Greyscale marker for the modeling of the fracture process of cement mortar considering heterogeneity of the microstructure

Cement-mortar is a type of particulate ceramic composite which is widely used as a binder in the construction industry.The complex fracture behavior of the structure depends mainly on the fracture characteristics of the cement in the mortar.Here, we have explored the microstructural characteristics of the cement-mortar using a novel X-ray computed tomography (XCT) technique.The cement mortar has been prepared using standard Madras sand and ordinary Portland cement.A specimen of size 20X20X20 mm 3 has been reconstructed with a resolution of 21.2 m.A reconstructed 2D image of the cement -mortar is used for the mesoscale finite element simulations of the crack propagation.In the proposed model, the material properties of the mortar have been distributed among the finite elements based on the greyscale histogram of the reconstructed image to represent the heterogeneity of the material.The correlation between the material properties and grey scale values covered by an element has been established using a grayscale marker.Here, the greyscale marker has been defined by averaging the grey levels of the image covered in the finite element grid/window using in-house MATLAB code.Later, the cohesive interface elements (CIEs) were inserted in the finite element mesh to simulate the complex nonlinear fracture behavior of mortar in tension.The mechanical and fracture properties of the CIEs have been used from the literature and are also mapped to the same distribution.The effect of the window size has been studied on the stressstrain response and fracture pattern of the specimen.Finally, an optimum size of grid/window is recommended for the cement mortar.