

Micromechanics theories such as Mori–Tanaka's approximation and Herve-Zaoui's layered-inclusion approximation have been used extensively to predict homogenized stiffness, inclusion stresses, and matrix strains in various composites. While these theories accurately predict homogenized properties, the accuracy of their predictions of stresses and strains within individual phases of cementitious composites has not been assessed with experimental measurements or used to infer phase properties. Here, we therefore use in-situ X-ray tomography, 3D X-ray diffraction, and digital volume correlation to evaluate homogenized stiffness, inclusion stresses, and matrix strains in two cementitious composites. We compare measurements with predictions of Mori–Tanaka's mean-field approximation and Herve-Zaoui's layered-inclusion approximation. We provide some of the first direct support that these micromechanics theories can accurately predict both homogenized sample stiffness and individual phase responses. We also show that combining in-situ X-ray measurements with these theories provides a novel route for inferring the properties of specific phases.